Anatomic considerations and the relationship between the piriformis muscle and the sciatic nerve

Department of Anatomy, School of Medicine, Dokuz Eylül University, 35340 Balçova/Izmir, Turkey.
Surgical and Radiologic Anatomy (Impact Factor: 1.05). 08/2008; 30(6):467-74. DOI: 10.1007/s00276-008-0350-5
Source: PubMed


STATING BACKGROUND: The piriformis syndrome is one of the non-discogenics causes of sciatica. It results from the compression of the sciatic nerve (SN) by the piriformis muscle (PM) in the neutral and piriformis stretch test position. The evidence of the increase in pain in the test position requires a detailed anatomical study addressing the changes that occurred in the SN and PM anatomy during the test position. The aim of this study is to examine this relationship morphometrically.
A total of 20 right and left lower limbs of ten adult cadavers were examined. The SN and the PM were made visible. The location of the SN was evaluated with respect to the consistent bony landmarks, including the greater and the lesser trochanter of the femur, the ischial tuberosity, the ischial spine of the hip bone, the posterior inferior iliac spine of the hip bone and the posterior superior iliac spine of the hip bone. The study was done in both neutral and test positions (i.e., 30 degrees adduction 60 degrees flexion and approximately 10 degrees medial rotation position of the hip joint).
The width of the greater sciatic notch was 63.09 +/- 13.59 mm. The length of the lower edge of the PM was 95.49 +/- 6.21 mm, and whereas the diameter of the SN where it emerged from the infrapiriforme was 17.00 +/- 3.70 mm, the diameter decreased to 11.03 +/- 2.52 mm at the level of the lesser trochanter of the femur. The SN intersected the PM most commonly in its medial second quarter anatomically. The vertical distance between the medial edge of the SN-PM intersection point and the ischial tuberosity was 85.62 +/- 17.23 and 72.28 +/- 7.56 mm (P < 0.05); the angle between the SN and the transverse plane was 66.36 degrees +/- 6.68 degrees and 71.90 +/- 8.48 degrees (P < 0.05); and the vertical distance between the medial edge of the SN and the apex of the ischial spine of the hip bone was 17.33 +/- 4.89 and 15.84 +/- 4.63 mm (P > 0.05), before and after the test position, respectively.
This study provides helpful information regarding the course and the location of the SN. The presented morphometric data also revealed that after stretch test position, the infrapiriforme foramen becomes narrower; the SN becomes closer to the ischial spine of the hip bone, and the angle between the SN and the transverse plane increases. This study confirmed that the SN is prone to be trapped in the test position, and diagnosis of this situation requires dynamic MR and MR neurography study.

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    • "Because of its proximity, similar pathway and function, most conservative treatments for patients with ‘piriformis syndrome’ would affect the internal obturator muscle as well [11]. Guvencer et al. [29] suggested that the internal obturator, gemelli and quadratus femoris tendons share common insertions with the piriformis tendon and can thereby compensate for the loss of its function. The fusion of the piriformis tendon with the obturator internus tendon has previously been confirmed [98]. "
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    ABSTRACT: The aim of this manuscript is to review the current knowledge in terms of retro-trochanteric pain syndrome, make recommendations for diagnosis and differential diagnosis and offer suggestions for treatment options. The terminology in the literature is confusing and these symptoms can be referred to as 'greater trochanteric pain syndrome', 'trochanteric bursitis' and 'trochanteritis', among other denominations. The authors focus on a special type of sciatica, i.e. retro-trochanteric pain radiating down to the lower extremity. The impact of different radiographic assessments is discussed. The authors recommend excluding pathology in the spine and pelvic area before following their suggested treatment algorithm for sciatica-like retro-trochanteric pain.
    Knee Surgery Sports Traumatology Arthroscopy 06/2011; 19(11):1971-85. DOI:10.1007/s00167-011-1573-2 · 3.05 Impact Factor
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    • "While reviewing the studies it was found that two studies (Beaton and Anson, 1937) were included in a textbook data set (Anson and McVay, 1971). Two further studies (Windisch et al., 2007; Guvencer et al., 2008) describing relationships between the piriformis and sciatic nerves were excluded because they did not describe the incidence of the nerve or part of the nerve piercing the PM. Thus, a total of 18 studies were included in the final analysis. "
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    ABSTRACT: 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.
    Clinical Anatomy 01/2010; 23(1):8-17. DOI:10.1002/ca.20893 · 1.33 Impact Factor
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    • "Spinal stenosis, facet syndrome, sacroiliac joint dysfunction, trochanteric bursitis, myofascial pain syndrome, pelvic tumor, endometriosis, and conditions irritating the sciatic nerve should be considered in the differential diagnoses of the syndrome. The clinical, radiologic and neurophysiological diagnosis of PS needs special attention [4] [7] [11] [12]. "
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    Journal of Back and Musculoskeletal Rehabilitation 01/2009; 22(1):55-8. DOI:10.3233/BMR-2009-0213 · 0.71 Impact Factor
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