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Open access

Sergejs Zadorožnijs and Konstantīns Kalnbērzs

Abstract

Published studies on the accuracy of digital templating in total knee replacement (TKR) have employed standard knee, but not hip-to-ankle radiographs. A retrospective study was conducted in our hospital on patients undergoing TKR due to osteoarthritis in a period of six consecutive months. Templating was performed using a calibrating 25 mm metallic ball and Agfa Orthopaedic Tools software by a surgeon not involved with the operation. The surgeon performing the templating was blinded to the size of the implants inserted. Postoperative knee anteroposterior and lateral radiographs were then checked for the presence of prosthetic overhang of ≥ 3 mm. In total, 132 Caucasian adults were included in the study. Femoral overhang occurred in 33%, whereas tibial overhang in only 6% of cases. The exclusion of prosthetic overhang cases significantly improved the accuracy of size detection; exact match for femur increased from 55% to 69%, and for tibia from 70% to 73%. All implants were predicted to within one size in all cases. Digital templating using a calibrating 25 mm metallic ball, Agfa Orthopaedic Tools software and hip-to-ankle and knee lateral radiographs is an accurate method of predicting the knee implant to within one size. Ignoring this procedure leads to prosthetic overhang.

Open access

Sergejs Zadorožnijs and Konstantins Kalnberzs

Summary

Introduction. Osteoarthritis of the knee is a common and frequently symptomatic illness. Total knee replacement (TKR) has evolved as an accepted, cost-effective and efficacious treatment modality for osteoarthritis and other forms of arthritic conditions of the knee joint. Preoperative planning is an important part of the surgical procedure. The inability to accurately determine the magnification factor of the radiograph is one of the major problems in analog preoperative planning of TKR. With the use of calibration objects, the digital images can be corrected for the magnification factor.

Aim of the Study. We aimed to determine the reliability and accuracy of digital templating in the pre-operative work-up for TKR.

Materials and Methods. A retrospective study was done in 105 caucasian adults, who had osteoarthritis of the knee. Digital templating was performed using a calibrating 25-mm metallic ball and Agfa Orthopaedic Tools digital software package by a surgeon not involved with the operation, who was blinded to the size of the implant inserted. The Press Fit Condylar Sigma Knee system was used in all the patients. Digital anteroposterior and lateral radiographs of the knee were used in measuring the implant size. The results from digital images were compared with the size of actual femoral and tibial implants used at the time of surgery.

Results. The correct size of the implant was predicted in 73 of 105 (69,5%) of the femoral and 70 of 105 (66,7%) of the tibial components. The correct size of the whole system was predicted in 58 of 105 (55,2%) cases. The digital preoperative planning predicted 104 of 105 (99,0%) femoral and tibial implants and 103 of 105 (98,1%) whole systems to within one size.

Conclusions. We conclude that digital templating using a calibrating 25-mm metallic ball and Agfa Orthopaedic Tools digital software is a reliable method of predicting the implant to within one size.