We identified patient and surgeon factors associated with patellar component failure in a series of 8530 TKAs performed in
5640 patients using the same posterior cruciate ligament-retaining TKA with all-polyethylene patellar components between January
1983 and December 2003. Patellar failure was defined as loosening, fracture, or patellar revision. All infections were excluded.
Statistical analysis using Kaplan-Meier and Cox regression was used to determine the risk of patellar failure. Followup averaged
7.0 years (range, 2–22 years). Patellar component loosening occurred in 4.8% of TKAs (409 knees). Patellar fracture was identified
in 5.2% of TKA (444 knees). Twenty-five patellae were revised (0.3%). TKA performed with a lateral release and patients with
a body mass index of greater than 30 kg/m
2 were at the greatest risk of patellar loosening and fracture, respectively. Male gender, preoperative varus alignment of
greater than 5°, and large patellar component size also predicted a higher risk of patellar fracture. Medial patellar component
position, tibial component thickness of greater than 12 mm, preoperative valgus alignment of 10° or more, and preoperative
flexion of 100° or more predicted patellar loosening. An awareness of these factors that predict patellar failure after TKA
may help determine the relative indications for TKA and influence surgical technique, especially when using this prosthesis.
Level of Evidence: Level IV, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.
The research institution of the authors has received funding from Biomet Inc, Warsaw, IN; Zimmer, Inc, Warsaw, IN; Stryker
Orthopaedics, Mahway, NJ; and St Francis Hospital, Mooresville, IN.
Each author certifies that his or her institution has approved the reporting of these cases, that all investigations were
conducted in conformity with ethical principles of research, and that informed consent for participation in the study was
obtained.