Biomechanical comparison of extensile exposures in total knee arthroplasty

The "banana peel" exposure is a novel technique for knee joint exposure that consists of partially peeling the patellar tendon off the tibia, leaving the extensor mechanism intact distally and laterally. Although good clinical results have been reported with this technique with no disruption of the extensor mechanism, concerns exist that it could cause extensor lag, quadriceps weakness, or patellar tendon rupture. We compared the banana peel exposure repair to tibial tubercle osteotomy repair, which we chose as our benchmark procedure because much is known about its associated healing and rehabilitation protocols. In our study of 16 paired, fresh-frozen human knee specimens, the 2 techniques were used alternately for the right and left knees. To measure acute strength, 10 pairs were tested. The patella was clamped and pulled superiorly at 25 mm/min until failure. For cyclical testing (6 pairs), the knee was extended from 90 degrees of flexion to 0 degrees for 2000 cycles at 0.25 Hz while we monitored the distance between the inferior pole of the patella and the tibial diaphysis using a passive optical kinematic measuring system. Mean failure strengths of the banana peel and osteotomy groups were 2642+/-1104 N and 2123+/-562 N, respectively, suggesting that the banana peel repair is not weaker than the osteotomy repair. Neither group had a significant increase (via paired Student t test, P>.05) in the distance between the inferior pole of the patella and the tibial diaphysis, suggesting that neither exposure would result in extensor lag.