Opening wedge high tibial osteotomy affects both the lateral patellar tilt and patellar height

In the current study, we evaluated changes in the patellofemoral joint indices in 49 knees from 39 patients (11 men and 28 women with a median age of 64 years; range 53-79) who had undergone an opening wedge high tibial osteotomy (OWHTO). Osteoarthritis had been diagnosed in 39 knees and osteonecrosis in the other 10 knees in this patient cohort. Radiographs showing anteroposterior and true lateral views of the knee joints while standing, and also skyline views while standing with a 30A degrees flexion, were taken both pre- and postoperatively. Radiographic assessments were then performed using the following five parameters: femorotibial angle (FTA), modified Blackburne-Peel ratio (mBP), tibial slope (TS), lateral patellar tilt (LPT), and lateral patellar shift (LPS). The average LPT decreased significantly from 7.4A degrees A A +/- A 3.7A degrees to 5.2A degrees A A +/- A 3.6A degrees (P < 0.01). Patients treated with a greater than 15A degrees correction showed a significantly bigger change in their LPT than those with corrections of 15A degrees or less. No statistical differences were found between the preoperative (10.2 +/- A 4.5%) and postoperative (10.2 +/- A 4.7%) LPS measurements. Changes in the radiographic parameters were also observed in the patellofemoral joint after OWHTO. It is unclear to what extent the postoperative patellar shift and tilt affects the long-term clinical outcomes but our current results suggest that OWHTO negatively affects the congruency of the patellofemoral joint and should not exceed a correction of 15A degrees.