Alignment of the lower extremity mechanical axis by computer-aided design and application in total knee arthroplasty

Abstract

Purpose: The success of total knee arthroplasty (TKA) depends on many factors. The position of a prosthesis is vitally important. The purpose of the present study was to evaluate the value of a computer-aided establishing lower extremity mechanical axis in TKA using digital technology. Methods: A total of 36 cases of patients with TKA were randomly divided into the computer-aided design of navigation template group (NT) and conventional intramedullary positioning group (CIP). Three-dimensional (3D) CT scanning images of the hip, knee, and ankle were obtained in NT group. X-ray images and CT scans were transferred into the 3D reconstruction software. A 3D bone model of the hip, knee, ankle, as well as the modified loading, was reconstructed and saved in a stereolithographic format. In the 3D reconstruction model, the mechanical axis of the lower limb was determined, and the navigational templates produced an accurate model using a rapid prototyping technique. The THA in CIP group was performed according to a routine operation. CT scans were performed postoperatively to evaluate the accuracy of the two TKA methods. Results: The averaged operative time of the NT group procedures was 46.8 ± 9.1 min shorter than those of the conventional procedures (57.5 ± 12.3 min). The coronal femoral angle, coronal tibial angle, posterior tibial slope were 89. 4 ∘± 1. 5 ∘, 89. 3 ∘± 1. 4 ∘, 6. 8 ∘± 1. 6 ∘ in NT group and 87. 3 ∘± 3. 8 ∘, 88. 1 ∘± 1. 9 ∘, 10. 9 ∘± 4. 6 ∘ in CIP group, respectively. Statistically significant group differences were found. Conclusions: The navigation template produced through mechanical axis of lower extremity may provide a relative accurate and simple method for TKA.