[Translated article] Knee osteoarthritis associated with extra-articular deformity treated by total knee arthroplasty...

Correct mechanical limb alignment is crucial in total knee arthroplasty (TKA) and is particularly difficult to achieve when the knee osteoarthritis (KOA) is associated with an extra-articular deformity (EAD). Our objective is to present a surgical option in cases of severe knee arthritis associated with an EAD (indications, mechanical planning and surgical technique), pros and cons and discuss the results with this one-stage technique.

We retrospectively reviewed all cases of severe KOA associated with EAD treated surgically in our institution from 2010 to 2016. In our study, we only included cases treated via simultaneous TKA and corrective osteotomy (CO) and with a minimum follow-up period of three years. In terms of imaging, we determined the apex and angulation of the EAD as well as the modification of the mechanical parameters post-treatment. The pre- and postoperative clinical assessment was performed using the Knee Society Score (KSS).

Ten patients (10 knees) underwent combined surgery (simultaneous TKA and CO). The mean age was 67.7 years and the mean follow-up period was 49.2 months. The mechanical parameters were consistently corrected in the post-operative period. The mechanical axis deviation (MAD) shifted from a mean value of 6.9cm to 0.45cm and the joint line was rendered horizontal in all cases. In none of the cases did the bone resection affect the insertion of the collateral ligaments. The mean KSS value improved from 32.3 points preoperatively to 79.4 postoperatively. There were no major complications, but there were two planning errors that did not impact upon the end result.

In severe associated KOA and EAD, the combined surgical treatment proposed achieves in one stage an effective anatomical and mechanical correction which is crucial to optimise clinical results and implant durability. The surgery is complex and requires careful planning.