[Unilateral patellar resurfacing in bilateral total knee arthroplasty: a randomized controlled study]

To perform unilateral patellar resurfacing and contralateral patellar retention in bilateral total knee arthroplasty (TKA) randomly, and to compare the clinical effects of patellar retention with patellar resurfacing in TKA.

In the study, 14 bilateral knee osteoarthritis (OA) patients were randomized in the bilateral TKA to receive unilateral patellar resurfacing and contralateral patellar retention, including 28 knees, all were females, 53 to 78 years old, with average (66.9±7.8) years, and the BMI was (26.3±1.8) kg/m². All subjects were followed up from 3 to 12 months. The clinical effects were evaluated based on measurements of American Knee Society score (KSS), range of motion (ROM), anterior knee pain, patellar clunk, and patellar tilt angle (PTA).

All the wounds healed primarily without significant complications, such as infection, aseptic loosening, patellar fracture and so on. The preoperative KSS scores of patellar resurfacing group were 38.9±22.2, and the scores changed to be 92.4±6.7 after operation, which were added by 53.5±20.3. While in the patellar retention group, the KSS scores were 38.4 ± 20.5 preoperatively, and after operation, which were added to be 92.1±4.2, and improved by 53.7±21.4. The differences in the changed KSS scores between TKA with and without patellar resurfacing were not statistically significant (Independent t-test, P=0.98). The ROM was changed from 95.4°±13.5° preoperatively to 120.4°±8.9° postoperatively in the patellar resurfacing group and from 92.9°±19.1° preoperatively to 120.4±8.4° postoperatively in the patellar retention group. The ROM of the two group were increased by 25.0°±14.5° and 27.5°±19.4° respectively. However, no remarkable differences were observed between the 2 groups in the knee ROM (Independent t-test, P=0.70). At the end of the latest follow-up, 3 knees in the patellar resurfacing group and 2 knees in the patellar retention group had knee anterior pain, the incidences of anterior knee pain were 21.4% and 14.3% respectively. There was no obvious difference for the incidence of post-operative anterior knee pain (Chi-square test, P=0.62). The incidences of post-operative patellar clunk in the 2 groups were all with 3 knees (21.4%), which had no significant difference in the 2 groups (Chi-square test, P=1.00). The post-operative PTA were 2.6°±2.6° in the patellar resurfacing group and 3.6°±2.9° in the patellar retention group, respectively. There was also no statistical difference between the 2 groups (Chi-square test, P=0.36).

For knee OA patients with mild or moderate patellar cartilage damage, performing patellar resurfacing or not didn't significantly affect anterior knee pain, patellar clunk, functional outcomes or patellar tracking after TKA. So we suggest retain patella in TKA for OA patients with mild or moderate patellar cartilage damage.