Objective: To measure and analyze the radiographic characteristics of the leg length discrepancy in adult patients with unilateral developmental dysplasia of the hip (DDH).
Methods: The clinical data of 112 patients with unilateral DDH who met the selection criteria between January 2016 and June 2018 were retrospectively analyzed. There were 16 males and 96 females with an age of 20-76 years (mean, 42.9 years). According to the Crowe classification, there were 25 hips of type Ⅰ, 26 hips of type Ⅱ, 15 hips of type Ⅲ, and 46 hips of type Ⅳ (26 hips of type ⅣA without secondary acetabular formation, and 20 hips of type ⅣB with secondary acetabular formation). Full-length X-ray films of the lower limbs in the standing position were used to measure the following parameters: greater trochanter leg length (GTLL), greater trochanter femoral length (GTFL), lesser trochanter leg length (LTLL), lesser trochanter femoral length (LTFL), tibial length (TL), and intertrochanteric distance (ITD). The above parameters on the healthy and affected sides were compared and the difference of each parameter between the healthy and affected sides was calculated. Taking the difference of 5 mm between the healthy side and the affected side as the threshold value, the number of cases with the healthy side was greater than 5 mm and the affected side was greater than 5 mm were counted respectively. The difference of the imaging parameters between the healthy side and the affected side were compared between different Crowe types and between type ⅣA and type ⅣB.
Results: There was no significant difference in GTLL and LTFL between healthy and affected sides ( P>0.05); LTLL and TL of affected side were longer than healthy side, GTFL and ITD were shorter than healthy side, and the differences were significant ( P<0.05). The constituent ratio of long cases on the affected side of TL and LTLL was greater than the constituent ratio of long cases on the healthy side, while the constituent ratio of long cases on the healthy side of GTFL and ITD was greater than the constituent ratio of long cases on the affected side; there was no obvious difference in the constituent ratio of long cases on the healthy side or the affected side of GTLL and LTFL. The comparison between different Crowe types showed that only the difference in TL between type Ⅰ and type Ⅳ was significant ( P<0.05), the difference of each imaging parameter among the other types showing no significant difference ( P>0.05). Compared with type ⅣB, the differences of GTLL, TL, and ITD of type ⅣA were bigger, and the differences were significant ( P<0.05); the differences of other parameters between type ⅣA and type ⅣB were not significant ( P>0.05).
Conclusion: In adult unilateral DDH patients, the leg length on the healthy side and the affected side is different, and the difference mainly comes from the TL and ITD, which should be paid attention to in preoperative planning.
目的: 测量并分析成人单侧发育性髋关节发育不良（developmental dysplasia of the hip，DDH）患者影像学下肢长度差异的特点。.
方法: 回顾分析 2016 年 1 月—2018 年 6 月符合选择标准的 112 例单侧 DDH 患者临床资料。其中男 16 例，女 96 例；年龄 20～76 岁，平均 42.9 岁。DDH 根据 Crowe 分型，Ⅰ型 25 髋、Ⅱ型 26 髋、Ⅲ型 15 髋、Ⅳ型 46 髋（其中无继发臼形成的ⅣA 型 26 髋、有继发臼形成的ⅣB 型 20 髋）。摄站立位下肢全长 X 线片，测量以下参数：大转子下肢长度（greater trochanter leg length，GTLL）、大转子股骨长度（greater trochanter femoral length，GTFL）、小转子下肢长度（lesser trochanter leg length，LTLL）、小转子股骨长度（lesser trochanter femoral length，LTFL）、胫骨长度（tibial length，TL）、大小转子间距离（intertrochanteric distance，ITD）。比较健患侧上述参数，并计算各参数健患侧差值；以健患侧差值 5 mm 作为阈值，分别统计上述参数健侧较患侧>5 mm（健侧长）以及患侧较健侧>5 mm（患侧长）的例数；比较各影像学参数健患侧差值在不同 Crowe 分型之间以及 Crowe ⅣA 型和ⅣB 型之间的差异。.
结果: 健患侧 GTLL 和 LTFL 比较差异均无统计学意义（ P>0.05）；患侧 LTLL 和 TL 长于健侧，GTFL 和 ITD 短于健侧，差异均有统计学意义（ P<0.05）。TL、LTLL 患侧长构成比大于健侧长构成比，而 GTFL、ITD 健侧长构成比大于患侧长构成比，GTLL 和 LTFL 健侧长或患侧长构成比无明显差异。不同 Crowe 分型间比较显示，仅Ⅰ型和Ⅳ型间 TL 健患侧差值比较差异有统计学意义（ P<0.05），其余各分型间各影像学参数健患侧差值比较差异均无统计学意义（ P>0.05）。与 CroweⅣB 型比较，ⅣA 型 GTLL、TL 和 ITD 健患侧差值较大，差异均有统计学意义（ P<0.05）；其余指标ⅣA 型和ⅣB 型间比较差异均无统计学意义（ P>0.05）。.
结论: 成人单侧 DDH 患者双下肢不等长，差异主要来自于 TL 和 ITD，术前规划时需注意这点。.
Keywords: Adult; developmental dysplasia of the hip; leg length discrepancy; leg length measurement.