Plateau-patella angle in evaluation of patellar height after total knee arthroplasty.

The plateau-patella angle (PPA) has been proposed as a new and simpler method to describe patellar height. This method has not been used or validated in knees following total knee arthroplasty (TKA). A modified PPA (mPPA) was developed for use in this population. The method was validated by determining the interobserver and intraobserver reliability of the technique in 50 consecutive patients compared to three well-described methods of describing patellar height after TKA. Three observers then evaluated the mPPA of 297 post-operative radiographs to describe a normal range after TKA for a given technique and implant. The interobserver reliability was the highest for the mPPA compared to the other methods. The mean mPPA for the entire cohort was 21.06, 20.49, and 19.94 for the three observers. The modified plateau-patella angle is a reliable way to evaluate patellar height in patients who have undergone total knee arthroplasty.