Objective: To study the imaging features of the hip joint by measuring the imaging parameters of spine, pelvis, and hip joint before and after total hip arthroplasty (THA) in patients with ankylosing spondylitis (AS) undergoing THA so as to provide reference for selection of operation methods and prosthesis.
Methods: Between January and July 2015, 38 patients (56 hips) with AS underwent primary THA as AS group, and 36 patients (45 hips) with osteonecrosis of the femoral head underwent THA as control group. There was no significant difference in side ( χ2=1.14, P=0.95). The acetabular abduction angle (ABA), acetabular anteversion angle (AVA), center collum diaphyseal (CCD), offset, height from rotation center to lesser trochanter (HRCLT), femoral intertrochanteric distance (FID) were measured by CT three-dimensional morphology. The canal flare index (CFI), cortical thickness index (CTI), pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) were measured by X-ray film before operation. The AVA, ABA, and the filling ratio were measured on the postoperative X-ray film.
Results: There was no significant difference in preoperative AVA and ABA and postoperative ABA between 2 groups ( P>0.05), but significant difference was found in postoperative AVA ( t=6.71, P=0.00). The mean PI, SS, and PT in AS group were 48.37° (range, 41-58°), 5.64°(range, 2-11°), and 12.85° (range, 5-26°), respectively. There was significant difference in CCD, CFI, and CTI between 2 groups ( t=3.63, P=0.04; t=5.12, P=0.02; t=3.91, P=0.04), but offset, HRCLT, and FID all showed no significant difference ( t=0.41, P=0.36; t=0.33, P=0.56; t=0.59, P=0.12). On the basis of the Noble classification, medullary cavity of the femur was rated as chimney type, ordinary type, and champagne flute type in 32, 18, and 6 hips of AS group, and in 4, 28, and 13 hips of control group respectively. Filling ratio of distal segment in AS group was significantly lower than that in control group ( t=5.64, P=0.02), but there was no significant difference in the filling ratio of middle and proximal segments between 2 groups ( t=0.29, P=0.61; t=0.55, P=0.13).
Conclusion: Compared with patients having osteonecrosis of the femeral head, there is no significant difference in preoperative AVA and ABA, but postoperative AVA significantly increase in patients with AS. Because AS patients have mainly chimney type medullary cavity of the femur, the filling ratio of middle and distal segment is lower when tapered stems are used, and the filling ratio of anatomic stems is higher.
目的: 通过测量初次行人工全髋关节置换术（total hip arthroplasty，THA）的强直性脊柱炎（ankylosing spondylitis，AS）患者手术前后骨盆、髋臼及股骨相关影像学参数，初步分析其影像学特征，以期为此类患者 THA 手术方法及假体选择提供参考。.
方法: 以 2015 年 1 月—7 月初次行 THA 且符合选择标准的 AS 患者 38 例（56 髋）作为研究对象（AS 组），并以同期接受 THA 的股骨头缺血性坏死患者 36 例（45 髋）作为对照（对照组）。两组患者病变侧别比较，差异无统计学意义（ χ2=1.14， P=0.95）。所有患者术前均行髋关节 CT 扫描及三维重建，测量髋臼外展角、前倾角、中心颈干角（center collum diaphyseal，CCD）、偏心距、旋转中心至小粗隆高度以及大、小粗隆间距；术前摄 X 线片测量两组股骨髓腔开大指数（canal flare index，CFI）、皮质指数（cortical thickness index，CTI），以及 AS 组骨盆入射角（pelvic incidence，PI）、骶骨倾斜角（sacral slope，SS）、骨盆倾斜角（pelvic tilt，PT）；术后摄 X 线片测量股骨假体髓腔填充率，并测量髋臼外展角、前倾角。.
结果: 两组术前髋臼前倾角以及手术前后髋臼外展角比较，差异均无统计学意义（ P>0.05）；术后髋臼前倾角比较，差异有统计学意义（ t=6.71， P=0.00）。AS 组患者 PI 为 41～58°，平均 48.37°；SS 为 2～11°，平均 5.64°；PT 为 5～26°，平均 12.85°。AS 组患者 CCD、CFI、CTI 与对照组比较，差异均有统计学意义（ t=3.63， P=0.04； t=5.12， P=0.02； t=3.91， P=0.04）；而偏心距、旋转中心至小粗隆高度以及大、小粗隆间距比较，差异无统计学意义（ t=0.41， P=0.36； t=0.33， P=0.56； t=0.59， P=0.12）。根据 Noble 等提出的分型标准，AS 组中股骨髓腔为烟囱型 32 髋、正常型 18 髋、倒立香槟型 6 髋，对照组分别为 4、28、13 髋。AS 组假体柄远端髓腔填充率显著低于对照组（ t=5.64， P=0.02）；两组近端及中段髓腔填充率比较，差异无统计学意义（ t=0.29， P=0.61； t=0.55， P=0.13）。.
结论: AS 患者术前髋臼外展角、前倾角与股骨头缺血性坏死患者相比无明显差异，但术后髋臼假体前倾角明显偏大。AS 患者股骨髓腔多为烟囱型，采用锥形柄假体置换后中、远端髓腔填充率偏小，解剖型假体填充率更高。.
Keywords: Ankylosing spondylitis; CT three-dimensional reconstruction; imaging features; total hip arthroplasty.