Steppacher Simon D, Zurmühle Corinne A, Puls Marc, Siebenrock Klaus A, Millis Michael B, Kim Young-Jo, Tannast Moritz
Department of Orthopaedic Surgery, Inselspital, University of Bern, Freiburgstrasse, 3010, Bern, Switzerland,
Clin Orthop Relat Res. 2015 Apr;473(4):1404-16. doi: 10.1007/s11999-014-4089-5.
Residual acetabular dysplasia is seen in combination with femoral pathomorphologies including an aspherical femoral head and valgus neck-shaft angle with high antetorsion. It is unclear how these femoral pathomorphologies affect range of motion (ROM) and impingement zones after periacetabular osteotomy.
QUESTIONS/PURPOSES: (1) Does periacetabular osteotomy (PAO) restore the typically excessive ROM in dysplastic hips compared with normal hips; (2) how do impingement locations differ in dysplastic hips before and after PAO compared with normal hips; (3) does a concomitant cam-type morphology adversely affect internal rotation; and (4) does a concomitant varus-derotation intertrochanteric osteotomy (IO) affect external rotation?
Between January 1999 and March 2002, we performed 200 PAOs for dysplasia; of those, 27 hips (14%) met prespecified study inclusion criteria, including availability of a pre- and postoperative CT scan that included the hip and the distal femur. In general, we obtained those scans to evaluate the pre- and postoperative acetabular and femoral morphology, the degree of acetabular reorientation, and healing of the osteotomies. Three-dimensional surface models based on CT scans of 27 hips before and after PAO and 19 normal hips were created. Normal hips were obtained from a population of CT-based computer-assisted THAs using the contralateral hip after exclusion of symptomatic hips or hips with abnormal radiographic anatomy. Using validated and computerized methods, we then determined ROM (flexion/extension, internal- [IR]/external rotation [ER], adduction/abduction) and two motion patterns including the anterior (IR in flexion) and posterior (ER in extension) impingement tests. The computed impingement locations were assigned to anatomical locations of the pelvis and the femur. ROM was calculated separately for hips with (n = 13) and without (n = 14) a cam-type morphology and PAOs with (n = 9) and without (n = 18) a concomitant IO. A post hoc power analysis based on the primary research question with an alpha of 0.05 and a beta error of 0.20 revealed a minimal detectable difference of 4.6° of flexion.
After PAO, flexion, IR, and adduction/abduction did not differ from the nondysplastic control hips with the numbers available (p ranging from 0.061 to 0.867). Extension was decreased (19° ± 15°; range, -18° to 30° versus 28° ± 3°; range, 19°-30°; p = 0.017) and ER in 0° flexion was increased (25° ± 18°; range, -10° to 41° versus 38° ± 7°; range, 17°-41°; p = 0.002). Dysplastic hips had a higher prevalence of extraarticular impingement at the anteroinferior iliac spine compared with normal hips (48% [13 of 27 hips] versus 5% [one of 19 hips], p = 0.002). A PAO increased the prevalence of impingement for the femoral head from 30% (eight of 27 hips) preoperatively to 59% (16 of 27 hips) postoperatively (p = 0.027). IR in flexion was decreased in hips with a cam-type deformity compared with those with a spherical femoral head (p values from 0.002 to 0.047 for 95°-120° of flexion). A concomitant IO led to a normalization of ER in extension (eg, 37° ± 7° [range, 21°-41°] of ER in 0° of flexion in hips with concomitant IO compared with 38° ± 7° [range, 17°-41°] in nondysplastic control hips; p = 0.777).
Using computer simulation of hip ROM, we could show that the PAO has the potential to restore the typically excessive ROM in dysplastic hips. However, a PAO can increase the prevalence of secondary intraarticular impingement of the aspherical femoral head and extraarticular impingement of the anteroinferior iliac spines in flexion and internal rotation. A cam-type morphology can result in anterior impingement with restriction of IR. Additionally, a valgus hip with high antetorsion can result in posterior impingement with decreased ER in extension, which can be normalized with a varus derotation IO of the femur. However, indication of an additional IO needs to be weighed against its inherent morbidity and possible complications. The results are based on a limited number of hips with a pre- and postoperative CT scan after PAO. Future prospective studies are needed to verify the current results based on computer simulation and to test their clinical importance.
残余髋臼发育不良常伴有股骨形态异常，包括股骨头非球形、颈干角外翻以及前倾角增大。目前尚不清楚这些股骨形态异常如何影响髋臼周围截骨术后的活动范围（ROM）和撞击区域。
问题/目的：（1）与正常髋关节相比，髋臼周围截骨术（PAO）能否恢复发育不良髋关节通常过度的ROM；（2）与正常髋关节相比，发育不良髋关节在PAO前后的撞击位置有何不同；（3）合并凸轮型形态是否会对内旋产生不利影响；（4）合并内翻-旋转粗隆间截骨术（IO）是否会影响外旋？
1999年1月至2002年3月，我们对200例发育不良患者实施了PAO；其中，27例髋关节（14%）符合预先设定的研究纳入标准，包括有术前和术后包含髋关节及股骨远端的CT扫描。一般来说，我们获取这些扫描以评估术前和术后髋臼及股骨形态、髋臼重新定向程度以及截骨愈合情况。基于27例髋关节PAO前后的CT扫描以及19例正常髋关节创建了三维表面模型。正常髋关节取自基于CT的计算机辅助全髋关节置换术患者群体，排除有症状的髋关节或影像学解剖异常的髋关节后使用对侧髋关节。然后，我们使用经过验证的计算机化方法确定ROM（屈曲/伸展、内旋[IR]/外旋[ER]、内收/外展）以及两种运动模式，包括前撞击试验（屈曲时的IR）和后撞击试验（伸展时的ER）。计算得出的撞击位置被指定到骨盆和股骨的解剖位置。对有（n = 13）和无（n = 14）凸轮型形态的髋关节以及有（n = 9）和无（n = 18）合并IO的PAO分别计算ROM。基于主要研究问题进行的事后功效分析，α为0.05，β错误为0.20，结果显示最小可检测差异为屈曲4.6°。
PAO后，屈曲、IR以及内收/外展与可获得数据的非发育不良对照髋关节相比无差异（p值范围为0.061至0.867）。伸展角度减小（19°±15°；范围为-18°至30°，而对照为28°±3°；范围为19° - 30°；p = 0.017），屈曲0°时的ER增加（25°±18°；范围为-10°至41°，而对照为38°±7°；范围为17°至41°；p = 0.002）。与正常髋关节相比，发育不良髋关节在髂前下棘处发生关节外撞击更为常见（48%[27例中的13例]对5%[19例中的1例]，p = 0.002）。PAO使股骨头撞击的发生率从术前的30%（27例中的8例）增加到术后的59%（27例中的16例）（p = 0.027）。与球形股骨头的髋关节相比，有凸轮型畸形的髋关节在屈曲时的IR减小（屈曲95° - 120°时p值范围为0.002至0.047）。合并IO可使伸展时的ER恢复正常（例如，合并IO的髋关节在屈曲0°时ER为37°±7°[范围为21°至41°]，而非发育不良对照髋关节为38°±7°[范围为17°至41°]；p = 0.777）。
通过计算机模拟髋关节ROM，我们发现PAO有可能恢复发育不良髋关节通常过度的ROM。然而，PAO可能会增加非球形股骨头继发性关节内撞击以及屈曲和内旋时髂前下棘关节外撞击的发生率。凸轮型形态可导致前撞击并限制IR。此外，高前倾角的外翻髋关节可导致伸展时后撞击并使ER减小，而股骨内翻旋转IO可使其恢复正常。然而，是否进行额外的IO需要权衡其固有的发病率和可能的并发症。这些结果基于PAO后有术前和术后CT扫描的有限数量的髋关节。未来需要进行前瞻性研究以验证基于计算机模拟的当前结果并测试其临床重要性。
