Early efficacies of total knee arthroplasty for knees with severe lateral instability

Abstract

To evaluate the outcomes of primary total knee arthroplasty (TKA) in the treatment of knee with severe lateral instability and summarize the essential points of operation and rehabilitation. From February 2005 to August 2010, primary TKA was performed in 27 severe lateral unstable knees (25 cases), including 3 males (3 knees) and 22 females (24 knees). Their mean age was 57.8 (37-71) years. And their primary diseases included rheumatoid arthritis (22 knees in 21 cases) and osteoarthritis (5 knees in 4 cases). Thirteen lateral unstable knees were accompanied with 18.08° ± 5.96°(15-35°) varus deformity; in the rest 14 knees, there was medial instability with 20.71° ± 7.03° (15-35°) valgus deformity. Blood loss volume, operative duration and complications were recorded. During the follow-up period, HSS score, knee stability and varus/valgus status were recorded preoperatively, 1, 3, 6, 12 months and then annually postoperatively. AORI type I bone defect was found at the proximal tibia in 18 knees and distal lateral femoral condyle in 10 knees. All defects were reconstructed with cement or autograft. AORI type II bone defects at proximal tibia in 3 knees were reconstructed with metal augmentation. Blood loss during the first 24 hours were (438.9 ± 109.5) (400-700) ml and operative duration (91.1 ± 11.6) (70-110) min. The mean follow-up period was (41.6 ± 10.9) (27-60) months. At the final follow-up, the HSS score increased from (45.8 ± 5.4) to (85.4 ± 4.5) (t = 30.15, P < 0.01) .Five knees in 5 cases had mild postoperative instability. All cases were allowed to walk with knee orthosis for 4-6 weeks. At the end of follow-up, mild lateral instability of 2 knees persisted. One augmented knee had osteolysis beneath metal block. TKA for knees with severe lateral instability requires a deep understanding of causes and a rational treatment. Proper handling of bone defects and careful release of lateral soft tissue are two critical points for postoperative knee stability. Wearing knee orthosis during the early postoperative stage may be helpful or residual mild instability.