Functional outcome comparison of single-radius and multi-radius femur in total knee arthroplasty

Abstract

Objective: The aim of this study is to compare the clinical and functional results of single-radius (SR) and multi-radius (MR) femoral components in total knee arthroplasty (TKA). Methods: A total of 74 patients who underwent TKA surgery by a single surgeon between 2018 and 2021 were included in the study. The patients were then divided into 2 groups according to their femoral component design: group SR (38 patients) and group MR (36 patients). Except for gender and follow-up duration (P < .05), no significant difference was observed in age, American Society of Anesthesiologists scores, and BMI (P > .05). Knee range of motion, visual analogue scale (VAS), and combined KSS (Knee Society Score) were evaluated at the preoperative and final controls of the patients. In addition, frequency of anterior knee pain (AKP), AKP scale, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Hospital for Special Surgery (HSS) score, and the Forgotten Joint Score-12 (FJS12) were evaluated at the final follow-up. Results: There was no difference between the 2 groups in terms of postoperative range of motion (ROM), VAS, combined KSS, and HSS (P > .05). The frequency of AKP in patients with SR was found to be statistically lower than those with MR (P=.021; P < .05). The AKP scale was found to be statistically significantly lower in patients with prosthetic type MR compared to patients with SR (P=.04; P < .05). Singleradius patients had significantly better FJS-12 (P=.014; P < .05) and WOMAC scores (P=.003; P < .05). Conclusion: The results of this research showed that good clinical and functional results are obtained with TKA regardless of the femoral component design. Single-radius prostheses show better results than MR prostheses in terms of the frequency and severity of AKP. While there is no difference between femoral designs in terms of TKA-specific functional results such as KSS and HSS, the WOMAC score, which measures disease-related functions, provides better clinical results in SR designs. Additionally, SR designs show significantly better results in functional scores indicating patient satisfaction, such as FJS-12.

Figure 1.

Measurement of radiographic parameters; (1.a-1.b) preoperative AP/lateral knee x-ray; (1.c) FTA = femorotibial angle; (1.d) LDFA = lateral distal femoral angle; (d) MPTA = medial proximal tibial angle; (e) FEFA = flexion-extension femoral angle; (1.e) TSA = tibial slope angle; (1.f) PCO = posterior condylar offset (a/b); (1.f) ACO = anterior condylar offset (c/b); (1.g) Insall-Salvati index (d/e). The femorotibial angle (FTA) (°) was measured as the angle between the anatomical axes of the femur and tibia on the AP knee radiograph. The LDFA (°) was measured as the angle between the anatomical axis of the femur and a line tangential to the distal femoral condyles on the AP knee radiograph. The MPTA (°) was measured as the angle between the anatomical axis of the tibia and a line tangential to the tibial plateau on the AP knee radiograph. The TSA (°) was calculated as the angle between a line passing through the middle of the tibial diaphysis and a line tangential to the tibial plateau on the lateral knee radiograph. The FEFA (°) was measured as the angle between a line passing through the anatomical axis of the femur and the neutral line of the femoral component on the lateral knee radiograph. The PCO was calculated as the ratio of the length of the condyle remaining posterior to the line passing through the posterior cortex of the femoral diaphysis to the distal femoral diameter on the lateral knee radiograph. The anterior condylar offset (ACO) was calculated as the ratio of the length remaining anterior to the femoral anterior cortex line in the condylar region to the distal femoral diameter on the lateral knee radiograph. The Insall-Salvati index was calculated as the ratio of the length of the patellar tendon to the length of the patella. Values between 0.8 and 1.2 are considered normal.