Hiroshi Jojima

Effect of tibial slope or posterior cruciate ligament release on knee kinematics.

An experimental study using fresh human cadaver knees was designed to evaluate the effect of partial posterior cruciate ligament release or posterior tibial slope on knee kinematics after total knee arthroplasty. Varus and valgus laxity, rotational laxity, anteroposterior laxity, femoral rollback, and maximum flexion angle were evaluated in a normal knee, an ideal total knee arthroplasty, and a total knee arthroplasty in which the ligaments were made to be too tight in flexion. The total knee arthroplasty specimens then were subjected to either partial posterior cruciate ligament release or increased posterior tibial slope, and the tests were repeated. Posterior tibial slope increased varus and valgus laxity, anteroposterior laxity, and rotational laxity in the knee that had flexion tightness. Posterior cruciate ligament release corrected only anteroposterior tightness, and had no effect on the abnormal collateral ligament tightness. Increased posterior tibial slope significantly improved varus and valgus laxity and rotational laxity in the knee that was tight in flexion more than with release of the posterior cruciate ligament. Therefore increasing posterior tibial slope is preferable for a knee that is tight in flexion during total knee arthroplasty.

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.