摘要
背景：在MRI上测量相加坏死角度可预测股骨头坏死致髋关节塌陷的危险性。
方法：对连续33例37髋患者的早期骨坏死的髋关节进行研究。采用改良Kerboul等方法，测量正中冠状位和正中矢状位MRI上（非前后位和侧位X线片）骨坏死累及股骨头表面的弧度，计算两角度之和。基于计算的相加坏死角度的度数，将髋关节分为四组：1级（〈200°），2级（200°-249°），3级（250°-299°），4级（≥300°在初始评估后，患者被随机分入髓芯减压组或非手术组进行治疗，同时接受正规随访直至股骨头出现塌陷或至少观察5年。
结果：7例4级的髋关节和16例3级的髋关节在36个月出现了股骨头塌陷。9例2级的髋关节中的6例出现塌陷，5例1级的髋关节均未出现塌陷（10g-rank检验，p〈0．01）。研究期间，4例相加坏死角度≤190。（低风险组）的髋关节无1例出现塌陷，25例相加坏死角度≥240°（高风险组）的髋关节均出现塌陷，8例相加坏死角度界于190°-240°（中风险组）的髋关节中有4例（50％）出现塌陷。
结论：使用MRI扫描代替X线片测量Kerboul相加坏死角度评估股骨头坏死致髋关节塌陷的可能性是一种好的方法。
可信水平：预后性研究，上级。进一步可信度参见作者介绍。
Background： The hypothesis that the combined necrotic angle measurement from magnetic resonance imaging scans predicts the subsequent risk of collapse in hips with femoral head necrosis was tested.
Methods： Thirty-seven hips with early stage osteonecrosis in thirty-three consecutive patients were investigated. With use of the modified method of Kerboul et al., we measured the arc of the femoral surface involved by necrosis on a midcoronal as well as a midsagittal magnetic resonance image （rather than an anteroposterior and a lateral radiograph） and then calculated the sum of the angles. On the basis of the magnitude of the resulting combined angle, hips were classified into four categories： grade 1 （〈 200°）, grade 2 （200° to 249°）, grade 3 （250° to 299°）, and grade 4（≥300°）. After the initial evaluations, the hips were randomly assigned to a core decompression group or a nonoperative group. Patients underwent regular follow-up until femoral head collapse or for a minimum of five years.
Results： Seven grade-4 hips and sixteen grade-3 hips had development of femoral head collapse by thirty-six months. Six of the nine grade-2 hips and none of the five grade-1 hips Collapsed （log-rank test, p 〈 0.01）. None of the four hips with a combined necrotic angle of ≤ 190° （the low-risk group） collapsed, all twenty-five hips with a combined necrotic angle of ≥240° （the high-risk group） collapsed, and four （50%） of the eight hips with a combined necrotic angle between 190° and 240° （the moderate-risk group） collapsed during the study period.
Conclusions： The Kerboul combined necrotic angle, as ascertained with use of magnetic resonance imaging scans instead of radiographs, is a good method to assess future collapse in hips with femoral head osteonecrosis.
Level of Evidence： Prognostic Level Ⅰ. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.
