Anatomical evaluation of the tibial nerve within the popliteal fossa.

The purpose of this study was to evaluate the inter-hamstring position (medial to lateral intertendinous position) of the tibial nerve within the popliteal fossa. A descriptive cadaver model study was performed to permit controlled and direct measures of the tibial nerve. Fourteen embalmed lower extremities (8 left, 6 right) from nine cadavers (4 males, 5 females; 84.3 +/- 10.7 years of age) were examined. Nine anatomical variables were measured. All measurements, except the diameter of the tibial nerve at the apex of the popliteal fossa, were performed at the level of the femoral condyles, at their widest medial-to-lateral point. The tibial nerve's diameter increased as it descended from the apex (3.95 +/- 0.50 mm; CI = 2.94-4.96 mm) to the condyles (4.46 +/- 0.92 mm; CI = 2.62-6.31 mm). The distance between the semimembranosus tendon and the biceps femoris tendon in the popliteal fossa (the mid-intertendinous distance) was 48.50 +/- 11.50 mm. The location of the tibial nerve between these two tendons was highly variable: 21.45 +/- 8.40 mm lateral of the semimembranosus tendon and 22.60 +/- 4.90 mm medial of the biceps femoris tendon. Therefore, in 95% of the patients the tibial N could be located within 48.2% of midpoint of the inter-hamstring distance.