Stryker Orthopaedics, Mahwah, NJ, USA.
Clin Orthop Relat Res. 2014 May;472(5):1535-44. doi: 10.1007/s11999-014-3469-1. Epub 2014 Jan 24.
Dual-mobility acetabular cups have been marketed with the purported advantages of reduced dislocation rates and improvements in ROM; however, the relative efficacies of these designs in terms of changing joint stability via ROM and dislocation distance have not been thoroughly evaluated.
QUESTIONS/PURPOSES: In custom computer simulation studies, we addressed the following questions: (1) Do variations in component geometry across dual-mobility designs (anatomic, modular, and subhemispheric) affect the posterior horizontal dislocation distances? (2) How do these compare with the measurements obtained with standard hemispheric fixed bearings? (3) What is the effect of head size on posterior horizontal dislocation distances for dual-mobility and standard hemispheric fixed bearings? (4) What are the comparative differences in prosthetic impingement-free ROM between three modern dual-mobility components (anatomic, modular, and subhemispheric), and standard hemispheric fixed bearings?
CT scans of an adult pelvis were imported into computer-aided design software to generate a dynamic three-dimensional model of the pelvis. Using this software, computer-aided design models of three dual-mobility designs (anatomic, modular, and subhemispheric) and standard hemispheric fixed bearings were implanted in the pelvic model and the posterior horizontal dislocation distances measured. Hip ROM simulator software was used to compare the prosthetic impingement-free ROMs of dual-mobility bearings with standard hemispheric fixed-bearing designs.
Variations in component design had greater effect on posterior horizontal dislocation distance values than increases in head size in a specific design (p < 0.001). Anatomic and modular dual-mobility designs were found to have greater posterior horizontal dislocation distances than the subhemispheric dual-mobility and standard hemispheric fixed-bearing designs (p < 0.001). Increasing head sizes increased posterior horizontal dislocation distances across all designs (p < 0.001). The subhemispheric dual-mobility implant was found to have the greatest prosthetic impingement-free ROM among all prosthetic designs (p < 0.001; R(2) = 0.86).
The posterior horizontal dislocation distances differ with the individual component geometries of dual-mobility designs, with the anatomic and modular designs showing higher posterior horizontal dislocation distances compared with subhemispheric dual-mobility and standard hemispheric fixed-bearing designs.
Static, three-dimensional computerized simulation studies suggest differences that may influence the risk of dislocation among components with varying geometries, favoring anatomic and modular dual-mobility designs. Clinical studies are needed to confirm these observations.
双动髋臼杯具有降低脱位率和改善活动范围的优点；然而，这些设计在通过活动范围和脱位距离改变关节稳定性方面的相对疗效尚未得到彻底评估。
问题/目的：在定制计算机模拟研究中，我们解决了以下问题：（1）双动设计（解剖型、模块型和亚半球型）中组件几何形状的变化是否会影响后向水平脱位距离？（2）与标准半球形固定轴承的测量值相比如何？（3）头大小对双动和标准半球形固定轴承的后向水平脱位距离有什么影响？（4）三种现代双动组件（解剖型、模块型和亚半球型）与标准半球形固定轴承之间的无假体撞击活动范围有何比较差异？
将成人骨盆的 CT 扫描导入计算机辅助设计软件，生成骨盆的动态三维模型。使用该软件，将三种双动设计（解剖型、模块型和亚半球型）和标准半球形固定轴承的计算机辅助设计模型植入骨盆模型，并测量后向水平脱位距离。使用髋关节活动范围模拟器软件比较双动轴承与标准半球形固定轴承设计的无假体撞击活动范围。
组件设计的变化比特定设计中的头尺寸增加对后向水平脱位距离值的影响更大（p < 0.001）。解剖型和模块型双动设计的后向水平脱位距离大于亚半球型双动和标准半球形固定轴承设计（p < 0.001）。增加头尺寸会增加所有设计的后向水平脱位距离（p < 0.001）。亚半球型双动植入物在所有假体设计中具有最大的无假体撞击活动范围（p < 0.001；R² = 0.86）。
双动设计的后向水平脱位距离因个体组件几何形状而异，解剖型和模块型设计与亚半球型双动和标准半球形固定轴承设计相比，后向水平脱位距离更高。
静态、三维计算机模拟研究表明，不同几何形状的组件之间可能存在影响脱位风险的差异，有利于解剖型和模块型双动设计。需要进行临床研究来证实这些观察结果。
