St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
Smith & Nephew Inc, Memphis, TN, USA.
Hip Int. 2024 Jul;34(4):476-481. doi: 10.1177/11207000231220031. Epub 2024 Feb 19.
Dislocation remains 1 of the leading causes of revision after primary total hip arthroplasty (THA) and there is clear evidence the dual-mobility (DM) is used more frequently to minimise this. But in smaller cups, whether the use of DM with smaller 22-mm heads imparts any increased stability compared to standard bearing is unknown; especially when those smaller cups now allow for large single-bearing (SB) heads.
3 primary cup sizes (48 mm, 50 mm, 52 mm) were chosen for modelling. Head sizes trialled for the standard bearing (SB) constructs group were 28-0 mm, 32-0 mm and 36-0 mm against neutral polyethylene liners. In the modular sub-hemispheric DM constructs the inner head sizes for the DM constructs were altered where appropriate (22-0 mm vs. 28-0 mm). Cup position, stem offset, and stem size were standardised.
Both DM constructs outperformed all SB constructs because of a statistically significant jump distance increase ( < 0.001). However, there was no difference in range of motion (ROM) or jump distances between the 22-mm and 28-mm DM inner heads.The ROM angle before impingement between the DM (with 22-mm or 28-mm heads) and SB (with different head sizes where appropriate) showed no statistically significant difference. However, DM constructs presented significantly larger jump distances than SB constructs for both provocative dislocation tests across all 3 cup sizes.Of interest, for 50-mm and 52-mm cup sizes (for which this particular DM construct design can accommodate both 22-mm and 28-mm inner heads), there were no differences in ROM or jump distance between 22-mm versus 28-mm inner heads.
In this computer-modelling study, DM constructs are advantageous over SB constructs for improving jump distances in clinically provocative positions, but not range of motion angles. Inner head diameter of DM has no effect on stability.
在初次全髋关节置换术（THA）后，脱位仍然是翻修的主要原因之一，有明确的证据表明，双动（DM）的使用频率更高，以尽量减少这种情况。但在较小的髋臼杯中，使用较小的 22 毫米头的 DM 是否比标准轴承具有更大的稳定性尚不清楚；特别是当这些较小的髋臼杯现在允许使用大型单轴承（SB）头时。
选择了 3 种主要的髋臼杯尺寸（48mm、50mm、52mm）进行建模。用于标准轴承（SB）结构组的头尺寸试验为 28-0mm、32-0mm 和 36-0mm 与中性聚乙烯衬垫相对。在模块化亚半球 DM 结构中，适当改变了 DM 结构的内头尺寸（22-0mm 与 28-0mm）。杯的位置、柄的偏移量和柄的尺寸都标准化了。
由于跳跃距离显著增加（<0.001），DM 结构在两种情况下都优于所有 SB 结构。然而，22 毫米和 28 毫米 DM 内头之间的运动范围（ROM）或跳跃距离没有差异。DM（带 22 毫米或 28 毫米头）和 SB（在适当情况下带不同头尺寸）之间在撞击前的 ROM 角度没有统计学上的显著差异。然而，对于所有 3 个髋臼杯尺寸，DM 结构的跳跃距离明显大于 SB 结构，对于两种有挑衅性的脱位测试。有趣的是，对于 50mm 和 52mm 杯尺寸（对于这种特殊的 DM 结构设计可以容纳 22mm 和 28mm 内头），22mm 与 28mm 内头之间在 ROM 或跳跃距离方面没有差异。
在这项计算机建模研究中，与 SB 结构相比，DM 结构在改善临床挑衅性位置的跳跃距离方面具有优势，但在运动范围角度方面没有优势。DM 的内头直径对稳定性没有影响。
