Objective: To explore the effect of false acetabulum on the development and anatomical morphology of proximal femur in Crowe type Ⅳ developmental dysplasia of the hip (DDH), providing a theoretical basis for the development of femoral reconstruction strategy and prosthesis selection for total hip arthroplasty.
Methods: The medical records of 47 patients (54 hips) with Crowe type Ⅳ DDH between February 2008 and March 2020 were retrospectively analyzed, of which 21 patients (26 hips) were Crowe type Ⅳa (type Ⅳa group) and 26 patients (28 hips) were Crowe type Ⅳb (type Ⅳb group). There was no significant difference in general data such as gender, age, height, weight, body mass index, and side between the two groups ( P>0.05), which were comparable. The height of femoral head dislocation, the height of pelvis, and the proportion of dislocation were measured based on preoperative anteroposterior pelvic X-ray film. Based on the preoperative femoral CT scan data, the anatomical parameters of the femur and femoral medullary cavity were measured after three-dimensional reconstruction using Mimics19.0 software to calculate the canal fare index; and the femoral medullary cavity parameters were matched with the modular S-ROM prosthesis parameters.
Results: The results of X-ray film measurement showed that the height of femoral head dislocation and the proportion of dislocation in type Ⅳa group were significantly higher than those in type Ⅳb group ( P<0.05). There was no significant difference in the height of pelvis between the two groups ( P>0.05). The results of CT three-dimensional reconstruction measurements showed that compared with the type Ⅳb group, the type Ⅳa group had less isthmus height, smaller femoral head, shorter femoral neck, narrower neck-shaft angle, increased anteversion angle, and higher greater trochanter, and the differences were significant ( P<0.05). There was no significant difference in the height of femoral head, femoral offset, and height difference between greater trochanter and femoral head between the two groups ( P>0.05). There was no significant difference in the mediolateral width (ML), anteroposterior width (AP), and diameter of the isthmus (Ci level) and the AP of the medullary cavity in the plane 40 mm distal to the most prominent point on the medial side of the lesser trochanter (C -40 level) ( P>0.05), and the size of medullary cavity was significantly smaller in type Ⅳa group than in type Ⅳb group at the other levels ( P<0.05). Compared with the type Ⅳb group, the difference between the outer diameter of the prosthetic sleeve and the diameter of the medullary cavity fitting circle in the plane where the center of femoral head rotation was located from the medial most prominent point of the lesser trochanter (C 0 level) in type Ⅳa group was smaller, and the proportion of negative values was greater ( P<0.05). The difference between the longest diameter of the prosthetic sleeve triangle and the ML of the medullary cavity in the plane 10 mm proximal to the most prominent point on the medial side of the lesser trochanter (C +10 level) in type Ⅳa group was smaller, and the proportion of negative values was greater ( P<0.05).
Conclusion: False acetabulum has a significant impact on the morphology of the proximal femur and medullary cavity in patients with Crowe type Ⅳ DDH, and the application of three-dimensional reconstruction technique can accurately evaluate the femoral morphology and guide the selection of femoral prosthesis.
目的: 探讨假臼对Crowe Ⅳ型发育性髋关节发育不良（developmental dysplasia of the hip，DDH）股骨近端发育和解剖形态的影响，为人工全髋关节置换术股骨重建策略制定和假体类型选择提供理论依据。.
方法: 回顾性分析2008年2月—2020年3月收治的47例（54髋）Crowe Ⅳ型DDH患者临床资料，其中21例（26髋）为Crowe Ⅳa型（Ⅳa型组），26例（28髋）为Crowe Ⅳb型（Ⅳb型组）。两组患者性别、年龄、身高、体质量、身体质量指数及侧别等一般资料比较，差异均无统计学意义（ P>0.05），具有可比性。基于术前骨盆正位X线片，测量股骨头脱位高度、骨盆高度以及脱位比例。基于术前股骨CT扫描数据，采用Mimics19.0软件三维重建后测量股骨近端以及股骨髓腔参数，计算髓腔开口指数；并对股骨髓腔参数与组配式S-ROM假体参数进行匹配研究。.
结果: X线片测量示Ⅳa型组股骨头脱位高度和脱位比例均高于Ⅳb型组（ P<0.05）；两组骨盆高度比较，差异无统计学意义（ P>0.05）。CT三维重建测量示，与Ⅳb型组相比，Ⅳa型组峡部高度、股骨头直径、股骨头颈长及颈干角较小，前倾角、大转子高度较大，差异均有统计学意义（ P<0.05）。两组股骨头高度、偏心距及大转子股骨头高度差比较，差异无统计学意义（ P>0.05）。两组峡部（Ci 层面）髓腔前后径、内外径及拟合圆直径比较，小转子内侧最突出点远端40 mm所在平面（C –40层面）髓腔前后径比较，差异无统计学意义（ P>0.05）；余各层面Ⅳa型组股骨髓腔参数均小于Ⅳb型组（ P<0.05）。与Ⅳb型组相比，Ⅳa型组小转子内侧最突出点所在平面（C 0层面）的髓腔拟合圆直径与假体套袖外径差值、小转子内侧最突出点近端10 mm层面（C +10层面）髓腔内外径与假体套袖三角最长径差值更小、差值为负值的患者比例更大（ P<0.05）。.
结论: 假臼对于Crowe Ⅳ型DDH患者股骨近端结构和髓腔形态具有显著影响，应用三维重建技术能精准评估股骨形态和指导股骨假体选择。.
Keywords: Developmental dysplasia of the hip; computed tomography; false acetabulum; proximal femur morphology; three-dimensional reconstruction.