Emerson R H, Head W C
Presbyterian Hospital of Dallas, TX.
Semin Arthroplasty. 1993 Jan;4(1):2-8.
The complexity of acetabular anatomy makes operative planning for revision difficult. Plain radiographs do not provide as much detail about structural damage to the acetabulum as the surgeon would like in order to decide on the need for special components and bone grafts. The authors have found that analysis of acetabular implant migration has been a reliable surgical planning technique to indirectly assess residual acetabular bone stock. Superior shift on the anterioposterior radiograph implies posterior superior acetabular roof loss, seriously compromising the major weight-bearing area of the acetabulum. Although this may require a structural allograft, the authors have found that bone stock at the level of the true acetabulum is much better than in the false acetabulum created by the migration. Therefore, rather than a small cup placed high on the ilium, a large jumbo cup can frequently restore better hip biomechanics and take advantage of all of the remaining host bone for component stability and support, without the need for structural grafts. Medial shift implies medial superior migration leaving the physiologically strong rim of the acetabulum intact and therefore, less structurally damaging than posterior superior migration. Because the acetabular rim is anatomically designed for load bearing, a rim fit cup restores physiological weight transfer across the pelvis. Bone graft behind such a cup is protected from full weight-bearing forces and has proven to be very reliable.
髋臼解剖结构的复杂性使得翻修手术的规划变得困难。普通X线片无法提供外科医生在决定是否需要特殊假体组件和骨移植时所期望的关于髋臼结构损伤的详细信息。作者发现，分析髋臼假体的移位情况是一种可靠的手术规划技术，可间接评估髋臼剩余骨量。前后位X线片上的向上移位意味着髋臼后上缘缺失，严重损害了髋臼的主要负重区域。尽管这可能需要结构性同种异体骨移植，但作者发现，真髋臼水平的骨量比假体移位形成的假髋臼中的骨量要好得多。因此，与在髂骨高位放置小髋臼杯相比，大的超大号髋臼杯通常能更好地恢复髋关节生物力学，并利用所有剩余的宿主骨来实现假体的稳定性和支撑，而无需结构性移植。向内移位意味着向上向内移位，使髋臼生理上坚固的边缘保持完整，因此，其对结构的破坏比后上移位要小。由于髋臼边缘在解剖学上是为负重设计的，边缘贴合型髋臼杯可恢复骨盆的生理重量传递。这种髋臼杯后方的骨移植受到保护，免受全部负重力量的影响，并且已被证明非常可靠。
