1、MRI Evaluation of Collapsed Femoral Heads in Patients 60 Years Old or Older: Differentiation of Subchondral Insufficiency Fracture From Osteonecrosis of the Femoral Head,2011.4.17From AJR:195, July 2010,Words,Subchondral Insufficiency Fracture：软骨下不全骨折 Osteonecrosis of the Femoral Head：股骨头坏死 Convex 凸
2、 ncavity 凹,软骨下不全骨折（Subchondral insufficiency fracture,简称SIFs）,1、软骨下机能不全性骨折是非外伤性的一种骨折。2、最常见的病因：骨质疏松，不常见的病因是骨质软化症或骨不全症、甲状旁腺功能亢进和类风湿性关节炎等。3、发病原理：正常软骨可忍受正常的生物机械应力，当由于上述病因变得软弱时，可出现软骨下骨折，并发展为软骨下萎陷，为此需认识此病作出早期诊断，多数患者经保守治疗后可自愈。,OBJECTIVE,The purpose of this article is to verify the hypothesis that osteonecr
3、osis and subchondral insufficiency fracture of the femoral head can be differentiated on the basis of their appearance on MRI.,SUBJECTS AND METHODS 1,Between May 1998 and February 2009, we reviewed 30 consecutive hips in 30 patients, 60 years old or older at the time of onset of hip pain, with radio
4、logic evidence of subchondral collapse of the femoral head and with both MR images and histologic results available.,SUBJECTS AND METHODS 2,The patients were divided into two group according to the shape of low-intensity bands on T1-weighted images. The first group showed concavity of the articular
5、surface, which is characteristic of osteonecrosis, and the second group showed an irregular convexity of the articular surface, which is characteristic of subchondral insufficiency fracture.,A In osteonecrosis, low-intensity band is smooth, concave to articular surface, and circumscribes all of necr
6、otic segments. B In subchondral insufficiency fracture, low-intensity band is irregular, convex to articular surface, and discontinuous.,RESULTS,Sixteen hips (53.3%) showed evidence of osteonecrosis, and 14 (46.7%) showed evidence of subchondral insufficiency fracture, which was consistent with the
7、corresponding histopathologic diagnoses. In all cases of osteonecrosis, the patient had a history of either corticosteroid intake or alcohol abuse. Among patients with subchondral insufficiency fracture, the proportion of women was significantly higher than that among patients with osteonecrosis. A
8、crescent sign (subchondral fracture) was present radiographically in about half of all cases in both groups.,TABLE 1: Clinical Characteristics of Patients With Osteonecrosis or Subchondral Insufficiency Fracture,CONCLUSION,The results of the present study suggest that the shape of the low-intensity
9、band on MRI is useful for the differentiating subchondral insufficiency fracture from osteonecrosis. In addition, among osteoporotic elderly women without any history of corticosteroid intake or alcohol abuse, a diagnosis of subchondral insufficiency fracture should be considered.,64-year-old man wi
10、th history of alcohol abuse and osteonecrosis.,A, Anteroposterior radiograph of left hip (Singh index of severity of osteoporosis, grade V) obtained at time of onset of pain shows both crescent sign and collapse of femoral head at superolateral portion (arrows).,B, Coronal T1-weighted image (TR/TE,
11、470/15) shows diffuse low signal intensity in femoral neck at lateral portion and intertrochanteric area. Low-intensity band on T1-weighted image is concave to articular surface (arrows).,“线样征”位于股骨头颈前上部病灶周围多呈空间锥形分布,锥尖指向股骨头基底部或股骨颈。 Glimcher认为修复开始后,肉芽组织自股骨颈或股骨头基底部向死骨区爬行。肉芽组织到达并吸收骨皮质时,皮质承载力减弱。在重力作用下自此皮
12、质薄弱区于松质骨内产生多条微骨折线,因应力作用微骨折线多位于股骨头前上部周围。肉芽组织在微骨折处大量增生堆积、吸收坏死骨小梁并于外围大量成骨,从而形成T2WI上的“双线症”。,D, Axial slice of T1-weighted image (500/15) shows that low-intensity band circumscribes all of necrotic segments (arrows).,E, Cut section of resected femoral head shows zonal pattern (necrotic, reparative, and v
13、iable zones). Subchondral fracture line (arrow) corresponding to crescent sign on radiograph (A) is seen.,新月征形成机制,因皮质断裂塌陷时,关节软骨在一段时间内尚保持完整,形成软骨下负压。股骨头体液内气体在负压作用下溢出并进入囊腔。,F, Histopathologic appearance of necrotic region, which shows accumulation of bone marrow cell debris, and bone trabeculae with em
14、pty lacunae beneath fracture line are seen. (H and E, 40),G, There is repair tissue in reparative zone, including vascular granulation tissue, fibrous tissue. (Hand E, 20),Fig. 375-year-old woman, without history of either corticosteroid intake or alcohol abuse, with subchondral insufficiency fractu
15、re.,Anteroposterior radiograph of left hip (Singh index of severity of osteoporosis, grade V) obtained at time of onset of pain shows both crescent sign and collapse of femoral head at superolateral portion (arrows).,The frequency of the crescent sign in the subchondral insufficiency fracture group
16、was similar to that in osteonecrosis group in the current study, thus indicating that the crescent sign is not sufficient to differentiate osteonecrosis from subchondral insufficiency fracture.,B, Coronal T1-weighted image (TR/TE, 470/25) shows diffuse low signal intensity in femoral head and neck.
17、Low-intensity band is parallel to subchondral bone endplate (arrows). The low-intensity band on T1-weighted images in subchondral insufficiency fracture corresponds histologically to the fracture line and associated fracture repair tissue . Therefore, the shape of the low-intensity band generally te
18、nds to be irregular, disconnected, and convex to the articular surface .,D, Axial slices of T1-weighted image (500/15) show low-intensity band mainly in anterior region, which is interrupted in middle (arrows).,E, Fat-saturated contrast-enhanced MRI (from image shown in D) (605/14) in which part of
19、proximal portion beyond low-intensity band shows contrast enhancement indicating perfusion (arrows).,F, Cut section of resected femoral head shows subchondral fracture line (black arrow) and whitish linear shaped area beneath articular cartilage (white arrow).,G, Band region histopathologically corr
20、esponds to fracture callus, reactive cartilage, and granulation tissue. (H and E, 40),Limititions,样本量小 对于软骨下不全骨折早期表现，如软骨下水肿，由于在平片上未见异常，未被纳入。 仅4例进行了增强MR检查。,真爱生命，拒绝酒精,统计学方法,Statistical analyses were performed using Fishers exact probability test with regard to sex, a history of corticosteroid intake o
21、r alcohol abuse, and the radiologic findings (i.e., demarcating sclerosis,crescent sign, and vertebral compression fracture). Age and BMI of groups A and B were compared using the unpaired Students t test the Singh index was compared using the Mann-Whitney U test. Statistical analyses were performed
22、 using StatViewJ-5.0 software (SAS Institute), and p values less than0.05 were considered to be statistically significant.,TABLE 2: Intra- and Interobserver Variability for Classification of Osteonecrosis or Subchondral Insufficiency Fracture according to Shape of Low-Intensity Band on T1-Weighted MR Images,kappa statistics.,
