tailieunhanh - Chỉnh hình hiện đại đầu gối

Điện thoại di động mang đầu gối arthroplasty (MBKA) có lợi thế tiềm năng so với cố định thông thường có chứa tổng arthroplasty đầu gối (TKA). Bằng cách cho phép không bị quay trục, MBKA có thể cung cấp phù hợp khớp lớn hơn mà không có một xác suất tăng của nới lỏng do tăng mô-men xoắn trục. | Perspectives on Modern Orthopaedics Mobile Bearings in Primary Knee Arthroplasty Christopher J. Vertullo MBBS FRACS Ortho Mark E. Easley MD W. Norman Scott MD and John N. Insall MD Abstract Mobile-bearing knee arthroplasty MBKA has potential advantages compared with conventional fixed-bearing total knee arthroplasty TKA . By allowing unconstrained axial rotation MBKA can offer greater articular conformity without an increased probability of loosening due to increased axial torque. Increased articular conformity minimizes polyethylene contact stresses thereby reducing linear wear and subsurface fatigue failure. Axial rotation of the platform also enables self-correction of tibial component malrotation. Despite these advantages the long-term clinical results obtained with current MBKA devices are similar to those obtained with well-designed fixed-bearing TKA prostheses with no data suggesting their superiority. The disadvantages of MBKA include bearing dislocation and breakage soft-tissue impingement a steep technique learning curve and concerns about volumetric wear. Hypothetically longer-term followup of MBKA results may reveal a significant difference from fixed-bearing TKA results as the fatigue failure threshold of incongruent polyethylene is exceeded. J Am Acad Orthop Surg 2001 9 355-364 breakage stability clinical results and indications. Types of MBKA Devices The term MBKA describes a variety of dissimilar knee prostheses that feature a mobile polyethylene bearing that articulates with a metallic femoral condyle and a metallic tibial tray. Walker and Sathasivam9 have classified current designs into four types on the basis of bearing mobility 1 The internal-external rotation only design Fig. 1 allows the knee to locate to a preferred rotational ori- Mobile-bearing knee arthroplasty MBKA was introduced in the late 1970s for two main 2 The first was to increase contact area so as to reduce long-term wear and the second was to recreate normal knee .