Correcting fixed varus deformity with flexion contracture during total knee arthroplasty: the "inside-out" technique: AAOS exhibit selection.

BACKGROUND

Traditional methods for correcting a severe varus and flexion deformity of the knee during total knee arthroplasty can often lead to excessive release of the medial collateral ligament, hematoma formation, and reliance on constrained implants. The "inside-out" technique for correction of varus deformities involves performing a posteromedial capsulotomy at the level of the tibial cut and incising the superficial medial collateral ligament in a pie-crust manner in extension followed by serial manipulations with valgus stress. Our hypothesis was that this technique effectively corrects severe knee varus and flexion deformity with a reduced risk of complications.

METHODS

Thirty-one consecutive patients (thirty-four knees) with a severe fixed varus and flexion deformity (varus alignment of ≥ 15° and flexion contracture of ≥ 5°) underwent total knee arthroplasty with use of the inside-out technique between October 2006 and December 2009. Physical examination, radiographs, and multiple outcome instruments were used to evaluate the results.

RESULTS

The mean duration of follow-up was 3.1 ± 1.1 years (range, 1.7 to 4.9 years). There were no cases of hematoma formation, excessive release of the medial collateral ligament, or acute or delayed instability. A semi-constrained TC3 implant was used in two cases. The mean preoperative coronal alignment was 21.1° ± 4° of varus, which was corrected to 4.5° ± 1.6° of valgus after surgery. The mean preoperative flexion contracture was 10° ± 3.5°. Postoperatively, two patients (three knees) had a residual flexion contracture, which was ≤5° in all cases. The mean range of knee motion improved from 103.3° ± 14.1° preoperatively to 119.1° ± 8° at the time of final follow-up. The mean Knee Society Score pain subscore improved from 39.5 ± 12.6 to 93.2 ± 10.5, and the function subscore improved from 47.1 ± 17.8 to 78.5 ± 21.9. There was no evidence of implant loosening or osteolysis on radiographs.

CONCLUSIONS

The technique described was safe, reproducible, and effective in treating combined varus and flexion deformity of the knee during total knee arthroplasty. It reduced the risks of over-release of the medial collateral ligament, hematoma formation, and the need for constrained implants.