Post-operative Patellar Tilt More than 10° Can Affect Certain Components of Knee Society Score After Total Knee Arthroplasty at 2-Year Follow-Up

Introduction The effect of post-operative patella tilt on functional outcomes after total knee arthroplasty remains unclear. Our study aimed to analyze the relationship of post-operative patellar tilt with functional outcome scores after total knee arthroplasty. Materials and Methods Patient data were retrieved from our institution's prospectively maintained total knee arthroplasty. Three hundred three patients who underwent unilateral TKA from Jan 2012 to March 2017 were included in the study. After excluding patients with incomplete and lost follow-up data, 213 patients were analyzed. Radiographs of pre-operative and post-operative skyline views were used for patella tilt and patella displacement measurement at pre-op, post-op 1 year, and post-op 2 years. Three functional outcome scoring systems, SF-36, KSS, and WOMAC, were applied for function evaluation at different post-operative time points. Patients were divided into three subgroups according to the patella tilt, which includes less than 5 degrees, 5.1-10 degrees, and more than 10 degrees. Statistical analysis was done to identify the relationship between patella tilt and functional outcomes. Results Mean post-operative patella tilt was significantly lower than the mean pre-operative patella tilt (3.35 +/- 3.91 vs. 5.65 +/- 4.41, p < 0.001). There was no significant difference in patella displacement among pre- and post-operative status. KSS functional score was significantly poor at post-op 1 year and KSS objective score at post-op 2 years in patients with more than 10 degrees patella tilt. SF-36 and WOMAC were not significantly different among the groups. There was no significant difference in post-operative function between non-resurfaced and resurfaced patella patients evaluated with three scoring systems. Conclusion We have found significantly less post-operative patella tilt after TKA than pre-operative patella tilt with or without patella resurfacing. Increased post-operative patella tilt of more than 10 degrees can affect specific functional outcomes. Patella resurfacing does not affect the post-operative functional outcome compared to non-resurfacing of the patella post-op 2 years.