Can implant size be determined with radiographic measurements before operation in total KNEE atroplasty ?

Objective: We aimed to determine the reliability, accuracy and clinical role of the implant size to be used with pre-operative imaging of patients who are planned to have a total knee replacement. Material & Method: In this study, 499 patients and 625 knees who applied to Çukurova University Medical Faculty Balcalı Hospital Orthopedics Traumatology Outpatient Clinic with the complaint of knee pain and were followed up between March 2011 and March 2020 with the diagnosis of primary osteoarthritis, and knees with primary total knee prosthesis were analyzed retrospectively. 160 patients from 499 patients, equally from four different implant brands, with appropriate radiographic imaging were included in the study. Estimated implant size was selected by measurements of distal femur and proximal tibia according to pre-operative anteroposterior and lateral knee radiographs. The implant sizes used for the femur and tibia at the surgery time were compared with the estimated implant sizes selected before the operation. The compatibility and reliability between the selected and recommended prostheses were evaluated. Results: Cronbach's alpha coefficient was examined for all patients according to the prosthesis used in the operation, and it was found that there was a high agreement between the selected prosthesis and the proposed prosthesis. However, the kappa accuracy between the proposed tibia prosthesis type and the one used in the operation was 0.54 moderate; 0.70 was found to be a high accuracy for the femur. According to the brands, the highest accuracy was Depuy (kappa: 0.71) and Stryker (kappa: 0.72) in femur, and the highest fit was Depuy (kappa: 0.64) for tibia. A statistically significant difference was found between the prostheses used for tibia and femur and the recommended prostheses. (p < 0.05) Overall femoral component accuracy was 76.9% (123) in the whole study group, while it was 96.8% (155) for the ± 1 dimension. Tibial component accuracy was 64.4% (103), while it was 92.5% (148) according to ± 1 dimension. Conclusion: Satisfactory and acceptable results were found in determining the appropriate prosthesis size with direct radiographic measurements before total knee atroplasty surgery. Proper implant estimation will increase surgical efficacy and efficiency. Orthopedic surgeons will be able to have information about the prosthesis that can be used in pre-operative planning without additional imaging.