No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
The Effect of Wallet Thickness on Spine Posture, Seat Interface Pressure, and Perceived Discomfort During Sitting
Abstract
OCCUPATIONAL APPLICATIONS Occupational sitting has been associated with an increased risk for developing low back pain. The present investigation examined the effects of asymmetrical sitting surfaces induced by a wallet on acute changes in spine/pelvis posture, interface pressure, and discomfort. Compared to level sitting, sitting on a wallet resulted in greater sagittal and lateral spine flexion, a smaller total contact area with the seat pan, and greater gluteal discomfort. At wallet thicknesses of 22 mm and thicker, seat pan contact pressure area decreased and thoracic spine and pelvic angles deviated laterally compared to the no-wallet condition. At a 32-mm wallet thickness, gluteal discomfort increased. These results indicate that sitting for brief periods (15 minutes) on an uneven seating surface greater than 32 mm in thickness causes postural deviations from neutral spine positions and increases gluteal discomfort. This study supports the removal of rear pocket items, especially larger ones, during sitting.
... Wallet neuritis or fat wallet syndrome, a compressive tunnel neuropathy, where ipsilateral sciatic nerve gets compressed from exogenous wallet beneath piriformis muscle, proliferating clinical features mimicking lumbago sciatica [1]. While using a thick wallet, posture of pelvis, dorsolumbar spine gets compromised, mounting pressure on pelvic muscles, inter-vertebral discs, nerve roots, and nerves unevenly [2]. Most importantly, the scenario is not that much scarce as we would reckon before [3]. ...
... Wallet neuritis has been well-described in men; and synonyms frequently used in literature to describe the condition are hippocket syndrome, wallet-neuropathy, wallet sciatica, walletosis, fat wallet neuritis, fat wallet syndrome, creditcarditis, etc [1,3]. When men sit on their large, fatty wallet for long-time, it adversely affects their postural balance, stressing low back anatomy [2]. Hip pocket syndrome reportedly focused in affluent society first in 1966 [4]; a lawyer who used to bear a congested back pocket wallet that compressed adjacent sciatic nerve, generating sciatica like manifestations. ...
Background:
Wallet neuritis is an example of extra-spinal tunnel neuropathy concerning sciatic nerve. Its clinical appearance often gets confused with sciatica of lumbar spine origin. Wallet-induced chronic sciatic nerve constriction produces gluteal and ipsilateral lower extremity pain, tingling, and burning sensation. It was Lutz, first describing credit-card wallet sciatica in an Attorney, surfaced on Journal of American Medical Association (JAMA), 1978; however, the condition has not been well-studied in various other occupations.
Case summary:
In this write-up, I take the privilege of demonstrating wallet neuritis as an example of peripheral sensitization in three different professionals namely specialist doctor, driver, and banker first time in Bangladesh. All the three patients demonstrated about aggravated gluteal pain with radiation on the ipsilateral lower extremity while remained seated on heavy wallet for a while, fortunately improved discontinuing such stuff with. Alongside, radical wallectomy, piriformis stretching exercise on the affected side had also been recommended and found worthy in terms of pain relief.
Conclusion:
long-standing use of rear pocket wallet may compress and sensitize ipsilateral sciatic nerve, generating features resembling lumbago sciatica; thereby, remains a source of patients' misery and diagnostic illusion for pain physicians as well.
... Such postures are not recommended even for short time periods. The asymmetry discussed above results in a reduction in pan-seat contact area [10]. ...
Prolonged asymmetrical sitting is common and can exacerbate musculoskeletal back pain and spinal deformities. Monitoring sitting posture can help maintain correct posture and prevent health problems. Currently posture is assessed by expert clinicians using subjective visual observation. More objective methods involve the use of a gold-standard motion capture system in Laboratories, which is expensive and not widely available. We develop a Smart-Cover, an automatic system to provide real time visualization and information about sitting posture. A Sitting Pressure Sensor (SPS) is built using Velostat, conductive fabric and foam to collect pressure distribution information within the seat surface. The data are collected from 10 healthy young subjects where each subject sits for 30 min and are transferred to a cloud server using Internet-of-Things (IoT). A rule-based classifier is used to provide timely notification to users about sitting duration and level of asymmetry. A new end-point device application is developed to show sitting balance. Dial based displays show level of asymmetry, active and static sitting, and daily summary score. Our system is user friendly, inexpensive, automatic and quantitative method for evaluating posture in real time, which has the capability of providing quantitative information about sitting behaviour. The results show that our system can be used for objective monitoring of sitting posture which has medical and social benefits. Smart-Cover can support the management of patients during their rehabilitation by monitoring pressure areas and balance when seated. In addition, it offers users at home, schools and offices the means to improve their sitting posture.
... The main motivation for this work stemmed from the work done in the Department of Kinesiology of the University of Waterloo, that made the first studies on uneven seating surfaces [30]. They studied the outcomes of a non-levelled sitting surface on trunk kinematics, the distribution of seat-pan pressure levels, and discomfort using wallets of different thickness. ...
Maintaining a stable upright position and body orientation are fundamental tasks to perform everyday activities and ensure the quality of life. The ability to maintain these can be damaged by various pathologies/disfunctions, such as stroke and aging. Therefore, it is important to quantify how the postural control reacts to different situation and how is affected by different pathologies, which could bring a big contribution in a clinical context, by helping to diagnose pathologies that can bring postural impairments. An experimental protocol was developed that combines both electromyography and posturography. To help validate this protocol, 53 patients (43 healthy and 10 stroke patients) performed it twice within a two-week period. By comparing the results from the two runs, it was possible to assess that these were not statistical different, and thus prove that the protocol is viable tool to build a normative database.
... Asymmetrical sitting promotes non-neutral spine postures and reduces seat pan contact area [3] therefore not recommended, even for short duration exposures. It alters the body mechanics, puts various body segments under strain, hence, contributing to musculoskeletal pain [4]. ...
Asymmetrical sitting posture (ASP) affects the body mechanics and puts various body segments under strain which may lead to health problems including musculoskeletal pain, low back pain and spinal deformity resulting increased care costs. The tools and methodologies used to assess human posture are often arbitrary and studied by physicians, physiotherapists and researchers in clinical settings. For example, clinical scales such as the Posture Index or Postural Assessment Scale are subjective or semi-subjective, based on visual observation and require clinical expertise to identify asymmetry. More objective gold standard methods such as Motion Capture Systems rely on access to expensive complex equipment based in laboratories. These are not widely available for several reasons including, scarcity of equipment, need for technical staff, time consuming procedures and overall expense. Therefore, there is a need for a low cost, portable automatic posture monitoring system which would help address this challenge. We develop an automatic ASP monitoring system to provide real time visualization and information about sitting posture. We build flexible pressure sensor (FPS) at six different locations on a chair to collect pressure information using piezoresistive conductive film. The collected data from FPSs are then transferred to a smartphone application using Bluetooth. We develop a dedicated Android App to collect FPSs reading and provide real time visualizations of information. The results show that FPS can be used for objective monitoring of sitting posture. It can also be utilized to provide useful information about patients with pelvic asymmetry in rehabilitation medicine. Our system would significantly simplify the sitting posture monitoring protocols and open possibilities for office, school and home based assessment and support for posture improvement. Furthermore, results from this study will be used to develop a new quantitative posture measurement tool for clinical use.
... Asymmetrical sitting promotes non-neutral spine postures and reduces seat pan contact area [3] therefore not recommended, even for short duration exposures. It alters the body mechanics, puts various body segments under strain, hence, contributing to musculoskeletal pain [4]. ...
Asymmetrical sitting posture (ASP) affects the body mechanics and puts various body segments under strain which may lead to health problems including musculoskeletal pain, low back pain and spinal deformity resulting increased care costs. The tools and methodologies used to assess human posture are often arbitrary and studied by physicians, physiotherapists and researchers in clinical settings. For example, clinical scales such as the Posture Index or Postural Assessment Scale are subjective or semi-subjective, based on visual observation and require clinical expertise to identify asymmetry. More objective gold standard methods such as Motion Capture Systems rely on access to expensive complex equipment based in laboratories. These are not widely available for several reasons including, scarcity of equipment, need for technical staff, time consuming procedures and overall expense. Therefore, there is a need for a low cost, portable automatic posture monitoring system which would help address this challenge. We develop an automatic ASP monitoring system to provide real time visualization and information about sitting posture. This is based on the pressure distribution located at six different locations on a chair. We build flexible pressure sensor (FPS) to collect pressure distribution information using piezoresistive conductive film. The collected data from FPSs are then transferred to a smartphone application using Bluetooth. We develop a dedicated Android App to collect FPSs reading and provide real time visualizations of information. The results show that FPS can be used for objective monitoring of sitting posture. It can also be utilized to provide useful information about patients with pelvic asymmetry in rehabilitation medicine. Our system would significantly simplify the sitting posture monitoring protocols and open possibilities for office, school and home based assessment and support for posture improvement. Furthermore, results from this study will be used to develop a new quantitative posture measurement tool for clinical use.
... The main motivation for this work stemmed from the work done in the Department of Kinesiology of the University of Waterloo, that made the first studies on uneven seating surfaces [30]. They studied the outcomes of a non-levelled sitting surface on trunk kinematics, the distribution of seat-pan pressure levels, and discomfort using wallets of different thickness. ...
Wearing an object in the rear pocket alters the interface between the body and the chair, leading to the compression of the sciatic nerve. Prolonged sitting behaviors with such objects can lead to a health disorder called Piriformis Syndrome. In this paper, we use an intelligent office chair in order to detect the wallet usage as a “bad sitting posture”, as sitting on a wallet can create an uneven sitting surface, subsequently tilting the pelvis in the frontal plane. The system is comprised of a pneumatic circuit and is able to detect and classify, based on Artificial Neural Network, 12 standardized sitting postures, with an accuracy of 80.9%. In this test, we asked 36 subjects (24 males-M and 12 females-F) to wear a wallet in the back pocket in 12 testing levels, based on 3 wallets sizes (small, medium and large) and 4 levels of wallet heights (no paper cards, 8 cards, 16 cards and 24 cards). We detected the usage of wallets as an incorrect posture in 58.8% for all levels (61.1% for Male and 54.2% for Female). We observed that the size of the wallet did not alter results significantly (60.4% for smaller area versus 57.6% in the larger area), while the wallet height had a large influence (46.2% for no cards versus 71.3% for 24 cards). We also tested wallet usage in the front pocket with an average of 16.7%, showing that this usage doesn't alter significantly the sitting posture. This work shows that the creation of an alert protocol for the wallet usage is possible to be implemented in our intelligent chair system.
Prolonged driving has been linked to the development of low back pain. Methods to examine time varying postural changes of the lumbar spine during driving have been scarcely investigated. Distinguishing postural variation as movement patterns such as lumbar shifts and fidgets may provide novel insight, which may otherwise be lost with analyses that parameterize variation as a single value. This investigation aimed to identify if lumbar spine shifts or fidgets typically occur in automotive sitting and if differences occur across sex or time. An additional objective was to investigate the extent these movement patterns can capture variation across time. Forty participants (18 F, 22 M) performed a one hour driving simulation. Number, duration and amplitude of shifts and fidgets as well as the mean and standard deviation (SD) of lumbar angle were calculated. Reported discomfort and pain were also recorded. Shifts and fidgets occurred in the absence of discomfort or pain and did not vary on average across time or sex (p > 0.05). Movement patterns characterized variation with a higher resolution compared to lumbar angle SD. Identifying lumbar shifts and fidgets provide an increased potential to understand individual time varying postural responses during driving, including the development of low back discomfort or pain.
The aim of this study was to evaluate the efficacy of a 9-day accommodation protocol on reducing perceived discomfort while sitting on a stability ball (SB); trunk muscle activity levels and lumbar spinal postures were also considered.
Previous studies have compared SB sitting with office chair sitting with few observed differences in muscle activity or posture; however, greater discomfort during SB sitting has been reported. These findings may indicate an accommodation period is necessary to acclimate to SB sitting.
For this study, 6 males and 6 females completed two separate, 2-hr sitting sessions on an SB. Half the participants completed a 9-day accommodation period between the visits, whereas the other half did not use an SB during the time. On both occasions, self-reported perceived discomfort ratings were collected along with erector spinae and abdominal muscle activity and lumbar spinal postures.
Discomfort ratings were reduced in female participants following the accommodation; no effects on muscle activation or lumbar spine postures were observed.
Accommodation training may reduce perceived low-back discomfort in females.Trunk muscle activity and lumbar spine postures during seated office work on an SB did not differ between groups; however, greater sample power was required to conclusively address these variables.
Regarding whether to use an SB in place of a standard office chair, this study indicates that females electing to use an SB can decrease discomfort by following an accommodation protocol; no evidence was found to indicate that SB chair use will improve trunk strength or posture, even following an accommodation period.
In this narrative review, we aim to provide the pathophysiology and diagnostic criteria of the piriformis syndrome (PS), an underdiagnosed cause of buttock and leg pain that can be difficult to treat. Based on existing evidence, frequencies of clinical features are estimated in patients reported to have PS. In view of the increasing popularity of ultrasound for intervention, the ultrasound-guided technique in the treatment of PS is described in detail.
A literature search of the MEDLINE(®) database was performed from January 1980 to December 2012 using the search terms e.g., " piriformis injection", " ultrasound guided piriformis injection", " botulinum toxin", "pain management", and different structures relevant in this review. There was no restriction on language.
A review of the medical literature pertaining to PS revealed that the existence of this entity remains controversial. There is no definitive proof of its existence despite reported series with large numbers of patients.
Piriformis syndrome continues to be a controversial diagnosis for sciatic pain. Electrophysiological testing and nerve blocks play important roles when the diagnosis is uncertain. Injection of local anesthetics, steroids, and botulinum toxin into the piriformis muscle can serve both diagnostic and therapeutic purposes. An ultrasound-guided injection technique offers improved accuracy in locating the piriformis muscle. Optimizing the therapeutic approach requires an interdisciplinary evaluation of treatment.
Physical therapists commonly associate lateral pelvic tilt (LPT) with a variety of musculoskeletal adaptations, syndromes and altered function. Such musculoskeletal adaptations have been suggested in many reports to cause unequal sitting pressure distribution (SPD) at the buttock/chair interface. However, those reports have failed to provide objective evidence to support that hypothesis. This study was conducted to examine the relationship between LPT and SPD in a sample of healthy female volunteers. Subjects were tested for pelvic symmetry using an anthropometric frame, then assigned to two groups: symmetrical (n = 36) and LPT (n = 9). SPD was measured in an upright sitting posture using an interface pressure mat. Although the results indicated that there were no significant differences between the two groups in the magnitude and position of the peak pressure, there was a greater variability among subjects in the LPT group than the symmetrical group. This observation is worth further investigation as it tends to indicate that persons with LPT are less likely able to maintain a steady sitting position.
Unlabelled:
Dynamic sitting has been proposed to reduce low back pain (LBP) and/or low back discomfort (LBD) while sitting. This is supported by studies suggesting that subjects with LBP assume more static, sustained postures while sitting. This systematic review investigated the effect of dynamic sitting on LBP among subjects with LBP and the development of LBD among pain-free subjects. Electronic databases were searched by two independent assessors. All prospective studies which compared the effect of a dynamic sitting condition on LBP or LBD to another sitting condition were eligible, with no minimum follow-up period applied. The quality of the included studies was assessed using the PEDro scale. Seven high-quality studies were eligible, including five crossover studies and two randomised controlled trials. The results suggest there is currently no evidence to support the use of dynamic sitting as a stand-alone approach in the management of LBP.
Practitioner summary:
This systematic review investigated the effect of dynamic sitting on LBP or LBD. Seven high-quality studies met the inclusion and exclusion criteria. Overall, the evidence suggests that dynamic sitting approaches are not effective as a stand-alone management approach for LBP.
The use of lumbar supports has been associated with decreased reports of low back pain during driving exposures. However, there has been limited work investigating whether lumbar supports actually change spine and pelvic postures at the level of the vertebrae.
To investigate the effectiveness of a lumbar support in changing radiological measures of lumbar spine and pelvic postures and to examine the impact of support excursion magnitudes on these postures.
Eight male subjects were recruited with no history of back injury, pathologies or low back pain within the past 6 months. Radiographs were taken in four postures: standing, and sitting with 0 cm, 2 cm and 4 cm lumbar support prominence (LSP).
Lumbar lordosis angle increased from 20° with no support to 25° with 2 cm support and 30° with 4 cm support. Lumbar lordosis angles were significantly different between 0 cm support and 4 cm support (p < 0.0001) and between 2 cm support and 4 cm support (p = 0.0256). Increasing lumbar support reduced the flexion at intervertebral disc joints throughout the lumbar spine, however, these remained significantly different from upright standing (p > 0.001) with the exception of L1/L2 in 4 cm support (p = 0.1381) and L5/S1 for all seated postures (p = 0.0687). All measures of pelvic posture were significantly different in sitting compared to standing (p < 0.0001), however, the lumbar support had no significant impact on seated pelvic posture.
Lumbar supports were shown to impact the vertebral rotations of the lumbar spine yet had no effect on pelvis postures. Increasing support from the current maximum of 2 cm-4 cm resulted in increased lumbar lordosis. The changes were mostly imparted at the upper lumbar spine joints with the most marked change being exhibited at the approximate level of the lumbar support apex: in the L2/L3 joint.
To compare radiographic analysis on the sagittal lumbar curve when standing, sitting on a chair, and sitting on the floor.
Thirty asymptomatic volunteers without a history of spinal pathology were recruited. The study population comprised 11 women and 19 men with a mean age of 29.8 years. An independent observer assessed whole lumbar lordosis (WL) and segmental lordosis (SL) between L1 and S1 using the Cobb's angle on lateral radiographs of the lumbar spine obtained from normal individuals when standing, sitting on a chair, and sitting on the floor. WL and SL at each segment were compared for each position.
WL when sitting on the floor was reduced by 72.9% than the average of that in the standing position. Of the total decrease in WL, 78% occurred between L4 to S1. There were significant decreases in SL at all lumbar spinal levels, except L1-2, when sitting on the floor as compared to when standing and sitting on a chair. Changes in WL between the positions when sitting on a chair and when sitting on the floor were mostly contributed by the loss of SL at the L4-5 and L5-S1 levels.
When sitting on the floor, WL is relatively low; this is mostly because of decreasing lordosis at the L4-5 and L5-S1 levels. In the case of lower lumbar fusion, hyperflexion is expected at the adjacent segment when sitting on the floor. To avoid this, sitting with a lordotic lumbar curve is important. Surgeons should remember to create sufficient lordosis when performing lower lumbar fusion surgery in patients with an oriental life style.
Piriformis syndrome, sciatica caused by compression of the sciatic nerve by the piriformis muscle, has been described for over 70 years; yet, it remains controversial. The literature consists mainly of case series and narrative reviews. The objectives of the study were: first, to make the best use of existing evidence to estimate the frequencies of clinical features in patients reported to have PS; second, to identify future research questions. A systematic review was conducted of any study type that reported extractable data relevant to diagnosis. The search included all studies up to 1 March 2008 in four databases: AMED, CINAHL, Embase and Medline. Screening, data extraction and analysis were all performed independently by two reviewers. A total of 55 studies were included: 51 individual and 3 aggregated data studies, and 1 combined study. The most common features found were: buttock pain, external tenderness over the greater sciatic notch, aggravation of the pain through sitting and augmentation of the pain with manoeuvres that increase piriformis muscle tension. Future research could start with comparing the frequencies of these features in sciatica patients with and without disc herniation or spinal stenosis.
Sciatica is defined as pain or discomfort along the regions innervated by the sciatic nerve. Compression or irritation of lumbar spinal roots, most commonly because of lumbar disc herniation or spinal stenosis, causes sciatica in the vast majority of cases. Although it is rather uncommon, many pathologies have reported to cause nondiscogenic sciatica. A 70-year-old woman presented with intractable sciatic pain which was not elicited by posture change or cough. Sitting on the affected side provoked more pain than standing or walking. Magnetic resonance imaging revealed both spondylolisthesis with lumbar stenosis and compression of the gluteal portion of the sciatic nerve by varicotic gluteal veins. Given the atypical presentation of spinal root compression, gluteal vascular compressive neuropathy was suspected. Ligation and resection of varicotic vein resulted in relief of the patient's pain. To our knowledge, cases with varicosity-caused sciatica were limited in the literature review.
The purposes of this study were to determine which seat features/occupational demands contributed to police officer discomfort and whether an automobile seat fitted with an active lumbar system (ALS) could reduce driving discomfort. Fifty-eight officers were given questionnaires to assess driving discomfort. High discomfort levels were associated with computer use, duty belt, sidearm/radio, body armour and lumbar support interface. Discomfort was highest in the lumbar, sacrum, upper pelvis and mid-back regions. Twelve officers spent one shift each in a police vehicle seat and an ALS seat. Discomfort was assessed every 2 h during 8-h shifts. Reduced discomfort was reported with the ALS seat. Three lumbar support features, the duty belt, and the lumbar and right upper pelvis regions, showed reduced discomfort. Overall seat discomfort decreased by 47% after 8 h of exposure to the ALS. Modifying the automobile seat helps to reduce officer discomfort during prolonged vehicle usage.
The effect of mild leg length inequality (lower extremity length difference less than 3 cm) on posture and gait has been the source of much controversy. Many opinions have been expressed both for and against the need for intervention to reduce the magnitude of the discrepancy. This paper emphasizes the need for accurate and reliable assessment of leg length differences using a clinically functional radiographic technique, and reviews the biomechanical implications of leg length inequality as related to the development of stress fractures, low back pain and osteoarthritis.
Repetitive, low-intensity loading from normal daily activities can generate fatigue damage in trabecular bone, a potential cause of spontaneous fractures of the hip and spine. Finite element models of trabecular bone (Guo et al., 1994) suggest that both creep and slow crack growth contribute to fatigue failure. In an effort to characterize these damage mechanisms experimentally, we conducted fatigue and creep tests on 85 waisted specimens of trabecular bone obtained from 76 bovine proximal tibiae. All applied stresses were normalized by the previously measured specimen modulus. Fatigue tests were conducted at room temperature; creep tests were conducted at 4, 15, 25, 37, 45, and 53 degrees C in a custom-designed apparatus. The fatigue behavior was characterized by decreasing modulus and increasing hysteresis prior to failure. The hysteresis loops progressively displaced along the strain axis, indicating that creep was also involved in the fatigue process. The creep behavior was characterized by the three classical stages of decreasing, constant, and increasing creep rates. Strong and highly significant power-law relationships were found between cycles-to-failure, time-to-failure, steady-state creep rate, and the applied loads. Creep analyses of the fatigue hysteresis loops also generated strong and highly significant power law relationships for time-to-failure and steady-state creep rate. Lastly, the products of creep rate and time-to-failure were constant for both the fatigue and creep tests and were equal to the measured failure strains, suggesting that creep plays a fundamental role in the fatigue behavior of trabecular bone. Additional analysis of the fatigue strain data suggests that creep and slow crack growth are not separate processes that dominate at high and low loads, respectively, but are present throughout all stages of fatigue.
To develop a new sitting spinal model and an optimal driver's seat by using review of the literature of seated positions of the head. spine, pelvis, and lower extremities.
Searches included MEDLINE for scientific journals, engineering standards, and textbooks. Key terms included sitting ergonomics, sitting posture, spine model, seat design, sitting lordosis, sitting electromyography, seated vibration, and sitting and biomechanics.
In part I, papers were selected if (1) they contained a first occurrence of a sitting topic, (2) were reviews of the literature, (3) corrected errors in previous studies, or (4) had improved study designs compared with previous papers. In part II, we separated information pertaining to sitting dynamics and drivers of automobiles from part 1.
Sitting causes the pelvis to rotate backward and causes reduction in lumbar lordosis, trunk-thigh angle, and knee angle and an increase in muscle effort and disc pressure. Seated posture is affected by seat-back angle, seat-bottom angle and foam density, height above floor, and presence of armrests.
The configuration of the spine, postural position, and weight transfer is different in the 3 types of sitting: anterior, middle, and posterior. Lumbar lordosis is affected by the trunk-thigh angle and the knee angle. Subjects in seats with backrest inclinations of 110 to 130 degrees, with concomitant lumbar support, have the lowest disc pressures and lowest electromyography recordings from spinal muscles. A seat-bottom posterior inclination of 5 degrees and armrests can further reduce lumbar disc pressures and electromyography readings while seated. To reduce forward translated head postures, a seat-back inclination of 110 degrees is preferable over higher inclinations. Work objects, such as video monitors, are optimum at eye level. Forward-tilting, seat-bottom inclines can increase lordosis, but subjects give high comfort ratings to adjustable chairs, which allow changes in position.
The aim was to examine lumbar spine kinematics, spinal joint loads and trunk muscle activation patterns during a prolonged (2 h) period of sitting. This information is necessary to assist the ergonomist in designing work where posture variation is possible -- particularly between standing and various styles of sitting. Joint loads were predicted with a highly detailed anatomical biomechanical model (that incorporated 104 muscles, passive ligaments and intervertebral discs), which utilized biological signals of spine posture and muscle electromyograms (EMG) from each trial of each subject. Sitting resulted in significantly higher (p<0.001) low back compressive loads (mean +/- SD 1698 +/- 467 N) than those experienced by the lumbar spine during standing (1076 +/- 243 N). Subjects were equally divided into adopting one of two sitting strategies: a single 'static' or a 'dynamic' multiple posture approach. Within each individual, standing produced a distinctly different spine posture compared with sitting, and standing spine postures did not overlap with flexion postures adopted in sitting when spine postures were averaged across all eight subjects. A rest component (as noted in an amplitude probability distribution function from the EMG) was present for all muscles monitored in both sitting and standing tasks. The upper and lower erector spinae muscle groups exhibited a shifting to higher levels of activation during sitting. There were no clear muscle activation level differences in the individuals who adopted different sitting strategies. Standing appears to be a good rest from sitting given the reduction in passive tissue forces. However, the constant loading with little dynamic movement which characterizes both standing and sitting would provide little rest/change for muscular activation levels or low back loading.
Seated work has been shown to constitute a risk factor for low-back pain. This is attributed to the prolonged and monotonous low-level mechanical load imposed by a seated posture. To evaluate the potential health effects with respect to the low back of office chairs with a movable seat and back rest, trunk kinematics, erector spinae EMG, spinal shrinkage and local discomfort were assessed in 10 subjects performing simulated office work. On three separate occasions subjects performed a 3 h task consisting of word processing, computer-aided design and reading. Three chairs were used, one with a fixed seat and back rest and two dynamic chairs, one with a seat and back rest movable in a fixed ratio with respect to each other, and one with a freely movable seat and back rest. Spinal shrinkage measurements showed a larger stature gain when working on the two dynamic chairs as compared with working on the chair with fixed seat and back rest. Trunk kinematics and erector spinae EMG were strongly affected by the task performed but not by the chair type. The results imply that dynamic office chairs offer a potential advantage over fixed chairs, but the effects of the task on the indicators of trunk load investigated were more pronounced than the effects of the chair.
When measuring treatment effect in chronic low back pain with multi-item outcome instruments, it is necessary, both for clinical decision-making and research purposes, to understand the clinical importance of the outcome scores. The aims of the present study were three-fold. Firstly, it aimed to estimate the minimal clinically important difference of three multi-item outcome instruments (the Oswestry Disability Index, the General Function Score and the Zung Depression Scale) and of the visual analogue scale (VAS) of back pain. Secondly, it aimed to estimate the error of measurement of these instruments; and its third aim was to describe the clinical meaning of score change. The study population consisted of 289 patients treated surgically or non-surgically in a randomised controlled trial. The minimal clinically important difference was estimated with patient global assessment as the external criterion. It was compared with the standard error of measurement of the instruments. The individual items of the instruments were compared for score changes related to improvement and deterioration. The standard error of measurement of the Oswestry Disability Index, the General Function Score and the Zung Depression Scale was 4, 6 and 3 units, respectively. The 95% tolerance interval was 10, 16 and 8 units, respectively. The minimal clinically important difference was 10, 12 and 8-9 units, respectively, thus not significantly exceeding the tolerance interval. The minimal clinically important difference of VAS back pain was 18-19 units, well exceeding the 95% tolerance interval, which was 15 units. Improvement after treatment for chronic low back pain tends to occur to a greater extent in sleep disturbance, ability to do usual things and psychological irritability, but to a lesser extent in the ability to sit, stand and lift. We conclude that the VAS of back pain is responsive enough to detect the minimal clinically important difference, whereas the smallest acceptable score changes of the Oswestry Disability Index, the General Function Score and the Zung Depression Scale may require an increase to exceed the 95% tolerance interval when used for clinical decision making and for power calculation. Despite improvement after treatment, the ability to sit, stand and lift, remain notable problems.
The objective of this study was to conduct gender- and time-based comparisons of postural and discomfort responses during prolonged simulated driving. Prolonged driving has been linked with low back disorders (LBD), however underlying mechanisms of pain or injury are not well understood despite many efforts to delineate the biomechanics of automobile seating. Twelve males and 12 females were exposed to one hour of simulated automobile driving. Body postures, body-seat pressure distributions, and ratings of perceived discomfort were documented and gender- and time-based comparisons were performed. Females exhibited approximately 10° greater changes in lumbo-pelvic orientation when upright standing postures were compared to those in automobile seating. Attributed to gender-based differences in body size was the finding that males experienced significantly greater body-seat interface pressures. Many of the postural, pressure, and discomfort measures varied significantly over 30 to 45 minutes, and these variations were mostly consistent between genders. Many variables examined varied as a function of gender and duration of driving. Future biomechanical investigations of automobile seating design for more effective LBD prevention should consider these potential effects in order to gain further insight into potential low back pain- or injury-generating mechanisms.
A number of experimental studies in our laboratory have been designed to evaluate the functional response of the median nerve at the wrist to various degrees of acute local compression in healthy volunteers and hypertensive patients. The relative significance of ischemia and mechanical deformation in early nerve compression, the critical threshold pressure for nerve conduction impairment, and the clinical sensibility testing system most accurate for evaluating and following patients with acute and chronic compressive neuropathies have been determined using a human model for median nerve compression in the carpal tunnel.
Between 40 mmHg and 50 mmHg there exists a critical threshold pressure in normotensive people at which peripheral nerve is acutely jeopardized. The critical pressure threshold is higher in hypertensive patients. The threshold exists at 30 mmHg below diastolic blood pressure and 45 mmHg below mean arterial blood pressure in both normotensive and hypertensive individuals. The correlation between systemic blood pressure and the function of the nerve in response to local compression favors the concept that reduced microvascular perfusion plays the major role in the early stages of low pressure nerve compression. In acute and chronic compression neuropathy, threshold tests (Semmes-Weinstein pressure, vibratory sensibility) detect the earliest abnormalities of nerve function.
The introduction of mobile computing within a constrained vehicle environment has led to changes in the task demands of occupational groups such as professional drivers and law enforcement officers. The purpose of this study was to examine how mobile data terminal (MDT) use interacts with prolonged driving to induce postural changes or low-back discomfort. Eighteen participants (9 male, 9 female) completed two 120-min simulated driving sessions. Time-varying lumbar spine and pelvis postures, seat pan interface pressures and ratings of perceived discomfort were recorded at 15-min intervals. The introduction of a computer interface decreased pelvic posterior rotation by an average of 15° with respect to upright standing and increased peak average discomfort in the neck (5.9 mm), left shoulder (6.8 mm), midback (10.9 mm), low back (10.6 mm) and pelvis (11.5 mm) compared to driving alone. The incorporation of mobile computing warrants consideration in the design of vehicle work environments.
The time course of full lumbar flexion under a prolonged flexion moment, lasting 20 min, was documented in 27 male and 20 female subjects. Peak flexion increased by 5.5° over the 20 min. The flexion-creep data was fitted with a first-order step input response having a time constant of 9.4 min. Maximum flexion was also documented over the recovery phase, lasting 30 min, indicating that subjects regained approximately 50% of their resting joint stiffness within 2 min of resuming relaxed lordosis, although full recovery took longer than the flexion-creep, indicating the presence of viscoelastic hysteresis. For this reason it may be prudent to advise those who experience prolonged full flexion postures (as might a seated warehouse shipper/receiver, gardener, or construction worker) to stand and walk for a few minutes prior to performing demanding manual exertions. Indeed, temporary joint flexion laxity, following a bout of full flexion, may increase the risk of hyperflexion injury to certain tissues.
The application of a static load causes the spine to deform with time, that is to say the spine 'creeps'. This phenomenon has been measured in vivo as a change in body height. Fifteen females within three different age groups were exposed to repeated five minute sessions of sitting, during which the shrinkage of the spine was measured continuously. All the subjects demonstrated shrinkage during these exposures. A trend towards increased shrinkage in the oldest group was observed and statistical differences on initial shrinkage were also noted. These findings were contrary to those observed in some other studies, but were, however, in agreement with recent in vitro studies. Apart from the aim of studying differences in 'creep' behaviour between subjects of different ages, the endeavour was to improve the technique so as to measure the continuous change in height due to a certain static load.
Gender differences in lumbar and pelvic posture have been reported previously in prolonged sitting, both in an office chair and automobile seat. To date, it is not known whether these postural exposures during prolonged driving affect the passive lumbar spine flexion stiffness. The purpose of this study was to examine time-varying responses of passive lumbar spine stiffness, lumbar spine and pelvic postures during a 2 h simulated driving trial. Secondary goals investigated the influence of gender on lumbar spine stiffness, discomfort scores and seat pressure profiles. Twenty (10 males, 10 females) subjects were recruited to complete a 2 h simulated driving task. Passive lumbar range of motion was measured on a customized frictionless jig before, halfway through and at the end of 2 h. During driving there was a time-varying difference in the lumbar flexion angles adopted by the gender groups. A significant interaction (p = 0.0458) was found for gender and time with women being found to sit significantly different than males in the second hour of driving exhibiting greater maximum lumbar flexion (60.0% ROM (±1.27) than men 50.0% ROM (±1.5). Both men and women demonstrated similar passive stiffness changes characterized by an initial increase in transitional zone stiffness after 1 h (+0.1 Nm/degree for males and +0.3 Nm/degree for females, p = 0.2372). Over 2 h of driving there was a non-significant trend of genders to respond differently to the seated exposure. Specifically transitional zone stiffness was found to increase in males (0.86 (SD 0.31) to 0.92 (SD 0.31) Nm/degree) and decrease in females (0.81 (SD0.88) to 0.73 (SD 0.52) Nm/degree) (p = 0.1178). Differences in lumbar posture and passive stiffness over 2 h of simulated driving were demonstrated between genders in this study.
Unlabelled:
Police officers spend large amounts of time performing duties within a police cruiser and report a high prevalence of musculoskeletal problems. This study evaluated the effects of driver seat and duty belt design on posture, pressure and discomfort. Ten male and 10 female university students attended two sessions involving simulated driving in a standard police seat (CV) and an active lumbar support (ALS) seat. Participants wore a full duty belt (FDB) or reduced duty belt (RDB) in each seat. Lumbar postures, driver-seat and driver-duty belt pressures and perceived discomfort were measured. Gender × Seat interactions were found for pelvic (p = 0.0001) and lumbar postures (p = 0.003). Females had more lumbar flexion than males and were more extended in the ALS seat (-9.8 ± 11.3°) than CV seat (-19.8 ± 9.6°). The FDB had greater seat pressure than the RDB (p < 0.0001), which corresponded to increased pelvis discomfort. This study supports the use of an ALS seat and RDB to reduce injury risk associated with prolonged sitting in police officers.
Practitioner summary:
Police officers report a high prevalence of musculoskeletal problems to the lower back, associated with prolonged driving and further investigation is needed to reduce injury risk. This simulated driving study investigated seat and duty belt configuration on biomechanical measures and discomfort. Seat design had the greatest impact, regardless of gender and males benefited more from a reduced belt configuration.
Animal and human experimental studies have suggested the importance of spatial summation in the nociception processing and in the activation of descending inhibition. However, the relationship between the areas (size) of muscles stimulated and the recruitment of descending inhibition has not been addressed. Consequently, we tested whether bilateral versus unilateral injection of hypertonic saline into trapezius muscles caused hypoalgesia to pressure pain (pressure pain thresholds, PPTs) in the local pain areas (the trapezius muscles) and the referred pain areas (the posterolateral neck muscles). Two groups of volunteers participated. One group received a unilateral injection (one injection) and the other group bilateral injections (two injections). In the bilateral group, hypertonic saline was injected in one trapezius first, and 45 s later, while pain was still present from the first injection, a second injection was performed into the contralateral trapezius muscle. The saline-evoked time to maximal pain was significantly shorter after the second injection than after the first injection. More subjects developed referred pain after the bilateral compared with the unilateral injection. In the referred pain areas, the PPTs 7.5 and 15 min after the second injection were significantly increased compared with the first injection, while no changes in the PPT were observed in local and referred pain areas after unilateral injection. This suggests that the induction of descending inhibition was triggered by spatial summation during the later phase of experimentally induced muscle pain. The present experimental model might be used for further investigation of descending inhibition related to the spatial characteristics of nociceptive stimuli in humans.
Background:
The sitting position has become the most common posture in today's workplace. In relation to this position, kinematic analysis of the lumbar spine is helpful in understanding the causes of low back pain and its prevention.
Methods:
In this study, we investigated the relationship between sagittal lumbar alignment and pelvic alignment in the standing and sitting positions for 50 healthy adults. Lumbar lordotic angle (LLA), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI) were measured on lateral lumbar spine standing and sitting radiographs.
Results:
Regarding changes from the standing to sitting positions, average LLA, SS, and PT were -16.6° (-49.8 %), -18.7° (-50.3 %), and 18.3° (284.8 %), respectively (P < 0.01). In the sitting position, lumbar lordosis was reduced and pelvic rotation became posterior.
Conclusions:
This study showed that LLA decreased by approximately 50 % and PT increased by approximately 25 % in the sitting position compared with the standing position. No significant gender differences were observed for LLA, SS, and PT in the standing position. In the sitting position, however, LLA and SS were markedly larger for women.
Fluctuating asymmetry (FA), a pattern of bilateral variation that is normally distributed around a mean of zero, appears to correlate inversely with fitness and health. In this study, we compared the FA of asymptomatic control subjects (n = 51) and patients with low back pain (n = 44). We measured eight traits, from the upper and lower limbs, and used them to obtain asymmetry indices for each subject. We also measured pelvic asymmetry in standing subjects. The low back pain (LBP) group showed significantly higher asymmetry in the pelvis, and in ulnar length and bistyloid breadth. Our results demonstrate a link between LBP and asymmetry not only in a weight-bearing trait (i.e., pelvic configuration), but in two traits that are not functionally related to the back (i.e., ulnar length and bistyloid breadth). We can now consider LBP as another health and fitness measure correlated with FA.
The objective of this study was to determine the changes in left and right gluteal pressures and posterior inclination angles between the anterior superior iliac spine (ASIS) and posterior superior iliac spine (PSIS) on both sides after continuous cross-legged sitting.
Fourteen young adults (nine males and five females) were recruited. The statistical significance of differences in parameters between before and after continuous cross-legged sitting was tested by paired t-tests.
After sitting in a right-crossed-leg position for 10 minutes and then returning to a upright sitting posture, the subjects' right gluteal pressure increased significantly compared to before cross-legged sitting (p< 0.05). After sitting in a right-crossed-leg position and then returning to an upright standing posture, the posterior inclination between the right ASIS and PSIS increased significantly compared to before cross-legged sitting (p< 0.05).
These results indicate that continuous cross-legged sitting may cause malalignment of the pelvis after the cross-legged sitting period.
This study investigated changes in craniocervical and trunk flexion angles and gluteal pressure on both sides during visual display terminal (VDT) work with continuous cross-legged sitting.
The gluteal pressures of ten VDT workers, who were recruited from laboratories, were measured using a Teckscan system and videotaped using a single video camera to capture the craniocervical and trunk flexion angles during VDT work at 30 s, 10, 20 and 30 min.
The craniocervical angle was significantly increased at 10 and 20 min compared with the initial angle (p<0.05). The trunk flexion angle was significantly decreased at 30 s, 10, 20 and 30 min (p<0.05). The gluteal pressure of the crossed-leg side significantly increased at 30 s, 10 and 20 min (p<0.05). The gluteal pressure of the uncrossed-leg side significantly decreased at 30 s (p<0.05).
We found that cross-legged sitting during VDT work may exert disadvantageous postural effects resulting from craniocervical and trunk flexion angles and gluteal pressure. Therefore, this posture could not be recommended during long-term VDT work.
Wheelchair dependent children with neuropathic and neuromuscular diseases have up to 90% risk for progressive spine deformities. An unbalanced sitting can induce progression of spinal and pelvic deformities. Many current clinical assessment methods of sitting of such patients are semi-quantitative, or questionnaire-based. A 3D movement analysis offers quantitative and objective biomechanical analysis of sitting. The aim was to validate a method to describe quiet sitting and differences between patients and controls as well as to apply the methodology for pre- and post-operative comparison. The analysis was performed on 14 patients and 10 controls. Four patients were retested after spine surgery. Seat load asymmetry was up to 30% in the patient group comparing to maximum 7% in the control group. The asymmetric position of Ground Reaction Force vector between left and right sides was significant. Plumb line of cervical 7th vertebra over sacral 1st was different only in rotation. The location of Common Center of Pressure relative to inter-trochanteric midpoint was more anterior in controls than in patients. Pelvic inclination in patients was smaller, the obliquity and rotation was similar. There were no significant differences between patients and controls of the thorax position. Results with more changes in the seat-loading domain in comparison with posture indicate good postural control compensation of spinal deformity induced disequilibrium despite neuromuscular disease in the background. The comparison of the pelvic obliquity data from kinematics and X-ray showed good correlation. The four patients tested postoperatively improved after surgery.
Low back pain (LBP) development has been associated with occupational standing. Increased hip and trunk muscle co-activation is considered to be predisposing for LBP development during standing in previously asymptomatic individuals. The purpose of this work was to investigate muscle activation and LBP responses to a prescribed exercise program. Pain-developing (PD) individuals were expected to have decreased LBP and muscle co-activation following exercise intervention.
Electromyography (EMG) data were recorded from trunk and hip muscle groups during 2-h of standing. An increase of >10mm on visual analog scale (VAS) during standing was threshold for PD categorization. Participants were assigned to progressive exercise program with weekly supervision or control (usual activity) for 4 weeks then re-tested.
Forty percent were categorized as PD on day 1, VAS=24.2 (±4.0)mm. PD exercisers (PDEX) had lower VAS scores (8.93±3.66 mm) than PD control (PDCON) (16.5±6.3 mm) on day 2 (p=0.007). Male PDEX had decreased gluteus medius co-activation levels (p<0.05) on day 2.
The exercise program proved beneficial in reducing LBP during standing. There were changes in muscle activation patterns previously associated with LBP. Predisposing factors for LBP during standing were shown to change positively with appropriate exercise intervention.
Little is known about how lumbar spine movement influences mechanical changes and the potential injurious effects of prolonged flexion associated with seated postures. The purpose of this study was to examine the postural responses and pain scores of low back pain sufferers compared with asymptomatic individuals during prolonged sitting in order to understand the biomechanical factors that may be associated with sitting induced low back pain.
Sixteen participants with sitting-aggravated low back pain were age- and gender-matched with 16 asymptomatic participants. Tri-axial accelerometers were used to monitor lumbar spine angles during 90 minutes of seated computer work. Lumbar spine postures were examined using a movement pattern analysis of two types of postural adjustments, termed shifts (step-like adjustments larger than 5 degrees and fidgets (small change and return to approximately the same position).
The LBP group reported large significant increases (P < 0.0001) in low back pain while asymptomatic individuals reported little to no pain. On average, every participant fidgeted every 40 to 50 seconds. However, only the LBP sufferers demonstrated a significant increase (P=0.04) in the number of shifts over 90 minutes of seated work; the LBP group shifted every 4 minutes in the last 30 minutes of sitting compared to every 10 minutes for the asymptomatic group. LBP sufferers also demonstrated larger amplitudes of shifts and fidgets when compared to the asymptomatic group.
Greater and more frequent movement was not beneficial and did not reduce pain in individuals with pre-existing LBP. Future work to understand the biomechanical effects of proactively inducing movement may help to explain the paradox of the relationship between movement and pain.
Sitting has been identified as a cause of mechanical low back pain. The purpose of this study was to use plain film x-rays to measure lumbar spine and pelvic posture differences between standing and sitting.
Eight male subjects were radiographed standing and sitting in an automobile seat. Measures of lumbar lordosis, intervertebral disk angles, lumbosacral angle, lumbosacral lordosis, and sacral tilt were completed. One-way analysis of variance (alpha = .05) was conducted on the variables stated above. A Bland-Altman analysis was conducted to assess agreement and repeatability of the lumbar lordosis angle using 2 raters.
Lumbar lordosis values in standing (average, 63 degrees +/- 15 degrees ) and sacral inclination (average, 43 degrees +/- 10 degrees ) decreased by 43 degrees and 44 degrees , respectively, in sitting. Intervertebral joint angles in sitting underwent substantial flexion (L1/L2-5 degrees [+/-3 degrees ], L2/L3-7 degrees [+/-3 degrees ], L3/L4-8 degrees [+/-3 degrees ], L4/L5-13 degrees [+/-3 degrees ], and L5/S1-4 degrees [+/-10 degrees ]). Measures of lumbar lordosis; intervertebral disk angles between L2/L3, L3/L4, and L4/L5; lumbosacral lordosis; lumbosacral angle; and sacral tilt were significantly decreased between standing and sitting (P < .001). Intervertebral disk angle between L5/S1 was not significantly different. Analysis using the Bland-Altman technique found good agreement and stable repeatability of measures with no statistical significant differences between or within raters (R1, P = .8474; R2, P = .4402; and R-R2, P = .8691).
The significant differences in lumbar and pelvic measures from standing to sitting further emphasize the range of motion experienced at vertebral levels in sitting. Based on the results of this study, interventions to return motion segments to a less flexed posture should be investigated because they may play a role in preventing injury and low back pain.
The deep gluteal region is often encountered when performing injections, when performing surgery such as total hip replacements, or diagnosing problems of this region or lower limbs using clinical or imaging techniques. Previously, the prevalence figures of piriformis and sciatic nerve anomalies have ranged from 1.5 to 35.8% in dissected specimens. This study systematically reviews and meta-analyses the prevalence of piriformis and sciatic nerve anomalies in humans using previously published literature. A further review is conducted regarding the anatomical abnormalities present in surgical case series of procedures for patients suffering from piriformis syndrome. After pooling the results of 18 studies and 6,062 cadavers, the prevalence of the anomaly in cadavers was 16.9%; 95% confidence interval (CI) 16.0-17.9%. The prevalence of the piriformis and sciatic nerve anomaly in the surgical case series was 16.2%, 95% CI: 10.7-23.5%. The difference between the two groups was not found to be significant 0.74%; 95% CI: -5.66 to 7.13; P = 0.824. Because of the high likelihood of an anomaly being present in a patient, clinicians and surgeons should be aware of the potential complications this anomaly may have on medical or surgical interventions. Furthermore, because the prevalence of the anomaly in piriformis syndrome patients is not significantly different from what is thought to be a normal population, it indicates that this anomaly may not be as important in the pathogenesis of piriformis syndrome as previously thought.
The current cross-sectional observational MR imaging study aimed to investigate the prevalence and risk factors of lumbar disc degeneration in a healthy population and to establish the baseline data for a prospective longitudinal study.
Two hundred healthy volunteers participated in this study after providing informed consent. The status of lumbar disc degeneration was assessed by 3 independent observers, who used sagittal T2-weighted MR imaging. Demographic data collected included age, sex, body mass index, episode(s) of low-back pain, smoking status, hours of standing and sitting, and Roland-Morris Disability Questionnaire scores. There were 68 men and 132 women whose mean age was 39.7 years (range 30-55 years). Eighty-two individuals (41%) were smokers, and the Roland-Morris Disability Questionnaire scores were averaged to 0.6/24.
The prevalence of disc degeneration was 7.0% in L1-2, 12.0% in L2-3, 15.5% in L3-4, 49.5% in L4-5, and 53.0% in L5-S1. A herniated disc was observed at the corresponding levels in 0.5, 3.5, 6.5, 25.0, and 35.0% of cases respectively. Spondylolisthesis was observed in < 3% of this population. Multiple logistic regression analysis demonstrated that age and hours sitting were significantly related to L4-5 disc herniation. Episode of low-back pain, smoking status, body mass index, and hours standing did not affect the prevalence of disc degeneration.
The current study established the baseline data of lumbar disc degeneration in a 30- to 55-year-old healthy population for a prospective longitudinal study. Hours spent sitting significantly increased the prevalence of disc herniation, but episode of low-back pain, smoking status, obesity, and standing hours were not significant risk factors.
Seated postures are achieved with a moderate amount of lumbo-sacral flexion and sustained lumbo-sacral spine flexion has been associated with detrimental effects to the tissues surrounding a spinal joint. The purpose of this study was to determine if the lower intervertebral joints of the lumbo-sacral spine approach their end ranges of motion in seated postures.
Static sagittal digital X-ray images of the lumbo-sacral region from L3 to the top of the sacrum were obtained in five standing and seated postures from 27 participants. Vertebral body bony landmarks were manually digitized and intervertebral joint angles were calculated for the three lower lumbo-sacral joints.
In upright sitting, the L5/S1 intervertebral joint was flexed to more than 60% of its total range of motion. Each of the lower three intervertebral joints approached their total flexion angles in the slouched sitting posture. These observations were the same regardless of gender. The results support the idea that lumbo-sacral flexion is driven by rotation of the pelvis and lower intervertebral joints in seated postures.
This is the first study to quantitatively show that the lower lumbo-sacral joints approach their total range of motion in seated postures. While not directly measured, the findings suggest that there could be increased loading of the passive tissues surrounding the lower lumbo-sacral intervertebral joints, contributing to low back pain and/or injury from prolonged sitting.
By measurement of intradiscal pressure in vitro, the hydrostatic properties of the nucleus pulposus of normal lumbar intervertebral disc was established. The stress distribution within normal discs subjected to vertical load was also explained, demonstrating the high tangential strains occurring in the posterior part of the annulus fibrosus. Intravitally performed measurements of disc pressure have demonstrated how the load on the lumbar disc varies according to the position of the subject's body. Compared to the pressure or load in the upright standing position, reclining reduces the pressure by 70%, while unsupported sitting increases the load by 40% and forward leaning and weight lifting by more than 100%. Similar relatively large augmentations of the load were observed in subjects performing various commonly used muscle-strengthening exercises. Measurement of intradiscal pressure is instrumental in explaining, from a mechanical point, the occurrence of posterior ruptures in the lumbar discs, and provides a basis for the rational treatment of patients with low-back pain in so far as these exhibit increase of pain on increased mechanical loads. For the majority of patients with low-back pain, the cause is unknown, although most evidence so far presented links the lumbar intervertebral disc to the pain syndromes. Results of recent studies have shown that both chemical and mechanical factors are probably of importance. So far we cannot successfully treat the chemical part of the disc syndrome. Since all our patients exhibit more pain when the spine is mechanically loaded, knowledge gained from intravital disc-pressure measurements provides a basis for successfully treating the mechanical part of the condition. Since none of the frequently prescribed and more spectacular remedies has ever been proved statistically superior to any of the others, it is most fair to our patients and to ourselves to use simpler, less expensive, and less dangerous programmes, such as bed-rest, administration of salicylates, and proper ergonomic advice. Based on a scientific approach, the low-back-pain school is intended to help the patient to be able to cope with these back troubles, to avoid excess therapy, and to decrease the cost both for the individual and for Society.
To the Editor.—
The most typical pressure neuropathies are readily recognized with investigation of the circumstances surrounding the beginning of the complaint, diligent examination of the part involved, and attention not just to intrinsic but to extrinsic factors. I present two cases of compression sciatica caused by extra-thick wallets.
Report of Cases.—Case 1.—
A 52-yearold man, seen for follow-up care after hospitalization for an acute paranoid psychosis, had an incidental complaint of left-sided "sciatica" of 14 months' duration. The pain was mild to moderate, at times vague and at times more localized along the course of the sciatic nerve from the left gluteal area down to the popliteal fossa. Rarely did it radiate to the lumbosacral area. The pain occurred primarily and most pronounced when the patient drove long distances. His condition had been diagnosed as a probable herniated disk, and he had also received chiropractic attention. Neurologic
The piriformis muscle syndrome is a controversial "clinical" syndrome primarily characterized by signs and symptoms of sciatic nerve compression at the region of the piriformis muscle as it passes through the greater sciatic notch. The syndrome is often referred to; however, cases are rarely reported, and it is generally an uncommon diagnosis. Of those cases reported, the incidence is six times more frequent in females than in males, and is typically temporally related to minor pelvic or buttock trauma. We describe a case of a 40-year-old woman presenting with signs and symptoms suggestive of piriformis muscle syndrome following a gynecologic procedure performed in the dorsal lithotomy position. Electromyographic findings were consistent with this clinical entity. Operative exploration, however, revealed the source of neural compression to be a pseudoaneurysm of the inferior gluteal artery adjacent to the piriformis muscle. The diagnostic features of this clinical syndrome are discussed.
We present a case of sciatic neuropathy due to the pyriformis syndrome after operation in the sitting position. Neither sciatic nerve injury nor the pyriformis syndrome has been reported after operation in the sitting position, although a low incidence of common peroneal nerve injury has been reported as a complication of operation on patients who are in the sitting position. The clinical findings of sciatic neuropathy, external rotation of the ipsilateral foot in the position of comfort, and a therapeutic response to local anesthetic injection into the pyriformis muscle are diagnostic of the syndrome. Nerve conduction studies should be performed to aid in the differentiation between a common peroneal and sciatic neuropathy. The syndrome may occur because of extreme flexion of the hips and prolonged pressure while in the sitting position, leading to pyriformis muscle trauma, resultant spasm, and sciatic compression. The prognosis is for complete recovery after symptomatic treatment with nonsteroidal antiinflammatory medication and physical therapy.
To the Editor.—
Dr J. R. Boyce's1 informative letter, "Meralgia Paresthetica and Tight Trousers," recalled to mind similar symptoms I recently experienced. Having grown up near the inner city, I soon learned that if a wallet was carried, it was safer in the front than in the rear pants pocket. This compromise, coupled with a chronically thin wallet, caused no problems until after completion of medical school and postgraduate education. As credit cards and membership cards proliferated, I noticed an aching, burning sensation along the left anterolateral thigh on the side of the wallet. It also was worse while driving any distance. This continued for months. Thinning the wallet of superfluous papers and even buying a thinner wallet didn't help. However, after switching the wallet to the back pocket (after all, what's worth more, your money or your health?), the symptoms abated. Apparently once the lateral cutaneous femoral nerve
A new apparatus was developed to compress the anterior compartment selectively and reproducibly in humans. Thirty-five normal volunteers were studied to determine short-term thresholds of local tissue pressure that produce significant neuromuscular dysfunction. Local tissue fluid pressure adjacent to the deep peroneal nerve was elevated by the compression apparatus and continuously monitored for 2-3 h by the slit catheter technique. Elevation of tissue fluid pressure to within 35-40 mm Hg of diastolic blood pressure (approximately 40 mm Hg of in situ pressure in our subjects) elicited a consistent progression of neuromuscular deterioration including, in order, (a) gradual loss of sensation, as assessed by Semmes-Weinstein monofilaments, (b) subjective complaints, (c) reduced nerve conduction velocity, (d) decreased action potential amplitude of the extensor digitorum brevis muscle, and (e) motor weakness of muscles within the anterior compartment. Generally, higher intracompartmental pressures caused more rapid deterioration of neuromuscular function. In two subjects, when in situ compression levels were 0 and 30 mm Hg, normal neuromuscular function was maintained for 3 h. Threshold pressures for significant dysfunction were not always the same for each functional parameter studied, and the magnitudes of each functional deficit did not always correlate with compression level. This variable tolerance to elevated pressure emphasizes the need to monitor clinical signs and symptoms carefully in the diagnosis of compartment syndromes. The nature of the present studies was short term; longer term compression of myoneural tissues may result in dysfunction at lower pressure thresholds.
Pathology of structures within the neuromusculoskeletal system can result from skeletal malalignment, which the authors define as either abnormal joint alignment or deformity within a bone. Pathology can also result from correlated or compensatory motions or postures, which may accompany skeletal malalignment. The purposes of this clinical perspective are to: 1) link common lower limb skeletal malalignments to their common correlated and compensatory motions and postures; and 2) document the age-specific normal skeletal postural alignment for joints and bones of the lower limb. The authors have combined literature review with their clinical perspectives and the clinical perspectives of selected colleagues in this paper to compile this information, which should be beneficial to health professionals involved in assessment, treatment, and prevention of lower quarter neuromusculoskeletal dysfunction.
It is generally believed that a backrest facilitates lumbar lordosis. To test this, the spontaneously adopted postures of 12 healthy subjects were measured by a statometric method during 2-h sitting periods on three types of chairs in a stratified sequence. The only difference between the three workstations regarded backrest: 'A' had no backrest; 'B' had a vertical lumbar backrest; and 'C' had an anteriorly curved backrest. In general, the most lordotic postures were assumed with backrest C, whereas backrest B rather facilitated kyphosis as compared with sitting without a backrest. However, when specifically considering passive sitting, i.e. reading, both types of backrest facilitated kyphosis. Moreover, spinal shrinkage was evaluated by measuring exact height before and after each 2-h sitting period. This was done to assess spinal load. From this perspective, backrest C induced the greatest load on the spine. In conclusion, the traditional conception that a backrest facilitates lordosis is apparently not true. It seems rather that backrests actually facilitate the opportunity for the user to stabilize their lumbar spines by providing their lower backs with support, resulting in relative kyphotic increases. The practical ergonomic applications from this study are unclear. However, traditional concepts in backrest ergonomy should be re-considered.
To determine the minimum clinically significant difference in visual analog scale (VAS) pain scores for acute pain in the ED setting and to determine whether this difference varies with gender, age, or cause of pain.
A prospective, descriptive study of 152 adult patients presenting to the ED with acute pain. At presentation and at 20-minute intervals to a maximum of three measurements, patients marked the level of their pain on a 100-mm, nonhatched VAS. At each follow-up they also gave a verbal rating of their pain as "a lot better," "much the same," "a little worse," or "much worse." The minimum clinically significant difference in VAS pain scores was defined as the mean difference between current and preceding scores when pain was reported as a little worse or a little better. Data were compared based on gender, age more than or less than 50 years, and traumatic vs nontraumatic causes of pain.
The minimum clinically significant difference in VAS pain scores is 9 mm (95% CI, 6 to 13 mm). There is no statistically significant difference between the minimum clinically significant differences in VAS pain scores based on gender (p=0.172), age (p=0.782), or cause of pain (p=0.84).
The minimum clinically significant difference in VAS pain scores was found to be 9 mm. Differences of less than this amount, even if statistically significant, are unlikely to be of clinical significance. No significant difference in minimum significant VAS scores was found between gender, age, and cause-of-pain groups.
The technique of interface pressure measurement has generated considerable interest in the automotive industry as a method, which could be used to predict driver discomfort during the development of prototype seat designs. Two repeated measures experiments were carried out to evaluate the practical application of the technique. The variables of foam density and posture were used to create discomfort, the whole emphasis of the work being to generate results with real-world applicability. A clear, simple and consistent relationship between interface pressure and driving discomfort was not identified. Future studies using this technique should provide information regarding such factors as gender, body mass, anthropometric data, posture and foam hardness due to the confounding nature of these variables.
Between 1982 and 1997, the authors treated 32 patients with sciatica who subsequently were found to have a tumor along the extraspinal course of the sciatic nerve.
Extraspinal compression of the sciatic nerve by a tumor is a rare cause of sciatica. Signs and symptoms overlap those of the more common causes of sciatica (i.e., herniated disc and spinal stenosis).
To characterize the unique clinical presentation of these patients and to formulate guidelines that may lead to early diagnosis.
All pertinent clinical data and studies were reviewed retrospectively, and standard demographic data were collected for analysis.
These patients typically sought treatment for an insidious onset of sciatic pain that was constant, progressive, and unresponsive to change in position or bed rest. The mean time to final diagnosis was 11.9 months (median, 6 months). Seventeen patients were able to locate their pain to a specific point along the extraspinal course of the sciatic pain, and a mass was noted in 13 patients. Eighteen of these tumors were in the pelvis, 10 in the thigh, and 4 in the popliteal fossa and calf.
A high index of clinical suspicion is the key to early diagnosis of bone or soft-tissue tumors as a cause of sciatica; special attention should be given to pain pattern, physical examination of the entire course of the sciatic nerve, and selection of proper imaging studies. Routine anteroposterior plain radiography of the pelvis as part of the initial imaging screening process is recommended.
The factors in volved in occupational low back pain occurring in professional drivers were investigated epidemiologically with questionnaires (92 items) including low back symptoms, personal factors and occupational factors. The responses of one hundred fifty-three of one hundred eighty-one truck drivers who work in a large chemical industry corporation were analyzed after they had completely filled in questionnaires. As analysis of the results shows, the prevalence of LBP in one month of the survey was 50.3%. Correlating among data of personal factors and LBP, the prevalence of LBP was significantly higher in the drivers (Odd's ratio of 2.7) who answered "yes" to the item "shortage of spending time with family than in the drivers who didnt answer "yes. The occupational factors, working load and working environment showed no correlation with the prevalence of LBP. In contrast, 3 items of the working format related significantly to the prevalence of LBP: "irregular duty time (Odd's ratio of 3.0), "short resting time (2.4), and "long driving time in a day (2.0). Eighty-one of the 153 drivers (52.9%) pointed out the relationship between LBP and work, especially work which muolves vibration or road shock. Our results and the results from previous published studies suggested that vibration is an obvious risk factor for LBP. From the viewpoint of prophylaxis, an improvement in working conditions reduces the incidence of drivers' LBP to some extent.
Musculoskeletal pains are often characterised by referred pain and hyperalgesia. The aim of the present study was to examine the sensitivity to pressure and pinprick at sites ipsi- and contralateral to capsaicin-induced pain in the tibialis anterior (TA) muscle. Visual analogue scale (VAS) scores of the sensation to sub- and supra-pain threshold stimuli by pressure and pinprick were recorded before, during and after experimental muscle pain. It was found that pressure stimulation (120% of baseline pain threshold) delivered over the ipsilateral deep peroneal nerve between the 1st and 2nd metatarsal bones showed a significant increase in VAS scores during muscle pain. The referred pain did not overlap this hyperalgesic site. Ipsilateral test sites at the TA muscle, great toe and between the 3rd and 4th metatarsal bones did not show any changes in response to pressure stimulation during pain. In contrast, test sites at the ipsilateral ankle showed hypoalgesia to pressure during muscle pain. In the contralateral leg hypoalgesia to pressure was found at all sites during pain. The decreased sensitivity to pressure was confirmed with both sub- and supra-pressure pain-threshold stimuli. VAS scores to pinprick were either decreased or unchanged during pain compared to before pain. Naloxone administrated in a placebo-controlled manner had no effect on hypoalgesia to pressure or pinprick during muscle pain. Thus, the generalised decreased sensitivity may reflect activation of non-opioid endogenous pain inhibitory systems. The lack of change in sensitivity at some sites could indicate a competitive balance between excitatory and inhibitory mechanisms. The deep peroneal nerve specifically innervates both the TA muscle and the only site of hyperalgesia indicating spatial summation of afferent activity from these structures.
The biomechanics, histology and electromyography of the lumbar viscoelastic tissues and multifidus muscles of the in vivo feline were investigated during 20 min of static as well as cyclic flexion under load control and during 7 h of rest following the flexion. It was shown that the creep developed in the viscoelastic tissues during the 20 min of static or cyclic flexion did not fully recover over the 7 h of following rest. It was further seen that a neuromuscular disorder with five distinct components developed during and after the static and cyclic flexion. The neuromuscular disorder consisted of a decreasing magnitude of reflexive EMG from the multifidus upon flexion as well as of superimposed spasms. The recovery period was characterized by an initial muscle hyperexcitability, a slowly increasing reflexive EMG and a delayed hyperexcitability. Histological data from the supraspinous ligament demonstrate significant increase (x 10) in neutrophil density in the ligament 2 h into the recovery and even larger increase (x 100) 6 h into the recovery from the 20 min flexion, indicating an acute soft tissue inflammation. It was concluded that sustained static or cyclic loading of lumbar viscoelastic tissues may cause micro-damage in the collagen structure, which in turn reflexively elicit spasms in the multifidus as well as hyperexcitability early in the recovery when the majority of the creep recovers. The micro-damage, however, results in the time dependent development of inflammation. In all cases, the spasms, initial and delayed hyperexcitabilities represent increased muscular forces applied across the intervertebral joints in an attempt to limit the range of motion and unload the viscoelastic tissues in order to prevent further damage and to promote healing. It is suggested that a significant insight is gained as to the development and implications of a common idiopathic low back disorder as well as to the development of cumulative trauma disorders.
The concepts of comfort and discomfort in sitting are under debate. There is no widely accepted definition, although it is beyond dispute that comfort and discomfort are feelings or emotions that are subjective in nature. Yet, beside several subjective methodologies, several objective methods (e.g. posture analysis, pressure measurements, electromyography (EMG) are in use to assess sitting comfort or discomfort. In the current paper a theoretical framework is presented, in which comfort and discomfort were defined and the hypothetical associations with underlying factors were indicated. Next, the literature was reviewed to determine the relationships between objective measures and subjective ratings of comfort and discomfort. Twenty-one studies were found in which simultaneous measures of an objective parameter and a subjective rating of comfort or discomfort were obtained. Pressure distribution appears to be the objective measure with the most clear association with the subjective ratings. For other variables, regarding spinal profile or muscle activity for instance, the reported associations are less clear and usually not statistically significant.