Objective: Various factors such as the approach used, position of the patella component (PC), and rotation of the femoral component (FC) affect the postoperative results of total knee arthroplasty (TKA) for the patellofemoral joint (PFJ). In this study, we aimed to clarify the factors involving PFJ pain, lateral tilt of the PC, and lateral displacement (LD) of the PC from preoperative, intraoperative and postoperative measurement values of various factors in daily clinical practice.
Methods: TKA with patellar resurfacing was performed on 129 knees by the same surgeon. The surgical procedure was performed using the medial parapatellar or subvastus approach, and a modified gap technique was used. The observation period was an average of 12.5 months. PFJ pain, the lateral tilt angle, and lateral displacement amount were examined. The values of various factors were measured before, during and after the surgery.
Results: PFJ pain was observed in 15 knees (11.6%). Age (P = 0.024), and difference between LD and PCs (P = 0.030) were significantly related factors. The lateral tilt angle increased 5° or more compared with that immediately after surgery in seven knees (5.4%), whereas it decreased 5° or more in 12 knees (9.3%), respectively. The difference between TD and PCs (P = 0.015) was a significantly related factor. The lateral displacement amount was increased 3 mm or more compared with that immediately after surgery in 12 knees (9.3%), whereas it decreased 3 mm or more in 13 knees (10.1%), respectively. The PC setting position (P = 0.044), and difference between LD and PCs (P = 0.016) were significantly related factors. No relationships were observed between PFJ pain, lateral tilt, and lateral displacement.
Conclusion: For improving the postoperative results of patellar resurfacing, we have performed grasp activity, set the PC with medialization at 10% of the patellar diameter from the patellar center, and selected PCs similar to the patellar diameter.
