Computer-assisted osteotomy for valgus knees: medium-term results of 29 cases.

INTRODUCTION: Computer-assisted surgery has been shown to be beneficial for correcting misaligned lower limbs. The purpose of this study was to analyze the medium-term results of computer-assisted osteotomy for 29 valgus knees. The hypothesis was that computer navigation would allow a valgus deformity to be corrected with similar precision as varus deformity. MATERIAL AND METHODS: The series consisted of 27 patients (29 knees); there were 7 men and 20 women with ages ranging from 15 to 63 years (mean: 42.4±14.3 years). Twenty-four varus osteotomies of the femur (14 medial closing and 10 lateral opening) and five double osteotomies (proximal tibia and distal femur) were performed. The pre-operative functional status was evaluated with the Lysholm-Tegner score. The mean score was 64±20.5 points (range: 18-100). According to Ahlbäck's modified classification for knee osteoarthritis, 12 patients were at stage 1, nine were at stage 2, five at stage 3 and one at stage 4. Two of the knees had no radiological signs of osteoarthritis but had a particularly unsightly deformity; one of these was secondary to high tibial valgus osteotomy. The mean pre-operative hip-knee-angle (HKA) angle was 189.3±3.9°; the mean mechanical medial distal femoral angle (mMDFA) was 97.2±2.6° and mechanical medial proximal tibial angle (mMPTA) was 90.1±2.8°. The goal was to achieve an HKA angle of 179±2° and mMPTA of 90±2° to avoid an oblique joint line. Functional outcomes were evaluated with the Lysholm-Tegner, KOOS and IKS scores. RESULTS: No complications other than a transient paralysis of the common fibular nerve were observed. Twenty-three patients (25 knees) were reviewed at a mean follow-up of 50.9±38.8 months (range: 6-144). The mean Lysholm-Tegner score was 92.9±4 points (86-100), the mean KOOS was 89.7±9.3 (range: 68-100), the mean IKS "knee" score was 88.7±11.4 points (range: 60-100) and the "function" score was 90.6±13.3 points (range: 55-100). Twenty-two patients were satisfied or very satisfied. The mean HKA angle was 180.1±1.9°, the mean mMDFA 90.7±2.5° and the mean mMPTA 89.1±1.9°. The pre-operative goal was achieved in 86.2% of cases (25/29) for the HKA angle and 100% of cases of the mMPTA angle. At the follow-up, none of the knees had been revised with a prosthesis. CONCLUSION: Computer-assisted osteotomy for cases of osteoarthritis secondary to valgus knee leads to excellent medium-term results. Navigation provides reliable and accurate deformity correction. LEVEL OF EVIDENCE: IV. Retrospective study.