Developmental dislocation of the hip in children: enhanced MRI in the observation of femoral blood supply

doi:10.3969/j.issn.2095-4344.2015.04.023

Abstract

Abstract:

BACKGROUND: The early diagnosis and treatment of the hip developmental dislocation in children have a great influence on the prognosis of the disease. Once the diagnosis is delayed, the difficulty of treatment and surgery failure rate will be increased. The imaging diagnosis is not only the indispensable accessory examination in the early diagnosis and treatment of the hip developmental dislocation, but also the research focus on this field.

OBJECTIVE: To introduce the etiology and pathogenesis of the hip developmental dislocation in children, and summarize the new research progress from the aspects of the imaging diagnosis.

METHODS: A computer-based retrieval was performed by the first author in the CNKI database and PubMed database to search papers on the hip developmental dislocation in children published between January 2004 and December 2014, using the key words of “developmental dysplasia of the hip, X-Ray, computed tomography, magnetic resonance, and ultrasound” in Chinese and English. According to inclusion and exclusion criteria, 51 papers were included in the final analysis.

RESULTS AND CONCLUSION: The etiology of the hip developmental dislocation includes genetic factor, endocrine factors, intrauterine factors, mechanical factors and so on. The common accessory examinations include ultrasound, X-Ray, computed tomography and magnetic resonance imaging. Because of easy operation and low costs, X-Ray becomes the common examination to screen the hip developmental dislocation. Computed tomography can observe the shape and the positional relationship between the femoral head and the acetabulum in three-dimension, but for infants and young children, the radiation is large and the operation is difficult. Because of the early detection of pathological changes in cartilage during hip dislocation, magnetic resonance imaging becomes an indispensable examination for the early diagnosis of developmental dysplasia of the hip. Especially the enhanced magnetic resonance imaging has significant contribution to observe the blood supply, and is regarded as the focus to evaluate the postoperative treatment effect of developmental dysplasia of the hip.

中国组织工程研究杂志出版内容重点：人工关节；骨植入物；脊柱；骨折；内固定；数字化骨科；组织工程

全文链接：

Key words: Tissue Engineering, Hip Joint, Acetabulum, Dysplasia

CLC Number:

R318

Ge Wei, Li Qi, Li Lian-yong, Pan Shi-nong. Developmental dislocation of the hip in children: enhanced MRI in the observation of femoral blood supply[J]. Chinese Journal of Tissue Engineering Research, 2015, 19(4): 623-628.

Figures/Tables 1

2.1 纳入资料基本概况符合纳入标准的51篇文献中，文献[1-11]探讨了小儿发育性髋脱位的病因、发病机制及临床表现，文献[12-51]探讨了小儿发育性髋脱位的影像学检查。 2.2 纳入资料的研究结果特征 2.2.1 发育性髋关节脱位发病率、发病机制及预防在所有新生儿当中，发育性髋关节脱位发病率高达0.1%-0.3%[3-4]，研究结果显示，80%发生于女孩，29%的成年人原发性髋关节置换与髋关节发育不良相关[5]。20%发生于双侧髋关节，80%发生于单侧，而且左侧髋关节更易受累。同胞兄弟姊妹中有髋关节发育不良者其发育性髋关节脱位发生率增加5%。导致发育性髋脱位的病因有很多，难以用单一的因素来解释，一般包括遗传因素、内分泌因素、宫内因素和机械因素等。一些遗传因素可以导致髋臼发育不良、髋关节过度松弛以及髋臼前倾程度的增加等，这些因素都可以引发髋脱位。同时，遗传因素引发的雌激素和松弛激素增多等内分泌因素容易造成韧带松弛，以至髋关节不稳定，提高了髋脱位的发病率，因此，女孩髋脱位的发病率是男孩的四五倍[6]，因为女孩对雌激素及松弛激素的敏感性高于男孩。导致发育性髋关节脱位的环境因素包括：臀位分娩、过期妊娠、羊水过少、初期胎儿宫内位置和多胎妊娠等宫内因素。研究显示臀先露自然分娩婴儿发育性髋关节脱位发病率增加17倍，臀位剖宫产婴儿发病率也增加7倍[7]。头臼同心是髋关节得以正常发育的必要前提，臀位分娩时产生异常的髋关节屈曲应力，容易导致股骨头与髋臼不同心，从而引发髋臼发育不良及发育性髋脱位。Leutekort等[8]发现47%臀位产的婴儿存在髋关节不稳定因素。除此之外，襁褓方式不当也可导致发育性髋关节脱位，Salter等[9]发现，在印第安的部落里把婴儿放在木板框架里并用皮带捆扎使髋关节保持伸直和内收的姿势，这导致髋脱位的发病率提高了10倍。此后，Price等[10]采用Salter的建议发明了特殊的襁褓方法，即让婴儿髋关节保持轻度屈曲及轻度外展的姿势，在一定程度上能够预防髋臼发育不良。 2.2.2 发育性髋关节脱位临床表现发育性髋关节脱位在新生儿和婴儿期多表现为髋关节活动障碍、患肢短缩，常呈屈曲状，臀部及大腿内侧皮肤皱褶不对称；幼儿期，单侧髋脱位患儿表现为跛行，患肢短缩、内收畸形。双侧髋脱位患儿行走时呈左右摇摆步态，这种步态被形象的称为“鸭步”，除此之外，患儿臀部明显后突，腰前凸增大[11]。针对新生儿和婴儿的发育性髋脱位，临床上常用的体格检查有Ortolani试验、Barlow试验、Allis征和套叠试验，因其在查体过程中需要患儿配合，如若哭闹不能检查，因此，具有一定限制，而对于能独自站立或行走的患儿，可通过外展试验、屈氏试验(Trendelenburg征)和Nelaton线等进行体格检查。在临床上，查体是诊断发育性髋脱位的基础，对于阳性患儿需进一步行影像学检查，明确病理形态，用以诊断及鉴别诊断，为治疗方案的选择提供重要参考价值。 2.2.3 发育性髋关节脱位影像学诊断影像学检查以其诊断速度快、准确率高的优点在临床疾病鉴别、诊断以及治疗中起着重要作用，目前发育性髋关节脱位的影像学检查手段多种多样，主要有超声、传统X射线检查、CT检查和MRI检查等[12-17]。各种影像方法因其自身特点或其它外界因素影响使其在实际临床应用中表现出各自的优势与特色。超声检查：髋关节超声检查对于出生到四五个月患儿尤为重要，此时髋关节呈软骨质样。Graf法技术基于髋臼冠状面对髋关节形态进行评估。虽然超声无法动态评价髋关节是否稳定，但是能够评价髋关节不稳所导致的不同病理程度[18-19]。目前，超声检查更常用于髋关节形态及稳定性修复治疗疗效评估[20-21]。从形态学上来说，在新生儿期，正常髋关节存在发育不良的风险，尽管未成熟的髋关节存在脱位可能，但97%的病例没有经过治疗也能够正常发育[22]。关于轻度发育不良自然过程的报道较少，但两个前瞻性研究结果表明这种髋关节倾向于向正常方向发展[23]。对于髋臼形态和深度的测量用以评估股骨头被骨性髋臼缘覆盖率，股骨头位于中心时，覆盖率男孩< 47%、女孩< 44% 为异常，见于1%-6%的新生儿[22]。当同时存在髋关节不稳和发育不良时，该覆盖率将发生变化，使测量不准确。值得注意的是，如果没有测量误差，那么临床表现与超声报告应该相一致。超声和临床检查互相制约、互相依赖。传统X射线检查：髋关节的X射线检查有助于综合评价髋关节发育不良，监测髋关节发育程度，指导治疗并评价发育性髋脱位的治疗效果[24]，且由于该方法操作简单、快速且价格便宜，目前临床上主要应用该影像学方法进行发育性髋关节脱位的诊断[25]。检查方法通常投照两次，一次为仰卧位双髋内旋15°摄骨盆前后位，一次为摄髋关节蛙式位。 X射线检查常用测量指标如下：①髋臼指数(AI)：骨盆前后位像上，通过双侧髋臼“Y”形软骨顶点绘制一条直线(即H线)并向两边延长，再经“Y”形软骨顶点及骨性髋臼顶部外上缘最突出的点绘制另一条直线，两线夹角即为髋臼指数或髋臼角。正常值为20°-25°，新生儿期髋臼角通常<30°，小儿独立行走以后该角逐渐减小，12岁时基本恒定约15°，超过正常值则提示髋臼发育不良。②Sharp角：经双侧泪滴下缘绘制连线，再经泪滴外缘与髋臼上缘绘制连线，两线夹角即为Sharp角。通常成年女性Sharp角比男性要大，小儿当“Y”形软骨闭合后髋臼指数已无法测量，此时可以进行Sharp角的测量，该角男性女性间无显著差异，通常介于42°-50°之间，故Sharp角> 50°时提示异常。③Perkins方格：沿双侧髋臼上缘分别做H线的2条垂线，构成由4个象限组成的Perkins方格，正常时股骨头骨骺位于Perkins方格内下象限，超出时提示髋关节脱位(位于Perkins方格外下象限提示髋关节半脱位，位于Perkins方格外上象限提示髋关节全脱位)。3周岁以下的儿童应用此方法测量有参考意义。④沈通氏线(Shenton线)：该线为一条沿闭孔上缘、股骨颈内缘及股骨近端内缘光滑弧线，该线大于5 mm的中断则提示髋关节发育不良伴股骨头半脱位或脱位。⑤中心边缘角(CE角)：第1条线经股骨头中心垂直于H线，第2条线为股骨头中心点与髋臼外缘连线，两线夹角称为CE角，CE角> 25°为正常，< 20°提示存在有髋臼发育不良或髋脱位。CE角越小，表示髋臼发育不良或脱位越严重。正常值上限虽然没有明确的定义，然而，CE角> 40°则提示髋臼过深，可能有钳夹撞击的风险。⑥ACM角：经髋臼上下缘连线中点向髋臼中心做垂线，连接髋臼上下缘至中心点，形成髋臼上下缘中点垂线间的夹角，正常范围为40°-50°，ACM角不存在性别差异，如< 40°则提示异常。⑦臼头指数(acetabular head index，AHI)：股骨头内缘到髋臼外缘距离(A)与股骨头最大横径(B)间百分比，即AHI=A/B×100%，正常范围为84%-85%，用以检查髋臼对股骨头覆盖情况。⑧上方间隙：股骨上端距H线的距离，正常值为9.5 mm；内侧间隙：股骨上端距坐骨支外缘距离，正常值为4.3 mm。若上方间隙< 8.5 mm，内侧间隙> 5.1 mm，高度怀疑髋关节发育不良；若上方间隙< 7.5 mm，内侧间隙> 6.1 mm，能够确定髋关节发育不良。⑨后壁征[9](posterior wall sign)：骨盆前后位像上，髋臼后壁边缘正常情况下位于股骨头中心的外侧，若位于内侧则为后壁征阳性，提示髋臼后壁覆盖面范围不足，可能引起髋臼后倾或髋臼发育不良[14]。⑩α角：在蛙式位X射线片上，经股骨头中心做股骨颈轴线，再经股骨头中心向头颈连接处中点绘制直线，两线夹角即为α角，α角< 50°为正常，α角> 50°，提示可能存在髋关节撞击综合征。 CT检测：CT扫描同X射线摄影相比，通过多平面重建提供更全面的影像信息，准确观察正常和发育不良的髋臼及股骨头解剖情况，在术前评估以及术后评价上均有突出优点。髋关节的CT测量指标如下：①扇形角(sector angle)：由Anda等[26]首先提出，将髋臼在CT上分为前后两部分。前扇形角(AASA)：CT横断面上，经股骨头中心点到髋臼前缘绘制一条直线，该线与双侧股骨头中心点连线的夹角为AASA；后扇形角(PASA): CT横断面上，经股骨头中心点到髋臼后缘绘制一条直线，该线与双侧股骨头中心点连线的夹角为PASA。前后扇形角可以用来衡量髋臼对股骨头的覆盖率。②股骨颈前倾角：1954年由Billing首先提出，该角由股骨长轴和股骨髁间连线所确定的髁平面与股骨干长轴和股骨颈轴线所确定的前倾平面间夹角构成。前倾角在CT上有多种测量方法[27-28]，包括Weiner法，Reikeras法及Murphy法等。股骨颈前倾角增大是发育性髋脱位的一个重要病理特征，其测量对发育性髋脱位的诊断及治疗具有至关重要的指导价值。③三维CT股骨颈前倾角：在骨盆三维CT后处理图像中，将骨盆前正面观图像向后方旋转，至两侧髂前上棘与两耻骨联合达同一水平，髋臼外缘连线与耻骨联合前缘连线的垂线之间的夹角为该股骨颈前倾角。三维CT作为一个功能强大的工具评估骨性解剖，在髋臼重建治疗及行髋关节成形术时，对于评估正常和发育不良骨盆形态的差异至关重要。CT扫描的局限性在于从仰卧到站立位骨盆斜度将发生改变，但目前的CT成像只能进行仰卧位扫描，骨盆倾斜角度与患者扫描时的位置相关，它影响着髋臼倾斜角的测量[29]。三维CT重建需要正确的体位和准确的后处理重建技术，通常不作为常规CT成像[30-31]。除此以外，髋臼发育不良的CT成像广泛应用受限主要来自较高的辐射剂量，特别是对儿童患者而言，其中女性患者辐射相关癌症罹患的风险最高[32]。 2.2.4 MRI检测近年来，随着MRI技术的出现，部分学者将其应用于发育性髋关节脱位的诊断，获得良好的效果[17]。MRI能显示X射线、CT不能显示的软骨成分，对于软骨、盂唇、滑膜和软组织等结构均能提供详细信息，同时不受骨化的限制，可清晰显示未骨化的股骨头，通过多平面扫描能够直观的对股骨头位置进行三维评价[33-37]。Fisher等[36]利用MRI获得软骨清晰图像，首先提出了MRI骨性髋臼指数与软骨性髋臼指数的概念。采用髋关节冠状位、轴位MRI检查能够清楚观察到髋臼顶壁、髋臼前壁、髋臼后壁的病理形态等变化。髋关节的MRI测量指标包括：①冠状位骨性髋臼指数(BAI)、软骨性髋臼指数(CAI)：冠状位MR T1加权成像中，经“Y”形软骨中点至骨性髋臼上缘绘制一条直线，该线与H线夹角即为骨性髋臼指数；经“Y”形软骨中点至软骨性髋臼上缘绘制一条直线，该线与H线夹角即为软骨性髋臼指数；二者表示髋臼顶壁的指数。②轴位骨性、软骨性前后髋臼指数：在经健侧股骨头中心的MRI 轴位图像上分别测量双髋的骨性、软骨性前后髋臼指数。骨性、软骨性前髋臼指数(ABAI、ACAI)：前者为骨性髋臼前壁外缘至“Y”形软骨中点连线与H线的夹角，后者为软骨性髋臼前壁外缘至“Y”形软骨中点连线与H线的夹角。骨性、软骨性后髋臼指数(PBAI、PCAI)：前者为骨性髋臼后壁外缘至“Y”形软骨中点连线与H线夹角，后者为软骨髋臼后壁外缘至“Y”形软骨中点连线与H线的夹角。③冠状面骨性臼头指数(BCAHI)、软骨性臼头指数(CCAHI)：在磁共振冠状面T1加权成像上，在股骨头软骨性内缘上做一切线，从髋臼骨性外缘做该线的垂线，再从股骨头骨性外缘向该线做垂线，两线之比为BCAHI；再从股骨头软骨性内缘上做一切线，从髋臼软骨性外缘做该线的垂线，再从股骨头软骨性外缘向该线做垂线，两线之比为BCAHI。④矢状位骨性臼头指数(BSAHI)、软骨性臼头指数(CSAHI)：在磁共振矢状面T1加权成像上，从股骨头软骨性后缘画一切线，从髋臼及股骨头骨性前缘各向该线做一垂线，两线之比为BSAHI；从股骨头软骨性后缘画一切线，从髋臼及股骨头软骨性前缘各向该线做一垂线，两线之比为CSAHI。⑤骨性髋臼商(BAQ)、软骨性髋臼商(CAQ)：在MRI冠状位T1加权图像上，骨性髋臼深度与骨性髋臼顶上缘至骨性髋臼顶下缘距离之比为骨性髋臼商；软骨性髋臼深度与软骨性髋臼顶上缘至软骨性髋臼顶下缘距离之比为软骨性髋臼商。 MRI增强检查已广泛应用于临床研究，对小儿发育性髋关节脱位的鉴别诊断具有重要意义。软骨延迟增强MRI显像(delayed gadolinium enhanced MRI of cartilage，dGEMRIC)技术可用于评价髋关节软骨发育及受损情况，发育性髋关节脱位的患儿因其髋关节发育存在异常，故患处及相邻区域的生长代谢受到不同程度的影响，利用高浓度负电荷糖胺聚糖(GAG)分子，该分子是构成软骨黏蛋白的组成部分。静脉注射对比剂后 30 min的MRI延迟成像能够使对比剂渗透到关节软骨后方，利用这一方法可以在T1增强图像上定量测量GAG含量以进行间接关节造影[38-40]。与常规MRI相比，dGEMRIC指数对于髋臼周围截骨等治疗疗效及预后评估能够提供重要指标[41-43]，该方法主要缺点是钆注射相关风险，在肾功能不全患儿中慎用。同时，增强MRI可以用于对股骨头血流灌注的观察[44-51]，有利于诊断发育性髋关节脱位治疗后股骨头坏死，也可应用于髋关节不同固定体位的股骨头血运变化。"

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