Relationship of the common peroneal nerve and its branches to the head and neck of the fibula.

The common peroneal nerve (CPN) lies on the neck of the fibula, which forms the floor of the so-called 'fibular tunnel.' The tunnel entrance is a musculo-aponeurotic arch derived from the soleus and peroneus longus muscles and it is here that the CPN is commonly compressed in cases of peroneal nerve palsy. This study aims to define the relationship of the CPN and its branches to the apex of the head of the fibula and to the tunnel, with special regard to possible sites of entrapment. The distances from the apex of the fibula to the opening of the fibular tunnel, the CPN bifurcation, and the exit point of the deep peroneal nerve (DPN) from the tunnel, were measured in 30 legs to ascertain possible sites of entrapment. The angle that the CPN subtended with the long axis of the fibula was measured to gauge the range of positions of the CPN at the neck of the fibula. An unyielding musculo-aponeurotic fibular arch at the entrance to the fibular tunnel was confirmed in all specimens. The DPN exited through a crescentic opening in the anterior intermuscular septum in all cases and no DPN branches were found in the lateral compartment in any specimen. The mean (+/-SD) distance from the apex of the head of the fibula to the opening of the fibular tunnel was 3.2 +/- 1.0 cm, to the CPN bifurcation was 3.8 +/- 0.9 cm, and to the DPN exit point was 7.0 +/- 1.5 cm. The mean angle subtended anteriorly from the long axis of the fibula by the CPN was 18.9 +/- 9.0 degrees. We recommend further study of the mean distances and reference angle in relation to fibular landmarks, for use in possible minimally invasive surgical procedures to decompress the fibular tunnel.