Effect of Resurfaced Patellar Thickness on Outcomes after Total Knee Arthroplasty

Total knee arthroplasty (TKA) is the gold standard for the treatment of end-stage knee osteoarthritis. Patellar resurfacing is an optional step in the procedure and remains a controversial topic of discussion. This retrospective study aims to assess the impact of over-resecting and under-resecting the patella during resurfacing on patient-reported outcomes and range of motion (ROM) after surgery. Out of 475 patients who underwent TKA between August 2017 and November 2019 at a single center by a single surgeon, 438 (92.2%) were included in the analysis. Patients were split into three study groups based on reconstructed patellar thickness; normal resection (NR) was defined as within 2 mm native thickness, over-resected was defined as ≤ -2 mm, and under-resected (UR) was defined as ≥ 2 mm. Statistical analyses included chi-squared tests, mixed effect models, and Cox proportional hazards models. There were 364, 41, and 33 patients in the NR, OR, and UR groups, respectively. The cohort's mean age at the time of surgery was 67.1 ± 9.1 and had a mean length of follow-up of 2.1 ± 1.7 years with no difference among cohorts. Significant differences were found in gender (p < 0.001) and BMI (p = 0.0134) with UR having fewer males, OR having more males, and OR having lower BMI. At 6 months, the complete cohort ROM improved from 108.7 ± 14.4 to 111 ± 11 degrees, objective knee society score (KSS) increased from 15.4 ± 11.2 to 36.2 ± 12, functional KSS increase from 47.3 ± 18.9 to 65.6 ± 22.2, and knee injury and osteoarthritis outcome score increase from 46.1 ± 15 to 70.7 ± 15 with no significant differences among cohorts. There were no patellofemoral-related complications. This study supports that while it is important to restore the anatomy in the anterior compartment of the knee, minor changes in patellar thickness from patellar resurfacing likely have minimal impact on outcomes for patients. Further studies with a larger sample size are necessary to further validate these findings.