Variations of the piriformis and sciatic nerve with clinical consequence: A review

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.

Variações anatômicas do nervo ciático em um grupo de cadáveres brasileiros

“…The anatomy of the sciatic nerve and its relationship with the piriformis muscle are better studied in cadavers 1,2 . Recording the findings of such anatomical studies may help in understanding piriformis syndrome, a condition that according to some physicians is well established, but according to others does not even exist 3 .…”

“…The type "A" relationship is considered to the normal one between the sciatic nerve and piriformis muscle, while types ''B'' to ''F'' are variants that may lead to piriformis syndrome. A clear schematic representation of these types A-F can be found in the recent and detailed work 2 . This work included a systematic review and meta-analysis of the literature, assessing the prevalence of anatomical variations from 18 anatomical studies on over 6,000 limbs 2 .…”

A Rare Case of Bilateral Supra Piriformis Pelvic Exit of Common Peroneal Nerve: Significance in Pelvic and Hip Surgery

“…an aberrant pelvic exit of the sciatic, tibial and common peroneal nerves were made during the cadaveric dissection in teaching laboratories, while only a few were reported from performing hip surgery [4]. Atypical pelvic exit of the sciatic nerve was also observed in the dissection of a human fetus [5].…”

“…Atypical pelvic exit of the sciatic nerve was also observed in the dissection of a human fetus [5]. A detailed systematic review and meta-analysis of the occurrence of anomalous piriformis/sciatic nerve relationships that included 18 studies with over 6062 cadaveric specimens and 7 studies of 130 surgical cases [4] resulted in 6 types of sciatic nerve division (Table 1). In rare cases, the common peroneal and the tibial nerves are separated in their intrapelvic origin and follow an altered course.…”

“…The sciatic nerve exits the pelvis normally through the greater sciatic foramen inferior to the piriformis muscle [1]. Variations in the pelvic exit of the tibial, common peroneal and the sciatic nerve have been observed and classified into 6 types ( Figure 1) [2][3][4]. Predominantly, the sciatic nerve, at the apex of the popliteal fossa, divides into the tibial and common peroneal nerves.…”