Results of Revision Surgery and Causes of Unstable Total Knee Arthroplasty

BACKGROUND: The aim of this study was to evaluate causes of unstable total knee arthroplasty and results of revision surgery. METHODS: We retrospectively reviewed 24 knees that underwent a revision arthroplasty for unstable total knee arthroplasty. The average follow-up period was 33.8 months. We classified the instability and analyzed the treatment results according to its cause. Stress radiographs, postoperative component position, and joint level were measured. Clinical outcomes were assessed using the Hospital for Special Surgery (HSS) score and range of motion. RESULTS: Causes of instability included coronal instability with posteromedial polyethylene wear and lateral laxity in 13 knees, coronal instability with posteromedial polyethylene wear in 6 knees and coronal and sagittal instability in 3 knees including post breakage in 1 knee, global instability in 1 knee and flexion instability in 1 knee. Mean preoperative/postoperative varus and valgus angles were 5.8degrees/3.2degrees (p = 0.713) and 22.5degrees/5.6degrees (p = 0.032). Mean postoperative alpha, beta, gamma, delta angle were 5.34degrees, 89.65degrees, 2.74degrees, 6.77degrees. Mean changes of joint levels were from 14.1 mm to 13.6 mm from fibular head (p = 0.82). The mean HSS score improved from 53.4 to 89.2 (p = 0.04). The average range of motion was changed from 123degrees to 122degrees (p = 0.82). CONCLUSIONS: Revision total knee arthroplasty with or without a more constrained prosthesis will be a definite solution for an unstable total knee arthroplasty. The solution according to cause is very important and seems to be helpful to avoid unnecessary over-constrained implant selection in revision surgery for total knee instability.

Comparison of Two Year Follow-Up Results in High Flexion Total Knee Arthroplasty with Lospa and Scorpio NRG / 대한정형외과학회잡지

PURPOSE: The purpose of this study is to evaluate the clinical and radiologic results after high flexion Lospa (Corentec Inc.) and Scorpio NRG (Stryker Inc.) total knee arthroplasty. MATERIALS AND METHODS: We prospectively compared 205 knees in 128 patients who underwent arthroplasty using Lospa (group A) and 164 knees in 102 patients who underwent arthroplasty using Scorpio NRG (group B) from September 2010 to March 2012 at Department of Orthopaedic Surgery, Sun General Hospital (Daejeon, Korea). Mean follow-up period was 23 months in group A and 24 months in group B. The radiologic analysis included the change of mechanical axis deviation and femoro-tibial angle, implant position (alpha, beta, gamma, delta), and patellar tilt. The clinical results were evaluated according to hospital for special surgery (HSS), knee society score (KSS), and range of motion. RESULTS: Mechanical axis deviations were change in varus from 34.8 mm to 2.6 mm (p=0.02) in group A, and change in varus from 34.3 mm to 3.1 mm (p=0.04) in group B; no statistically significant difference was observed between them (p=0.13). Femoro-tibial angles were varus 4.3degrees to valgus 6.6degrees (p=0.02) in group A, and varus 4.4degrees to valgus 6.5degrees (p=0.03) in group B; no significant difference was observed between them (p=0.25). No significant difference in implant position was observed between the two groups (p=0.25 in alpha, p=0.17 in beta, p=0.12 in gamma, p=0.17 in delta). Mean HSS improved from 48.5 to 93.6 (p=0.02) in group A, and from 41.4 to 94.4 (p=0.01) in group B. CONCLUSION: Lospa total knee arthroplasty showed excellent early radiologic, clinical results and no statistically significant difference in the results was observed between Lospa and Scorpio NRG.