臀肌挛缩症的一种新X线征象--髂骨致密线

目的：明确髂骨致密线与臀肌挛缩症之间的关系，探讨髂骨致密线的形成机制。方法：分析103例臀肌挛缩症的骨盆平片及其中8例骨盆CT片，并与200例非臀肌挛缩症的骨盆平片及其中13例骨盆CT作对照。结果：臀肌挛缩组85例（82．5％）骨盆平片见骶髂关节旁髂骨致密线，对照组仅见5例（2．5％）。103例臀肌挛缩症中，髂骨致密线出现于5岁以上组和5岁以下组分别为81例（81／88）和4例（4／15）；出现于臀大肌挛缩为主组和臀中肌挛缩为主组分别为83例（83／94）和2例（2／9）。CT扫描示正常骨盆的髂骨骶髂关节部外缘皮质呈后内向前外走行的斜面，而在臀肌挛缩症患者，髂骨后部增厚、变形，外缘皮质斜面变小，近乎前后走行。结论：骨盆平片上髂关节旁髂骨致密线是臀肌挛缩症的1种征象；这一征象是由于挛缩的臀大肌长期、持续的牵拉作用，导致本呈后内向前外斜行的髂骨骶髂关节部外缘皮质变为前后走行使其形成轴位投影所致。

Iliac hyperdense line: a new X-ray sign of gluteal muscle contracture

Objective To elucidate the relationship between gluteal muscle contracture(GMC) and the iliac hyperdense line on pelvic plain film, and to explore how the iliac hyperdense line is formed. Methods The pelvic plain films of 103 cases with GMC confirmed by operation and those of 200 individuals as control were analyzed. Pelvic CT scanning was performed in 8 cases of GMC and 13 cases of normal controls. Results The iliac hyperdense line at the side of sacroiliac joint was found on the pelvic plain film in 85 of 103 cases with GMC and 5 of 200 in control group. In 103 cases of GMC, the iliac hyperdense line was detected in 81 of 88 patients beyond 5 years, and 83 of 94 was mostly the gluteus maximus contracture. In control group, pelvic CT showed that the outer cortex of posterior ilium at the level of sacroiliac joint appeared as an oblique plane, oriented from posteromedial side to anterolateral side, while in GMC group, the oblique plane became steeper and almost oriented posteroanteriorly. In addition, the posterior part of the ilium which gave the attachment of contracted gluteus maximus muscle deformed and widened. Conclusion The iliac hyperdense line on the pelvic plain film is resulted from the long and persistent pulling effect of contracted gluteus maximus muscle, which causes the change the oblique plane of posterior ilium into a posteroanterior course parallel to the X ray beam.