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The Journal of Bone and Joint Surgery (American) 86:935-939 (2004)
© 2004 The Journal of Bone and Joint Surgery, Inc.

Long-Term Changes of the Nonresurfaced Patella After Total Knee Arthroplasty

Hsin-Nung Shih, MD1, Lih-Yuann Shih, MD1, Yon-Cheong Wong, MD1 and Robert Wen-Wei Hsu, MD1

1 Departments of Orthopedic Surgery (H.-N.S., L.-Y.S., and R.W.-W.H.) and Radiology (Y.-C.W.), Chang Gung Memorial Hospital, Chang Gung University, 5, Fu-Shin Street, Kweishan, Taoyuan, Taiwan

Investigation performed at the Departments of Orthopedic Surgery and Radiology, Chang Gung Memorial Hospital, Chang Gung University, Taoyuan, Taiwan

The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

A commentary is available with the electronic versions of this article, on our web site (www.jbjs.org) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM).

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.


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E. E. Pakos, E. E. Ntzani, and T. A. Trikalinos
Patellar Resurfacing in Total Knee Arthroplasty. A Meta-Analysis
J. Bone Joint Surg. Am., July 1, 2005; 87(7): 1438 - 1445.
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