Marmor Meir, McDonald Erik, Buckley Jenni M, Matityahu Amir
Orthopaedic Trauma Attending Surgeon, Biomechanical Testing Facility, Orthopaedic Trauma Institute, University of California San Francisco and San Francisco General Hospital, California.
Am J Orthop (Belle Mead NJ). 2013 Sep;42(9):412-5.
Treatment of posterior wall (PW) fractures of the acetabulum is guided by the size of the broken wall fragment and by hip instability. Biomechanical testing of hip instability typically is done by simulating the single-leg-stance (SLS) phase of gait, but this does not represent daily activities, such as sit-to-stand (STS) motion. We conducted a study to examine and compare hip instability after PW fractures in SLS and STS loading. We hypothesized that wall fragment size and distance from the dome (DFD) of the acetabulum to the simulated fracture would correlate with hip instability and, in the presence of a PW fracture, the hip would be more unstable during STS loading than during SLS loading. Incremental PW osteotomies were made in 6 cadaveric acetabula. After each osteotomy, a 1200-N load was applied to the acetabulum to simulate SLS and STS loading until dislocation occurred. All hip joints in the cadaveric models were more unstable in STS loading than in SLS loading. PW fragments at time of dislocation were larger (P<.001) in SLS loading (85% ± 13%; range, 81%-100%) than in STS loading (40% ± 7%; range, 33%-52%). Mean (SD) DFD at time of dislocation was 15.0 (3.5) mm (range, 14.4-19.6 mm) in STS loading and 5.3 (4.3) mm (range, 0.1-10.0 mm) in SLS loading (P<.04). There was more hip instability in STS loading than in SLS loading. In STS loading, hips dislocated with a PW fracture size of 33% or more and a DFD of 20 mm or less.
髋臼后壁（PW）骨折的治疗取决于骨折壁碎片的大小以及髋关节的稳定性。髋关节稳定性的生物力学测试通常通过模拟步态的单腿站立（SLS）阶段来进行，但这并不能代表诸如从坐起到站立（STS）等日常活动。我们开展了一项研究，以检查和比较在SLS和STS负荷情况下PW骨折后的髋关节稳定性。我们假设，壁碎片大小以及髋臼穹顶到模拟骨折处的距离（DFD）与髋关节稳定性相关，并且在存在PW骨折的情况下，髋关节在STS负荷期间比在SLS负荷期间更不稳定。在6具尸体的髋臼上进行了递增式PW截骨术。每次截骨后，对髋臼施加1200 N的负荷，以模拟SLS和STS负荷，直至发生脱位。尸体模型中的所有髋关节在STS负荷下比在SLS负荷下更不稳定。脱位时，SLS负荷下的PW碎片（85%±13%；范围81%-100%）比STS负荷下的更大（P<0.001）（40%±7%；范围33%-52%）。脱位时的平均（标准差）DFD在STS负荷下为15.0（3.5）mm（范围14.4-19.6 mm），在SLS负荷下为5.3（4.3）mm（范围0.1-10.0 mm）（P<0.04）。STS负荷下的髋关节不稳定情况比SLS负荷下更多。在STS负荷下，当PW骨折大小为33%或更大且DFD为20 mm或更小时，髋关节发生脱位。
