Observations on patellar height following opening wedge proximal tibial osteotomy.

Patellar height and patellar ligament length were assessed pre- and postoperatively in 28 patients who underwent a medial opening wedge proximal tibial osteotomy for varus gonarthrosis. This procedure produced no significant change in patellar ligament length. Pre- and postoperative Insall-Salvati ratios were 0.96+/-0.12 and 0.97+/-0.15, respectively (P=.30). The Insall-Salvati ratio decreased in 29% of patients, and no patient experienced a decline >0.07. The distance between the patella and tibiofemoral joint line ("patellar height") decreased in 100% of patients. The mean Blackburne-Peel ratio declined from 0.75+/-0.13 to 0.53+/-0.15 (P<.001). Sixty-four percent of the postoperative Blackburne-Peel values satisfied the radiographic criterion for patella infera (Blackburne-Peel ratio <0.54). Whereas the loss of patellar height, historically associated with lateral closing wedge proximal tibial osteotomy, is a function of patellar ligament contracture, the decreased distance between the patella and the tibiofemoral joint line following medial opening wedge proximal tibial osteotomy is a function of joint line elevation. The high incidence of patella infera following medial opening wedge proximal tibial osteotomy may have deleterious effects on patellofemoral biomechanics or may complicate subsequent total knee arthroplasty.