山西省兒童醫(yī)院

別名: 山西省婦幼保健院
公立三甲兒童醫(yī)院

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臨界髖關節(jié)發(fā)育不良Borderline DDH (2)：疼痛性臨界髖關節(jié)發(fā)育不良的治療臨界髖關節(jié)發(fā)育不良BorderlineDDH(2)：疼痛性臨界髖關節(jié)發(fā)育不良的治療作者：MichaelCWyatt,MartinBeck.作者單位:KlinikfürOrthop?dieundUnfallchirurgieLuzernerKantonsspital6004Luzern,Switzerland.譯者：陶可（北京大學人民醫(yī)院骨關節(jié)科）摘要在過去的幾十年里，影像技術的改進和手術技術的進步使得保髖手術得到了快速發(fā)展。然而，疼痛性臨界髖關節(jié)發(fā)育不良的治療仍然存在爭議。在這篇評論中，我們將確定相關問題并描述患者評估和治療方案。我們將提供自己的建議，并確定未來的研究領域。簡介在過去的幾十年里，髖關節(jié)生物力學知識的提高和手術技術的進步使得保髖手術得到了快速發(fā)展。保髖手術適應范圍廣泛，從髖臼淺且不穩(wěn)定的髖關節(jié)到髖臼深且患有股骨髖臼撞擊(FAI)的髖關節(jié)。雖然人們普遍認為，不穩(wěn)定髖關節(jié)發(fā)育不良的最佳治療方法是重新定位髖臼以增加覆蓋范圍，但人們同樣認為，必須減小過度覆蓋的髖臼臨界以消除撞擊。所有這些髖關節(jié)都可能存在凸輪畸形，需要在手術矯正時加以解決[1]。在最極端的情況下，所需的治療是顯而易見的。然而，有一個過渡區(qū)，很難區(qū)分不穩(wěn)定性和股骨髖臼撞擊(FAI)。過去，這些髖關節(jié)被稱為“臨界”髖關節(jié)。通常，這包括外側中心臨界(LCE)角度在20°到25°之間的髖關節(jié)[2]。然而，“臨界”一詞是有問題的，因為它是一個放射學定義，只涉及描述髖關節(jié)穩(wěn)定性的幾個重要參數(shù)之一。髖臼頂傾斜角、前后覆蓋和股骨前傾是應納入髖關節(jié)穩(wěn)定性分析的其他因素。髖關節(jié)發(fā)育不良與髖關節(jié)骨關節(jié)炎之間的關聯(lián)已經(jīng)確定[3,4]，有不穩(wěn)定跡象的髖關節(jié)發(fā)育不良退化速度更快[5]。臨界髖關節(jié)可能不穩(wěn)定、撞擊或兩者兼而有之。臨界髖關節(jié)發(fā)育不良的穩(wěn)定性很難確定，并且容易受個人主觀影響，骨科界普遍傾向于低估不穩(wěn)定性，從而導致不適當?shù)闹委?。最近的研究表明，對患有臨界發(fā)育不良(LCEA?>?20°)的患者進行關節(jié)鏡髖關節(jié)手術（包括盂唇修復和關節(jié)囊折疊縫合術）可能會在短期內帶來適當?shù)母纳芠3,4]。然而，有證據(jù)表明，之前錯誤的髖關節(jié)鏡檢查會對此類髖關節(jié)的治療結果產(chǎn)生負面影響[6]。因此，疼痛性臨界髖關節(jié)發(fā)育不良的治療仍然是一個極具爭議的問題。臨界性髖關節(jié)發(fā)育不良在患有髖關節(jié)疼痛的年輕人中很常見，在選定的患者群中報告的患病率為37.6%[7]。在臨界髖關節(jié)發(fā)育不良中，可能與其他不穩(wěn)定原因（如韌帶松弛癥）有顯著重疊[8]。然而，根本問題是難以正確分類潛在的病理生物力學。定義第一個問題在于定義。在前后位骨盆X線片[9](LCEA)上測量的Wiberg外側中心邊緣角傳統(tǒng)上用于將髖關節(jié)分類為正常(LCEA?>25°)、發(fā)育不良(LCEA?<20°)或臨界(LCEA20–25°)，盡管這些定義值在文獻中差異很大[3,10]。然而，使用外側中心邊緣角(LCEA)存在兩個問題。首先是測量方法。為了測量外側中心邊緣角(LCEA)，首先通過與股骨頭輪廓相符的圓來定義股骨頭的中心。角度的第一個分支垂直穿過旋轉中心。第二個分支由股骨頭的中心和股骨最外側點定義（圖1a）。重要的是不要使用髖臼的最外側點（圖1b），因為這不符合Wiberg的定義，并且會給出錯誤的高值(外側中心邊緣角(LCEA)偏大)[11]。Fig.1.(a)CorrectmeasurementoftheLCEAusingtheedgeofthesourcil,indicatingmoderatedysplasia.(b)IncorrectmeasurementoftheLCEAinthesamehip.Usingthisvaluewouldfalselyclassifythishipasborderline.圖1(a)使用髖臼臨界正確測量外側中心邊緣角(LCEA)，表明中度髖關節(jié)發(fā)育不良。(b)同一髖關節(jié)的外側中心邊緣角(LCEA)測量不正確。使用此值會錯誤地將此髖關節(jié)歸類為臨界。其次，實際術語“臨界髖關節(jié)發(fā)育不良”是由Wiberg本人首次提出的，包括外側中心邊緣角(LCEA)在20°和25°之間的髖關節(jié)[2]。外側中心邊緣角(LCEA)是一種放射學測量，本身無法預測臨界髖關節(jié)發(fā)育不良的穩(wěn)定性，也無法完全描述股骨頭覆蓋范圍。因此，外側中心邊緣角(LCEA)無法指導手術決策[12–14]。部分原因是外側中心邊緣角(LCEA)本身無法涵蓋發(fā)育不良的精確位置，并且忽略了前后股骨頭覆蓋范圍。此外，髖臼指數(shù)(AI)和股骨前傾等其他參數(shù)也與髖關節(jié)穩(wěn)定性密切相關。如果外側中心邊緣角(LCEA)減少，AI可能正常，在這種情況下很難評估髖關節(jié)的穩(wěn)定性[15]。另一方面，股骨前傾過度可能會加劇髖關節(jié)前部不穩(wěn)定[16]。根本問題是什么？對于疼痛的臨界髖關節(jié)發(fā)育不良，很難僅通過二維射線測量將病理機制表征為撞擊（穩(wěn)定）或發(fā)育不良（不穩(wěn)定），尤其是僅由髖臼功能決定而不考慮股骨的測量。髖關節(jié)穩(wěn)定性的功能表征對于指導手術決策至關重要。不穩(wěn)定髖關節(jié)從邏輯上可以從髖臼重新定向截骨術中受益，而穩(wěn)定髖關節(jié)可以從撞擊手術（如股骨凸輪骨成形術）中受益。那么關于髖關節(jié)內病理學的了解有多少？應該如何評估這些患者？有哪些治療方案？手術結果如何？這組患者的潛在隱患是什么？未來的發(fā)展方向是什么？在這篇敘述性綜述文章中，我們旨在解決這些問題，并闡明這組具有挑戰(zhàn)性的患者的處理方法。髖關節(jié)發(fā)育不良和臨界髖關節(jié)不穩(wěn)定的潛在病理是什么？髖關節(jié)發(fā)育不良患者的關節(jié)接觸壓力異常增高，股骨頭（軟骨損傷，導致軟骨下）骨質相對暴露。髖臼通常較淺且前傾，盂唇經(jīng)常有代償性增大，但同時伴有髖臼后傾的情況也很高[17]。股骨通常呈外翻，前傾度高[10]。這些異常的解剖特征會導致病理性髖關節(jié)生物力學，表現(xiàn)為盂唇撕裂、軟骨損傷和髖關節(jié)不穩(wěn)定，這些很容易被誤解為撞擊。由于骨穩(wěn)定性受損，軟組織穩(wěn)定器（即纖維軟骨盂唇和髖關節(jié)囊）的重要性就凸顯出來[18]。一旦軟組織約束失效，髖關節(jié)就會變得不穩(wěn)定。然而，我們必須明白，主要的潛在病理是缺乏骨性穩(wěn)定性，這會導致髖關節(jié)失效，而不是軟組織穩(wěn)定性失效。半脫位髖關節(jié)發(fā)育不良的自然病史預后非常差，并且必然會導致關節(jié)退化[5]。惡化速度與半脫位嚴重程度和患者年齡直接相關，通常在癥狀出現(xiàn)后約10年，就會出現(xiàn)嚴重的退行性變化[19]。在沒有半脫位的情況下，自然病史很難預測退化速度。臨界髖關節(jié)發(fā)育不良也是如此。最近的一項研究強調了髖臼覆蓋的重要性。在一項為期20年的大型女性隊列研究中，研究顯示，如果外側中心邊緣角(LCE)低于28°，則每降低一度，放射學OA風險就會增加13%[20]。因此，除了短期緩解癥狀外，還必須考慮長期可能的發(fā)展。臨床表現(xiàn)臨界髖關節(jié)發(fā)育不良的臨床表現(xiàn)與其他年輕活躍成人髖關節(jié)疾病（如FAI綜合征[21]）非常相似，因此，徹底的病史、體格檢查和放射學評估對于正確診斷這些患者至關重要。病史重點記錄病史。臨界髖關節(jié)發(fā)育不良患者的主要癥狀是疼痛。這通常發(fā)生在腹股溝和髖關節(jié)外側，但也可能發(fā)生在臀部(臀后區(qū))。有必要記錄完整的疼痛病史。尋找特定的不穩(wěn)定和“避免疼痛”癥狀，這可能表明已經(jīng)達到因缺乏骨性穩(wěn)定性而需要的軟組織代償?shù)臉O限。咔嗒聲和卡住的癥狀也很常見。此外，還會詢問患者是否有任何跡象表明患者已經(jīng)患上髖關節(jié)炎，例如夜間疼痛。癥狀應結合患者的功能限制和已經(jīng)接受的醫(yī)療護理，包括物理治療、藥物、其他意見和手術。檢查隨后應進行髖關節(jié)的合理臨床檢查，包括恐懼試驗和撞擊測試。患者通常會表現(xiàn)出“膝內翻”步態(tài)，同時伴有髖關節(jié)內收肌力矩增加和髖關節(jié)內旋增加，這與股骨前傾增加一致。為了功能性地增加前覆蓋，可能存在前凸過度。應確定大轉子處有無壓痛[22]。務必記住檢查患者的旋轉輪廓、進行神經(jīng)血管檢查以及檢查全身關節(jié)松弛的跡象，并使用Beighton評分對此進行量化。具體關鍵目標包括排除(i)晚期退化過程的存在，例如表現(xiàn)為固定屈曲畸形和運動范圍減少，以及(ii)其他病理，例如腰椎病或L5神經(jīng)根病引起的疼痛。調查診斷成像應從骨盆的標準化AP平片和股骨頸側位片（穿桌側位、Dunn位、假斜位）[23]開始。仔細檢查這些圖像以測量LCEA、AI、擠壓指數(shù)、股骨頸干角和FEAR指數(shù)（見下文）。應確定骨關節(jié)炎的Tonnis等級以及是否存在凸輪形態(tài)。應仔細檢查不穩(wěn)定的直接跡象，這些跡象包括股骨頭移位，可通過與髂坐線的距離增加、Shenton線斷裂和AP視圖上股骨頭重新定位來識別，髖關節(jié)處于外展狀態(tài)，使用MR關節(jié)造影時后關節(jié)間隙中有釓，這表明股骨頭向前移位，因此不穩(wěn)定。FEAR指數(shù)與不穩(wěn)定性有很高的相關性（見下文）。必須精確測量和記錄各種參數(shù)。有必要使用三維計算機斷層掃描(CT)進行橫斷面成像，以獲得有關骨解剖結構和發(fā)育不良位置的精確信息，包括髖關節(jié)周圍囊腫的存在和位置[24-26]。此外，CT還應包括股骨前傾的評估，如果前傾過大，可能會加劇髖關節(jié)前部不穩(wěn)定。磁共振成像(MR-關節(jié)造影)應遵循專門的髖關節(jié)檢查方案，包括徑向圖像采集或重建和關節(jié)內造影劑應用[27]，以檢查關節(jié)內結構和盂唇和關節(jié)軟骨的病理?？梢詤^(qū)分引起類似癥狀的其他原因，例如缺血性壞死、轉子滑囊炎或臀肌病變。其他測量包括盂唇大小[13,28]和髂關節(jié)囊體積[29]。對于這些患者，我們還提倡進行非牽引性MR關節(jié)造影檢查，以檢查是否存在釓積聚，即所謂的“新月征”，這是軸向視圖上不穩(wěn)定的細微征兆[30]。這些測量值的價值是什么？在平片上，那些直接表明不穩(wěn)定的測量值是股骨頭移位，與髂坐線的距離增加，Shenton線斷裂，髖關節(jié)外展時AP視圖上股骨頭重新定位，以及FEAR指數(shù)。在MR關節(jié)造影中，后下關節(jié)間隙中釓的存在表明股骨頭移位，因此不穩(wěn)定。AI、NSA、AT、高髂囊體積和盂唇體積可能存在增加，但不能預測不穩(wěn)定性[30]（表1）。表1.用于評估髖關節(jié)不穩(wěn)定性的各種參數(shù)概述TheFemoro-EpiphysealAcetabularRoof(FEAR)index:股骨骨骺髖臼頂指數(shù)Thefemoralneck-shaftangle(NSA):頸干角FEAR指數(shù)是最近描述的參數(shù)，似乎對預測髖關節(jié)穩(wěn)定性具有很高的價值[27]。它是由髖臼頂與股骨生長板中央1/3處之間的角度形成的（圖2）。其依據(jù)是：在生長過程中，股骨的骨骺生長板會垂直于髖關節(jié)的關節(jié)反作用力。股骨頸的生長和方向受股骨頸下生長板的控制[31]。Pauwels和Maquet[32]提出理論，合力作用于骨骺軟骨的中心，在生長過程中，根據(jù)Heuter-Volkman原理，骨骺板會垂直于關節(jié)反作用力。Pauwels和Maquet的理論后來得到了Carter等人[33]的證實，他們通過二維有限元分析研究了髖關節(jié)負荷的影響。閉合的骨骺板的角度表示跨股骨近端骨骺[34]的力的平衡，也表示跨關節(jié)力在過去的作用方式。因此，它是一個功能參數(shù)，反映了髖關節(jié)在生長過程中長期的關節(jié)反作用力。如果FEAR<0°，則認為髖關節(jié)穩(wěn)定。統(tǒng)計分析表明，5°的臨界值預測穩(wěn)定性的概率為80°。最近的研究表明，2°的臨界值預測穩(wěn)定性的概率為90%（Batailler等人，正在準備發(fā)表中）。使用FEAR指數(shù)的案例如圖3a和b所示。Fig.2.TheFEARindex.Theangleismeasuredbetweenalineconnectingthemostmedialandlateralpointofthesourcilandalineconnectingthemedialandlateralendofthestraightpart(usuallycentralthird)ofthephysealscarofthefemoralhead.AnegativeFEARindex,withtheangleopeningmediallyasshowninFig.3a,indicatesastablehip.圖2.?FEAR指數(shù)。測量連接股骨最內側和外側點的線與連接股骨頭骨骺直線部分（通常為中央三分之一）內側和外側端的線之間的角度。如圖3a所示，角度向內側打開的陰性FEAR指數(shù)，表示髖關節(jié)穩(wěn)定。Fig.3.(a)CaseexamplesusingtheFEARindex.17-year-oldmale,LCEA20°,FEAR0°.Hipdeemedthereforestableandpatientmanagedwithhiparthroscopy.(b)CaseexamplesusingtheFEARindex.17-year-oldfemale,LCEA20°,FEAR8°.HipdeemedthereforeunstableandpatientmanagedwithPAO.圖3.(a)使用FEAR指數(shù)的病例。17歲男性，LCEA20°，F(xiàn)EAR0°。因此髖關節(jié)穩(wěn)定，患者接受髖關節(jié)鏡治療。(b)使用FEAR指數(shù)的病例。17歲女性，LCEA20°，F(xiàn)EAR8°。因此髖關節(jié)不穩(wěn)定，患者接受PAO截骨治療。有哪些治療方案？治療取決于髖關節(jié)的穩(wěn)定性。疼痛性臨界髖關節(jié)發(fā)育不良的治療方案包括非手術治療、解決關節(jié)內撞擊的手術治療（通過髖關節(jié)鏡或髖關節(jié)外科脫位進行的FAI手術）和解決不穩(wěn)定性的手術治療（采用PAO和/或股骨截骨術的重新定位截骨術）（見圖2）。非手術治療包括患者教育、活動調整、簡單的止痛藥、非甾體抗炎藥和髖關節(jié)腔內注射藥物[35]。有針對性的物理治療可以改善肌肉調節(jié)、疼痛和本體感受控制。以下段落將討論包括關節(jié)鏡和/或截骨術的臨界髖關節(jié)發(fā)育不良的手術治療方案。這組患者接受髖關節(jié)鏡檢查的結果如何？隨著髖關節(jié)鏡技術的最新發(fā)展，許多外科醫(yī)生正在使用它來治療臨界髖關節(jié)發(fā)育不良，尤其是因為人們認為髖臼周圍截骨術等替代技術的風險更高，術后恢復時間更長。臨界髖關節(jié)發(fā)育不良的髖關節(jié)鏡檢查還可以讓外科醫(yī)生處理髖關節(jié)內病變，如盂唇撕裂或股骨凸輪畸形[3,12,36]。如果考慮使用PAO來解決骨穩(wěn)定性不足的問題，那么關節(jié)鏡檢查不僅可以讓外科醫(yī)生了解髖關節(jié)的關節(jié)內狀態(tài)，還可以了解患者在隨后進行更大規(guī)模手術時的表現(xiàn)[37]。然而，關于臨界髖關節(jié)發(fā)育不良的髖關節(jié)鏡檢查的已發(fā)表文獻很少，而且短期隨訪也存在局限性。在Jo等的系統(tǒng)綜述中，確定了13項關于髖關節(jié)發(fā)育不良的關節(jié)鏡檢查的研究[10]。這些研究各不相同，所有研究都是病例系列。僅有6項研究報告了主觀和/或客觀結果。關節(jié)鏡檢查的手術指征不明確，患者事先接受過多種非手術治療。此外，臨界髖關節(jié)發(fā)育不良的確切定義各不相同，只有兩項研究使用了Byrd和Jones的定義[36]。三項研究報告了髖關節(jié)鏡作為輔助工具，三項研究報告了髖關節(jié)鏡作為獨立治療。盂唇撕裂的總患病率為77.3%，主要位于髖臼緣的前部或前上部。髖臼軟骨病變比股骨病變更常見（59-75.2%比11-32%），并且位于盂唇病變的鄰近。僅有兩項研究檢查了臨界髖關節(jié)發(fā)育不良病例（LCEA20-25°）的關節(jié)鏡檢查結果，其中只有一項描述了患者報告的結果測量。后者是Byrd和Jones[36]的前瞻性臨床病例系列，其中66%的髖關節(jié)（32髖）患有臨界髖關節(jié)發(fā)育不良。關節(jié)鏡檢查后，平均改良Harris髖關節(jié)評分從50（差）改善到77（一般）。作者得出結論，髖關節(jié)鏡治療可能解決髖關節(jié)內病理而不是發(fā)育不良的放射學證據(jù)的結果。對臨界髖關節(jié)發(fā)育不良進行髖關節(jié)鏡檢查有什么危險？臨界髖關節(jié)發(fā)育不良患者進行關節(jié)鏡盂唇切除術和髖臼外側緣切除術可導致爆發(fā)性髖關節(jié)不穩(wěn)定[38]。即使修復了盂唇，也必須保留髂股韌帶和髖關節(jié)的其他靜態(tài)穩(wěn)定器，以防止不可逆的后果或導致髖關節(jié)不穩(wěn)定[39–41]。沒有確鑿的文獻支持在這些情況下進行關節(jié)囊修復，但這似乎是一種安全合理的做法[42]。關節(jié)囊復位技術可提高臨界髖關節(jié)發(fā)育不良的穩(wěn)定性[12]。如果髖關節(jié)在術前足夠不穩(wěn)定，那么僅通過髖關節(jié)鏡治療關節(jié)內病變是不夠的，患者將需要進行PAO截骨術[43,44]。必須記住，髖關節(jié)的穩(wěn)定性首先取決于髖骨幾何形狀。在輕微不穩(wěn)定（臨界發(fā)育不良）中，穩(wěn)定性可能由次級軟組織結構來確保。一旦這些結構因微創(chuàng)傷或大創(chuàng)傷而失效，髖關節(jié)就會變得不穩(wěn)定。恢復軟組織穩(wěn)定性可能只會在短時間內改善髖關節(jié)穩(wěn)定性，但軟組織很可能再次磨損。因此，必須首先解決潛在的骨病理問題，才能取得良好的長期效果。最近的一份報告顯示，髖關節(jié)發(fā)育不良患者在髖關節(jié)鏡檢查失敗后，PAO的髖關節(jié)特定功能結果較差[6]。因此，對這組患者單獨進行髖關節(jié)鏡檢查應謹慎處理。但是，對于那些由于髖關節(jié)狀況不佳（即AI和股骨前傾正常）或高齡（即>40歲）而不適合進行PAO的患者，它可能有用。重新定向髖臼周圍截骨術對這組患者有何影響？通過髖臼周圍截骨術進行髖臼重新定向已成為髖關節(jié)發(fā)育不良最常見的治療方法，據(jù)報道術后20多年效果良好。傳統(tǒng)上，PAO時關節(jié)內病變的處理方法是進行前關節(jié)切開術。然而，隨著PAO微創(chuàng)技術的發(fā)展，情況已不再如此。微創(chuàng)PAO技術縮短了術后恢復時間[45]。最近的一項研究表明，一些可改變的因素，例如較高的體力活動量和較高的BMI（大于30kg/m2）可導致PAO的發(fā)病年齡下降[46]。此外，患有較重發(fā)育不良程度的患者患PAO的年齡也較早：LCEA是手術年齡的獨立預測因素，即LCEA較低的患者往往需要在較早的年齡接受PAO手術。但是，輕度和中度發(fā)育不良患者的PAO預后沒有差異。在本研究中，輕度發(fā)育不良被歸類為15-25°，這涵蓋了我們對臨界髖關節(jié)發(fā)育不良的定義。最近的一項多中心前瞻性隊列研究檢查了患者報告的PAO結果指標，結果表明，雖然總體結果良好，但臨界髖關節(jié)發(fā)育不良患者和男性的改善程度低于發(fā)育較重的患者[47]。作者討論了小范圍矯正的危險，這可能導致過度矯正和醫(yī)源性FAI、股骨前傾增加和軟組織松弛。建議和未來方向在臨界髖關節(jié)中，關鍵步驟是確定穩(wěn)定性。關于髖關節(jié)的穩(wěn)定性，只有兩種情況：髖關節(jié)穩(wěn)定或不穩(wěn)定。沒有中間狀態(tài)。如果接受這個概念，治療就會變得相對簡單。不穩(wěn)定可能與其他病癥（如FAI或超負荷/過度使用和軟骨疾?。┫嘟Y合，需要同時治療。如果髖關節(jié)不穩(wěn)定，則需要髖臼重新定位。僅解決磨損的二級穩(wěn)定器并不能解決潛在的生物力學問題，最多只能產(chǎn)生令人滿意的短期結果。在穩(wěn)定的髖關節(jié)中，可以進行開放或關節(jié)鏡關節(jié)保留手術。然而，我們必須記住，低于28°的LCE角度每減少一度，骨關節(jié)炎的發(fā)病率就會增加13%[20]。因此，如果有疑問，為了最大限度地提高獲得良好長期結果的機會，我們主張進行髖臼重新定向PAO截骨手術。重要的是要確定我們缺乏知識的領域，以指導進一步的研究。將對這些患者進行長期隨訪研究，比較髖臼重新定向和髖關節(jié)鏡檢查，理想情況下，將記錄所有成像參數(shù)和Beighton評分。此外，還應獲得患者報告的結果測量和恢復時間，以及包括運動在內的活動恢復時間。?TheFEARindexisarecentlydescribedparameterthatseemstohaveahighvaluetopredictstabilityofthehip[27].Itisformedbytheanglebetweentheacetabularroofandthecentralthirdofthefemoralgrowthplate(Fig.2).Itisbasedonthefactthatduringgrowththeepiphysealgrowthplateofthefemurorientsitselfperpendicularlytothejointreactingforcesofthehip.Growthandtheorientationofthefemoralneckareunderthecontrolofthesubcapitalgrowthplate[31].PauwelsandMaquet[32]theorizedthattheresultantforceactsfromthecenteroftheepiphysealcartilageandthatduringgrowth,theepiphysealplateorientsitselfperpendiculartothejointreactionforceinaccordancewiththeHeuter–Volkmanprinciple.PauwelsandMaquet’stheorylaterwasconfirmedbyCarteretal.[33]whostudiedtheinfluenceofhiploadingbybi-dimensionalfiniteelementanalysis.Theangleoftheclosedepiphysealplateindicatesthebalanceofforcesacrosstheproximalfemoralphysis[34]andindicateshowthetransarticularforcesactedinthepast.Therefore,itisafunctionalparameterthatreflectsthejointreactingforcesoveralongperiodoftimeduringgrowthofthehip.IftheFEARis?<0°thehipisconsideredstable.Statisticalanalysishasshownthatacutoffvalueof5°predictsstabilitywith80°probability.Morerecentworkhasshownthatacutoffvalueof2°predictsstabilitywith90%probability(Batailleretal.,inpreparation).CaseexamplesofusingtheFEARindexareshowninFig.3aandb.ThemanagementofthepainfulborderlinedysplastichipAbstractImprovedimagingandtheevolutionofsurgicaltechniqueshavepermittedarapidgrowthinhippreservationsurgeryoverthelastfewdecades.Themanagementofthepainfulborderlinedysplastichiphoweverremainscontroversial.Inthisreview,wewillidentifythepertinentissuesanddescribethepatientassessmentandtreatmentoptions.Wewillprovideourownrecommendationsandalsoidentifyfutureareasforresearch.INTRODUCTIONImprovedknowledgeabouthipbiomechanicsandtheevolutionofsurgicaltechniqueshavepermittedarapidgrowthinhippreservationsurgeryoverthelastfewdecades.Thespectrumcoversawiderangefromhipswithshallowacetabuli,whichareunstable,tohipswithdeepacetabulithataresufferingfromfemoro-acetabularimpingement(FAI).Whilethereisageneralagreementthatthebesttreatmentfortheunstabledysplastichipisareorientationoftheacetabulumtoincreasecover,thereisequalagreementthattherimoftheover-coveringacetabulumhastobereducedtoremoveimpingement.Onallthosehipsacamdeformitymaybepresentthatneedstobeaddressedatthetimeofsurgicalcorrection[1].Atthefarendsofthespectrumtherequisitetreatmentisobvious.However,thereisatransitionzonewhereitisdifficulttodiscriminateinstabilityfromFAI.Inthepastthesehipswerereferredtoas‘borderline’hips.Usually,thisincludedhipswithalateralcenteredge(LCE)anglebetween20°and25°[2].However,theterm‘borderline’isproblematic,becauseitisaradiographicdefinitionandonlyaddressesoneofseveralparametersimportanttodescribehipstability.Acetabularroofobliquity,anteriorandposteriorcoverandfemoralantetorsionareotherfactorsthatshouldbeincludedintoananalysisofhipstability.Theassociationofhipdysplasiawithhiposteoarthritisisestablished[3,4]anddysplastichipswithsignsofinstabilitydegenerateatahigherrate[5].Aborderlinehipcaneitherbeunstable,impingingormaybeboth.Thestabilityoftheborderlineisdifficulttodetermineandsubjecttointerpretationwithageneraltendencyintheorthopaediccommunitytounderestimateinstabilitythatthenleadstoinappropriatetreatment.Recentstudiessuggestthatarthroscopichipsurgerywithlabralrepairandcapsularplicationinpatientswithborderlinedysplasia(LCEA?>?20°)mayresultinappropriateshort-termimprovements[3,4].However,thereisevidencethatawronglydoneprevioushiparthroscopyhasanegativeimpactontheoutcomeonthetreatmentofsuchhips[6].Therefore,themanagementofthepainfulborderlinedysplastichiphoweverremainsanissueofgreatcontroversy.Borderlinehipdysplasiaiscommoninyoungadultswithhippainwithareportedprevalenceof37.6%inselectedpatientcohorts[7].Intheborderlinedysplastichiptheremaybesignificantoverlapwithothercausesofinstabilitysuchasconnectivetissuelaxity[8].However,thefundamentalissueisthedifficultyincorrectlyclassifyingtheunderlyingpatho-biomechanics.DEFINITIONThefirstproblemliesinthedefinition.TheLateralCentreEdgeAngleofWibergasmeasuredonanAntero-posteriorpelvicradiograph[9](LCEA)hastraditionallybeenusedtoclassifyhipsasnormal(LCEA?>25°),dysplastic(LCEA?<20°)orborderline(LCEA20–25°)althoughthesedefiningvaluesvarywidelyintheliterature[3,10].However,theuseoftheLCEAhastwoproblems.Firstlythemethodbywhichitshouldbemeasured.TomeasuretheLCEAthecenterofthefemoralheadisfirstdefinedbyacirclefittingthecontourofthefemoralhead.Thefirstbranchoftheanglerunsperpendicularthroughthecenterofrotation.Thesecondbranchisdefinedbythecenterofthefemoralheadandthemostlateralpointofthesourcil(Fig.1a).Itisimportantnottousethemostlateralpointoftheacetabulum(Fig.1b),becausethisdoesnotfollowthedefinitionofWiberg,andwillgivefalsehighvalues[11].Secondlytheactualterm‘Borderlinehipdysplasia’wasfirstintroducedbyWiberghimself,includinghipswithaLCEAbetween20°and25°[2].LCEAisaradiographicmeasureandpersecannotpredictstabilityintheborderlinedysplastichipnordoesfullydescribefemoralheadcoverage.ThereforetheLCEAcannotdirectsurgicaldecisionmaking[12–14].PartofthereasonisthatLCEAalonedoesnotencompassthepreciselocationofdysplasiaanddisregardsanteriorandposteriorfemoralheadcoverage.Alsootherparameterssuchasacetabularindex(AI)andfemoralantetorsionareveryrelevantforstabilityofthehip.InthepresenceofadecreasedLCEAAImaybenormalinwhichcasethestabilityofthehipisdifficulttoassess[15].Ontheotherhand,excessivefemoralanteversionmaypotentiateanteriorhipinstability[16].WHATISTHEFUNDAMENTALISSUE?Inthepainfulborderlinedysplastichipitisdifficulttocharacterizethepathologicalmechanismasimpingement(stable)ordysplasia(unstable)byatwo-dimensionalradiographicmeasurementalone,especiallyonethatissolelyafunctionoftheacetabulumandtakesnoaccountofthefemur.Thisfunctionalcharacterizationofhipstabilityisofparamountimportancetoguidesurgicaldecision-making.Anunstablehipwouldlogicallybenefitfromacetabularreorientationosteotomywhilstastablehipwouldbenefitfromimpingementsurgerysuchasfemoralcamosteoplasty.Sowhatisknownabouttheintra-articularpathology?Howshouldthesepatientsbeassessed?Whatarethetreatmentoptions?Whatarethesurgicaloutcomes?Whatarethepotentialpitfallswiththisgroupofpatients?Whatarethefuturedirections?Inthisnarrativereviewarticleweaimtoaddressthesequestionsandelucidatethemanagementofthischallenginggroupofpatients.WHATISTHEUNDERLYINGPATHOLOGYOFHIPDYSPLASIAANDUNSTABLEBORDERLINEHIPS?Inhipdysplasia,thereareabnormallyhigharticularcontactpressuresandrelativebonyuncoveringofthefemoralhead.Theacetabulumistypicallyshallowandantevertedwithanoftencompensatoryenlargedlabrum,butthereisalsoahighprevalenceofconcomitantacetabularretroversion[17].Thefemurisclassicallyinvalguswithhighantetorsion[10].Theseabnormalanatomicalfeaturescausepathologicalhipbiomechanicswhichmanifestaslabraltears,chondrallesions,andhipinstability,whichcaneasilybemisinterpretedasimpingement.Astheosseousstabilityiscompromisedtheimportanceofthesofttissuestabilisers,namelythefibrocartilaginouslabrumandthehipcapsule,isaccentuated[18].Oncethesofttissueconstraintsfailthenthehipbecomesunstable.However,onehastounderstandthattheprincipalunderlyingpathologyisthelackofosseousstability,whichleadstofailureofthehipandnotthefailingsofttissuestability.Thenaturalhistoryofthesubluxingdysplastichipisaverypoorprognosisandinvariablyleadstojointdegeneration[5].Therateofdeteriorationisdirectlyrelatedtosubluxationseverityandpatientageandusuallyabout10?yearsafteronsetofsymptomsseveredegenerativechangeshavedeveloped[19].Thenaturalhistoryintheabsenceofsubluxationismoredifficulttopredictconcerningthespeedofdegeneration.Thesameaccountsforborderlinedysplastichips.Arecentstudyhighlightstheimportanceofacetabularcover.Inalargecohortoffemales,followedfor20?years,itwasshownthateachdegreereductioninLCEbelow28°isassociatedwith13%increasedriskofradiographicOA[20].Therefore,besidesshort-termreliefofsymptoms,thelong-termpossibleevolutionhastobekeptinmind.CLINICALPRESENTATIONTheclinicalpresentationofborderlineacetabulardysplasiaisverysimilartothatofotheryoungactiveadulthipdisorders,suchasFAIsyndrome[21]soathoroughhistory,physicalexamination,andradiographicevaluationareessentialtoproperlydiagnosethesepatients.HISTORYAfocusedhistoryistaken.Theprimarysymptominpatientswithborderlinehipdysplasiaispain.Thisistypicallyperceivedingroinandlateralhipbutcanalsobeinthebuttock.Afullpainhistoryiswarranted.Particularsymptomsofinstabilityand‘givingway’aresoughtthatmayindicatethatthelimitsofsofttissuecompensationforalackofosseousstabilityhavebeenreached.Symptomsofclickingandcatchingarealsocommon.Furthermoreanyindicationsthatthepatienthasestablishedhiparthritis,suchasnightpain,areaskedfor.Thesymptomsshouldbeputintothecontextofthepatient’sfunctionallimitationsandmedicalattentionalreadyreceivedincludingphysiotherapy,medications,otheropinionsandsurgery.EXAMINATIONAlogicalclinicalexaminationofthehipshouldfollowincludingapprehensionandimpingementtests.Thepatientwilloftendisplaya‘kneeing-in’gaitinassociationwithanincreasedhipadductormomentandincreasedinternalhiprotationconsistentwithincreasedfemoralantetorsion.Hyperlordosismaybepresentinordertofunctionallyincreaseanteriorcover.Tendernessoverthegreatertrochantershouldbedetermined[22].Itiscrucialtoremembertoexaminethepatient’srotationalprofile,performaneurovascularexaminationandtocheckforsignsofgeneralizedjointlaxityandquantifythisusingBeighton’sscore.Specifickeyaimsincluderefutingthepresenceof(i)anadvanceddegenerativeprocessmanifestforexamplewithfixedflexiondeformityanddecreasedrangeofmotionand(ii)alternativepathologysuchaspainreferredfromlumbarspondylosisorL5radiculopathy.INVESTIGATIONSDiagnosticimagingshouldcommencewithstandardizedplainAPradiographofthepelvisandalateralfemoralneckviews(lateralcrosstable,Dunnview,falseprofileviews)[23].TheseimagesarescrutinizedtomeasuretheLCEA,AI,extrusionindex,femoralneck-shaftangleandFEARindex(seebelow).TheTonnisgradeofosteoarthritisshouldbedeterminedalongwithwhetherthereiscammorphology.Directsignsofinstabilityshouldbescrutinizedforandthesecomprisefemoralheadmigration,recognizedbyanincreaseddistancefromtheilioischialline,abreakinShenton’slineandrecenteringofthefemoralheadonanAPviewwiththehipinabductionandGadoliniumintheposteriorjointspacewhenusingMR-arthrography,thatindicatesanteriormigrationandthusinstabilityofthefemoralhead.TheFEARindexhasahighassociationwithinstability(seebelow).Thevariousparametershavetobemeasuredpreciselyandrecorded.Cross-sectionalimagingwiththree-dimensionalcomputerizedtomography(CT)forpreciseinformationonbonyanatomyandlocationofdysplasiaincludingthepresenceandlocationofperiarticularcystsiswarranted[24–26].FurthermoreCTshouldincludeestimationoffemoralantetorsionwhich,ifhighmaypotentiateanteriorhipinstability.Magneticresonanceimaging(MR-arthrography)shouldfollowadedicatedprotocolfortheexaminationofthehip,includingradialimageacquisitionorreconstructionandintra-articularapplicationofcontrast[27]toexamineforintra-articularstructuresandpathologyofbothlabrumandarticularcartilage.Othercausesforsimilarsymptomssuchasavascularnecrosis,trochantericbursitisorglutealpathologycanbedifferentiated.Additionalmeasurementsincludelabralsize[13,28]andiliocapsularisvolume[29].Inthesepatients,wealsoadvocatenon-tractionMRarthrographytoexamineforaaccumulationofgadoliniumknownasa‘crescentsign’whichisasubtlesignofinstabilityontheaxialview[30].WHATISTHEVALUEOFTHESEMEASUREMENTS?Onplainfilmsthosemeasurementsthataredirectsignsofinstabilityarefemoralheadmigrationwithanincreaseofthedistancefromtheilioischialline,abreakinShenton’slineandrecenteringofthefemoralheadontheAPviewwithhipsinabductionandtheFEARindex.OnMR-arthrographythepresenceofGadoliniuminthepostero-inferiorjointspaceindicatesmigrationofthefemoralheadandthusinstability.TheAI,NSA,AT,highiliocapsularisvolumeandincreasedlabralvolumemaybepresentbutarenotpredictiveofinstability[30](Table1).WHATARETHETREATMENTOPTIONS?Treatmentdependsonthestabilityofthehip.Thetreatmentalternativesforthepainfulborderlinedysplastichipincludenon-operativetreatment,surgicaltreatmenttoaddressintra-articularimpingement(FAIsurgerybyeitherhiparthroscopyorsurgicalhipdislocation)andsurgicaltreatmenttoaddressinstability(reorientationosteotomywithPAOand/orfemoralosteotomy)(seeFig.2).Non-operativemanagementincludespatienteducation,activitymodification,simpleanalgesics,non-steroidalanti-inflammatorymedications,andintra-articularinjections[35].Targetedphysiotherapycanimprovemuscularconditioning,painandproprioceptivecontrol.Thesurgicaltreatmentoptionsfortheborderlinedysplastichipwhichcomprisearthroscopyand/orosteotomywillbediscussedinthefollowingparagraphs.WHATARETHERESULTSOFHIPARTHROSCOPYINTHISGROUPOFPATIENTS?Withtherecentevolutioninhiparthroscopymanysurgeonsareusingthistoaddressborderlinedysplastichips,notleastbecauseofperceivedhigherrisksandlongerpost-operativerecoveryassociatedwithalternativetechniquessuchasperiacetabularosteotomy.Hiparthroscopyinborderlinedysplastichipspermitsthesurgeontoaddressintra-articularpathologysuchasalabraltearorfemoralcamdeformity[3,12,36].IfPAOisbeingconsideredtoaddresstheinadequatebonystabilitythenarthroscopymaygivethesurgeonvaluableinsightsnotonlyintotheintra-articularstatusofthehipbutalsohowthepatientislikelytofarewithamuchlargersubsequentoperation[37].However,thereislittlepublishedliteratureonhiparthroscopyinborderlinedysplastichipsandwhatthereislimitedbyshort-termfollow-up.InthesystematicreviewbyJoetal.,13studieslookingatarthroscopyindysplastichipswereidentified[10].Thestudieswereheterogeneousandallstudieswerecaseseries.Onlysixstudiesreportedonsubjectiveand/orobjectiveoutcomes.Thesurgicalindicationsforarthroscopywereambiguousandpatientshadreceivedvariablenon-operativemanagementapriori.FurthermoretheprecisedefinitionofborderlinehipdysplasiavariedandonlytwostudiesusedthedefinitionofByrdandJones[36].Threestudiesreportedonhiparthroscopyasanadjuvanttoolandthreeasastand-alonetreatment.Labraltearshadanoverallprevalenceof77.3%andtheseweremostlylocatedintheanteriororanterosuperiorportionoftheacetabularrim.Acetabularchondrallesionsweremorecommonthanfemorallesions(59–75.2%versus11–32%)andlocatedadjacenttothatofthelabralpathology.Therewereonlytwostudiesthatexaminedtheoutcomesofarthroscopyinborderlinehipdysplasticcases(LCEA20–25°)ofwhichonlyonedescribedpatientreportedoutcomemeasures.Thelatter,aprospectiveclinicalcaseseriesbyByrdandJones[36],had66%ofhips(32hips)withborderlinedysplasia.ThemeanmodifiedHarrisHipscoreimprovedfrom50(poor)to77(fair)followingarthroscopy.Theauthorsconcludedthatthetreatmentresponseislikelyafunctionofaddressingtheintra-articularpathologyratherthantheradiographicevidenceofdysplasia.WHATARETHEDANGERSWITHDOINGHIPARTHROSCOPYINBORDERLINEDYSPLASTICHIPS?Arthroscopiclabralresectionandremovaloflateralacetabularriminborderlinehipdysplasiacanleadtofulminantjointinstability[38].Evenifthelabrumisrepaireditisimperativetopreservetheiliofemoralligamentandotherstaticstabilizersofthehiptopreventtheirreversibleconsequencesorrenderingthehipunstable[39–41].Thereisnoconclusiveliteraturetosupportcapsularrepairinthesecasesbutthisseemsasafeandsensiblepractice[42].Capsularreductiontechniquestoimprovestabilityhavebeendescribedinborderlinedysplastichips[12].Ifthehipissufficientlyunstablepre-operativelythenaddressingtheintra-articularpathologyalonebyhiparthroscopywillbeinsufficientandthepatientwillrequireaPAO[43,44].Onehastobearinmindthatstabilityofthehipfirstlinedependsontheosseousgeometry.Insubtleinstability(borderlinedysplasia)stabilitymaybesecuredbysecondarysofttissuestructures.Oncethesefailduetomicro-ormacrotraumathehipbecomesunstable.Restoringsofttissuestabilitymayimprovehipstabilityforashortperiodoftimeonly,butitislikelythatthesofttissueswearoutagain.Thereforetheunderlyingosseouspathologyhastobeaddressedfirsttoachievegoodlong-termresults.ArecentreportshowedaninferiorhipspecificfunctionaloutcomeofPAOafterfailedhiparthroscopyinhipdysplasia[6].Hiparthroscopyaloneinthisgroupofpatientsshouldbethereforeapproachedwithcaution.However,itmayhavearoleinthosepatientswhoareeitherunsuitableforPAOeitherbecausetheirhipsareunfavourable(i.e.haveanormalAIandnormalfemoralanteversion)orbecausetheiradvancedage(i.e.>40years).WHATARETHERESULTSOFREORIENTINGPERIACETABULAROSTEOTOMYINTHISGROUPOFPATIENTS?Acetabularreorientationviatheperiacetabularosteotomyhasbecomethemostcommontreatmentforacetabulardysplasiawithgoodoutcomesreportedatover20?yearspostoperatively.Traditionallyintra-articularpathologywasaddressedatthetimeofPAObyperformingananteriorarthrotomy.HoweverwiththedevelopmentofminimallyinvasivetechniquesforPAOthisisnolongernecessarilythecase.LessinvasivePAOtechniqueshavedecreasedthetimetopostoperativerecovery[45].ArecentstudyshowedmodifiablefactorssuchashigherphysicalactivityandhigherBMIgreaterthan30?kg/m2leadtoadecreasedageofpresentationforPAO[46].FurthermorepatientsalsopresentedearlierforPAOwithworsedegreesofdysplasia:theLCEAwasindependentlypredictiveofageatsurgery,i.e.patientswithalowerLCEAtendedtorequirePAOsurgeryatanearlierage.However,therewasnodifferenceinoutcomesfollowingPAObetweenmildandmoderatedysplasia.Inthisstudymilddysplasiawasclassifiedas15–25°whichencompassesourdefinitionofborderlinehipdysplasia.Arecentmulticenterprospectivecohortstudythatexaminedpatient-reportedoutcomemeasuresofPAOshowedthat,althoughoverallresultsweregood,improvementsinborderlinehipdysplasticsandmaleswerelessthaninthosepatientswhohadmoreseveredysplasia[47].TheauthorsdiscussedthiswiththedangerofasmallcorrectionthatmayleadtoovercorrectionandiatrogenicFAI,increasedfemoralantetorsionandsofttissuelaxity.RECOMMENDATIONSANDFUTUREDIRECTIONSInborderlinehipsthecrucialstepistodefinestability.Regardingthestabilityofthehipthereareonlytwoconditions:Thehipiseitherstableorunstable.Thereisnothinginbetween.Ifthisconceptisaccepted,thetreatmentgetscomparablysimple.InstabilitymaybecombinedwithotherpathologieslikeFAIoroverload/overuseandcartilagediseasewhichneedconcomitanttreatment.Ifthehipisunstable,acetabularreorientationisnecessary.Addressingonlywornoutsecondarystabilizersdoesnotsolvetheunderlyingbiomechanicproblemandatbestwillyieldsatisfactoryshorttermresults.Instablehips,openorarthroscopicjointpreservingsurgerymaybeperformed.However,wehavetokeepinmindthateachdegreedecreaseoftheLCEanglebelow28°isassociatedwitha13%increaseofosteoarthrosis[20].Therefore,ifindoubt,inordertomaximizethechanceofgoodlong-termresults,wewouldadvocateforanacetabularreorientationoperation.Itisimportanttoidentifytheareaswherewelackknowledgeinordertoguidefurtherresearch.Longer-termfollow-upstudiescomparingacetabularreorientationandhiparthroscopyinthesepatients,ideallyinwhichallimagingparametersandBeightonscoresarerecordedwouldbeperformed.Inadditionpatient-reportedoutcomemeasuresandtimetorecoveryandresumptionofactivitiesincludingsportshouldbeattained.文獻出處：MichaelCWyatt,MartinBeck.Themanagementofthepainfulborderlinedysplastichip.ReviewJHipPreservSurg.2018Apr5;5(2):105-112.doi:10.1093/jhps/hny012.
臨界髖關節(jié)發(fā)育不良Borderline DDH：什么時候、怎么判定為異常？臨界髖關節(jié)發(fā)育不良BorderlineDDH：什么時候、怎么判定為異常？作者：SarahDBixby,MichaelBMillis.作者單位:DepartmentofRadiology,BostonChildren'sHospital,Main2,300LongwoodAve.,Boston,MA,02115,USA.sarah.bixby@childrens.harvard.edu.譯者：陶可（北京大學人民醫(yī)院骨關節(jié)科）摘要臨界髖關節(jié)發(fā)育不良是指髖臼形狀和覆蓋范圍輕度低于正常范圍，可能導致兒童易患機械功能障礙和不穩(wěn)定。臨界發(fā)育不良通常包括外側中心邊緣角(CEA)為18-24°的兒童。一些具有臨界X線測量值的兒童具有正常的關節(jié)力學和功能，而其他兒童則需要進行髖臼截骨手術。雖然臨界髖關節(jié)發(fā)育不良的X線檢查結果可能表明不穩(wěn)定，但最終診斷基于病史和體格檢查以及影像學相結合?；加信R界髖關節(jié)發(fā)育不良的兒童有時還需要進行其他橫斷面成像研究，如MRI成像，以評估不穩(wěn)定的次要證據(jù)，包括沿髖臼邊緣的損傷或盂唇退化和肥大。CT也有助于描繪3-D髖臼形態(tài)，以進行術前評估和規(guī)劃。兒童放射科醫(yī)生通常是第一個在X線片上發(fā)現(xiàn)邊緣性或輕度發(fā)育不良的人。兒童放射科醫(yī)生必須充當有效的顧問，并作為針對這一復雜患者群體的連貫多學科診療團隊的一部分提供適當?shù)慕ㄗh。圖1?一名16歲女孩的髖關節(jié)X線片顯示了外側中心邊緣角(CEA)、髖臼指數(shù)和前CEA的測量方法。a標記了三個點以便進行后續(xù)測量：點1位于股骨頭(旋轉)中心，點2位于股骨髖關節(jié)(負重關節(jié)面的)內側邊緣，點3位于股骨髖關節(jié)(負重關節(jié)面的)外側邊緣。b右髖關節(jié)的前后位X線片展示了測量外側CEA的方法。外側CEA是連接點1和點3的線與垂直線之間形成的夾角（正常為25-40°）。c髖臼指數(shù)由連接點2和點3的線與水平線之間形成的夾角決定（正常為0-10°）。d右髖關節(jié)的假斜位片顯示了確定前CEA的測量方法。前側CEA由點1到點4（在髖臼前緣）的連線與垂直線之間的角度決定（正常值為25–40°）圖2?一名19歲女性嚴重雙側髖關節(jié)發(fā)育不良。a骨盆前后位X線片顯示右側髖關節(jié)外側中心邊緣角(CEA)為5°，b髖臼指數(shù)為16°。左髖關節(jié)同樣發(fā)育不良。c右髖關節(jié)假斜位X線片顯示前方中心邊緣角為8°。圖3?一名右側髖關節(jié)疼痛的16歲女孩的外側中心邊緣角(CEA)。a前后位(AP)骨盆X線片顯示外側CEA為19°。左側髖關節(jié)正常。b同一女孩的假斜位X線片顯示前方CEA為19°。c延遲釓增強軟骨MRI(dGEMRIC)檢查的冠狀T1圖顯示軟骨正常。女孩沒有不穩(wěn)定的跡象，接受了腰肌勞損治療，癥狀在沒有手術的情況下得到改善。由于腰肌勞損仍然可能與潛在的微不穩(wěn)定有關，女孩在髖關節(jié)外科醫(yī)生的護理下接受長期觀察。圖4?一名有髖關節(jié)發(fā)育不良家族史的11歲女性足球運動員的左側髖關節(jié)疼痛。a前后位(AP)X線片顯示為正常。b女孩現(xiàn)在13歲，仍然有左側髖關節(jié)疼痛。雙側髖關節(jié)被認為是淺的，左側測量的外側中心邊緣角(CEA)為16°，右側為23°。左側髖臼指數(shù)也被認為是升高的13°。陽性恐懼測試反映了體格檢查中左側髖關節(jié)的不穩(wěn)定，右側沒有發(fā)現(xiàn)不穩(wěn)定。C假斜位X線片顯示前方覆蓋充分，前方CEA為27°。d左側髖臼周圍截骨術后前后位AP骨盆X線片狀態(tài)顯示側方覆蓋改善。女孩報告癥狀有所改善。e一年后的前后位AP骨盆X線片，癥狀緩解并恢復正?；顒印Ｋ覀扔休p微間歇性疼痛，并定期監(jiān)測癥狀。圖5?股骨骨骺髖臼頂(FEAR)指數(shù)。a與圖1中相同的16歲女孩的髖關節(jié)前后位(AP)X線片。FEAR指數(shù)是沿髖臼頂連接點2和點3的線（黑線）與沿股骨骨骺線中央三分之一繪制的線（白線）之間形成的角度。陽性FEAR指數(shù)定義為向外側傾斜的角度，頂點指向內側。這個女孩的FEAR指數(shù)小于5°。與FEAR指數(shù)<5°相比，F(xiàn)EAR指數(shù)>5°與不穩(wěn)定性具有更大的相關性。b一名13歲女孩的髖關節(jié)前后位X線片顯示左側髖臼外側輕微上翻（箭頭）。c一名13歲男孩的右側髖關節(jié)疼痛的左側髖關節(jié)正常前后位X線片顯示外側正常。黑線表示髖臼頂部，白線表示骨骺線的中央三分之一。此正常髖關節(jié)的FEAR指數(shù)顯示FEAR指數(shù)，角度頂點指向外側。圖6?一名18歲女子田徑運動員的右側髖關節(jié)疼痛影像。a前后位(AP)骨盆X線片顯示右側髖關節(jié)發(fā)育不良，左髖關節(jié)正常。b右側髖臼周圍截骨術后前后位(AP)骨盆狀態(tài)顯示外側覆蓋增加，但該女性報告癥狀惡化。c術前（回顧性）進行的右髖關節(jié)矢狀質子密度脂肪抑制MR圖像顯示前髖臼內有骨樣骨瘤（箭頭）。射頻消融后，該患者的癥狀得到緩解。?Theborderlinedysplastichip:whenandhowisitabnormal?AbstractBorderlineacetabulardysplasiareferstomildlysub-normalpatternsofacetabularshapeandcoveragethatmightpredisposechildrentomechanicaldysfunctionandinstability.Borderlinedysplasiagenerallyincludeschildrenwithalateralcenteredgeangle(CEA)of18-24°.Somechildrenwithborderlineradiographicmeasurementshavenormaljointmechanicsandfunctionwhileothersbenefitfromacetabularreorientingsurgery.Althoughradiographicfindingsofborderlinedysplasiamightsuggestinstability,theultimatediagnosisisbasedonhistoryandphysicalexaminadditiontoimaging.Childrenwithborderlineacetabulardysplasiasometimesbenefitfromothercross-sectionalimagingstudiessuchasMRimagingtoevaluateforsecondaryevidenceofinstability,includingdamagealongtheacetabularrim,orlabraldegenerationandhypertrophy.CTisalsohelpfulfordepictionof3-Dacetabularmorphologyforpreoperativeassessmentandplanning.Pediatricradiologistsareoftenthefirsttoidentifyborderlineormilddysplasiaonradiographs.Itisimperativethatpediatricradiologistsserveaseffectiveconsultantsandofferappropriaterecommendationsaspartofacohesivemultidisciplinaryapproachtothiscomplexpatientpopulation.Fig.1Radiographsofthehipina16-year-oldgirldemonstratemeasurementtechniqueforlateralcenteredgeangle(CEA),acetabularindex,andanteriorCEA.aThreepointsaremarkedforsubsequentmeasurements:Point1atthecenterofthefemoralhead,Point2atthemedialedgeofthesourcil,Point3atthelateraledgeofthesourcil.BAnteroposteriorpelvicradiographconeddowntotherighthipdemonstratestechniqueformeasuringlateralCEA.ThelateralCEAistheangleformedbetweenthelineconnectingPoint1toPoint3andaverticalline(normal25–40°).cAcetabularindexisdeterminedbytheangleformedbetweenalineconnectingPoint2toPoint3andahorizontalline(normal0–10°).dFalseprofileviewoftherighthipdemonstratesmeasurementtechniquefordetermininganteriorCEA.AnteriorCEAisdeterminedbytheanglebetweenalinefromPoint1toPoint4(attheanteriormarginofthesourcil)andaverticalline(normal25–40°)Fig.2Severebilateralhipdysplasiaina19-year-oldwoman.aAnteroposteriorradiographofthepelvisdemonstratesalateralcenteredgeangle(CEA)oftherighthipof5°and(b)acetabularindexof16°.Thelefthipissimilarlydysplastic.cFalseprofileradiographoftherighthipdemonstratesanteriorcenteredgeangleof8°.Fig.3Borderlinelateralcenteredgeangle(CEA)ina16-year-oldgirlwithrighthippain.aAnteroposterior(AP)pelvisradiographrevealsborderlinelateralCEAof19°.Thelefthipisnormal.bFalseprofileradiographofthesamegirlrevealsanteriorCEAof19°.cCoronalT1mapfromdelayedgadolinium-enhancedMRIofcartilage(dGEMRIC)examinationrevealsnormalcartilage.Thegirldidnothavesignsofinstability,wastreatedforpsoasstrain,andsymptomsimprovedwithoutsurgery.Becausepsoasstraincouldstillberelatedtounderlyingmicroinstability,thegirlwasunderlong-termobservationundercareofahipsurgeon.Fig.4Lefthippaininan11-year-oldfemalesoccerplayerwithafamilyhistoryofhipdysplasia.aAnteroposterior(AP)radiographinterpretedasnormal.bGirlnowisage13years,stillwithlefthippain.Bilateralhipswereconsideredshallow,withlateralcenteredgeangle(CEA)measuredat16°ontheleftand23°ontheright.Acetabularindexontheleftwasalsoconsideredelevatedat13°.Positiveapprehensiontestreflectedinstabilityofthelefthiponphysicalexamination,withnoinstabilitynotedontheright.cFalseprofileradiographrevealsadequateanteriorcoverage,withanteriorCEAof27°.dAPpelvisradiographstatuspostleft-sideperiacetabularosteotomydemonstratesimprovedlateralcoverage.Thegirlreportedimprovedsymptoms.eAPpelvisradiograph1yearlater,afterreliefofsymptomsandreturntonormalactivity.Shehadmildintermittentpainontherightandwasbeingmonitoredperiodicallyforsymptoms.Fig.5Femoro-epiphysealacetabularroof(FEAR)index.AAnteroposterior(AP)radiographofthehipinthesame16-year-oldgirlasinFig.1.TheFEARindexistheangleformedbetweenalineconnectingPoint2andPoint3alongtheacetabularroof(blacklines),andalinedrawnalongthecentralthirdofthefemoralphysealscar(whiteline).ApositiveFEARindexisdefinedbyalaterallydirectedanglewiththeapexpointingmedially.TheFEARindexinthisgirlislessthan5°.AFEARindex>5°hasagreatercorrelationwithinstabilitycomparedtoFEARindex<5°.bAPradiographofthehipina13-year-oldgirlwithmildleftacetabularsourcildemonstratesamildlyupturnedlateralsourcil(arrow).cNormalAPradiographofthelefthipina13-year-oldboywithrighthippaindemonstratesanormallateralsourcilforcomparison.Theblacklineindicatestheacetabularroofandthewhitelineindicatesthecentralthirdofthephysealscar.TheFEARindexisdemonstratedinthisnormalhiptoillustrateanegativeFEARindexwiththeapexoftheangledirectedlaterally.Fig.6Imaginginan18-year-oldfemaletrackathletewithrighthippain.aAnteroposterior(AP)pelvisradiographreportedasborderlinerightacetabulardysplasiaandnormallefthip.bAPpelvisstatuspostrightperiacetabularosteotomydemonstratesincreasedlateralcoverage,thoughthewomanhadreportedworseningsymptoms.cSagittalproton-densityfat-suppressedMRimageoftherighthipperformedpreoperatively(retrospectively)revealsanosteoidosteomawithintheanterioracetabulum(arrow).Thewoman’ssymptomsresolvedafterradiofrequencyablation.?AdvancinginvestigationTheterm“borderlinedysplasia”isalsofallingoutoffavor.Advancedimagingmodalitieshaverevealedpatternsofdysplasiathatarenotapparentonradiographs.FocalanteriorandposteriordysplasiagroupshaveanormallateralCEAontheAPradiograph[9].Refinedandupdatedradiographicmeasurementshavebeenproposedthatwouldenablebetteridentificationofchildrenwithfocaldysplasia,suchastheanteriorwallindexandposteriorwallindex[48].Earlystudiesdemonstrateddifferencesintheanteriorandposteriorwallindicesinsymptomaticdysplasticpatientscomparedtothosewithanormalacetabulum[48].Subsequentinvestigationrevealedthatevenasymptomaticpeoplehaveradiographicanteriorandposteriorwallindexmeasurementsthatoverlapthoseofpeoplewithdysplasia[49].Thisindicatesthatsomedegreeofvariationinthe3-Dmorphologyoftheacetabulumisnormal.Furthervalidationoftheseindiceswithcross-sectionalimagingandlongitudinalfollow-upisnecessarybeforethesenewreferencestandardscanbeconsideredreliableindicatorsofdisease.Inthepresenceofinstabilityrelatedtoacetabulardysplasia,thereisoftenovergrowthofsoft-tissuestructuresthatcompensatesforthedeficientbonysupport.Thisincludesenlargementoftheacetabularlabrum[50,51],evenintheabsenceoflabraltearordegeneration.Focalmuscleenlargementhasalsobeennotedinunstablepatients,specificallytheiliocapsularismuscle[52].MRImightbeusefulinidentifyingthesesecondarysignsofinstability.Still,noclearlypositivefindingsconfirmthepresenceofinstability.Femoralversionisalsoakeycomponentindetermininghipstability,asanantevertedfemurisbemoreanteriorlyuncoveredthananeutralfemur[53].Overtfeaturesofacetabularrimdamagealsosupportthediagnosisofdysplasia,includinglabraldegenerationandtearingandcartilageloss,thoughadolescentswhohaveborderlinedysplasiamightnotyethavevisiblemanifestationsofosteoarthritis,evenifinstabilityisthepaingenerator.Giventheseareasofinvestigationanduncertainty,theborderlinedysplastichiphasattractedwell-deservedattentionintheliterature.Specificconcernshavebeenraisedaroundwhethertheterm“borderlinedysplasia”isanadequatelabelandwhetherthisisasinglecondition.ItismorelikelythatchildrenwithaborderlinelateralCEAof18–24°consistofclustersofpatients,someofwhommighthavecamimpingement,andsomeofwhomhavefocalacetabulardeficiency[13].Specificpatternsofacetabulardeficiencyandfemoralmorphologyarebestcharacterizedwithcross-sectionalimagingexaminations,suchasMRIorCT,whichmightalsodetectothercausesforhippain.ItisrecommendedthatanychildinwhomthereisconcernfordysplasiaundergoanMRIaspartofacompleteevaluationbecausetheremightbeanotherfindingthatexplainsthechild’ssymptoms(Fig.6),orevidenceofintra-articulardamagethatsupportsrimloading.MRIiswellsuitedfordetectingcartilageandlabralabnormalitiesaswellasmarrowlesionsthatarepresentinthesettingofalteredbiomechanicsandearlyosteoarthritis[8].Low-dosepelvicCTisalsovaluableforpreoperativeassessmentofthehipmorphologywithprecisecharacterizationofthebonydeficienciesinthreedimensions.Itiscrucialthatthesechildrenaredirectedtoanexperiencedhipspecialistwhoisabletocontextualizetheimagingfindingswithacomprehensivephysicalexamandanappropriatehistory.Thesechildrenshouldbeinterrogatedwithrespecttothenatureandlocationoftheirpainwithspecificquestionsaroundinstability.Acomprehensivephysicalexamshouldfollow,includingattentiontothechild’sgait,pelvicpositionandrotationalprofile.ConclusionTheterm“borderlinedysplasia”referstopatternsofacetabularcoveragethatmightpredisposechildrentoinstability.Somechildrenwithborderlineradiographicmeasurementshavenormaljointmechanicsandfunction(Fig.1ShouldsayFigure3),whileothersbenefitfromacetabularreorientingsurgery(Fig.2ShouldsayFigure4)[11].Itisimportantthatradiologistsreflectthisuncertaintyintheirreportswithappropriatemanagementrecommendations.Instabilitymightbesuggestedbyradiographs,butultimatediagnosisisconfirmedonthebasisofhistoryandphysicalexamassessingforinstability.Thesechildrenshouldundergohigh-resolutionMRimagingofthehiptoevaluateforjointdamage,andCTmightbehelpfulforbetter3-Dcharacterizationofthebonyshapeandcontour.Dynamicultrasonographyhasbeenvalidatedasahelpfuladjunctinthedeterminationofinstabilitybymeasuringanteriorfemoralheadtranslationwithdynamicmaneuversreplicatingtheapprehensiontest[54].Aspediatricradiologists,weareoftenthefirsttoidentifyborderlineormilddysplasiaonthebasisofradiographs.Itisimperativethatweserveaseffectiveconsultantsandofferappropriaterecommendationsaspartofacohesivemultidisciplinaryapproachtothiscomplexpatientpopulation.?文獻出處：SarahDBixby,MichaelBMillis.Theborderlinedysplastichip:whenandhowisitabnormal?ReviewPediatrRadiol.2019Nov;49(12):1669-1677.doi:10.1007/s00247-019-04468-4.Epub2019Nov4.??IntroductionDevelopmentalhipdysplasia(DDH)isoneofthemostimportantandmostcommonpediatricmusculoskeletalconditions.Whileasmanyas80%ofcasesarepresentatbirth,manyremainundiagnosed.Whenpresentininfancy,DDHmightbedetectedonthebasisofphysicalexaminationfindings(i.e.BarlowandOrtolanimaneuvers)andstaticanddynamicultrasoundfeaturesoriginallydescribedbyGraf[1,2].Thelong-termimplicationsofDDHaresignificantbecausetheconditionleadstodevelopmentofosteoarthritisin25–50%ofpatientsbytheageof50years[3].Thereducedsizeandtheincreasedobliquityoftheacetabularweight-bearingsurfacecreateshearingforcesonthearticularcartilageandcausechronicoverloadingoftheanteriorandanterolateralacetabularrim[4].Thismechanicaldysfunction,ifuncorrected,leadsinadulthoodtopain,abductorfatigueandoftensymptomsofinstability,culminatingingradualfailureofthecartilageandleadingtoprogressiveosteoarthritis.Treatmentstrategiesdependonthemechanicalstabilityofthehipandthetypeanddegreeofbonydeformity.IninfantswithmildDDH,capsularlaxityandmildacetabulardysplasiaaretheissues,andsimplepositioningofthehipsinabductionandflexioninaprotectivebraceorPavlikharnessusuallyleadstotighteningofthecapsuleandresolutionofthedysplasia.Inchildrenwithfullcongenitaldislocations,particularlyifdiagnosedafterinfancy,aformalmanipulativereductionmightberequired,withspicacastingforseveralmonths.Atanyage,treatmentisfocusedonreducingandmaintainingthefemoralheadtoaconcentricpositionwithintheacetabulum.IfbonymalalignmentispresentintheolderchildwithDDH,realignmentsurgeryisoftenneededtorestorestability.Infantsandchildrenwithdevelopmentalhipdysplasiamightbetreatedtocurebyvirtueoftheseearlystrategies,ortheymighthavepersistentsubluxationthatrequiresfurthersurgerylaterinadolescenceoryoungadulthood.DysplasiainadolescentsAdolescentsandyoungadultswhohadbeenasymptomaticwithrespecttothehipmightalsohavemildformsofacetabulardysplasiadetectedonradiographsbasedoncriteriaoriginallydefinedbyWiberg(Figs.1and2)[5].Inmanychildrentheindicationforradiographsishippain,thoughforsomechildrenradiographsareperformedforotherindications.Intheabsenceofadedicatedexaminationbyahipspecialistwhocanassessforsignsorsymptomsofinstability,itisnotknownwhethermildorsubtleradiographicabnormalitiesarethesourceofthechild’ssymptoms.Radiographicmeasurementsoffemoralheadcoverageandpositionmightsuggestthepossibilityofmechanicaldysfunctionofthehip,thoughitisthemechanicsthatdefinetheunderlyingdisease,nottheradiographs.IncontrasttoinfantileDDH,adolescentdysplasiahasahighermalepredominanceandismoreoftenbilateral[6].Thedifferenceindemographicsbetweengroupshaspromptedmanytoquestionwhetheradolescentandinfantilehipdysplasiasaretwodistinctentities.Thestandinganteroposterior(AP)radiographofthepelvisremainsthegoldstandardofimagingforadolescenthipdysplasia,supplementedbyotherviewsincludingthefalseprofileradiograph[4].Anumberofradiographicmeasurementshavebeendescribedthatdefinethedysplastichip,thethreemostfundamentalincludingthelateralcenteredgeangle(CEA),theacetabularindexandtheanteriorCEA[7].ThelateralCEAandtheacetabularindexarebothmeasuredonaproperlypositionedstandingAPradiographofthepelvis,whereastheanteriorCEAismeasuredonthefalseprofileradiograph(Figs.1and2).In1939Wiberg[5]definedanormallateralCEAasbeingover25°,anabnormalangleaslessthan20°(Fig.2)andeverythinginbetweenasuncertain.Theserangeswerevalidatedinsubsequentinvestigations[8,9].SimilarcriteriaexistfortheanteriorCEAasmeasuredonafalseprofileradiograph,wherethisangleisconsiderednormalabove25°,borderlineat20–24°anddeficientbelow20°(Fig.2)[10].Incertainchildrentheanterioracetabularroofinsufficiencyismoreseverethanthelateralroofinsufficiency,andthefalseprofileviewmighthelptoidentifythesechildren,withthecaveatthattheanteriorCEAisthemostdependentonradiographictechnique[11].Theacetabularindexisconsiderednormalat0–10°[7],thoughsomehavesuggestedthatanglesupto13°arenormal[8].Valuesabovethisareconsideredindicativeofdysplasia.BorderlinemeasurementsWhilefloridacetabulardysplasiaisincontrovertiblewhenidentifiedradiographically(Fig.2),thecorrectdiagnosisbecomesmoredifficultwhenthemeasurementanglesareonlymildlyoutofthenormalrange,leadingtothecreationofan“uncertain”or“borderline”category(Figs.3and4).Thesechildrenremainasourceofconfusionandcontroversyamongradiologistsandhipspecialists.Ultimately,achildfallingintoanuncertaincategoryhaseitherahealthyoranunhealthyhip,andthisdistinctiondependsonavarietyoffactorsuniquetoeachchildthatgobeyondasimpleradiographicmeasurement.Thelabel“borderlinedysplasia”hasbeenadoptedtodefineagroupthatfallsintoanuncertainmeasurementcategorywithlateralCEAof18–24°[12–14],inwhomfurtherevaluationisnecessarybeforeadiagnosiscanbemade.Giventhemechanicalbasisforthejointdamageinacetabulardysplasia,itisareasonableassertionthathipswithslightlydiminishedcoveragearepredisposedtojointdamagerelatedtoincreasedwearontheacetabularrim.Childrenwithmilddysplasiaareknowntohaveevidenceoflabralandcartilagedamageathiparthroscopy[15].ThisdoesnotmeanthatallchildrenwithalateralCEAof18–24°developosteoarthritis.Earlystudiesevaluatingtherelationshipbetweencenteredgeangleanddysplasiafocusedprimarilyonhipfunctionratherthanspecificevidenceofjointdamage[16],thoughitislikelythatnormallyfunctionalhipsmightovertimealsohavelabraltearsandcartilagelesions.Delayedgadolinium-enhancedMRIofcartilage(dGEMRIC)measurementsDelayedgadolinium-enhancedMRIofcartilage(dGEMRIC)wasdevelopedtoidentifyhipswithearlybiomechanicaldamagetothecartilagematrixinadvanceofmorphologiccartilageloss[17].Whenintroducedviaintravenousorintraarticularinjection,ananionicmoleculesuchasgadopentetate?2(Gd-DTPA?2)distributesovertimeincartilageinverselytotheconcentrationofnegativelychargedglycosaminoglycans.TheconcentrationofGd-DTPA?2canbeindirectlydeterminedwithmeasurementsofT1andisexpectedtobelowerinnormalcartilagecomparedtodegradedcartilagewithlossofglycosaminoglycans.Thismeasurementisreferredtoasthe“dGEMRICindex”(Fig.3).EvaluationofthedGEMRICindexinpeoplewithnoormilddysplasiarevealedthatthedGEMRICindexofmildlydysplastichipsdidnotdiffersignificantlyfromthatofnormalhips[17].ItshouldbenotedthatinthisstudypeoplewithmilddysplasiaweredefinedbyalateralCEA>15°,whichislowerthanwhatwouldnowbeconsideredthethresholdofmilddysplasia.Thesedatasuggestthatchildrenwithmildorborderlinedysplasiamightnotbeatincreasedriskofdevelopingend-stageosteoarthritis,thoughbecausethesepeoplewerenotfollowedlongitudinallyovertimeitisunknownwhethercartilagedegenerationevolvedovertime.ThedGEMRICindexalsodoesnotaddresswhetherchildrenhavesignsorsymptomsofinstability,whichmightbewhatbringsthemtomedicalattention.RadiographiclandmarksMeasurementsobtainedfromconventionalradiographsrelyonidentificationofpreciselandmarks,includingthecenterofthefemoralhead,themedialmarginoftheacetabularsourcil,andthelateralmarginoftheacetabularsourcil(Fig.1).Thesourcilisnotalwayswell-defined,especiallyinchildrenyoungerthan15years.Inyoungerchildrenitisuncommonforthelateralmarginofthesourciltoalsobethelateralmarginoftheacetabulum,promptingsomeinvestigatorstodevelopa“modifiedlateralCEA”thatincludesonlythescleroticportionoftheacetabularsourcil.ThisisincontrasttothetraditionalCEA,whichismeasuredtothelateralacetabularmargin[18].Therangeofnormaldependsontechniquebecausethemodifiedanglehasalowerstandardrange(15–20°)comparedtothetraditionalangle.Withoutstrictattentiontoradiographiclandmarksthevariabilitybetweenmeasurementscanbeextreme[19–21].Themostreliablemethodistoautomatetheprocesswithcomputer-aidedsoftware,eitherbyincorporatingacomputerizedmeasurementprogram[22]orbystandardizingtheprojectionoftheradiograph[23].Unlessrigorouscriteriaarebeingusedformeasurement,amildlyabnormalmeasurementshouldnotbeconsideredamarkofdiseaseunlessthereareothercompellingimagingandclinicalfindings.Anadhocmeasurementperformedby“eyeballing”theradiographisunlikelytobeaccurate.Itisbesttomeasuremultipletimes,especiallyintheabsenceofcomputer-aidedsystems.NormalvariantsCrossoversignRadiologistsarewisetoproceedcautiouslyaroundthehip,giventhefrequencywithwhichpreviouslyreportedradiographicmeasurementsorfindingshavebeensubsequentlydeterminedtorepresentnormalvariants.AnexampleofthisisthecrossoversignontheAPpelvisradiographs.In2007itwasdemonstratedthatthepresenceofacrossoversignwasahighlyreliableindicatorofcranial(superioracetabular)anteversionoflessthan4°[24].Forreference,thesuperioraspectoftheacetabulumisantevertedapproximately10–14°.Atangleslessthan0°,theanteriorwallislateraltotheposteriorwall,leadingtothecrossoversignonradiographswherethetwowallsoverlap.ItbecamestandardforradiologistsandhipspecialiststocommentonthepresenceofacrossoversignonAPradiographsofthepelvisassuggestiveofacetabularretroversion.Inclinicalpractice,however,thesechildrendidnotalwayshavesignsorsymptomsofretroversion,nordidcross-sectionalimagingconfirmretroversion.Overtime,theliteraturerefutedanassociationbetweencrossoversignandclinicallyconfirmedacetabularretroversion.Evenasymptomaticchildrenwithouthipdiseaseorsymptomatologydemonstratedacrossoversignonawellpositionedradiograph,reflectingvariationsinpatientpositioningaswellasthevariablemorphologyoftheanteriorinferioriliacspine[25,26].CoxaprofundaInsimilarfashion,theterm“coxaprofunda”fellinandoutoffavoralmostasquickly.Coxaprofundaisdefinedaspresentiftheflooroftheacetabularfossaliesmedialtotheilioischialline.Itisconsideredanindirectsignofacetabularovercoverageofthefemoralheadandwasproposedasanimagingfeatureofpincer-typefemoroacetabularimpingementin2007[27].Withthisawareness,radiologistsreadilyofferedthisimagingfindingasevidenceofanunderlyingcondition:acetabularover-coverage.Overtime,coxaprofundawasclaimedtobeanormalradiographicfindingthatdoesnotsupportadiagnosisofpincerimpingement[28–30].CamdeformityFinally,thedefinitionof“cam”deformityinchildrenwithfemoroacetabularimpingementhasbeenasubjectofinterestanddebateformanyyears.Camlesionsarebonyprotuberancesalongthefemoralhead/neckjunctionthatimpingeagainsttheacetabularriminhipflexion.Themostobjectivemeansofmeasuringthesizeofacamdeformityisthealphaangle,anangleformedbyalineconnectingthecenterofthefemoralheadtothecenterofthefemoralneck,andalinefromthecenterofthefemoralheadtothepointatwhichthefemoralneckfallsoutsideabest-fitcirclearoundthehead.Intheearly2000sitwasacceptedthatchildrenwithanalphaangleintherangeof50°likelyhadcam-typefemoroacetabularimpingement(FAI)[31–34].OverthelastdecadetherehasbeenincreasingawarenessthatsomepreviouslydefinedcamlesionsinpeoplewithFAImightbepresentinasymptomaticpopulationswithnohipdisease[35–38].Moreoverapositiveimpingementtest,oftenassociatedwiththepresenceofanteriorFAI,hasbeendemonstratedinhealthyyoungadultswhomightnothaveFAI[39],makingthisanunreliableindicatorofdiseaseinisolationofotherevidence.RadiographictechniqueGiventhatourinterestinidentifyingandtreatingpainfulanddebilitatingdiseaseinchildrenmightoutpaceourunderstandingofnormalanatomicalvariation,radiologistsneedguidelinesforinterpretingradiographsthatrevealanuncertaindegreeoffemoralheadcoverage.Acautiousapproachwouldbetosuggestthepossibilityofborderlinehipdysplasiaandrecommendreferraltoahipspecialist.Thisrecommendationshouldbeperformedwhentheimagingfindingshavebeendeemedreliable,whichrequiresstrictadherencetoproperimagingtechnique.ThefollowingshouldbeassessedoneveryAPradiographofthepelvis:(1)Isthepelvistiltedorrotated?Asaguideline,thedistancebetweenthesuperioredgeofthepubicsymphysisandthecoccyxshouldbe1–3cm[40].(2)Howwelldefinedarethemeasurementlandmarks?Ifthereisdoubtastowherethelandmarksarelocated,themeasurementsarelikelytobeinaccurate.(3)Aremeasurementsperformedusingelectroniccalipersorwithavalidatedcomputer-assistedprogram?Ifperformedbyhand,havetheinitialmeasurementsbeenvalidatedwitharepeatattempt?(4)Isthepatientolderthan15years,andifnotisthemodifiedlateralCEAstandardbeingemployedratherthantheclassiclateralCEA?Theanswerstothesequestionshaveagreatimpactonthereportedmeasures.Iftheimagingtechniqueisadequateandthechildstillfallsintoanindeterminatecategoryoftheborderlinedysplastic(alateralCEAthatfallsbetween18°and24°),thisisstillonlythefirststepinacomplexdiagnosticprocess.Ourunderstandingofhipdiseasehasevolvedconsiderablyoverthelastdecade.Itisimpossibletoaccuratelycharacterizeallofthedifferentpatternsofinstabilityandunder-coveragewith2-Dradiographicviews.RelyingsolelyonthelateralCEAtodeterminenormalversusdeficientcoverageassumesalldysplasiaisglobal,orprimarilyinvolvesthesuperioracetabulum.Wenowknowthatatleastthreedistinctpatternsofacetabulardeficiencyexist:anterosuperior,global,andposterosuperiorinsufficiency[41],andAPradiographsarenotdesignedtodetectafocalanteriororposteriordeficiency.Thepresenceofborderlinedysplasiaonradiographsalsodoesnotconfirmthepresenceofinstability,whichisultimatelywhatleadstosymptomsandjointdamage.Thepresenceorabsenceofinstabilityorimpingementmustbedeterminedthroughcarefulhistoryandphysicalexam,aswellasfromstaticandpossiblydynamicimaging.Thefemoroepiphysealacetabularroof(FEAR)indexhasbeenproposedasausefulradiographicmarkerofinstability(Fig.5)[42].Anotherhelpfulradiographiccluetothepresenceofinstabilityistheupslopinglateralsourcilmargin[43].Alloftheseobservations,however,requirefurthervalidationbeforetheycanbeconsideredreliablemarkersofdisease.Wiberg[5]laidtheimportantgroundworkwithhisseminalarticledescribingthe“normal”lateralcoverageofthefemoralhead,andformanydecadesthoseassertionshavenotbeendisproved;subsequentinvestigationshaveonlysubstantiatedhisoriginalfindings[44–46],thoughthelowerendofthenormalthresholdhasshiftedmoretowardthedysplasticendofthespectrum.Largerpopulation-basedstudieshaverecentlysuggestedthattheserangesaregender-specificandthatmaleandfemalepatientsshouldnotbemeasuredagainstthesamestandard.UpdatedreferencestandardsproposedbyLaborieetal.[39]suggestedthatcutoffvaluesformalepatientsshouldbe21°comparedto20°infemalepatients.Updatedupperthresholdvaluesforacetabularindexaccordingtothisstudywere15°formalesand16°forfemales,comparedtopreviouspublishedthresholdof10°forbothgroups.Accordingtothesenewcriteria,manypatientswhohadpreviouslybeencharacterizedasmildlyorborderlinedysplasticmightnowbeconsiderednormal.Additionally,age,gender,heightandbodymassindex(BMI)havebeenfoundtobefactorsinwhatareconsideredtobenormalrangesofacetabularcoverage,shiftingthelowerrangeofnormalcoveragefurtherintothedysplasticrangeforcertainpopulations[47].?