Radiographic changes in the patella after total knee arthroplasty without resurfacing the patella. Comparison of osteoarthrosis and rheumatoid arthritis.

The necessity of patellar resurfacing has aroused considerable controversy. Between 1986 and 1996, we have routinely performed 208 primary total knee arthroplasties (TKAs) without resurfacing the patella. However, we have occasionally observed gradual postoperative patellar deterioration which caused peripatellar pain. This study observed the radiographic changes in the patella after TKA without resurfacing the patella to assess the effect of the changes on the clinical results. Sixty out of 208 TKAs were assessed in this study. The original diagnoses were osteoarthrosis (OA) in 17 joints and rheumatoid arthritis (RA) in 43 joints. Fourteen patients (23.3%) complained of postoperative peripatellar pain: 2 of the 17 patients with OA (11.8%) and 12 of the 43 with RA (27.9%). Lateral tilt of the patella slightly decreased with time, but lateral shift increased slightly. Patellar length and width increased throughout the follow-up period. The thickness of the patella, especially in the RA cases, significantly (Mann-Whitney, p < 0.05) decreased with time. According to these radiographic findings, as time passed the thickness of the patella decreased, its length and width increased, and the patella as a whole became flattened. On examining the effect of this flattening on postoperative pain, it was found that about 70% of those patients whose patellar thickness had decreased to 80% or less complained of peripatellar pain. In the case of the OA patients, however, there was no statistically significant correlation between patellar flattening and pain. It is concluded that patellar resurfacing should be considered for the patient with rheumatoid arthritis. Because patellar flattening did not develop in many patients with OA and few of them complained of peripatellar pain, patellar resurfacing should not be performed routinely.