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The prevalence of the extensor indicis tendon and its variants: a systematic review and meta-analysis
Abstract
The tendon of the extensor indicis (EI) is frequently used to restore the loss of function in other digits. However, it shows many variations which include splitting of the extensor indicis proprius (EIP) into two or three distal slips, attachment to fingers other than the index such as the extensor medii proprius (EMP), attachment onto the index and the third finger such as the extensor indicis et medii communis, or attachment to both the index and the thumb such as the extensor pollicis et indicis (EPI). This systematic review gathers the available data on the prevalence of EI tendon and its variation in the hand. Twenty-nine cadaveric studies met the inclusion criteria with a total of 3858 hands. Meta-analysis results yielded an overall pooled prevalence estimate (PPE) of EI of 96.5 % and PPEs of 92.6, 7.2 and 0.3 % for the single-, double- and triple-slip EIP, respectively. The single-slip EIP is frequently inserted on the ulnar side of the extensor digitorum communis of the index (EDC-index) in 98.3 %. The double-slip EIP is located on the ulnar side of the EDC-index in 53.5 %, on its radial side in 17 % and on both sides in 28.7 %. Indian populations showed the highest rate of single-slip EIP and the lowest rate of double-slip EIP when compared to Japanese, Europeans and North Americans. The pooled prevalence of EMP, EMIC and EPI were 3.7, 1.6 and 0.75 %, respectively. Knowledge of the variants of the EI tendon and their prevalence should help surgeons in correctly choosing the tendon to transfer in hand surgery.
... More unusual origins for the EIP include the lunate, scaphoid, and capitate bones with termination at the head of the proximal phalanx of the index finger or second finger [1]. The muscle belly of the EIP runs deep to the extensor digitorum communis tendons (EDCs) and is found rather invariably among humans, gorillas, and chimpanzees [1,2]. Variations in size, origin, insertion, duplications, and/or supernumerary tendons, however, can be found [1,2]. ...
... The muscle belly of the EIP runs deep to the extensor digitorum communis tendons (EDCs) and is found rather invariably among humans, gorillas, and chimpanzees [1,2]. Variations in size, origin, insertion, duplications, and/or supernumerary tendons, however, can be found [1,2]. Another variant of the EIP is a duplicated EIP (DEIP), which is a complete duplication of the EIP muscle and should not be confused with a distal splitting to have multiple tendons (Figure 1b). ...
... Multiple works, however, have reported the prevalence of other extensor tendon variants, including the EIP, EMP, EIMC, and extensor pollicis et indicis muscle tendon (EPI). Yammine (2015) describes the systematic review and meta-analysis of 21 studies and reports a pooled prevalence estimate of 1.6% for the EIMC, specifically [2]. The article further states that the EIMC was most often found in North American populations when compared to European, Indian, and Japanese populations [2]. ...
Forearm extensor muscle variations can be diverse and, in some instances, rare. During a routine anatomical dissection of human cadaveric donors during the 2021 first-year medical gross anatomy course and 2021 graduate nursing advanced anatomy course at the Uniformed Services University of the Health Sciences, bilateral agenesis of the extensor carpi ulnaris muscle was noted in one 70-year-old white male donor. This variation is described as extremely rare in the literature. The presence of an extensor indicis et digiti medii tendon, a variant of the extensor indicis tendon, appeared to be evident in post-dissection photographs on the left hand. The presence of a duplicated extensor indicis proprious tendon appears to be evident on the right hand. However, further inspection of this region was impeded as the body was sent for cremation prior to the variation being identified. The presence of various juncturae tendinum was also noted bilaterally. Reported prevalence of extensor indicis muscle variants ranges from 0.75% to 13%, depending on the specific type or grouping of variations observed. Knowledge of variations in the extensor compartment of the forearm and wrist is crucial for orthopedic surgeons and specialists. Alteration of surgical approaches may be necessary if such a variation is present. Such variations can be options for grafts, resulting in minimal functional change to the grafted area due to the continued existence of other muscles performing similar functions. Knowledge of such variations, and alternative, synonymous names for them, is also important for anatomy instructors, who may need to assist students in identifying these rare variations during anatomical dissection.
... A thorough literature review indicated that variations, in the form of additional tendons to the index finger, were observed in two categories. In the first category, the additional tendon did not arise from ED but arose as a separate muscle either from the radius [20,24] or the ulna [10]. In the second category, the additional tendon to the index finger arose from ED [3]. ...
... Von Schroeder et al. [23] described three types of JTs : Type 1 (thin, fascia-like), Type 2 (thicker, fibrous), and Type 3 (thickest, tendinous band). Yammine [24] reported the prevalence of JT between the index finger and middle finger as Type 1 (95%), Type 2 (5%), and Type 3 (0%). ...
... Furthermore, they showed that Type 1 JTs accommodated independent extension of the four medial digits whereas Type 2 and 3 JTs were restrictive [24]. In the present case, we observed thin fascia-like JTs similar to that described as Type 1. ...
Understanding anatomical variations, as well as, normal anatomy of the muscles and tendons of the hand is vital for successful clinical evaluation and surgery. A number of extensor muscle and tendon variations have been reported in the literature including duplication, triplication, and absence. We report a rare anatomical variation that includes bilateral absence of the extensor indicis (EI) muscles and bilateral duplication of the extensor digitorum (ED) tendon to the second digit in the forearm of an 83-year-old male cadaver during routine upper limbs dissection. In the present case, only three muscles were present in the deep compartment: extensor pollicis longus (EPL), extensor pollicis brevis (EPB), and abductor pollicis longus (APL) with bilateral absence of EI. The reported prevalence of bilateral absence of EI muscle and tendon ranges from 0.5 to 3.5% [1, 26]. The prevalence of an additional index tendon arising bilaterally from the ED muscle belly is 3.2 % of the population [1]. Extension of the index finger is governed by the actions of EI and ED. However, the four tendons of ED are linked to each other by juncturae tendinum (JT), restricting independent extension of the digits in certain postures, e.g. when the hand is fisted. With fisted hand, EI controls extension of the index finger. Clinically, EI tendons are used for tendon reconstruction procedures to restore function to the hand and thumb after trauma or tendon rupture. This report highlights the importance of anticipating anatomical variations and conducting pre-operative evaluations to confirm the presence of EI when planning tendon transfer procedures.
... The EI muscle was reported with a prevalence of 96,5% and with a single, two, or three tendons [4,6]. Yammine (2014) has reported in a meta-analysis the prevalence of EI variants, like extensor medii proprius muscle (EMP), extensor indicis et medii communis (EIMC), and extensor pollicis et indicis (EPI) [23]. The EMP is a muscular variant analogous to the EI, with insertion to the middle finger [18], and was described in the literature as separate muscle belly or fused with the muscle belly of EI [25] with a prevalence of 3.7% [23]. ...
... The EI muscle was reported with a prevalence of 96,5% and with a single, two, or three tendons [4,6]. Yammine (2014) has reported in a meta-analysis the prevalence of EI variants, like extensor medii proprius muscle (EMP), extensor indicis et medii communis (EIMC), and extensor pollicis et indicis (EPI) [23]. The EMP is a muscular variant analogous to the EI, with insertion to the middle finger [18], and was described in the literature as separate muscle belly or fused with the muscle belly of EI [25] with a prevalence of 3.7% [23]. ...
... Yammine (2014) has reported in a meta-analysis the prevalence of EI variants, like extensor medii proprius muscle (EMP), extensor indicis et medii communis (EIMC), and extensor pollicis et indicis (EPI) [23]. The EMP is a muscular variant analogous to the EI, with insertion to the middle finger [18], and was described in the literature as separate muscle belly or fused with the muscle belly of EI [25] with a prevalence of 3.7% [23]. A split EI tendon, inserted into both, index finger and long finger, was reported as an EIMC muscle [9,17,19,22] with a prevalence of 1,6% [24], and inserted into both, index and thumb was reported as an EPI muscle, with a prevalence of 0,75% [23]. ...
An unusual variation of the extensor muscles was found during the routine dissection of the posterior compartment of the forearm. The left forearm presented an extensor medii proprius muscle, the tendon of which had an unusual trajectory. It passed through the second extensor compartment between the tendons of the extensor carpi radialis longus and extensor carpi radialis brevis muscles. The right forearm presented two muscles for the index finger: one, the extensor indicis et medius communis, the tendon of which was split into three tendons, one radial and one ulnar for the index finger and a rudimentary tendon for the middle finger; the second muscle for the index finger had an unusual origin, common with the extensor carpi radialis brevis, and its tendon ran superficially to the tendon of the extensor indicis et medius communis muscle. Knowledge goes tendon variations can be significant not only for clinicians to misdiagnose a debilitating wrist extensor pain syndrome but also for surgeons to avoid iatrogenic injuries in hand surgery.
... A thorough understanding of comparative myology is also critical for developing hypotheses about the functional morphology of modern human musculature. Numerous studies and metaanalyses [1][2][3][4][5] have been conducted to study the anatomy and the prevalence of variations in these regions including the extensor indicis radialis (EIR) muscle, extensor medii proprius (EMP) muscle, extensor indicis et medii communis (EIMC) muscle, extensor pollicis et indicis (EPI) muscle, and extensor digitorum brevis manus (EDBM) muscle. Classification systems were also proposed to systematically identity these variants [1,6,7]. ...
... Classification systems were also proposed to systematically identity these variants [1,6,7]. According to recent meta-analyses [3,4], the prevalence of EMP, EIMC, EPI, and EDBM were 3.7%, 1.6%, 0.75%, and 4% respectively. The EIR is an extremely rare variation which existed in only 0.2% of limbs [8]. ...
... According to a recent classification system by Georgiev et al. [6], the two muscular variants can be classified as the EIR and EMP. The EIR and EMP are well-known variations, and numerous studies were conducted to study their anatomy and prevalence in detail [1,2,[4][5][6]. However, very little is known about the unusual fibromuscular structure originating from the EMP. ...
Posterior compartment of forearm and hand is among the most variable parts of the human body. During a routine dissection, we found two anatomical variants in the right forearm and hand of an 84-year-old male cadaver including the extensor indicis radialis and the extensor medii proprius associated with a fibromuscular slip. Histological analysis using hematoxylin and eosin staining revealed that this unusual fibromuscular slip associated with the extensor medii proprius was composed of dense connective tissue along with small amount of skeletal muscle fibers, and the innervation from the posterior interosseous nerve. Based on the existing literature, a fibromuscular slip associated with a hand extensor tendon on the dorsum of hand has never been reported. Further studies are needed to clarify the evolutionary origin of this structure, although it resembles to a certain extent the dorsometacarpales, a group of muscles that were once present in our mammalian ancestors.
... Injuries to the extensor tendons are more common because of their superficial location in hand and poor subcutaneous tissue protection. Moreover, the extensor muscles of the hand are one of the regions where variations in the human body are common [1]. Variations of the hand extensor muscles are often asymptomatic, and it is essential to know about them when evaluating trauma and diseased hands, for their treatment and tendon transfer from this region. ...
... In our study, no extremity was found in which the tendon did not extend from both the EIP and EIMC to the second finger. The share of the EIP with three tendons was reported to vary between 0.23% [1] and 4% [12]. Various studies have been performed on EIP tendon number [8,12,13,[17][18][19][20]. The results of our study are like the results of previous studies. ...
... The EIMC is a variant extensor muscle that is inserted on both the second and the third fingers. In a meta-analysis, Yammine [1] indicated that the frequency of the EIMC varied between 0% and 6.4% in the 24 studies examined, but in one study, it was observed at the rate of 16%. Our results are consistent with the rates reported in the literature. ...
We aimed to investigate tendon variations of the extensor digitorum (ED), extensor digiti minimi (EDM), and extensor indicis proprius (EIP) muscles. Our study was performed on 43 fetal cadavers (86 extremities), aged between 17 and 40 weeks of gestation. The number of ED tendons varied from three to six, proximal to the extensor retinaculum (ER), and from three to eight, distal to the ER. The ED most often had four tendons, both proximally and distally from the ER. The ED tendons of the fourth finger were observed to be most frequently duplicated. The most common juncturae tendinum (JT) was type 1 in the second intermetacarpal space (IMCS), type 2 in the third IMCS, and type 3r in the fourth IMCS according to von Schroeder classification. The number of EIP and EDM tendons varied from one to two and from one to five, respectively. The EIP double tendons inserted both into the ulnar and palmar sides of the extensor digitorum of the second finger, which had not been reported in the literature. In our study, 7% of hands had variant muscles. In 4.7% of hands, the extensor indicis et medii communis was observed, while the extensor medii proprius and the extensor digitorum brevis manus were observed in 1.2% and 1.2% of hands, respectively. Knowing the prevalence of the ED, EDM and EIP tendons and their variations in the fetal period should help to treat partial loss of hand function or injury after birth and to correct congenital hand deformities.
... While these structures are considered "normal" in the aforementioned non-human primate species, they are atavistic and are regarded as variations in humans. Numerous studies and meta-analysis have been conducted to study the anatomy and prevalence of variations in the deep extensor region [12,14], and a classification system was recently proposed by Georgiev et al. [6]. The extensor medii proprius (EMP) is a muscular variant analogous to the extensor indicis, but with the insertion to the middle finger. ...
... The extensor medii proprius (EMP) is a muscular variant analogous to the extensor indicis, but with the insertion to the middle finger. The EMP has a prevalence of 3.7% [14]. The extensor indicis et medii communis (EIMC) is another variant with a prevalence of 1.6% across the populations. ...
... The extensor indicis et medii communis (EIMC) is another variant with a prevalence of 1.6% across the populations. The EIMC, a muscular variant with insertions to the index and middle finger, has a prevalence of 1.6% [14]. The extensor policies et indicis (EPI), a common thumb and index extensor, is the rarest variant in this region having a prevalence of 0.75% [14]. ...
Purpose Anatomical variants in the posterior compartment of forearm and hand are not uncommon. Physicians should be aware of variations in this region for correct diagnosis and treatment of diseased hands.
Methods During a routine dissection at our department, an extremely rare case of deep hand extensor muscle was discovered. Results A complete extensor digitorum profundus complex was found in the fourth extensor compartment in addition to the extensor indicis proprius. The complex consisted of two muscle bellies originating from the lateral aspect of distal ulna and the adjacent interosseous membrane. The first belly resembled the conventional extensor indicis proprius. The second belly gave off two tendon slips: one inserted to the index and middle fingers and the other formed aponeurosis before inserting to the ring and little fingers.
Conclusion To our knowledge, a complete extensor digitorum profundus complex which inserts to all medial four digits has never been reported in humans. Awareness of variations in this region is critical for surgeons operating in the forearm and hand. The present case also provides insights into the evolutionary and developmental origin of these structures.
... Fourth, according to the review of the literature done by Straus (1941aStraus ( , 1941b, an exclusive insertion of the extensor indicis onto Digit II occurs in 68% in chimpanzees, 5% in orangutans and 0% in gibbons. While in gorillas, the muscle is commonly inserted onto Digit II only (Kaneff, 1980a(Kaneff, , 1980b, in modern humans it ends exclusively onto Digit II in 96.5% of the cases (Yammine, 2015b). Fifth, the extensor digiti minimi (EDM) often ends up onto Digits 4 and 5 in orangutans (Swindler and Wood, 1973;Gibbs, 1999;. ...
... Meta-analytical data of sesamoid frequency in the hand and muscle frequency were extracted from Yammine (2014) and Yammine (2015bYammine ( , 2015c, respectively. In the case of muscles with no previously reported meta-analytical frequency, average values obtained from weighted estimates were calculated by including the largest studies. ...
... A meta-analytical frequency of the EIP has reported by (Yammine, 2015b) to be at 96.5%. Thus, the overall muscle score is 0.965 and the overall digital score is 1.965. ...
Digital sesamoids are found in the metapodial-phalangeal joints of most mammals and quadrupedal tetrapods, yet their functional significance is still unclear. During primate evolution, a slight decline in their frequency has been associated with brachiation in gibbons, followed by a quasi-complete absence in orangutans then a slight resurgence occurred in gorillas and chimpanzees. Simultaneously, forearm muscles showed a progressive division in hominoid evolution towards a more “individualistic” musculature yielding more mobility and independence to some fingers. In humans, sesamoids are consistently observed in thumbs and big toes and frequently in other hypermobile digits such as the index and little fingers. Using a simple mathematical equation, this paper attempted to quantify a presumed association between hypermobile fingers and sesamoid frequency and distribution in humans. To this, an anatomic definition of digital independence has been formulated which includes three variables; a) number and b) frequency of independent flexor/extensor forearm muscles destined to a single finger, c) and number of free/absent webspace. Results of previous meta-analyses and means of big sample studies were used to evaluate the frequency of such muscles. The expected values obtained via this model were found to be very close to the observed (published) values of the ossified sesamoids in human hands, and that in terms of frequency and distribution. The findings in humans showed a quasi-linear association between the degree of mobility and sesamoid frequency. The more the number of independent muscles destined to a finger, the more its metacarpo-phalangeal joint is likely to bear sesamoids. Based on our results and on a new analysis of primates' forearm/hand muscles and sesamoid evolution, a new hypothesis is proposed to answer two questions; the evolution of digital sesamoid frequency in primates and its sesamoid distribution in human digits. It claims that the number/frequency of independent forearm/hand muscles, and particularly the independent extensors, is likely to be a major factor in sesamoid reversion in hominoids. The argument is based on the link between the metatarsal break induced by the digitigrade locomotion observed in quadrupedal mammals and tetrapods and the amount of extra-extension of the metacarpo-phalangeal joints conferred by the individualization of some forearm extensors. The same rationale yielded similar conclusions when applied to both the hand and foot. The manipulative function of the hand and the plantigrade locomotion of the foot required such extra-extension in specific digits and consequently, a higher frequency of digital sesamoids was associated with these two different functions. The new evolutionary analysis suggests evolutionary pathways for both, the sesamoids of the hands and feet, and speculates that muscle individualization would have induced a very slow re-acquisition of digital sesamoids when compared to their rapid decline after brachiation. It is the first hypothesis offering a plausible explication on the recent evolution of digital sesamoids; specifically, the progression of sesamoid frequency in African apes and its resurgence, prevalence and distribution in humans. This article is protected by copyright. All rights reserved.
... The lack of understanding of such anatomical variation and its prevalence can lead to false diagnosis, resulting in inappropriate treatment. A number of anatomical studies [11,20,24,34,43] and meta-analyses [36,[38][39][40] have been done to study the variations in extensor compartment of forearm and hand. However, no prior study has been conducted to study such variations in Thai population. ...
... Type D, where the double tendons of the EIP insert volar and radial to the EDC-I tendon, has never been reported elsewhere. Triple tendons of the EIP were not seen in this study, however, they were present in 9/3858 hands (0.23 %) as reported in a recent meta-analysis [40]. ...
... The EMP is also known as the extensor digiti medii [8]. A recent meta-analysis by Yammine [40] revealed that the EMP was present in 3.7 % of 3760 hands, with the range of 022 %. The EMP is the most frequent in Japanese and North American populations when compared to Indian, and European populations [40]. ...
A total of 100 cadaveric limbs were dissected to study the anatomy of the forearm and hand extensor musculature. Four types of contributions to the index finger were found for the extensor indicis proprius (EIP), including one new type where the double tendons of the EIP inserts volar and radial to the extensor digitorum communis of the index finger (EDC-I). Four variant muscles were identified including the extensor medii proprius (EMP) (in five cadavers), extensor digitorum brevis manus (EDBM) (in one cadaver), extensor indicis et medii communis (EIMC) (in four cadavers) and extensor pollicis et indicis (EPI) (in four cadavers). The absence of the EIP in four cases was substituted by either the EIMC or the EPI. Two unpreviously published cases were found. In one hand, the variant EIMC was present along with the EPI. In another hand, both the EMP and the EDBM were present, and the EMP tendon inserted to the tendon of the EDBM. Awareness of the variations on the dorsum of the hand is essential for diagnosis, surgical planning and treatment of diseased hands.
... The EIP and EDM tendons are present at the ulnar aspect of the ED tendons. 18 Fine fibrous connections or slips AJUM xxxx 0000 0 (0) 3 ...
... In the dorsal hand, the EIP tendon is present at the ulnar side of the ED tendon and overlies the dorsal aspect of the second MC and MC head, although variants where it has been observed to be present to the radial aspect of the ED have been reported. 18 Unlike the ED tendon, the EIP tendon does not insert distally onto bone, but rather inserts variably onto the ulnar aspect of the dorsal hood of the second finger, at the proximal phalanx (PP) level. 9 Sonographically, the EIP tendon can be identified at the level of the second MC head over its dorsal aspect, encapsulated by the sagittal band. ...
... The index finger has two independent tendons: the tendon of the extensor digitorum (ED-index) with a single slip, usually, and the tendon of the extensor indicis (EI), variable in size, origin, and insertion locations, as well as in number of distal slips present. The most common variant is a single-slip of the EI tendon inserting on the ulnar side of the ED-index tendon [25]. ...
... Becoming thoroughly acquainted with the extensor tendons' variants may be helpful for hand surgeons in planning tendon graft surgery [3,25] and allowing them to successfully perform tenosynovectomy for the treatment of de Quervain's syndrome [3,19]. The detailed anatomical knowledge of the extensor tendons is a determining factor in preserving healthy tendons during orthopedic procedures, hence accounts for good patient outcomes and improves their quality of life [3,5]. ...
The forearm extensor compartment is known for its wide variability in terms of muscle origin, number of tendons and their distal insertion. The index finger on its dorsal aspect is the typical place of insertion of the two tendons of the extensor digitorum (ED-index) and of the extensor indicis. Being acquainted with their anatomy is of immense importance to orthopedic surgeons in the treatment of e.g., de Quervain's syndrome.
The current report presents a rare finding of the ED-index tendon arising from the extensor carpi radialis brevis (ECRB). A routine dissection revealed their fused course from the lateral epicondyle of humerus, though separate from the extensor carpi radialis longus. The ED-index muscle belly separated from the ECRB, 119 mm distal to the lateral epicondyle. The distal insertion point of the ED-index was located radially to that of the extensor indicis. The deep branch of the radial nerve and the recurrent interosseous artery supplied the ED-index. No other musculotendinous variations were encountered neither on the ipsilateral nor the contralateral upper limb of the cadaver.
This study presents in detail a tendon of the ED-index arising from the ECRB, a knowledge that can be applied namely in the lateral epicondylitis treatment or approach to the ulnar nerve at the level of the elbow. Extensive depiction of both the proximal and distal attachment points of the muscles, their course and dimensions is indispensable to attain the best patient outcomes and avoid iatrogenic injuries.
... V ariations related to muscle of the extensor compartment of forearm are not uncommon and found incidentally during anatomical dissections and surgeries of hand [1,2]. The EIP, a deep extensors muscle of forearm originates from the posterior surface of distal two third of the shaft of ulna and adjacent interosseous membrane. ...
... The EMP has an incidence ranging between 1% and 12% in cadaveric studies and observed more frequently in males than females. A meta-analysis by Kaissar Yammine revealed that Indian populations showed lowest rate of EMP compared to Japanese, Europeans and North Americans [2,6,9]. In the present case, The EMP originates from the posterior surface of distal one third of Ulna with adjacent interosseous membrane and ulnar to the origin of the extensor indicis. ...
SrikanthV, Muraleedhar B, Ranade AV. Unilateral occurrence of extensor medii proprius: an incidental finding. Int J Anat Var. 2021;14(1):45-46. ABSTRACT The deep extensors muscle of forearm may contain inconsistent muscles like extensor digitorumbrevismanus (EDBM), extensor mediiproprius (EMP), extensor indicis et mediicommunis (EIMC) and anomalous extensor indicisproprius (aEIM). We report a rare case of EMP with its unusual course in insertion along with coexistence of extensor indicisproprius muscle (EIP). It originated along with EIP from the distal third of dorsum of ulna and adjacent interosseous membrane, just distal to extensor pollicislongus (EPL). Distally the tendon of the muscle merged with extensor expansion at metacarpophalangeal joint of third digit deep to the extensor digitorum tendon. The knowledge of such variations on the hand is essential to the clinicians and surgeons as hand injuries are one of the most common injuries occurring due to its superficial location and poor insulation. Additionally, this information may help them in accurate diagnosis and management of functional deformities, pathological lesions and various other disorders of hand.
... Anatomical variations of the finger extensor tendons are not uncommon and have been described by several authors GOLANO, 2014;AVDAR and SEHIRLI, 1996;LI and MAO, 2014;MEHTA et al., 2009;NAYAK, HUSSEIN, KRISHNAMURTHY et al., 2009;NAYAK, KRISHNAMURTHY, PAI et al., 2008;NAYAR and MCARTHUR, 2009;RAY, RANADE, D'COSTA et al., 2010;ROY, MEHTA, SURI et al., 2010;YAMMINE, 2014YAMMINE, , 2015ZAINO, MITGANG, RAWAT et al., 2014). Some of these studies included anatomical variations of the first dorsal compartment of the wrist in relation to their importance in de Quervain's disease (NAYAK, HUSSEIN, KRISHNAMURTHY et al., 2009;ROY, ROY, DE et al., 2012;ROY, MEHTA, SURI et al., 2010). ...
... Mehta, Jyoti, Suri et al. (2009) reported an accessory muscle arising from the origin of the EDC, passing to the index finger; this was in addition to the usual EI. Later, Yammine (2015) reviewed the prevalence of the EI and its variants. Avdar and Sehirli (1996) reported an accessory tendon of the EI muscle in between the EI and EPL muscles. ...
Introduction: Gantzer’s muscle has drawn attention from several authors owing to the possibility of interosseous nerve compression. This is a report of an accessory head of flexor pollicis longus (FPL, a variant of Gantzer’s muscle) and a review of the variations of all muscles of the forearm. Materials and Methods: An accessory head of FPL was discovered in both the right and left antebrachial regions during a cadaver dissection. The muscle was dissected and photographed. Results: The anatomical variation I report is a slender conical muscle joining the FPL. Its origin merged with fibers of the flexor digitorum superficialis. It inserted into the upper part of the middle third of the forearm by joining the medial tendinous part of the FPL; this join was by means of a short cylindrical tendon. The reported muscle was innervated by the anterior interosseous nerve, which was seen to be present posterolateral to the muscle in both forearms. Conclusion: The described muscle might cause pressure problems to the underlying structures especially the anterior interosseous nerve. Variations must be considered during surgical intervention to avoid unintentional damage to healthy tendons. In addition, accessory tendons can potentially be useful in the repair or replacement of damaged tendons through surgical transfer or transplantation. Variations of muscles, especially accessory muscles, may mimic the behavior of soft tissue tumors and can result in nerve compressions. This collection of variations of the forearm musculature will be useful to surgeons in practice as well as students in dissection labs.
... The second and fifth digits are more likely sources of extra slips/tendons for tendon transfer in surgery as they are more frequently present compared to the EMP [2]. A meta-analytic review of 22 studies with a combined sample size of 3,984 extremities reported the true prevalence of the EMP tendon as 3.7% with higher rates in Japanese and North American populations compared to European and Indian populations [10]. The presence of the EMP rarely causes clinical symptoms due to its narrow width [9]. ...
During routine dissection of 11 cadavers that originated with the Body Donor Program at Philadelphia College of Osteopathic Medicine (PCOM) Georgia, a 69-year-old African American male with bilateral extensor anomalies in the dorsal forearm compartment was encountered. The distinct muscle belly, identified as the extensor medii proprius (EMP), originated from the distal ulna and was inserted near the dorsal aponeurosis of the third digit. Manual traction of the right EMP tendon resulted in the extension of the third digit, suggesting the functional significance of the anomalous muscle. This case study analyzes the EMP found during dissection, as well as the anomalous muscle’s prevalence, embryologic origin, and clinical relevance. The presence of the EMP muscle and tendon can be considered when assessing pain in the dorsum of the hand and when preparing for surgical repair or tendon transfer.
... US also has an important role in detecting EIPM anatomical variants that can be bifidity with a double insertion on the index finger or by giving one tendon to the index and another to the middle finger or thumb. Exceptionally, EIPM can give three slips for the index or one for the index, one for the ring finger, and a third one for the middle [5][6]. ...
The extensor indicis proprius muscle (EIPM) is considered a key muscle in the assessment of the level of the neurologic lesion causing any motor or sensory medio-cubital impairment of the hand.
The aim of this study is to illustrate the anatomical peculiarities of the EIPM, the ultrasound (US) anatomy of the inferoposterior part of the forearm, and the technique of US-guided electromyography (EMG) of the EIPM.
The US-guided EMG of the EIPM is technically easy and safe for young practitioners, provided there is a good knowledge of US anatomy of the inferoposterior part of the forearm.
... is absent in approximately 4% of the population and thus should be confirmed before making a surgical plan. [21][22][23] In our method, we inserted the sutures for the tendon graft while keeping the wrist neutral and the thumb in full extension. Low et al performed a cadaver study and case series and concluded that EIP transfer tensioned with the wrist neutral and thumb in full extension provided better tensioning and resulted in good flexion and extension range for the thumb. ...
Background:
The main treatment choices for chronic extensor pollicis longus (EPL) tendon rupture consists of tendon transfer and tendon repair with tendon graft. Tendon transfer with extensor indicis proprius (EIP) is currently considered the gold standard treatment which yields predictable and satisfactory results, but potentially compromises the strength of independent extension of the index finger. We propose our method of using a partial extensor carpi radialis longus (ECRL) tendon graft to repair chronic EPL tendon tears.
Methods:
The distal stump of the EPL was located through an incision at the basal joint level. The proximal stump was located through a curved incision at the dorsoradial wrist where the partial ECRL tendon graft was harvested. The tendon graft was subcutaneously transposed, sutured at both ends and tensioned at full thumb extension with a neutral wrist position.
Results:
From March 2016 to June 2019, 23 patients (mean age: 59.7 years; mean follow-up: 29.6 months) were retrospectively reviewed. All the patients were followed for a minimum of 12 months. The final total active motion (TAM) was 93.2% of the contralateral thumb. The mean DASH score was 6.0. There was one complication possibly due to poor EPL muscle quality, and the patient was subsequently treated with EIP tendon transfer.
Conclusion:
Our study showed that using a partial ECRL tendon graft to repair chronic EPL tendon rupture results in satisfactory functional outcomes. The advantages of this method include preservation of EIP function and using the same incision for graft harvesting and tendon repair. This method can be considered an alternative to EIP tendon transfer in patients with high demand for their index finger function.
... Second, variations in the EI have been reported in some studies. According to several previous studies, there are extensor medii proprius or digiti, extensor indicis et medii communis or digiti, extensor pollicis et indicis, and extensor indicis ulnaris and radialis muscles [21,22]. In people with these variations, it may be difficult to identify the optimal insertion point using our method. ...
Objective:
To determine the most optimal needle insertion point of extensor indicis (EI) using ultrasound.
Methods:
A total 80 forearms of 40 healthy volunteers were recruited. We identified midpoint (MP) of EI using ultrasound and set MP as optimal needle insertion point. The location of MP was suggested using distances from landmarks. Distance from MP to medial border of ulna (MP-X) and to lower margin of ulnar head (MP-Y) were measured. Ratios of MP-X to Forearm circumference (X ratio) and MP-Y to forearm length (Y ratio) were calculated. In cross-sectional view, depth of MP (Dmp), defined as middle value of superficial depth (Ds) and deep depth (Dd) was measured and suggested as proper depth of needle insertion.
Results:
Mean MP-X was 1.37±0.14 cm and mean MP-Y was 5.50±0.46 cm. Mean X ratio was 8.10±0.53 and mean Y ratio was 22.15±0.47. Mean Dmp was 7.63±0.96 mm.
Conclusion:
We suggested that novel optimal needle insertion point of the EI. It is about 7.6 mm in depth at about 22% of the forearm length proximal from the lower margin of the ulnar head and about 8.1% of the forearm circumference radial from medial border of ulna.
... Variations in these muscles or tendons can lead to inflammatory conditions that impair the function of the hand [16]. The extensor tendons of the hand and thumb are one of the most common areas of variations in the human body [28]. ...
Purpose
The extensor pollicis longus (EPL) and brevis (EPB) and abductor pollicis longus (APL) are muscles located in the posterior compartment of the forearm. These muscles allow the thumb to move independently from the other four fingers by attaching to the thumb separately. This study’s goal was to investigate the tendon variations and insertions of these muscles.
Methods
Our study was conducted on 43 fetal cadavers (86 upper extremities) aged between 17 and 40 weeks of gestation. This study investigated the tendon numbers and insertions of the EPL, EPB, and APL.
Results
The tendon numbers of the EPL and EPB were observed to range between 1 and 2, and the tendon numbers of the APL ranged between 1 and 5. The EPL was found to insert into the distal phalanx via the dorsal aponeurosis in all extremities. It was observed that the EPB tendons inserted into the proximal phalanx, distal phalanx, and dorsal aponeurosis. It was determined that the APL tendons inserted into the basis of the first metacarpal, abductor pollicis brevis, opponens pollicis, and trapezium bone.
Conclusion
Knowing the tendon variations and insertions of the EPL, EPB, and APL muscles during the fetal period will be useful in planning treatments to correct the congenital thumb anomalies and the loss of function after injury.
... One of the rarest variations in 2-3% of people is Bruce's extensor, which originates in the form of a muscular ventricle in the back of the hand, from the lancet bone, and from the dorsal ligaments of the carpal radio [5,7,8]. And may be mistaken for ganglion or mass [9] Type 3 (A), which has the highest probability among other variations and according to M Komiyama studies in men and women, has the same probability but the probability of this possibility in the left hand compared to the right hand is 5: 3 (5 to 3), But in another study, it was stated that the frequency of the specific tendon of the middle finger is higher in women and in the right hand [10]. According to studies by Swee T. Tan and colleagues, type 1 had a common extensor indicis (EIMC), which has two tendons and is common in chimpanzees and gorillas, but in type 2. The tendon that goes to the middle finger and forefinger contains the muscular ventricle of their own, the Extensor MediiProprius and the Extensor Indicis proprius, and is more common in older monkeys [11]. ...
During routine dissection of an approximately 60-year-old female cadaver for training the Master students of the Anatomical Sciences at school medicine of Tehran University of Medical Sciences, we came across a variation in tendon of extensor indicis muscle. In this case extensor indicis muscle origin from posterior surface of ulna bone, and it tendon distribute to bifurcate tendon that one tendon of it insertion to medial side of tendon of second of extensor digitrom muscle and other tendon of it insertion to third metacarpophalangeal joint.
... Reported variations in the extensor forearm include accessory heads of muscles (extensor carpi radialis longus and brevis [23,24] and extensor indicis [35]), a wide variety of tendon anomalies (extensor digitorum [31], extensor indicis [11] abductor pollicis longus [1,2,6,8,26,27,30,34]), the absence of muscles [33], and even the presence of novel muscles [16,17]. ...
Muscle and tendon variations in the forearm, wrist and hand are commonly reported in the anatomical and surgical literature. They are frequently the source of inflammatory conditions such as de Quervain's tenosynovitis or carpal tunnel syndrome. During academic dissection, a cadaver presented with bilateral, additional muscles running parallel to the abductor pollicis longus muscles (APL) in the extensor compartment of the forearm. Both additional muscles had two bellies, one proximal and one distal, with an intervening tendon. The proximal bellies were separate and distinct from the adjacent APLs. The tendons traversed the first dorsal compartments with the tendons of the APLs and the extensor pollicis brevis muscles (EPB). The distal bellies lay adjacent to the abductor pollicis brevis (APB) muscles in the thenar compartments, and inserted onto the volar base of the proximal phalanges of the thumbs. Following a thorough search of the literature, we determined that these additional muscles constitute a previously unreported variation. This report details the variation, compares it with other reported variations, presents the related embryology, and reviews the significance of this variation as it relates to inflammatory conditions and surgical procedures.
... This anomalous muscle is more frequent in males compared to females and has an incidence between 0.8% and 12% [1,9,13]. In addition, meta-analysis reveals that the presence of an extensor medii proprius muscle is significantly lower in Indian and European populations than North American and Japanese populations [15]. In contrast, our study describes an unusual origin of this muscle from the distal part of the muscle belly of the extensor indicis muscle and its bundles have no relations to the ulna and interos- [5]. ...
In the current study, we established а variation of the forearm extensor muscles during a routine anatomical dissection of the left upper limb of a cadaver of 64-year-old woman. Тhe variant muscle was represented by the presence of an extensor medii proprius muscle-it originated from the distal part of the extensor indicis muscle and its bundles ran parallel in distal direction. The distal tendon passed through the fourth extensor compartment and inserted into the dorsal aspect of the capsule of the meta-carpophalangeal joint of the middle finger. Herein, we describe the unusual origin of this muscle, its relations to the adjacent structures and discuss its possible clinical significance.
... A rare occurrence of EIMC together with anomalous extensor pollicis et indicis (EPI) muscle has been reported by Suwannakhan et al. [18]. The collective prevalence of EMP, EIMC, and EPI was reported to be 3.7, 1.6, and 0.75%, respectively [19]. ...
Variations of radial artery, in both its course and branching pattern in the anatomical snuffbox, are clinically significant for the
plastic surgeons, cardiologists, and radiologists. Reports on its abnormal high origin and subsequent superficial course have been
well documented. Herein, we report an unusual superficial branch of the radial artery given off before its entry into the palm by
passing between the two heads of first dorsal interosseous. It eventually divided into princeps pollicis and radialis indicis arteries
at the first web space of palm as a unique vascular variation. Apart from this, in the present case, the tendon of extensor digiti
minimi and of extensor indicis divided into two parts. The split tendons of extensor digiti minimi were inserted to the dorsal
digital expansion of the digitus minimus. However, lateral tendon of split extensor indicis was inserted along with the tendon of
extensor digitorum to the index finger and the medial one was inserted along with the tendon of extensor digitorum to the middle
finger. Unusual superficial branch of radial artery on the dorsum of the hand is vulnerable for an iatrogenic injury during surgical
approaches in the region. Supplementary extensor tendons on the hand are one of the potential causes for the tenosynovitis.
... However, none of these studies are based on a reproducible protocol measuring index active extension strength. Moreover, some anatomical studies have shown that the EIP is absent in 3.5% of cases (Yammine, 2015). ...
The goal of this study was to establish a reproducible protocol to measure active extension strength in the index finger. The secondary objectives consisted in correlating the independent or associated index extension strength to the other fingers force of contraction of the extensor indicis propius with hand dominance. The population studied consisted of 24 healthy volunteers, including 19 women and 20 right-handed individuals. The independent and dependent index extension strength in each hand was measured three times with a dynamometer by three examiners at Day 0 and again at Day 7. Intra and inter-examiner reproducibility were, respectively, >0.90 and >0.75 in all cases. The independent extension strength was lower than the dependent one. There was no difference between the independent index extension strength on the dominant and non-dominant sides. The same was true for the dependent strength. Our results show that our protocol is reproducible in measuring independent and dependent index extension strength. Dominance did not come into account.
Level of evidence:
II.
Background:
The extensor indicis proprius (EIP) tendon is a frequently used donor for a variety of tendon transfers, most commonly for reconstruction of the extensor pollicis longus (EPL). EIP is known to have frequent anatomic variants including split tendons and variations in tendon arrangement.
Aim:
To characterize the anatomy of the EIP at the level of the extensor retinaculum, where tendon harvest is often performed, and share our preferred technique for EIP to EPL transfer.
Methods:
Twenty-nine fresh-frozen cadaveric forearms without history of forearm or hand injury or surgery were dissected. Tendon circumference and relationship of the EIP and extensor digitorum communis to the index (EDCI) at the metacarpophalangeal (MCP) joint and the distal extensor retinaculum were recorded. Distance from the distal extensor retinaculum to the EIP myotendinous junction was measured.
Results:
EIP was ulnar to the EDCI in 96.5% of specimens (28/29) at the distal edge of the extensor retinaculum. In the remaining specimen, EIP was volar to EDCI. Tendon circumference at the distal extensor retinaculum averaged (9.3 mm ± 1.7 mm) for EDCI and 11.1 mm (± 2.7 mm) for EIP (P = 0.0010). The tendon circumference at the index MCP joint averaged 11.0 mm (± 1.7 mm) for EDCI and 10.6 mm (± 2.1 mm) for EIP (P = 0.33). EIP had a greater circumference in 76% (22/29) of specimens at the distal extensor retinaculum whereas EIP had a greater circumference in only 31% (9/29) of specimens at the MCP joint.
Conclusion:
The EIP tendon is frequently ulnar to and greater in circumference than the EDCI at the distal extensor retinaculum, which can be taken into consideration for tendon transfers involving EIP.
Introduction
Independent movement of the pollex (thumb) and index finger is critical for proper hand function. Accordingly, extension of the pollex and index finger is predominantly performed by the separate extensor pollicis longus (EPL) and extensor indicis proprius (EIP) muscles, respectfully. Non-typical muscles such as the extensor pollicis et indicis accessorius (EPIA) can inhibit pollex and index finger independence by connecting the otherwise autonomous digits. The objective of this study was to present a case of bilateral EPIA muscles with gross imaging, MRI, histological inspection, biomechanical analysis, and clinical implications.
Materials and methods
Left and right EPIA muscles and tendons were discovered during routine cadaver dissection. Three-tesla (3T) T1-weighted magnetic resonance imaging (MRI) visualized the left EPIA in relation to contiguous anatomy. The dissection field of the left EPIA was cleaned and photographed, and the innervation and sites of proximal and distal attachment for EIP, EPIA, and EPL muscles were noted bilaterally. The bilateral EIP, EPIA, and EPL were detached, splayed, photographed, and weighed. Pennation angle, muscle length, and fascicle length for each muscle were measured, and left and right fascicle lengths were normalized via histological inspection of EPIA mean sarcomere lengths. Physiological cross-sectional area (PCSA), maximum isometric force (Fmax), and difference index (δ) were calculated to compare EIP, EPIA, and EPL biomechanics and structural similarity. Mean results of left and right structures were discussed when no significant difference existed between sides.
Results
Gross analysis and MRI showed an independent muscle belly of EPIA originating on the distal third of the ulna and interosseus membrane (posterior aspects), positioned between EIP and EPL. Its common tendon coursed through the fourth extensor compartment of the wrist, bifurcated over the trapezoid, and inserted on the first distal phalanx (via EPL and extensor expansion of the index finger. The posterior interosseous nerve (PIN) coursed through the EPIA to innervate EIP. Mean sarcomere lengths of left and right EPIA muscles were 2.38 ± 0.12 μm and 2.92 ± 0.07 μm, respectively. The PCSA of the EIP, EPIA, and EPL was 0.68 cm², 0.41 cm², and 0.76 cm² and constituted a Fmax of 15.22 N, 9.19 N, and 17.00 N, respectively. Left and right EPIA muscles were structurally similar (δ < 0.30), and EPIA was structurally similar to EIP bilaterally.
Conclusions
While EPIA generates synergistic movement of the pollex and index finger during simultaneous extension, it may limit extension and/or flexion during complex, antagonistic movements of the pollex and index finger. According to the present study, EPIA may increase the force of extension from EIP or EPL by 60.38% or 54.06% respectively, or 30.19% and 27.03% if distributed equally. EPIA may entrap PIN and the resulting compression could cause potential paralysis of EPL, exacerbating clinical implications and complicating diagnosis and symptom treatment. The gross analysis, MRI, histological inspection, biomechanical analysis, and clinical implications in this report may serve as valuable resources for orthopedic surgeons, occupational and physical therapy providers, and medical educators when presented with a similar clinical or educational case.
Résumé
Le pouce flexus adductus congénital est une déformation rare caractérisée par un flessum permanent de la métacarpophalangienne du pouce. En cas d’échec du traitement orthopédique, la solution est chirurgicale. Nous avons évalué les résultats des transferts d’extenseur propre de l’index dans la réanimation de l’extension du pouce chez les enfants atteints par cette pathologie. Il s’agit d’une étude rétrospective des enfants opérés dans notre centre en 2005 et 2019. Au total, huit enfants (douze mains) ont été opérés. L’âge moyen lors de l’intervention était de 18 mois (10 à 23 mois). Le transfert tendineux réalisé était toujours l’extenseur propre de l’index suturé sur le long extenseur du pouce. Le suivi postopératoire était fait en consultation à six semaines. Le durée moyenne de suivi est de 19 mois. Sept enfants (87,5 %) avaient une extension physiologique de la colonne du pouce à la première consultation postopératoire. Un cas de déficit partiel d’extension de l’index a été retrouvé. Un enfant a dû nécessiter une nouvelle intervention pour corriger la course du transfert. À six mois, tous les enfants utilisaient le pouce opéré de façon symétrique par rapport au côté non opéré. La chirurgie du pouce flexus adductus congénital doit être proposée en cas de déformation persistante après un traitement orthopédique bien mené pendant une durée minimale de quatre mois. L’utilisation de l’extenseur propre de l’index comme transfert tendineux reste pour nous la technique de choix, compte tenu des bons résultats fonctionnels et de la faible morbidité.
The choice of the donor tendon in tendon reconstruction of the hand theoretically influences the results of the surgery because of the interactions of its structure with the healing process. The objective of our study was to specify the surgical bases of vascularized extensor indicis proprius (EIP) in tendon reconstruction of the hand and to present its application from a series of observations. According to our observations, the EIP’s vascularization arises from a branch of the 2nd dorsal metacarpal artery, 3 to 4 cm proximally to the metacarpophalangeal joint (MCP). We demonstrate the feasibility and effectiveness of a vascularized EIP graft for finger flexor tendon reconstruction, for defects of the extensor mechanism at the MCP joint level and for reconstruction of the extensor pollicis longus. Our biomimetic approach in tendon reconstruction has led us to factor in the complexity of the tendon and peritendinous structure. The use of vascularized EIP offers theoretical advantages for the tendon healing process, demonstrates encouraging first results with interesting versatility and very low iatrogenicity.
Purpose: To evaluate the effect of the modified retrograde tendon flap technique for reconstructing the extensor tendon defect in zone Ⅱ of a finger.
Methods: 12 patients with the extensor tendon defect in zone Ⅱ were investigated retrospectively. They were all treated surgically by the modified retrograde tendon flap technique, featuring the creation of a new terminal slip to bridge the extensor tendon defect using extensor tendon inner lateral bands. At the final follow-up, the range of motion at each joint of the injured finger was recorded.
Results: Average follow-up was 18 months (ranging from 11 to 26 mos). Eight patients achieved full active DIPJ extension, whereas one patient had an extensor lag of 10° and three had a lag of 5°. All patients achieved normal active flexion ranges and full passive motion ranges of DIPJ compared with their uninjured side. All the involved finger joints were clinically stable, with no tenderness, pain, nail deformity, or limitation using their hands for daily life.
Conclusions: The modified retrograde tendon flap technique, which is easy to operate and popularize, may be the procedure of choice in patients with a gap deficiency in Zone Ⅱ of the extensor tendon of a finger.
OBJECTIVE. The purpose of this article is to review the general guidelines for MRI of the finger and emphasize normal finger anatomy as it relates to abnormalities and injuries. CONCLUSION. Advanced imaging, particularly MRI, is increasingly relied on to make the diagnosis and guide management of finger injuries. It is incumbent on radiologists to understand the complex anatomy of the fingers as well as to be familiar with common injuries and aspects of injuries that affect management in order to meaningfully contribute to patient care.
Entrapment of the extensor indicis proprius (EIP) after open reduction and internal fixation (ORIF) of the distal ulna with a plate and screw construct is rare. By literature review, we found evidence of such complication associated with distal radius fracture, but no past reports relating to the distal ulna. ORIF of the distal ulna is a common procedure for both fracture treatment and deformity correction. Due to the EIP muscle originating primarily from the dorsoradial surface of the distal ulna and the adjacent interosseous membrane, the muscle may be damaged or compressed by a fixation plate during ORIF, resulting in entrapment. We present two case reports of this rare complication, describing the method of clinical diagnosis, surgical treatment, and outcome. Our accompanying cadaver dissection provides an explanation for proper plate positioning during ORIF of the ulna to reduce the risk of EIP entrapment.
Complications following extensor indicis proprius (EIP) tendon transfer are loss of strength, independence and mobility in the index finger in extension. The main goal of this study was to measure the index finger's independent and dependent extension strength after a tendon transfer. Secondary goals were to determine if the index finger retained the ability to extend independently after the transfer and to evaluate second metacarpophalangeal (MCP) joint mobility. Our study consisted of 19 patients in whom the EIP tendon had been divided proximally to the extensor hood. The EIP tendon was retrieved through a proximal approach at the distal radius level and rerouted towards a recipient tendon. At an average follow-up of 41 months, the average independent extension strength was 5.6 N versus 11 N on the contralateral side and the dependent strength was 10.9 N versus 20 N. No patient complained of a loss of extension strength and all had retained independent active extension on the operated index finger. The second MCP joint on the operated side had an independent extension lag of 15.3° compared to the contralateral healthy side and a dependent extension lag of 0.2°. Two patients were impaired in their daily activities when moving the operated index finger. Our results show that EIP harvesting for tendon transfer leads to decreased independent and dependent strength as well as decreased active extension of the second MCP joint. However, the functional impact was negligible and should not compromise the use of the EIP as a tendon transfer.
Level of evidence
III.
The extensor tendons to the fingers were studied in dissections of 120 hands from 60 fresh cadavers, and the divisions of the tendons, as well as the intertendinous connection, were analyzed. One tendon of the extensor digito-rum communis (EDC) was present for the second finger in 88.33% of cases, one for the third finger in 55.8%, two for the fourth finger in 48.33%, and the absence of the extensor digitorum communis tendon to the fifth finger was noted in 26.66% of cases. The exten-sor indicis had only one tendon for the second finger in 96.66%, two tendons in 0.83% and absent in 2.5% cases. The extensor digiti min-imi (EDM) to fifth finger was present in 75.83%, while in 23.33% of the hands two tendons were present. Only one hand (0.83%) lacked the EDM. The most common inter-tendinous connections were seen between the EDC tendons of the fourth and third fingers in 96.66% cases. Surgeons must be familiar with these variations when performing tendon transfers for the correction of injury, paralytic defects or the treatment of tendon ruptures in rheumatoid arthritis, particularly those involving the use of the extensor indicis and the extensor digiti minimi. The symmetric study in both hands revealed the existence of individual variations and the pattern observed in one hand is not necessarily the same in the other hand.
Anatomy is a descriptive basic medical science that is no longer considered a
research-led discipline. Many publications in clinical anatomy are prevalence
studies treating clinically relevant anatomical variations and reporting their frequencies
and/or associations with variables such as age, sex, side, laterality,
and ancestry. This article discusses the need to make sense of the available literature.
A new concept, evidence-based anatomy (EBA), is proposed to find,
appraise, and synthetize the results reported in such publications. It consists in
applying evidence-based principles to the field of epidemiological anatomy
research through evidence synthesis using systematic reviews and metaanalyses
to generate weighted pooled results. Pooled frequencies and associations
based on large pooled sample size are likely to be more accurate and to
reflect true population statistics and associations more closely. A checklist of a
typical systematic review in anatomy is suggested and the implications of EBA
for practice and future research, along with its scope, are discussed. The EBA
approach would have positive implications for the future preservation of anatomy
as a keystone basic science, for sound knowledge of anatomical variants,
and for the safety of medical practice. Clin. Anat. 00:000–000, 2014.
This study was performed to investigate the anatomy and variations of the humanextensor tendons of the fingers and their intertendinous connections. Ninetyfive upper limbs of adult cadavers were dissected. The variations in the extensortendons of the fingers, both proximal and distal to the extensor retinaculum, andtheir mode of insertion were observed. Also, the intertendinous connections wereexplored and the obtained data were analysed. The extensor pollicis longus andbrevis tendons were found to be single, doubled or, rarely, absent. Their insertioncould be traced to either the proximal phalanx, or through the extensor expansionto both phalanges, or rarely to the distal phalanx of thumb. The extensor indicishad a single tendon in all specimens. In the majority of specimens, extensor digitorumhad no independent slip to the little finger; it gave off a single tendonto the index, double tendons to the middle finger and triple tendons to the ringfinger. Extensor digiti minimi muscle often had double or triple tendons distal tothe extensor retinaculum. Three types of juncturae tendinum (JT) were identifiedbetween the tendons of extensor digitorum in the 2nd, 3rd and 4th intermetacarpalspaces (IMS) of hands. Types 1 and 2 JT were seen in the three IMS. Type 3 JTwas the most frequently identified of all juncturae and was always absent in the2nd IMS. The percentages of the present data were compared with other researchers'data.
Variation in the extensor muscles of the hand is common. These anatomic deviations are rarely symptomatic. We report a unique case of an anomalous extensor indicis proprius causing a painful snapping wrist. Intraoperative examination revealed a disproportionately large muscle belly under the extensor retinaculum causing subluxation of the ring and small extensor tendons creating a painful snapping phenomenon. Following excision, the subluxation and pain resolved.
The extensor digitorum brevis manus, a supernumerary muscle in the fourth extensor compartment of the dorsum of the wrist, is a relatively rare anomalous muscle. Extensor digitorum brevis should be included in the differential diagnosis of soft tissue masses on the dorsal aspect of the hand as it may mimic cystic, neoplastic, inflammatory, and infectious masses arising in the dorsum of the wrist. Seventy-two upper limbs of male and female cadavers were dissected and examined to study the pattern of extensor tendons of the index finger. In the present study, we observed three cases (4.2%) of the extensor digitorum brevis manus on the left side. In one cadaver (0.72%), there was an additional tendon arising from the extensor indices which was inserted to the radial side of the dorsal digital expansion of the index finger. The extensor digitorum brevis manus muscle (EDBM), an anatomic variant of the extensor muscle of the dorsum of the hand, is found in approximately 2% to 3% of the population. This variation is, therefore, clinically and surgically relevant because the EDBM may be the only muscle responsible for the independent extension of the second digit. The aim of the present study is to report the incidences of this muscle thereby creating awareness of its existence and of its characteristic appearance to surgeons.
The complaint of dorsal hand pain is common among patients seen in a primary care practice. The differential diagnosis includes tenosynovial disease, ganglion, trauma, and soft-tissue tumors. Rarely is an anomalous muscle an etiologic factor. Reported here is an anomalous indicis proprius muscle that was manifested as a painful dorsal hand mass. Also discussed are the anatomic variations of the extensor indicis proprius syndrome.
Anomalous extensor muscles of the hand are not uncommon. Well-recognized anomalies anomalous extensor indicis proprius, extensor digitorum brevis manus, extensor medii proprius, and extensor indicis et medii communis are reviewed and discussed in detail. Anomalous extensor indicis proprius and extensor digitorum brevis manus may occasionally give rise to dorsal wrist pain and the diagnosis is often confused especially in the presence of other pathologic findings such as a ganglion. An analysis of the embryologic development of the extensor muscle mass with phylogenetic comparisons between species of the animal kingdom is presented to underscore the clinical relevance of these anomalous extensors.
We evaluated the results of extensor indicis proprius (EIP) to extensor pollicis longus (EPL) transfers for EPL ruptures secondary to rheumatoid arthritis.
Twenty-four patients (7 males, 17 females; mean age 41 years; range 22 to 72 years) with rheumatoid arthritis underwent EIP to EPL transfer for 25 ruptures. The mean duration from rupture to surgery was 4.3 months (range 1.5 to 11 months). Functional assessment of the fingers was made using a specific EIP-EPL evaluation method developed by Lemmen et al. Pinch and grip strengths were measured. Range of motion of the metacarpophalangeal and interphalangeal joints of the thumb was compared with the normal side. Patient satisfaction was evaluated by a visual analog scale. The mean follow-up period was 6.2 years (range 4.7 to 7.9 years).
Functional results were perfect in 14 fingers (56%), good in six fingers (24%), moderate in four fingers (16%), and poor in one finger (4%). The pinch and grip strengths were 86% and 92% of the uninvolved hand, respectively. The mean visual analog scale score was 74 (range 24 to 99). Compared to the uninvolved side, the range of motion of the thumb and index finger decreased by 23 degrees and 7 degrees , respectively, with a 9% loss of interphalangeal motion and a 17% loss of metacarpophalangeal motion in thumb extension. Independent extension of the index finger was possible in 21 hands.
The results of EIP to EPL transfers are successful in ruptures secondary to rheumatoid arthritis.
Anatomic variations of the extensor tendons of the forearm are frequent and its knowledge is important to assess the diseased and traumatized hand. During routine cadaveric dissection in the Department of Anatomy, Kasturba Medical College, Mangalore, India, we came across unusual variations in the left upper limb of a 51-years-old male cadaver. The variants are, the complete absence of the extensor pollicis brevis (EPB), the abductor pollicis longus (APL) having six slips of insertion with additional muscle slip from the brachio-radialis (BR). The extensor digitorum communis (EDC) had five tendon slips, the extra tendon splits close to the metacarpo-phalangeal (MP) joint and contribute to the tendons of the ring and little fingers. The number of accessory tendons of APL has functional significance in the development of de Quervain's stenosing tendovaginitis. The present case is unique in the sense that, all the three variations are present in the ipsilateral upper limb. The occurrence of these anomalies and its clinical and embryological significance are discussed.
Extensor digitorum brevis manus (EDBM) is a rare variant extensor muscle of the dorsum of the hand, which constitutes a diagnostic challenge in clinical practice. The aims of the review are to provide a better estimate of the frequency of EDBM and its association with variables such as ancestry, gender, laterality and side. Twenty-six studies met the inclusion criteria. The pooled rates of the meta-analyses yielded the following values: (a) an overall crude cadaveric prevalence of 4 %, (b) an overall true cadaveric prevalence of 2.5 %, (c) a true cadaveric prevalence of 2.6 % in European ancestry, (d) a true cadaveric prevalence of 2.3 % in Asian ancestry (2.07 % in Japanese and 4.2 % in Indian), (e) a bilateral occurrence in 26.3 %. Non-significant association was found between EDBM presence and ancestry, gender or side. The EDBM muscle was inserted on the index in 77 % of cases and on the long finger in the remaining 23 %. This is the first evidence-based anatomical review, which addresses the frequency of EDBM in humans.
Anatomy is a descriptive basic medical science that is no longer considered a research-led discipline. Many publications in clinical anatomy are prevalence studies treating clinically relevant anatomical variations and reporting their frequencies and/or associations with variables such as age, sex, side, laterality, and ancestry. This article discusses the need to make sense of the available literature. A new concept, evidence-based anatomy (EBA), is proposed to find, appraise, and synthetize the results reported in such publications. It consists in applying evidence-based principles to the field of epidemiological anatomy research through evidence synthesis using systematic reviews and meta-analyses to generate weighted pooled results. Pooled frequencies and associations based on large pooled sample size are likely to be more accurate and to reflect true population statistics and associations more closely. A checklist of a typical systematic review in anatomy is suggested and the implications of EBA for practice and future research, along with its scope, are discussed. The EBA approach would have positive implications for the future preservation of anatomy as a keystone basic science, for sound knowledge of anatomical variants, and for the safety of medical practice. Clin. Anat., 2014. © 2014 Wiley Periodicals, Inc.
The patterns of the tendons of extensor digiti minimi, extensor digitorum, and extensor indicis have been studied on the dorsum of the hands of 25 embalmed cadavers.
Each of the tendons of extensor digitorum (ED) is usually single, but those of the middle and ring fingers are occasionally multiple. Intertendinous connections are of variable pattern. The ED tendon of the little finger lies closely to that of the ring finger, with which it may be fused, or it may be absent. It is suggested that it may be undergoing evolutionary reduction.
Extensor digiti minimi (EDM) usually has two tendons, but may have three or four. In addition to EDM, the little finger also receives either a separate tendon, or a tendinous slip, from ED.
Extensor indicis (EI) varies in the number of its tendons, in its position relative to the ED tendon to index finger, and in its connection to extensor pollicis longus tendon.
Examples of supernumerary muscles (extensor digitorum brevis manus, extensor indicis brevis, and extensor pollicis et indicis communis) were also found. © 1992 Wiley‐Liss, Inc.
The anatomical knowledge of the dorsal aspect of the hand has been enriched these last years by a more surgically applied approach, especially of that of its integument and blood supply. The vascularization of the superficial nerves, the anastomoses between the dorsal and palmar arterial networks has allowed designing new flaps, ante- and retrograde, usable in the coverage of more and more distal defects. The extensor apparatus shows many anatomic variations, often asymptomatic, except the extensor digitorum brevis manus muscle, which can mimic a mass at the dorsal aspect of the hand.
In the present paper are given the results of observations, made with the greatest possible accuracy and care, of the muscular anatomy of thirty-four subjects, chiefly of the male sex, with an especial view to the study of the combinations of these abnormalities, and the directions in which they chiefly tend. To enable the reader more readily to comprehend these results, the author has tabulated them in the sheet appended to the paper. In the Table the names of the muscles placed at the head of each column refer to those in which more than one variety has been observed in the session. They will be found to correspond very closely with those given in the former papers by the author. In columns 21, and 27 are placed those of which only one example has been met with. Some of these, however, are of much importance. To explain the nature of the abnormality more precisely than could be done in the Table, a word or two will be necessary on such of the specimens as may be considered novel or typical.
1. The anatomical arrangement of the extensor tendons for the fingers is known to be quite variable on the dorsum of the hand.
2. A study of fifty-seven hands by dissection, observation, and photography revealed various anatomical arrangements of the extensor tendons.
3. Findings of surgical importance are enumerated and their clinical significance explained.
Common variations in muscles and tendons of the hand were determined by dissecting 40 pairs of hands (20 male, 20 female). Contrary to some anatomy textbooks which describe only three palmar interossei, with the thumb lacking one, this study found four palmar interossei present in 85% of hands and 90% of bodies. This first palmar interosseous typically arose from the base of the first metacarpal and inserted along with the tendon of the oblique head of adductor pollicis into the base of the proximal phalanx. Forty hands (50%) did not have the usual arrangement of lumbricals. Twenty-seven (34%) third lumbricals and four (5%) fourth lumbricals split at their insertions; four third lumbricals and four fourth lumbricals inserted on the ulnar side of the middle and ring fingers, respectively. The abductor pollicis longus inserted by 2 or 3 tendons in 91% of hands. The tendon of extensor digiti minimi split into 2 or 3 slips in practically all of the hands studied (96%). The tendon of extensor indicis split into 2 slips in more than a third (38%) of hands. In almost a third (30%) of hands there were accessory extensor muscles present deep to the tendons of extensor digitorum. Lastly, extra slips of origin of the abductor digiti minimi were present in 10% of hands. This study confirms the presence of a palmar interosseous muscle for the thumb and demonstrates that some variations occur more frequently than was expected. © 1993 Wiley-Liss, Inc.
To evaluate the incidence and anatomic insertion sites of extensor medii proprius and extensor indicis medii communis tendons to the long finger in cadaveric dissection and to describe the insertion of the extensor medii proprius.
Thirty randomly selected adult cadavers, 44 upper extremities, were examined for the presence or absence of an anomalous extensor tendon to the long finger. If present, tendon origin and insertion sites were documented, and the width of the tendon was evaluated.
The extensor medii proprius was observed in 4 of 44 extremities, an incidence of 9%. The extensor indicis medii communis was observed in 7 of 44 extremities, an incidence of 16%. Tendon widths for both the extensor medii proprius and extensor indicis medii communis specimens ranged from 1.5 to 3.0 mm.
The incidence of an anomalous slip of tendon to the long finger might be higher than previously reported, with a combined incidence of 25% in this cadaveric study. This anomalous slip can be a resource for surgical reconstruction.
The presence of anomalous tendinous slips to the long finger can be easily overlooked. Understanding the anatomical relationships, incidence, and donor tendon availability of these anomalous tendons might aid with surgical planning.
Awareness of the anatomy and variations of the extensor tendons on the dorsum of the hand is necessary when assessing the traumatized or diseased hand and when considering tendons for repair or transfer. A complete quantitative documentation of the extensor tendons is lacking.
The arrangements of extensor tendons to the medical four fingers namely, the extensor digitorum communis (EDC), extensor indicis proprius (EIP) and extensor digiti minimi (EDM) on the dorsum of the hand and the intertendinous connections between them were studied in 100 upper limb specimens. The findings were photographed, tabulated and analyzed statistically.
In 98% of the specimens, the EIP was a single tendon with a single insertion, whereas in two right upper limbs there were two EIP tendons with two insertions. In 77% of the specimens the EDC distally had tendons to the middle three fingers (EDC index, EDC longus and EDC ring). The EDC small was present in only 34% of samples and the EDM showed normal anatomy in only 20%. The most common types of juncturae tendinum in the 2nd, 3rd and 4th intermetacarpal spaces were Type 1, 2 and 3r, respectively. Two accessory muscles were seen. One was the extenson medii proprius in 5% of samples and the other, the extensor digitorum brevis manus, was seen in 3%.
Variations of the extensor tendons were common in this study, especially for the middle and ring fingers which showed multiple tendons of the EDC.
This study reports the presence of the extensor digiti medii muscle (EDM) in a population of cadavers dissected by students at a chiropractic college anatomy laboratory and determines its frequency, bilaterality, innervation, and sex differences.
Dissection of upper extremities of 47 human cadavers (24 males, 23 females) was conducted. Both upper extremities were examined for bilaterality. The long extensor tendons were exposed, separated, and cut to expose the EDM. Identifying the innervation of the variant muscle was attempted. The specimens were then photographed.
In this report, the prevalence of EDM is at 7.4%. The EDM was discovered in 5 male cadavers and 1 female cadaver (5:1 ratio). It also revealed that the EDM was prevalent on the left forearm than on the right forearm at a ratio of 5:2. Out of the 47 cadavers studied in this report, only one was observed to have EDM bilaterally (2.1%). In 2 cadavers, the EDM appeared to be supplied by the posterior interosseous nerve. The branch piercing through the extensor indicis muscle continued to give off a small branch entering the belly of the EDM.
The findings obtained in this report support previous observations regarding its prevalence in males more than females. The report also shows that the EDM occurs more in the left forearm than the right forearm as opposed to other reports of equal incidence between left and right forearms. This report also supports one previous study showing that the posterior interosseous nerve innervates the EDM.
We evaluated the clinical outcome of tendon reconstruction using tendon graft or tendon transfer and the parameters related to clinical outcome in 51 wrists of 46 patients with rheumatoid arthritis with finger extensor tendon ruptures. At a mean follow-up of 5.6 years, the mean metacarpophalangeal (MP) joint extension lag was 8 degrees (range, 0-45) and the mean visual analogue satisfaction scale was 74 (range, 10-100). Clinical outcome did not differ significantly between tendon grafting and tendon transfer. The MP joint extension lag correlated with the patient's satisfaction score, but the pulp-to-palm distance did not correlate with patient satisfaction. We conclude that both tendon grafting and tendon transfer are reliable reconstruction methods for ruptured finger extensor tendons in rheumatoid hands.
To lead a quality life, tendon repair must be performed in a trauma causing damage to the extensor tendon of the hand. The aim of this study is to study the structures that can be used as donor tendons. Fifty-four dissected adult hands were examined to study the pattern of the extensor tendons on the dorsum of the hand. The most common distribution patterns of the extensor tendons of the fingers were as follows: a single extensor indicis proprius (EIP) tendon which inserted ulnar to the extensor digitorum (ED)-index; a single ED-index; a single ED-middle; a single ED-ring; an absent ED-little; a double extensor digiti minimi (EDM), and a single ED-ring to the little finger. The frequency of the number of tendons is as follows: a single (87.03%) EIP, a single ED-index (100%), a single (92.6%) ED-middle, a single (75.9%) ED-ring, and an absent (68.5%) or a single (24.1%) ED-little. A double (88.9%) EDM tendons were seen. The thickest type of juncturae tendinum (JT) is found primarily between the ring and little fingers (90%). Suitable excessive tendon and the thickest JT as donor tendon were found in the fourth intermetacarpal space. The present findings, especially the fourth intermetacarpal space, may explain why incisions on the dorsum of the hand should be large and performed with particular care. It is necessary to have a thorough understanding of the arrangements of the multiple extensor muscles and their junctural connections of the hand when tenoplasty or tendon transfer is required.
Quail-to-chick grafting experiments performed during the third day of incubation demonstrate that somites can contribute to limb development. In orthotopic recombinations, migrating cells originating from the grafted unsegmented or segmented somitic mesoderm adjacent to the wing or leg field end up in the musculature respectively of the wing or the leg, where they express exclusively myogenic properties. Thus, in these heterospecific recombinations, the anatomical muscle has a double origin: muscle bulk of somitic origin; tendons and connective tissues of somatopleural origin. Similar features are observed in heterotopic recombinations with (segmented or unsegmented) somitic mesoderm located cranially or caudally to the limb levels.
In the reverse chick-to-quail grafting experiments, the somitic participation to the limb mesoderm can also be observed. But it is less regular than that obtained in the quail-to-chick recombinations, and the muscle bulk is made up in various proportions of graft-originated somitic cells and of host somatopleural cells.
The possible existence of juxtaposed and interdigitated myogenic and tendinogenic compartments is discussed in view of the dissimilarity between the results of the two kinds of heterospecific recombinations.
The extensor medii proprius is a muscle analogous to the extensor indicis proprius in that it has a similar origin, but inserts into the long finger. The extensor indicis et medii communis muscle is an extensor indicis proprius muscle that splits to insert into both the index and long fingers. The extensor tendons to the fingers were dissected in 58 adult hands to determine the incidence and anatomy of the extensor medii proprius and extensor indicis et medii communis. The incidence of the extensor medii proprius was 10.3% and the incidence of the extensor indicis et medii communis was 3.4% in this series. The extensor medii proprius and extensor indicis proprius muscles had a common origin in all cases. The insertion of the extensor medii proprius into the dorsal aponeurosis was palmar and ulnar to the extensor digitorum communis of the long finger, but in one case, the extensor medii proprius inserted into the deep fibrous tissue proximal to the metacarpophalangeal joint. The tendon slip of the extensor indicis et medii communis inserting into the long finger did not insert into the dorsal aponeurosis, but into the deep fibrous tissue near the metacarpophalangeal joint. Both the extensor medii proprius and the extensor indicis et medii communis may represent evolutionary remnants. Awareness of their potential presence and anatomy should be helpful in extensor identification, repair, and transfer.
An anatomical study on the extensor digitorum profundus muscle was made using 832 upper limbs from 416 Japanese adults. The separate muscles derived from the extensor digitorum profundus consist of 10 kinds: namely, the extensor pollicis longus, extensor pollicis et indicis accessorius, extensor indicis radialis, extensor indicis proprius, extensor indicis ulnaris, extensor indicis et medii accessorius, extensor medii proprius, extensor annularis proprius, extensor carpi profundus and extensor digiti brevis. The configuration of the muscles (except for the extensor digiti brevis) in the upper limb was classified into 13 types according to their arrangement and insertion. The most frequent type involved coexistence of the extensor pollicis longus and the extensor indicis proprius: it was observed in 664 limbs (79.8%). The next type involved coexistence of the extensor pollicis longus, extensor indicis proprius and the extensor medii proprius: it was observed in 67 limbs (8.1%). It appears that the extensor digiti brevis of man is derived from the most ulnar part of the extensor digitorum profundus which does not migrate proximally.
The extensor digitorum brevis manus muscle (EDBM) was found in 17 (3.0%) out of 559 dissected hands of 286 cadavers. The anatomy of the EDBM was classified into three types. The EDBM frequently arose on the distal margin of the radius, but without direct attachment to the carpal bones. The insertion of the EDBM was the same as that of the extensor indicis proprius. The EDBM and the extensor indicis proprius were often joined and had the same nerve and arterial supply. The EDBM muscle was considered to be a variant of the extensor indicis proprius muscle. Clinically five of 29 patients with an EDBM were treated.
On the basis of 150 dissections the authors show that, on the back of the hand, the tendinous formations ensuring the extension of the fingers can be arranged in four groups of a least two tendons for each finger, excepting the thumb. In the little finger the group comprises a constant tendon, the extensor proper, and two variables, the common extensor and the expansion of the extensor carpi ulnaris. In the index finger the extensor proper and the common extensor nearly always coexist. In the middle finger the great common extensor, sometimes divided, can be accompanied at depth, by an extensor tendon. Finally, in the ring finger, two or three more or less intricate slips are found forming the common extensor. The presence of anastomoses and the numerous slips originating in the tendon-forming band can reduce functional deficiency following the section or rupture of a tendon. On account of these variations the surgeon should operate with caution in tendon transplantations.
A clinical test has proved helpful in confirming the diagnosis of extensor indicis proprius syndrome. It is presented herewith.
The extensor indicis proprius syndrome is presented. It is characterized by dorsal wrist pain, aggravated by activities, and associated with a synovitis of the extensor indicis proprius muscle within the fourth dorsal compartment of the wrist.
The extensor tendons to the fingers were dissected in 43 adult hands. The most common distribution pattern of the extensor tendons of the fingers was: (1) a single extensor indicis proprius (EIP) tendon that inserted ulnar to the extensor digitorum communis (EDC) of the index; (2) a single EDC-index; (3) a single EDC-long; (4) a double EDC-ring; (5) an absent EDC-small; and (5) a double extensor digiti quinti (EDQ) with a double insertion. Frequent variations included, a double EIP tendon; a double or triple EDC-long tendon; a single or triple EDC-ring tendon; and a single or double EDC-small tendon. The extensor medii proprius was noted in 5 specimens. Increased multiplicity of any tendon was not associated with multiplicity of any other tendon, but was associated with a thinner (type 1) junctura tendinum between EDC-index and EDC-long. An absent EDC-small was related to an increased incidence of a double EDC-ring and the presence of a thick type 3 junctura tendinum between the EDC-ring and the EDQ or dorsal aponeurosis of the small finger. Knowledge of potential tendon multiplicity and variations may help in the identification and repair of these structures.
Anatomical studies on the extensor pollicis et indicis accessorius and extensor indicis radialis muscles were conducted on 952 upper limbs from 476 Japanese adult cadavers. Each anomalous muscle occurred between the extensor pollicis longus proprius and extensor indicis proprius muscles in the dorsum of the forearm and hand. The extensor pollicis et indicis accessorius muscle was present in 13 of the limbs (1.4%). It was not coexistent with another anomalous muscle of the extensor digitorum profundus mass in 9 cases, and it was coexistent with that muscle in 4. The extensor indicis radialis muscle was present in 34 limbs (3.6%). It was accompanied by another anomaly of the extensor digitorum profundus mass in 5 cases, and not accompanied by that muscle in 29. The extensor pollicis et indicis accessorius and extensor indicis radialis muscles were innervated by the posterior interosseus nerve of the radial nerve. It seems that the former anomalous muscle supplies the extensor control of the thumb and index finger, and the latter one of the index finger only. Each anomalous muscle was considered to be differentiating on the radial side of the extensor digitorum profundus mass in humans.
One hundred eighty‐one dissected hands were examined to study the pattern of extensor tendons on the dorsum of the hand. Extensor digitorum often had multiple tendons for the middle and ring fingers. Its contribution to the little finger was usually by a bifurcating tendon common with that of the ring finger. The index finger always received a single tendon. Intertendinous connections between the various tendons of the extensor digitorum were variable but were most frequent between ring and middle fingers.
Extensor indicis had one tendon in most of the specimens and it was always on the ulnar side of the extensor digitorum tendon. This remained true even when there were multiple tendons.
Extensor digiti minimi had two tendons in most cases. It was always linked to extensor digitorum either by receiving one or part of its tendon or by an intertendinous connection.
Two accessory muscles were seen, one was extensor indicis brevis replacing the proper muscle. The other, the extensor medii brevis, was distributed to the middle finger. © 1995 WiIey‐Liss, Inc.
Isolated extension of the index finger after extensor indicis proprius (EIP) transfer was studied. In cadavers, the extensor digitorum communis (EDC) muscle of the index finger received distinct innervation from the posterior interosseous nerve and was well separated, with its own innervation, from the other EDC muscle. Examination of von Schroeder's type I juncturae tendinum (JT) between the index and long finger showed two types: von Schroeder type IA (16 of 27 hands; 59%) was fascia only; von Schroeder type IB (11 of 27 hands; 41%) was thin filamentous bands. In clinical cases, 3 hands were type IA and 10 were type IB. Retained independent index finger extension was obtained in all patients with excision of the JT between the index and long finger following EIP transfer.
An anatomic study was performed to better delineate the extensor tendons of the index finger. Seventy-two cadaver hands were dissected. Classically, a single slip of the extensor digitorum communis (EDC) and a single slip of the extensor indicis proprius (EIP) are said to run to the index finger. The EIP is said to be ulnar to the EDC at the level of the metacarpal head. In dissections in this study, the classic description was noted in 58 of the hands. Ten hands had a double slip of the EIP. Two hands had a double slip of the EDC running to the index. Two hands had a single slip of the EIP either volar or radial to the EDC at the level of the metacarpal head. Thirteen hands (19%) showed anatomic variants of the EIP and EDC tendons at the level of the metacarpal head, differing from the classic description. Additionally, two hands showed aberrant tendons. A knowledge of these variants when performing tendon repair or EIP transfer is necessary.
Variations of the extensor indicis muscle were examined in 164 hands from 86 Japanese cadavers. Anomalous cases exhibiting supernumerary muscles or tendons were found in 22 hands. These variations were classified into four types: type 1, an additional tendon slip from the extensor indicis tendon; type 2, an extensor indicis radialis or extensor pollicis et indicis accessorius; type 3, an extensor medii proprius with or without extensor medii brevis; and type 4, an extensor indicis radialis and extensor medii proprius. The extensor medii proprius was the most common variation, followed by extensor indicis radialis. There were no clear differences in incidence of variations between men and women or between right and left hands. When variations were bilateral, both sides were identical or similar in type.
Intrinsic and extrinsic hand muscles power finger extension. These two muscle groups have different anatomy that allows complimentary function at the interphalangeal joints and opposing function at the metacarpophalangeal joints. Independent extension of each finger is not possible because of anatomic constraints including the juncturae tendinum and intertendinous fascia between the extrinsic extensor tendons on the dorsum of the hand. Anatomic variations of the extrinsic extensor tendons are frequent and knowledge is important when assessing the traumatized or diseased hand.
Are the supernumerary deep extensor tendons to the thumb in man of accessory or rudimentary origin?
Two findings of extensor pollicis et indicis (EPI) were classified referring to the literature of comparative anatomy.
Extensor pollicis longus (EPL) and extensor indicis (EI) developed phylogenetically from EPI. A common origin and proximal muscle belly of EPL and EI is a frequent manifestation of incomplete rudimentary EPI. A complete rudimentary EPI with absent EPL and EI has not yet been found in man. The accessory EPI coexisting with EPL and EI occurs in about 2 % of humans.
During the EI-tendon transposition to EPL, the tendons must be identified very carefully because of the numerous variants of the deep extensors. Transposition of extensor digitorum communis of the index or just one tendon of a double-tendoned EI to EPL by mistake, will make separate extension of the thumb impossible postoperatively.
An easy, safe, and less invasive surgical approach to the spinal accessory nerve for brachial plexus reconstruction is described. The technique avoids a longitudinal unsightly scar over the neck and preserves the branches innervating the upper part of the trapezius.
A total of 548 upper limbs (276 right and 272 left hands) from Japanese cadavers were dissected. The arrangements of extensor indicis proprius, extensor digitorum communis (EDC), and extensor digiti minimi tendons and the intertendinous connections were studied. The most common pattern of extensor tendons was as follows: the index finger had a single EDC tendon, the middle finger had a single EDC tendon, the ring finger had a single EDC tendon, and the small finger had a single EDC tendon or a single common EDC tendon distributed to the ring and small finger. A single extensor indicis proprius tendon ran along the ulnar side of the EDC, and the extensor digiti minimi tendon consisted of 2 slips. Intertendinous connections were classified into 3 types: type 1 with a filamentous band, type 2 with a fibrous band, and type 3 with a tendinous band subdivided to r-shaped and y-shaped. The most common patterns were type 1 in the second intermetacarpal space (IMCS), type 3r in the third IMCS, and type 3y in the fourth IMCS.
We assessed the outcome of tendon grafting of multiple finger extensor tendon ruptures in 14 patients with rheumatoid arthritis. Extensor lags improved from a preoperative mean of 33 degrees (range, 20 degrees-65 degrees) to a postoperative mean of 18 degrees (range, 0-60 degrees). However, loss of finger flexion was observed, with a mean postoperative fingertip to palm distance of 1.6 (range: 0-7.5) cm. Patient satisfaction correlated with the fingertip to palm distance, though not with the postoperative extensor lag. Because of the loss of finger flexion which was probably due to muscle contracture, we conclude that the results of tendon grafts in this situation are unsatisfactory.
The extensor tendons to the fingers were studied in dissections of 50 fresh cadaveric hands, and the divisions of the tendons, as well as the communications (juncturae), were analyzed. The pattern of distribution most frequently observed was as follows. The extensor digitorum communis provided one tendon to the index finger, one to the middle finger, two to the ring finger, and none to the little finger. The extensor indicis exhibited one tendon, whereas the extensor digiti minimi exhibited two tendons. The extensor indicis tendon was always observed to lack a junctura tendinum. The extensor indicis was absent in both hands of one cadaver. A tendon slip from the extensor digiti minimi to the ring finger was observed in one hand. All surgeons must bear in mind the existence of these variations when performing common tendon transfers.
The anatomical knowledge of the dorsal aspect of the hand has been enriched these last years by a more surgically applied approach, especially of that of its integument and blood supply. The vascularization of the superficial nerves, the anastomoses between the dorsal and palmar arterial networks has allowed designing new flaps, ante- and retrograde, usable in the coverage of more and more distal defects. The extensor apparatus shows many anatomic variations, often asymptomatic, except the extensor digitorum brevis manus muscle, which can mimic a mass at the dorsal aspect of the hand.
The aim of this study was to examine the existence of the extensor indicis et medii communis in detail. Thirty-one randomly selected adult cadavers (62 upper extremities) were examined for this project (22 males and 9 females between the ages 38 and 87). The muscle was observed in 3 of 62 hands, an incidence of 4.8%. One was in the right and the other two were in the left hands. Mean length and width of the muscle belly were 4.5 +/- 0.8 and 0.8 +/- 0.3 mm, respectively. Although the muscle did not have a junctura tendinum attachment between its two tendons, in one hand, the tendon to the index finger gave a thin slip to the tendon of the extensor digitorum communis for the same finger. Knowledge of variant muscle may be important when one is assessing the traumatized or diseased hand.