Anatomic consideration of nerve supply to the vastus medialis in knee surgery.

A medial approach for exposure of total knee arthroplasty that splits the vastus medialis muscles may damage the distal portion of the muscle. Ten fresh-frozen cadaver knees without deformity and three retrieved knees were used to dissect nerve branches along the femoral nerve distally until they ended in muscle. Two patterns of nerve distribution were observed. In three specimens, the main trunk ran in the midportion of the vastus medialis and then divided into multiple branches which entered the distal oblique fibers of the muscle at multiple points in the area where it blended with the main body of the muscle. In the remaining specimens, the main trunk ran in the posterior portion of the muscle and branched to the distal oblique fibers, but many branches entered these distal oblique fibers diffusely through the proximal area from branches in the main body of the muscle. No nerve branches were found crossing between the vastus intermedius and vastus medialis. These muscles appear to be innervated separately by direct branches from the femoral nerve. Dissecting between the vastus intermedius and medialis is unlikely to damage the nerve supply to the vastus medialis obliquus whereas dissecting between the vastus medialis obliquus and main body of the vastus medialis may damage the nerve supply of both.