成人发育不良髋关节的前覆盖测量方法

Measures of anterior hip coverage in adult patients with hip dysplasia

成人髋关节发育不良是因髋臼对股骨头覆盖不足引起髋关节稳定性下降, 造成髋部疼痛, 继发髋关节磨损和退变的一种疾病。髋臼对股骨头的覆盖是用来评价髋关节稳定性的重要指标, 其中前覆盖与外侧覆盖同等重要, 但测量方法却不像外侧覆盖那样获得关注和取得共识。现存的成人髋关节前覆盖的测量方法分为二维指标和三维指标两大类。二维指标包括假斜位X线片前中心边缘(anterior central-edge, ACE)角和前覆盖指数, 矢状面CT片ACE角, 骨盆站立前后位X线片前壁指数和三分法、交叉征和交叉指数。假斜位X线片ACE角和前覆盖指数是在假斜位X线片上直接测量获得, 反映髋关节站立位的负重功能状态, 适用于判断髋关节的稳定性, 有较多临床证据支持其与临床随访结果相关。矢状面CT片ACE角反映患者平卧位时的状态, 适用于判断髋关节矫形手术出现撞击的可能。前壁指数和三分法、交叉征和交叉指数在骨盆站立前后位X线片上获得, 反映患者站立位髋关节负重功能状态, 对影像技术要求最低, 可以迅速给予大体的初步判断;但影响因素较多, 准确性欠佳, 与临床的相关性尚不确定。三维指标包括基于CT的三维测量和基于统计模型的仿三维(2.5维)测量。三维测量对髋臼形态的细节显示准确性最高, 更多用于判断髋臼截骨术对髋关节活动度的影响以及产生医源性撞击的风险。2.5维测量虽然较二维观察更准确, 但无法脱离髋关节前后位X线片图像本身对结果的影响。通过假斜位X线片测量ACE角是目前临床上最常用的判断髋关节前覆盖的方法。

Hip dysplasia occurs when the acetabulum does not cover the femoral head sufficiently,causing hip instability and pain.Acetabular coverage of the femoral head is an important index to evaluate the stability of the hip joint.Further,anterior hip coverage is as important as lateral coverage in the stability of the hip joint.However,the measurements of anterior hip coverage received less attention and enjoyed less consensus than those of lateral hip coverage.The existing measurements of the adult hip joint can be divided into 2 categories,namely three-dimensional(3D)measurements and two-dimensional(2D)measurements.2D measurements include the anterior central-edge(ACE)angle and the anterior acetabular head index on false-profile radiographs,the ACE angle on sagittal CT radiographs,and the anterior wall index,the rule of thirds,the crossover sign and the crossover index on standing pelvic anteroposterior radiographs.Among the above indexes,the ACE angle and anterior acetabular head index can be directly measured on false-profile radiographs,which can reproduce the weight-bearing function of the standing hip joint.Currently,these indexes are widely used in the clinical practice to determine the stability of hip joints.Some evidence indicated correlation of these indexes with satisfied clinical outcomes.The ACE angle on CT sagittal radiographs acquired from CT data reproduces the patients'status in the supine position.It is used for determining the potential femoroacetabular impingement after hip correction.The anterior wall index,rule of thirds,crossover sign and crossover index are obtained on standing pelvic radiographs,which can reproduce the weight-bearing status of hip joints and reduce the need for a false-profile radiograph.The surgeon can reach a preliminary judgment from these measurements in a short time.However,due to some potential influence factors,the accuracies of these 2D measurement indexes are limited.Further,their clinical relevance according to published studies is not consistent.3D measurements include real 3D measurement based on CT and the simulated 3D(2.5D)measurement based on statistical models.The details of acetabular morphology are most accurately described in 3D measurements.They are used to determine the influence of acetabular osteotomy on the range of motion and to predict the risk of postoperative iatrogenic femoroacetabular impingement.Although 2.5D measurement based on statistical models is more accurate than that based on 2D measurements,it is still based on the anteroposterior radiographs of the pelvis.Therefore,the drawback caused by using anteroposterior radiographs cannot be eliminated completely.In summary,the ACE angle on false-profile radiographs is the most commonly method in clinical practice.