TKA in extraarticular deformities: technique with intraarticular correction without using more constraint in 29 knees

Background: Long-term success in total knee arthroplasty depends on restoring the mechanical axis and achieving precise soft tissue balance to optimize load distribution. Extra-articular deformities exceeding 10° in the coronal, sagittal, or axial planes complicate these objectives, creating a clinical controversy regarding whether to utilize compensatory intra-articular bone resections or formal corrective osteotomies.

Objective: This retrospective study evaluates the clinical and functional outcomes of total knee arthroplasty in patients with significant homolateral extra-articular femoral or tibial deformities, while detailing essential preoperative planning and surgical techniques.

Key Points: Twenty-nine arthroplasties were performed in 26 patients with an average follow-up of 7.2 years. Deformities primarily resulted from post-traumatic malunion or previous osteotomies. Preoperative planning utilized weight-bearing radiographs to identify the center of rotation of angulation and determine the necessity of "unusual" bone cuts. Intra-articular resections were successfully employed for femoral coronal deformities up to 20° and tibial deformities up to 30°, provided the medial collateral ligament insertion was preserved. These compensatory cuts necessitated extensive soft tissue releases to manage the resulting asymmetrical gaps. Postoperatively, average clinical Knee Society Scores improved from 24.3 to 86.0, and functional scores increased from 34.0 to 85.3. Complications included one deep infection and one case of medial instability requiring revision to a constrained prosthesis.

Conclusion: Total knee arthroplasty in the presence of extra-articular deformity requires individualized surgical strategies. Coronal deformities within specific thresholds (20° femur, 30° tibia) are manageable via intra-articular compensatory cuts and soft tissue balancing. Deformities exceeding these limits or compromising ligamentous insertions may necessitate concurrent corrective osteotomy stabilized with modular prosthetic stems.