Summary

Patients who undergo patellar resurfacing during total knee arthroplasty do not have a higher incidence of patella baja when compared to those who do not undergo patellar resurfacing.

Abstract

Purpose

While total knee arthroplasty (TKA) is a highly successful procedure, it is not without potential complications. Patella baja is a complication that results in an abnormally low-lying patella with associated anterior knee pain, crepitus, and decreased range of motion. To date, no studies have explored the association between patellar resurfacing and the incidence of patella baja. The aim of this study was to compare rates of patella baja between unresurfaced patellas and resurfaced patellas in patients undergoing TKA.

Methods

A retrospective review was conducted at a single institution of patients who underwent TKA between October 2009 and January 2020. Patients were included if they had at least one preoperative radiograph and one-year follow-up radiograph. Patients with a history of prior knee trauma or inflammatory arthropathy were excluded. Blackburne-Peel (BPR) and Insall-Salvati ratios (ISR) were measured on preoperative and one-year postoperative radiographs. An ISR of less than 0.8 in addition to a BPR of less than 0.5 was defined as patella baja whereas a BPR of less than 0.5 alone was defined as pseudopatella baja. Statistical analysis was performed using a linear model analysis of variance and Fishers exact test.

Results

318 TKAs underwent radiographic evaluation, 176 resurfaced and 142 unresurfaced patellas. Of the resurfaced patients 4% (7/176) were diagnosed with true patella baja, while of the unresurfaced patellas 5.6% (8/142) were found to have true patella baja. Of the resurfaced patellas 8% (14/176) were found to have pseudopatella baja compared to 7% (10/142) in the unresurfaced group. Patellar resurfacing was not associated with a higher incidence of patella baja (p=0.60) or pseudopatella baja (p=0.83). Lower preoperative ISRs (p=0.04) and BPRs (0.03) were highly predictive of a higher incidence of patella baja post TKA.

Conclusion

The added trauma of patellar resurfacing in TKA is not associated with a higher incidence of patella baja in TKA when compared to unresurfaced patellas. Lower preoperative ISRs and BPRs are highly predictive of a higher incidence of postoperative patella baja.