Background: The most common complications of total knee arthroplasty
involve the patellofemoral joint. However, the long-term fate of the
nonresurfaced patella after total knee arthroplasty has seldom been reported.
The purpose of this study was to evaluate the long-term changes of the
nonresurfaced patella after total knee arthroplasty.
Methods: We retrospectively evaluated the nonresurfaced patella in
227 knees (181 patients) at an average of 8.5 years after total knee
arthroplasty. Functional results were correlated with radiographic changes,
and risk factors leading to abnormal changes of the patella were analyzed.
Results: Preoperatively, 186 (82%) of the patellae tracked
centrally, thirty-nine (17%) displaced or tilted laterally, and two (1%)
subluxated laterally. At the time of the latest follow-up, 133 (59%) of the
patellae still tracked centrally with preservation of the cartilage thickness,
fifteen (7%) showed early lateral tilt, sixty-eight (30%) had progressive loss
of lateral cartilage thickness with lateral tilt and/or displacement, seven
(3%) had progressed to lateral subluxation, and four (2%) tilted medially. An
abnormal patellofemoral joint did not affect the knee and functional scores (p
= 0.90 and 0.89, respectively). However, symptoms such as difficulty rising
from a chair or reluctance to use the involved lower limb while climbing
stairs were noted. Preoperative patellar maltracking was identified as the
only risk factor leading to postoperative patellar abnormalities (relative
risk, 2.7; 95% confidence interval, 2.21 to 3.30; p = 0.003).
Conclusions: At the time of follow-up, at an average of 8.5 years,
patellar tracking and the patellofemoral joint remained normal after
approximately 60% of the total knee arthroplasties performed without
resurfacing of the patella. Progressive degenerative changes of the
nonresurfaced patella (mainly on the lateral facet) and patellar maltracking
were the most common abnormal radiographic changes. Patients with preoperative
patellar maltracking were at risk for the development of these changes and
clinical symptoms. Resurfacing of the patella during total knee arthroplasty
may benefit such patients.
Level of Evidence: Prognostic study, Level II-1
(retrospective study). See Instructions to Authors for a complete description
of levels of evidence.