Ramesh Angelika, Henckel Johann, Lim Xing, Tompsett Patrick, Hart Alister, Di Laura Anna
Department of Mechanical Engineering, University College London, London, England, UK.
Royal National Orthopaedic Hospital NHS Trust, Stanmore, England, UK.
Clin Orthop Relat Res. 2025 Mar 28. doi: 10.1097/CORR.0000000000003473.
Understanding the spinopelvic relationship is essential in THA planning, especially given the elevated hip dislocation risk in patients exhibiting abnormal spinopelvic movements. Rotations of the spinopelvic unit affect the functional orientation of the acetabulum and, in turn, the placement of the acetabular cup. Currently, however, the kinematic behavior of the pelvis is not considered preoperatively. Standard CT scans and radiographs only guide component positioning based on the supine position, which may result in suboptimal acetabular cup alignment in more functionally relevant positions. Therefore, the ideal imaging for 3-dimensional (3D) planning of hip surgery is full-length standing CT, which is yet to be implemented given the technical and logistical challenges and high radiation doses involved.
QUESTIONS/PURPOSES: (1) What is the pelvic tilt in the functional positions of supine, standing, and seated? (2) How does the pelvic orientation change when transitioning between these positions?
Between 2020 and 2023, we treated 36 patients for osteoarthritis (OA) who underwent preoperative CT and EOS imaging for their primary THA at our tertiary center. We considered all of those with a satisfactory CT and EOS scan as potentially eligible for this study. Based on that, 86% (31) were confirmed as eligible for analysis here; 14% (5) were excluded because of an incomplete scan field of view, presence of a spinal implant, or because of difficulty in identifying the anterior pelvic plane (APP). The final analysis included 31 patients with OA (23 women and 8 men, mean ± SD age 63 ± 13 years). We proposed a comparison method that uses 3D models of the supine CT-generated bony anatomy and standing and seated full-body biplanar radiography (EOS scans) to obtain the absolute and relative values of pelvic orientation in this patient cohort. To answer our first research question, we performed computational measurements of the patients' pelvic tilt in all three planes (sagittal, coronal, and axial) and in three functional positions: supine, standing, and seated. To answer our second question, we compared and studied each patient's pelvic rotation as they transitioned between these positions. The outcome measures were the angular measurements of (1) pelvic tilt from CT (supine) and EOS (standing and seated) and (2) the change in pelvic tilt when transitioning from supine-standing, supine-seated, and standing-seated.
The mean ± SD sagittal pelvic tilt was greatest in the seated position, least in the standing position, and intermediate in the supine position (-26° ± 12° versus -2° ± 9° versus 6° ± 7°, respectively; p < 0.001). A positive pelvic tilt value denoted an anterior tilt of the APP with respect to the coronal plane and a negative value denoted a posterior tilt. The mean difference in the sagittal pelvic tilt between the supine and standing position was 8° ± 6° (95% confidence interval [CI] 6° to 10°; p < 0.001). The mean difference in the sagittal pelvic tilt between the supine and seated position was 32° ± 13° (95% CI 27° to 38°; p < 0.001). The mean difference in the sagittal pelvic tilt between the standing and seated position was 26° ± 15° (95% CI 20° to 31°; p < 0.001). When comparing the supine to standing transition to the standing to seated transition, the mean difference in the sagittal pelvic rotation was -19° ± 18° (95% CI -26° to -12°; p < 0.001). When comparing the supine to standing transition to the supine to seated transition, the mean difference in the sagittal pelvic rotation was -26° ± 15° (95% CI -31° to -20°; p < 0.001). When comparing the supine to seated transition to the standing to seated transition, the mean difference in the sagittal pelvic rotation was 7° ± 5° (95% CI 5° to 9°; p < 0.001).
The findings from this study show that patients with hip arthritis exhibit pelvic rotations between their daily movements and postures; this rotation may be excessive for some individuals given the large sagittal pelvic tilts reported. This puts some patients at risk of dislocation, edge loading, and limited range of motion (ROM) given that cup orientation in THA is widely known to be affected by the sagittal pelvic tilt. Our work therefore emphasizes the importance of measuring patient-specific pelvic positions and rotations before hip replacement procedures and offers a method to do so.
The functional orientation of the pelvis and the anatomic-functional relationship between the pelvis and spine are seldom considered by surgeons when positioning prosthetic acetabular components. Performing EOS scans in addition to pelvic CT scans can help the surgeon better understand the spinopelvic relationship and the 3D pelvic orientation in the functional supine, standing, and seated positions. This can aid the planning of THA as patients with extreme pelvic parameters and an increased risk of instability can be identified prior to the surgery, and the orientation of the acetabular cup may be adjusted accordingly.
了解脊柱骨盆关系对于全髋关节置换术（THA）的手术规划至关重要，尤其是考虑到脊柱骨盆运动异常的患者髋关节脱位风险升高。脊柱骨盆单元的旋转会影响髋臼的功能方向，进而影响髋臼杯的放置。然而，目前术前并未考虑骨盆的运动学行为。标准CT扫描和X线片仅基于仰卧位来指导假体组件的定位，这可能导致在更具功能相关性的位置上髋臼杯的对线不理想。因此，用于髋关节手术三维（3D）规划的理想成像方式是全长站立位CT，但鉴于技术、后勤方面的挑战以及所涉及的高辐射剂量，这种成像方式尚未得到应用。
问题/目的：（1）仰卧位、站立位和坐位等功能位时的骨盆倾斜角度是多少？（2）在这些体位之间转换时，骨盆方向如何变化？
2020年至2023年期间，我们在三级中心为36例骨关节炎（OA）患者进行了初次THA手术，并对其进行了术前CT和EOS成像检查。我们将所有CT和EOS扫描结果满意的患者视为可能符合本研究条件。在此基础上，86%（31例）被确认为符合分析条件；14%（5例）因扫描视野不完整、存在脊柱植入物或难以识别骨盆前平面（APP）而被排除。最终分析纳入了31例OA患者（23例女性和8例男性，平均年龄±标准差63±13岁）。我们提出了一种比较方法，使用仰卧位CT生成的骨骼解剖结构的3D模型以及站立位和坐位的全身双平面X线摄影（EOS扫描）来获取该患者队列中骨盆方向的绝对值和相对值。为回答我们的第一个研究问题，我们对患者在所有三个平面（矢状面、冠状面和横断面）以及仰卧位、站立位和坐位这三个功能位的骨盆倾斜进行了计算测量。为回答第二个问题，我们比较并研究了每位患者在这些体位之间转换时的骨盆旋转情况。结果测量指标为：（1）CT（仰卧位）和EOS（站立位和坐位）测量的骨盆倾斜角度，以及（2）从仰卧位到站立位、仰卧位到坐位、站立位到坐位转换时骨盆倾斜的变化。
矢状面骨盆倾斜角度平均值±标准差在坐位时最大，站立位时最小，仰卧位时居中（分别为-26°±12°、-2°±9°和6°±7°；p<0.001）。骨盆倾斜正值表示APP相对于冠状面向前倾斜，负值表示向后倾斜。仰卧位和站立位之间矢状面骨盆倾斜的平均差值为8°±6°（95%置信区间[CI]6°至10°；p<0.001）。仰卧位和坐位之间矢状面骨盆倾斜的平均差值为32°±13°（95%CI27°至38°；p<0.001）。站立位和坐位之间矢状面骨盆倾斜的平均差值为26°±15°（95%CI20°至31°；p<0.001）。比较仰卧位到站立位的转换与站立位到坐位的转换时，矢状面骨盆旋转的平均差值为-19°±18°（95%CI-26°至-12°；p<0.001）。比较仰卧位到站立位的转换与仰卧位到坐位的转换时，矢状面骨盆旋转的平均差值为-26°±15°（95%CI-31°至-20°；p<0.001）。比较仰卧位到坐位的转换与站立位到坐位的转换时，矢状面骨盆旋转的平均差值为7°±5°（95%CI5°至9°；p<0.001）。
本研究结果表明，髋关节炎患者在日常活动和姿势之间存在骨盆旋转；鉴于所报告的矢状面骨盆倾斜角度较大，这种旋转对某些个体而言可能过大。考虑到全髋关节置换术中髋臼杯的方向众所周知会受到矢状面骨盆倾斜的影响，这使一些患者面临脱位、边缘负荷和活动范围（ROM）受限的风险。因此，我们的研究强调了在髋关节置换手术前测量患者特定骨盆位置和旋转的重要性，并提供了一种测量方法。
外科医生在放置髋臼假体组件时很少考虑骨盆的功能方向以及骨盆与脊柱之间的解剖功能关系。除骨盆CT扫描外，进行EOS扫描有助于外科医生更好地了解脊柱骨盆关系以及在仰卧位、站立位和坐位等功能位时的三维骨盆方向。这有助于全髋关节置换术的手术规划，因为在手术前可以识别出骨盆参数极端且不稳定风险增加的患者，并相应调整髋臼杯的方向。
