Abstract
Valgus knee is a complex deformity, characterised by varying degrees of flexion, external rotation and valgus deviation. Contracture of external ligamentous structures makes correction and soft tissue balance often difficult and may lead to persistent post-operative instability. Further problems include patellar tracking, bone defects, especially at the external femoral condyle, and the risk of external popliteal sciatic (EPS) nerve palsy after surgery. Krackow distinguished three types of valgus knee: type 1 with integral medial peripheral structures; type 2 with severe medial structure laxity and impossibility to correct passively; and type 3 which is the sequela of over-correction tibial osteotomy.
From 1996 to 2003 we performed 64 fusions due to valgus knee in 41 females and 23 males, aged between 55 and 76 years (mean 67.5). Of these, 52 deformities were type 1, nine type 2, and three type 3. For type-1 lesions we always used prostheses with posterior stabilisation (PS), and balanced the capsulo-ligamentous structures. In type-2 lesions we used a vincolo condilare prosthesis with CCK in two cases and a cerniera prosthesis in two cases, whereas in the remaining five cases we used a PS prosthesis. In type-2 deformities we used a PS prosthesis with a modular tibial component with metal augments. Mean follow up was 45 months.
Radiographically, valgus deformity fell from 22.4° (10° min – 35° max) to 5.4° (3° min – 9° max). Post-operative results, according to the HSS score, were excellent in 51 cases, fair in 11 cases, and poor in two cases, due to the need to perform revision in two stages in an infected prosthesis 6 months after surgery in one case, and aseptic loosening in another.
Valgus knee due to arthritis can be successfully treated by total knee arthroplasty using various techniques, according to the clinical severity. EPS nerve palsy has been cited as a potential problem in total knee arthroplasty. We did not observe this complication in our series, probably because we maintain the knee in continuous slight flexion for the first 18–24 h.
