The cubital tunnel: anatomic, histologic, and biomechanical study.

The anatomy of the cubital tunnel was examined in 19 human cadaveric elbows. Pressure measurements within the cubital tunnel were recorded at the medial epicondyle level and 3 cm distal to the epicondyle in various positions of elbow flexion. Histologic examination of the ulnar nerve was carried out at different levels. A common flexor aponeurosis (CFA) was consistently present in all specimens between the flexor carpi ulnaris and the flexor digitorum superficialis. Pressure measurements were greater distally at the CFA level than proximally in the fibrosseous tunnel. The pressure inside the cubital tunnel increased with increasing flexion at the 3 levels examined. Releasing the arcuate ligament decreased the pressure in the fibrosseous tunnel but not distally at the level of the CFA. An oligofascicular pattern of the ulnar nerve was observed at the level of the medial epicondyle and CFA. This finding was in contrast to the polyfascicular pattern present both proximal and distal to these structures. The findings of our study have shown that an intimate anatomic relationship exists between the ulnar nerve and the CFA. This proximity appears to affect the biomechanics of the cubital tunnel and to contribute to nerve compression by the CFA in the distal tunnel. We also found that elbow flexion increases the pressure in the distal tunnel and that releasing the arcuate ligament alone does not decompress the ulnar nerve in the distal tunnel.