Anatomy of the Tibial nerve and its branches: A cadaveric study

This study aims to examine the course of the tibial nerve in the popliteal fossa and the posterior region of the leg; to determine its thickness at the level of the intercondylar line and the tendinous arc of the soleus muscle; to measure the lengths and thicknesses of its branches innervating the lateralhead and medial heads of gastrocnemius muscle and soleus muscle to calculate the ratios of these branches' lengths and distances from specific reference points to leg length; and to compare the thicknesses at specific reference levels. In doing so, the study seeks to provide morphological insight into the region. Dissections were performed on the posterior thigh, posterior leg, and popliteal fossa of 20 lower limbs from 10 formalin-fixed cadavers. The area was carefully cleaned of adipose tissue, and all neural structures to be measured were fully exposed. All dissections and measurements were conducted by the same researcher. Cadavers without any prior lower extremity dissections were included. Each measurement was taken three times using a digital caliper with a sensitivity of 0.01 mm, and the intraclass correlation coefficient (ICC) was calculated. The average of the three measurements was used in the analysis. The ICC values ranged between 0.998 and 1.000. According to our data, the average leg length was 397.88 mm. The distance between the point where the tibial nerve crosses the intercondylar line and the point where it passes under the tendinous arc of the soleus muscle was 75.16 mm. This distance corresponds to 19% of the leg length. The ratios of the lengths of the branches innervating the heads of gastrocnemius muscle and soleus muscle to leg length were also evaluated. Considering that the absolute lengths of these nerves may vary with leg length, we believe that ratio-based evaluations provide more meaningful anatomical insights. At the level of the intercondylar line, the tibial nerve had a mean thickness of 7.05 mm, whereas at the level of the tendinous arc of the soleus muscle, its mean thickness was 7.20 mm. The ratio between these two values was 1.03. Although a decrease in thickness would be expected as the nerve gives off its motor branches to the soleus and the gastrocnemius heads between these two points, an increase was observed. We suggest that this unexpected thickening may be due to compression of the tibial nerve under the tendinous arc of the soleus muscle.