Objective To investigate the efficacy of patellar replacement for total knee arthroplasty(TKA) and its influencing factors.
Methods A retrospective study was carried out on 170 patients who underwent TKA for severe knee osteoarthritis at the Department of Orthopaedics, Shanghai Sixth People's Hospital from March 2020 to March 2021. Complete data were collected from the patients at one year after surgery. The exclusion criteria: those with a history of joint infection, patellar thickness <20 mm, severe osteoporosis and revision surgery. According to the operation procedures, patients were divided into three groups: the patellar preservation group (TKA only, no patellar resurfacing, 78 knees of 75 patients), the traditional patellar resurfacing group (TKA plus a patellar resurfacing with regular patella prosthesis, 65 knees of 65 patients), and the anatomical patellar resurfacing group (TKA plus a patellar resurfacing with anatomical patella prosthesis). American Knee Surgery Society (KSS) clinical and functional scores, West Ontario and McMaster Universities (WOMAC) osteoarthritis index, and patellar score (PS) were employed in the patient assessment. Pain in anterior knee, patellar crepitus and ability to squat during follow-up were observed and recorded. X-rays were taken to check the component position. Factors influencing postoperative scores, presence or absence of anterior knee pain, patellar crepitus and ability to squat were analysed by logistic regression.
Results It was found that there were no statistically significant differences in the preoperative PS scores, preoperative and one-year postoperative KSS clinical scores and WOMAC scores, as well as in the incidences of anterior knee pain, crepitus and difficulty in squatting one year after surgery among the three groups (all P>0.05). The KSS functional score at one year after surgery in both of the traditional patellar resurfacing group (74±10) and the anatomical patellar resurfacing group (75±9) was found higher than that in the patellar preservation group (70±12) (t=-2.487, P=0.014; t=-2.120, P=0.036). As for the PS score, the traditional patellar resurfacing group (21.7±4.9) was significantly higher than the patellar preservation group (19.5±3.9) (t=-2.862, P=0.005) at one year after surgery. It was also noticed that for every 1 kg/m2 increase in body mass index (BMI), the probability of having a low patella score was 1.186 times higher than the probability of having a high patella score [odd ratio (OR)=1.186, 95% confidence interval (CI)= (1.017, 1.384)]. No independent influence factor was observed for the other factors. X-rays showed neither fracture, loosening of the prosthesis nor infection during the follow-up.
Conclusion A patellar resurfacing in early postoperative TKA significantly improves clinical function scores in comparison with a patellar preservation. However, an anatomical patellar prosthesis shows no significant advantage compared with a traditional patellar prosthesis.