Search Results (2)

Background/Objectives: The level of the sciatic nerve bifurcation is clinically relevant for diagnostic ultrasonography, ultrasound-guided popliteal sciatic nerve block, posterior-thigh interventions, and surgical approaches to the hip, thigh, and popliteal region. Although the sciatic nerve is classically described as dividing near the popliteal fossa, its terminal branching level may vary considerably. This study aimed to evaluate the level of sciatic nerve bifurcation and its morphometric relationship to clinically relevant anatomical landmarks, with particular emphasis on the posterior intercondylar reference line. Methods: This study was conducted on 56 formalin-fixed adult human lower-extremity specimens. The bifurcation level was categorized as femoral-level, gluteal-level, or separate emergence of the tibial and common fibular components. The sciatic nerve–piriformis relationship was assessed according to the Beaton and Anson classification. Morphometric measurements were obtained from the bifurcation point to the greater trochanter, ischial tuberosity, and posterior intercondylar reference line. Results: Femoral-level bifurcation was observed in 51 of 56 specimens (91.1%), gluteal-level bifurcation in 1 specimen (1.8%), and separate emergence in 4 specimens (7.1%). Type A was the predominant Beaton and Anson pattern, observed in 50 specimens (89.3%). Type B and Type D were each observed in 2 specimens (3.6%), and 2 specimens (3.6%) demonstrated an atypical superior gemellus-related course. All measurable bifurcation points were located proximal to the posterior intercondylar reference line. Among femoral-level bifurcations, the mean distance from this line to the bifurcation point was 8.67 ± 4.89 cm. No statistically significant sex- or side-based differences were observed in the available morphometric parameters. Conclusions: Sciatic nerve bifurcation most commonly occurred at the femoral level, but clinically relevant variations were observed. The posterior intercondylar reference line may provide a useful distal femoral orientation landmark for posterior knee and distal thigh assessment. However, it should complement, rather than replace, direct ultrasonographic visualization of the sciatic nerve and its terminal branches. Full article

Variations of the sciatic nerve and piriformis muscle (SN-PM) relationship must be considered when discussing orthopedic procedures within the region as they may cause increased risk of SN injuries. Thirty-one formalin-embalmed, prosected donors were evaluated using the Beaton and Anson (B&A) classification system (1939). Major landmarks of the SN-PM relationship were identified, including the posterior superior iliac spine (PSIS), ischial tuberosity (IT), greater trochanter (GT), and the middle of the SN as it exits under the PM (S1). Distances measured included: PSIS-IT, PSIS-GT, IT-GT, PSIS-S1, IT-S1, GT-S1, S1-Q (distance of perpendicular line connecting S1 to PSIS-IT), and S1-R (distance of perpendicular line connecting S1 to PSIS-GT). Measurements from 49 lower extremities were evaluated using a two-tailed t-test to compare by sex and laterality; a one-tailed t-test was utilized to compare groups based on anatomical sex. Six donors displayed asymmetric B&A classifications, demonstrating gross anatomical differences within a single individual; however, no measurements were significant when comparing extremities. Seven measurements were statistically significant (p < 0.05) between sexes, indicating notable sex-based differences. These data highlight sex-based differences in the SN-PM relationship, as well as consistencies within measurements among extremities, which can be utilized by clinicians when treating male and female patients needing unilateral or bilateral orthopedic procedures or injections within the gluteal region. Full article