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臨界髖關(guān)節(jié)發(fā)育不良Borderline DDH (2)：疼痛性臨界髖關(guān)節(jié)發(fā)育不良的治療臨界髖關(guān)節(jié)發(fā)育不良BorderlineDDH(2)：疼痛性臨界髖關(guān)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(guān)節(jié)科）摘要在過去的幾十年里，影像技術(shù)的改進和手術(shù)技術(shù)的進步使得保髖手術(shù)得到了快速發(fā)展。然而，疼痛性臨界髖關(guān)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(guān)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(lǐng)域。簡介在過去的幾十年里，髖關(guān)節(jié)生物力學知識的提高和手術(shù)技術(shù)的進步使得保髖手術(shù)得到了快速發(fā)展。保髖手術(shù)適應(yīng)范圍廣泛，從髖臼淺且不穩(wěn)定的髖關(guān)節(jié)到髖臼深且患有股骨髖臼撞擊(FAI)的髖關(guān)節(jié)。雖然人們普遍認為，不穩(wěn)定髖關(guān)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(guān)節(jié)都可能存在凸輪畸形，需要在手術(shù)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(guān)節(jié)被稱為“臨界”髖關(guān)節(jié)。通常，這包括外側(cè)中心臨界(LCE)角度在20°到25°之間的髖關(guān)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(guān)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(yīng)納入髖關(guān)節(jié)穩(wěn)定性分析的其他因素。髖關(guān)節(jié)發(fā)育不良與髖關(guān)節(jié)骨關(guān)節(jié)炎之間的關(guān)聯(lián)已經(jīng)確定[3,4]，有不穩(wěn)定跡象的髖關(guān)節(jié)發(fā)育不良退化速度更快[5]。臨界髖關(guān)節(jié)可能不穩(wěn)定、撞擊或兩者兼而有之。臨界髖關(guān)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(dǎo)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(guān)節(jié)鏡髖關(guān)節(jié)手術(shù)（包括盂唇修復(fù)和關(guān)節(jié)囊折疊縫合術(shù)）可能會在短期內(nèi)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(guān)節(jié)鏡檢查會對此類髖關(guān)節(jié)的治療結(jié)果產(chǎn)生負面影響[6]。因此，疼痛性臨界髖關(guān)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(guān)節(jié)發(fā)育不良在患有髖關(guān)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(guān)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(cè)中心邊緣角傳統(tǒng)上用于將髖關(guān)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(cè)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(cè)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(zhuǎn)中心。第二個分支由股骨頭的中心和股骨最外側(cè)點定義（圖1a）。重要的是不要使用髖臼的最外側(cè)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(cè)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(cè)中心邊緣角(LCEA)，表明中度髖關(guān)節(jié)發(fā)育不良。(b)同一髖關(guān)節(jié)的外側(cè)中心邊緣角(LCEA)測量不正確。使用此值會錯誤地將此髖關(guān)節(jié)歸類為臨界。其次，實際術(shù)語“臨界髖關(guān)節(jié)發(fā)育不良”是由Wiberg本人首次提出的，包括外側(cè)中心邊緣角(LCEA)在20°和25°之間的髖關(guān)節(jié)[2]。外側(cè)中心邊緣角(LCEA)是一種放射學測量，本身無法預(yù)測臨界髖關(guān)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(cè)中心邊緣角(LCEA)無法指導(dǎo)手術(shù)決策[12–14]。部分原因是外側(cè)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(guān)節(jié)穩(wěn)定性密切相關(guān)。如果外側(cè)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(guān)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(guān)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(guān)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(guān)節(jié)穩(wěn)定性的功能表征對于指導(dǎo)手術(shù)決策至關(guān)重要。不穩(wěn)定髖關(guān)節(jié)從邏輯上可以從髖臼重新定向截骨術(shù)中受益，而穩(wěn)定髖關(guān)節(jié)可以從撞擊手術(shù)（如股骨凸輪骨成形術(shù)）中受益。那么關(guān)于髖關(guān)節(jié)內(nèi)病理學的了解有多少？應(yīng)該如何評估這些患者？有哪些治療方案？手術(shù)結(jié)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(guān)節(jié)發(fā)育不良和臨界髖關(guān)節(jié)不穩(wěn)定的潛在病理是什么？髖關(guān)節(jié)發(fā)育不良患者的關(guān)節(jié)接觸壓力異常增高，股骨頭（軟骨損傷，導(dǎo)致軟骨下）骨質(zhì)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(dǎo)致病理性髖關(guān)節(jié)生物力學，表現(xiàn)為盂唇撕裂、軟骨損傷和髖關(guān)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(guān)節(jié)囊）的重要性就凸顯出來[18]。一旦軟組織約束失效，髖關(guān)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(dǎo)致髖關(guān)節(jié)失效，而不是軟組織穩(wěn)定性失效。半脫位髖關(guān)節(jié)發(fā)育不良的自然病史預(yù)后非常差，并且必然會導(dǎo)致關(guān)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(guān)，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(yù)測退化速度。臨界髖關(guān)節(jié)發(fā)育不良也是如此。最近的一項研究強調(diào)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(cè)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(guān)節(jié)發(fā)育不良的臨床表現(xiàn)與其他年輕活躍成人髖關(guān)節(jié)疾?。ㄈ鏔AI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(guān)重要。病史重點記錄病史。臨界髖關(guān)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(guān)節(jié)外側(cè)，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(guān)節(jié)炎，例如夜間疼痛。癥狀應(yīng)結(jié)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(shù)。檢查隨后應(yīng)進行髖關(guān)節(jié)的合理臨床檢查，包括恐懼試驗和撞擊測試?；颊咄ǔ憩F(xiàn)出“膝內(nèi)翻”步態(tài)，同時伴有髖關(guān)節(jié)內(nèi)收肌力矩增加和髖關(guān)節(jié)內(nèi)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(yīng)確定大轉(zhuǎn)子處有無壓痛[22]。務(wù)必記住檢查患者的旋轉(zhuǎn)輪廓、進行神經(jīng)血管檢查以及檢查全身關(guān)節(jié)松弛的跡象，并使用Beighton評分對此進行量化。具體關(guān)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(diào)查診斷成像應(yīng)從骨盆的標準化AP平片和股骨頸側(cè)位片（穿桌側(cè)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(yīng)確定骨關(guān)節(jié)炎的Tonnis等級以及是否存在凸輪形態(tài)。應(yīng)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(guān)節(jié)處于外展狀態(tài)，使用MR關(guān)節(jié)造影時后關(guān)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(guān)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(guān)骨解剖結(jié)構(gòu)和發(fā)育不良位置的精確信息，包括髖關(guān)節(jié)周圍囊腫的存在和位置[24-26]。此外，CT還應(yīng)包括股骨前傾的評估，如果前傾過大，可能會加劇髖關(guān)節(jié)前部不穩(wěn)定。磁共振成像(MR-關(guān)節(jié)造影)應(yīng)遵循專門的髖關(guān)節(jié)檢查方案，包括徑向圖像采集或重建和關(guān)節(jié)內(nèi)造影劑應(yīng)用[27]，以檢查關(guān)節(jié)內(nèi)結(jié)構(gòu)和盂唇和關(guān)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(zhuǎn)子滑囊炎或臀肌病變。其他測量包括盂唇大小[13,28]和髂關(guān)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(guān)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(guān)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(guān)節(jié)造影中，后下關(guān)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(yù)測不穩(wěn)定性[30]（表1）。表1.用于評估髖關(guān)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(yù)測髖關(guān)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(guān)節(jié)的關(guān)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(guān)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(guān)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(guān)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(guān)節(jié)在生長過程中長期的關(guān)節(jié)反作用力。如果FEAR<0°，則認為髖關(guān)節(jié)穩(wěn)定。統(tǒng)計分析表明，5°的臨界值預(yù)測穩(wěn)定性的概率為80°。最近的研究表明，2°的臨界值預(yù)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(nèi)側(cè)和外側(cè)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(nèi)側(cè)和外側(cè)端的線之間的角度。如圖3a所示，角度向內(nèi)側(cè)打開的陰性FEAR指數(shù)，表示髖關(guān)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(guān)節(jié)穩(wěn)定，患者接受髖關(guān)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(guān)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(guān)節(jié)的穩(wěn)定性。疼痛性臨界髖關(guān)節(jié)發(fā)育不良的治療方案包括非手術(shù)治療、解決關(guān)節(jié)內(nèi)撞擊的手術(shù)治療（通過髖關(guān)節(jié)鏡或髖關(guān)節(jié)外科脫位進行的FAI手術(shù)）和解決不穩(wěn)定性的手術(shù)治療（采用PAO和/或股骨截骨術(shù)的重新定位截骨術(shù)）（見圖2）。非手術(shù)治療包括患者教育、活動調(diào)整、簡單的止痛藥、非甾體抗炎藥和髖關(guān)節(jié)腔內(nèi)注射藥物[35]。有針對性的物理治療可以改善肌肉調(diào)節(jié)、疼痛和本體感受控制。以下段落將討論包括關(guān)節(jié)鏡和/或截骨術(shù)的臨界髖關(guān)節(jié)發(fā)育不良的手術(shù)治療方案。這組患者接受髖關(guān)節(jié)鏡檢查的結(jié)果如何？隨著髖關(guān)節(jié)鏡技術(shù)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(guān)節(jié)發(fā)育不良，尤其是因為人們認為髖臼周圍截骨術(shù)等替代技術(shù)的風險更高，術(shù)后恢復(fù)時間更長。臨界髖關(guān)節(jié)發(fā)育不良的髖關(guān)節(jié)鏡檢查還可以讓外科醫(yī)生處理髖關(guān)節(jié)內(nèi)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(guān)節(jié)鏡檢查不僅可以讓外科醫(yī)生了解髖關(guān)節(jié)的關(guān)節(jié)內(nèi)狀態(tài)，還可以了解患者在隨后進行更大規(guī)模手術(shù)時的表現(xiàn)[37]。然而，關(guān)于臨界髖關(guān)節(jié)發(fā)育不良的髖關(guān)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(guān)于髖關(guān)節(jié)發(fā)育不良的關(guān)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(jié)果。關(guān)節(jié)鏡檢查的手術(shù)指征不明確，患者事先接受過多種非手術(shù)治療。此外，臨界髖關(guān)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(guān)節(jié)鏡作為輔助工具，三項研究報告了髖關(guān)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(guān)節(jié)發(fā)育不良病例（LCEA20-25°）的關(guān)節(jié)鏡檢查結(jié)果，其中只有一項描述了患者報告的結(jié)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(guān)節(jié)（32髖）患有臨界髖關(guān)節(jié)發(fā)育不良。關(guān)節(jié)鏡檢查后，平均改良Harris髖關(guān)節(jié)評分從50（差）改善到77（一般）。作者得出結(jié)論，髖關(guān)節(jié)鏡治療可能解決髖關(guān)節(jié)內(nèi)病理而不是發(fā)育不良的放射學證據(jù)的結(jié)果。對臨界髖關(guān)節(jié)發(fā)育不良進行髖關(guān)節(jié)鏡檢查有什么危險？臨界髖關(guān)節(jié)發(fā)育不良患者進行關(guān)節(jié)鏡盂唇切除術(shù)和髖臼外側(cè)緣切除術(shù)可導(dǎo)致爆發(fā)性髖關(guān)節(jié)不穩(wěn)定[38]。即使修復(fù)了盂唇，也必須保留髂股韌帶和髖關(guān)節(jié)的其他靜態(tài)穩(wěn)定器，以防止不可逆的后果或?qū)е麦y關(guān)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(guān)節(jié)囊修復(fù)，但這似乎是一種安全合理的做法[42]。關(guān)節(jié)囊復(fù)位技術(shù)可提高臨界髖關(guān)節(jié)發(fā)育不良的穩(wěn)定性[12]。如果髖關(guān)節(jié)在術(shù)前足夠不穩(wěn)定，那么僅通過髖關(guān)節(jié)鏡治療關(guān)節(jié)內(nèi)病變是不夠的，患者將需要進行PAO截骨術(shù)[43,44]。必須記住，髖關(guān)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(jié)構(gòu)來確保。一旦這些結(jié)構(gòu)因微創(chuàng)傷或大創(chuàng)傷而失效，髖關(guān)節(jié)就會變得不穩(wěn)定。恢復(fù)軟組織穩(wěn)定性可能只會在短時間內(nèi)改善髖關(guān)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(guān)節(jié)發(fā)育不良患者在髖關(guān)節(jié)鏡檢查失敗后，PAO的髖關(guān)節(jié)特定功能結(jié)果較差[6]。因此，對這組患者單獨進行髖關(guān)節(jié)鏡檢查應(yīng)謹慎處理。但是，對于那些由于髖關(guān)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(shù)對這組患者有何影響？通過髖臼周圍截骨術(shù)進行髖臼重新定向已成為髖關(guān)節(jié)發(fā)育不良最常見的治療方法，據(jù)報道術(shù)后20多年效果良好。傳統(tǒng)上，PAO時關(guān)節(jié)內(nèi)病變的處理方法是進行前關(guān)節(jié)切開術(shù)。然而，隨著PAO微創(chuàng)技術(shù)的發(fā)展，情況已不再如此。微創(chuàng)PAO技術(shù)縮短了術(shù)后恢復(fù)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(dǎo)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(shù)年齡的獨立預(yù)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(shù)。但是，輕度和中度發(fā)育不良患者的PAO預(yù)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(guān)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(jié)果指標，結(jié)果表明，雖然總體結(jié)果良好，但臨界髖關(guān)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(dǎo)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(guān)節(jié)中，關(guān)鍵步驟是確定穩(wěn)定性。關(guān)于髖關(guān)節(jié)的穩(wěn)定性，只有兩種情況：髖關(guān)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(jié)合，需要同時治療。如果髖關(guān)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(jié)果。在穩(wěn)定的髖關(guān)節(jié)中，可以進行開放或關(guān)節(jié)鏡關(guān)節(jié)保留手術(shù)。然而，我們必須記住，低于28°的LCE角度每減少一度，骨關(guān)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(jié)果的機會，我們主張進行髖臼重新定向PAO截骨手術(shù)。重要的是要確定我們?nèi)狈χR的領(lǐng)域，以指導(dǎo)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(guān)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(yīng)獲得患者報告的結(jié)果測量和恢復(fù)時間，以及包括運動在內(nèi)的活動恢復(fù)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(guān)節(jié)發(fā)育不良Borderline DDH：什么時候、怎么判定為異常？臨界髖關(guān)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(guān)節(jié)科）摘要臨界髖關(guān)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(dǎo)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(cè)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(guān)節(jié)力學和功能，而其他兒童則需要進行髖臼截骨手術(shù)。雖然臨界髖關(guān)節(jié)發(fā)育不良的X線檢查結(jié)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(jié)合?；加信R界髖關(guān)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(shù)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(fù)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(guān)節(jié)X線片顯示了外側(cè)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(zhuǎn))中心，點2位于股骨髖關(guān)節(jié)(負重關(guān)節(jié)面的)內(nèi)側(cè)邊緣，點3位于股骨髖關(guān)節(jié)(負重關(guān)節(jié)面的)外側(cè)邊緣。b右髖關(guān)節(jié)的前后位X線片展示了測量外側(cè)CEA的方法。外側(cè)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(guān)節(jié)的假斜位片顯示了確定前CEA的測量方法。前側(cè)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(cè)髖關(guān)節(jié)發(fā)育不良。a骨盆前后位X線片顯示右側(cè)髖關(guān)節(jié)外側(cè)中心邊緣角(CEA)為5°，b髖臼指數(shù)為16°。左髖關(guān)節(jié)同樣發(fā)育不良。c右髖關(guān)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(cè)髖關(guān)節(jié)疼痛的16歲女孩的外側(cè)中心邊緣角(CEA)。a前后位(AP)骨盆X線片顯示外側(cè)CEA為19°。左側(cè)髖關(guān)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(shù)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(guān)，女孩在髖關(guān)節(jié)外科醫(yī)生的護理下接受長期觀察。圖4?一名有髖關(guān)節(jié)發(fā)育不良家族史的11歲女性足球運動員的左側(cè)髖關(guān)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(cè)髖關(guān)節(jié)疼痛。雙側(cè)髖關(guān)節(jié)被認為是淺的，左側(cè)測量的外側(cè)中心邊緣角(CEA)為16°，右側(cè)為23°。左側(cè)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(cè)髖關(guān)節(jié)的不穩(wěn)定，右側(cè)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(cè)髖臼周圍截骨術(shù)后前后位AP骨盆X線片狀態(tài)顯示側(cè)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(fù)正?；顒印Ｋ覀?cè)有輕微間歇性疼痛，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(guān)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(cè)傾斜的角度，頂點指向內(nèi)側(cè)。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(guān)性。b一名13歲女孩的髖關(guān)節(jié)前后位X線片顯示左側(cè)髖臼外側(cè)輕微上翻（箭頭）。c一名13歲男孩的右側(cè)髖關(guān)節(jié)疼痛的左側(cè)髖關(guān)節(jié)正常前后位X線片顯示外側(cè)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(guān)節(jié)的FEAR指數(shù)顯示FEAR指數(shù)，角度頂點指向外側(cè)。圖6?一名18歲女子田徑運動員的右側(cè)髖關(guān)節(jié)疼痛影像。a前后位(AP)骨盆X線片顯示右側(cè)髖關(guān)節(jié)發(fā)育不良，左髖關(guān)節(jié)正常。b右側(cè)髖臼周圍截骨術(shù)后前后位(AP)骨盆狀態(tài)顯示外側(cè)覆蓋增加，但該女性報告癥狀惡化。c術(shù)前（回顧性）進行的右髖關(guān)節(jié)矢狀質(zhì)子密度脂肪抑制MR圖像顯示前髖臼內(nèi)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].?