334 Instructional Course Lectures J Korean Orthop Assoc 2013; 48: 334-341 http://dx.doi.org/10.4055/jkoa.2013.48.5.334 www.jkoa.org Introduction to Musculoskeletal Ultrasonography 정웅교 이순혁 고려대학교의과대학정형외과학교실 pissn : 1226-2102, eissn : 2005-8918 Ultrasonographic Findings of Musculoskeletal Tissues Woong-Kyo Jeong, M.D., Ph.D., and Soon-Hyuck Lee, M.D., Ph.D. Department of Orthopedic Surgery, Korea University College of Medicine, Seoul, Korea In order to accurately diagnose lesions of musculoskeletal tissue, evaluation not only of the abnormality of the bone, but the condition of soft tissue is important. Magnetic resonance imaging has been widely used in evaluation of the state of soft tissue, however, it has the disadvantage that testing is expensive and real-time scanning is not possible. In recent years, ultrasonography has been used for evaluation of musculoskeletal tissue and its usefulness has shown a gradual increase. The ultrasound image is determined by the tissue specific acoustic impedance and other factors. Highly reflective tissues such as bone, calcification, ligament, and tendon are expressed as hyperechoic images, and less reflective tissues such as muscle and nerve are expressed as hypoechoic images. Key words: musculoskeletal system, ultrasonography 서론 최근환자의진료시초음파를사용하는정형외과의사가점점 늘고있고이제는초음파가근골격계질환의진단및치료에유 용한도구로서자리매김하고있다. 하지만, 단순방사선사진, 전 산화단층촬영 (computed tomography), 자기공명영상 (magnetic resonance imaging) 등을주로접해온정형외과의사에게초음파 영상은생소한영상이며이때문에초음파검사를처음시작하기 를주저하곤한다. 하지만근골격계조직의해부학, 조직학적구 조에정통한정형외과의사들은초음파영상의원리및기본적인 영상을익히기만하면보다빠른시간에초음파를익숙하게이용 할수있을것이다. 1) 따라서본문에서는다양한근골격조직의정상초음파소견과 검사방법, 대표적인병적초음파소견에대하여논의하고자한다. Received August 9, 2013 Revised September 9, 2013 Accepted September 13, 2013 Correspondence to: Woong-Kyo Jeong, M.D., Ph.D. Department of Orthopedic Surgery, Korea University Anam Hospital, 73 Inchon-ro, Seongbuk-gu, Seoul 136-705, Korea TEL: +82-2-920-5924 FAX: +82-2-924-2471 E-mail: drshoulder@korea.ac.kr 본론 1. 골격근근육조직의기본적인단위는근섬유라고불리는하나하나의근육세포이며이들이평행하게배열되어근육을형성한다. 근섬유하나하나는모세혈관과신경이망을형성하고있는근내막 (endomysium) 으로둘러싸여있다. 이런여러개의근섬유가모여근속 (muscle bundle) 을이루며이는결체조직, 혈관, 신경, 지방조직으로구성되어있는근주막 (perimysium) 으로둘러싸여있다. 또한하나의근육은이런다수의근속이모여구성되며강한결체조직인근외막 (epimysium) 으로싸여있다. 사지의골격근은작용하는기능에따라근섬유가다양하게배열되게발달하였고흔히관찰되는배열은방추상 (fusiform) 배열, 깃털 (pennate form) 배열, 방사상 (radial) 배열등이있다. 이런조직학적특징때문에근섬유는초음파검사에서저에코영상으로나타나며, 근주막의섬유지방중격은근섬유를구분하는고에코의선으로구현된다. 근육을초음파로검사하기위해서먼저고려해야할것이적절한변환기 (transducer) 와초음파진동수의선택이다. 예를들어수부의근육과같이피부에서얕게위치하는근육을검사하기위해 The Journal of the Korean Orthopaedic Association Volume 48 Number 5 2013 Copyright 2013 by The Korean Orthopaedic Association This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
335 Figure 1. Ultrasonography (US) findings of normal skeletal muscle. Long axis (A) and short axis (B) US image of the biceps brachii muscle shows innumerable hyperechoic lines (arrowheads) consistent with perimysium. The epimysium (arrows) demarcates the outer boundaries of the muscle. H, humerus. Figure 2. Ultrasonography (US) findings of muscle contusion. (A) Long axis US image of the biceps brachii muscle shows a focal hypoechoic defect (arrowheads) within the muscle. (B) Six weeks after injury, resorption of hematoma and regeneration of muscle bundle is observed (arrowheads). B, biceps brachii muscle; H, humerus. 서는작고 7-15 MHz 의고주파를발생하는변환기가필요하고대퇴부, 둔부의근육과같이크고깊게위치하는근육을검사하기위해서는 3.5-10.0 MHz 정도의저주파를발생하는변환기를사용하여야적절한영상을얻을수있다. 정상골격근의초음파소견은장축영상에서근섬유들에의해비교적저에코의배경이관찰되고중간중간근주막에의한고에코의선들이관찰되며, 단축영상에서는근섬유로인한저에코사이에고에코의작은점들이관찰된다 (Fig. 1). 근육의초음파검사는다양한병변을진단하는데유용하며특히외상후에근육의파열을가장간편하고정확하게진단할수있다. 근육의파열은둔탁한물건등에의해직접적인압박손상을입은경우나근육이갑자기신장된경우에발생할수있다. 압박손상에의한근육손상의특징적인초음파소견은근섬유내에불규칙한저에코의음영이나타나는것이며주위에혈종등으로인한무에코영역 (anechoic area) 이보일수있다 (Fig. 2A). Lehto 와 Alanen 2) 에따르면손상초기보다는약 48시간에서 72시간이지난후에출혈, 혈종의초음파음영이보다명확하게구분되므로근육파열의범위를정확히평가할수있다고하였다. 시간이경과하여근육손상이회복되면서무에코영역의주변부부터음영이있는조직으로채워지는것을관찰할수있다 (Fig. 2B). 2. 건건은대부분제1형콜라겐으로이루어진건섬유와세포외기질로구성되어있으며결체조직, 탄성섬유, 작은혈관등으로구성된건내막 (endotendineum), 건주막 (peritendineum) 이콜라겐을둘러싸고있다. 이는다시건외막 (epitendineum) 과강하게결합되어있다. 정상적인건의초음파소견은장축영상에서세밀하고빽빽하게배열된고에코의선이섬유모양 (fibrillar pattern) 으로배열된것이특징적이며단축영상은다수의밝은점들이모여군락을
336 정웅교 이순혁 Figure 3. Ultrasonography (US) findings of a normal tendon. (A) Long axis US image of the flexor digitorum tendon (arrows) shows numerous echogenic intratendinous interfaces, resulting in the typical fibrillar appearance. (B) Short axis US image of the flexor digitorum tendon (arrowheads) shows a homogeneous intratendinous pattern made of bright stippled clustered dots. Figure 4. Long axis ultrasonography image of the supraspinatus tendon shows a focal hypoechoic area (arrowheads) due to anisotrophic artifact. GT, greater tuberosity; SSP, supraspinatus tendon. 이루고있는것이특징이고고주파의초음파변환기를사용할수 록저명해진다 (Fig. 3). 또한건의종류에따라단면이원형 ( 상완 이두건장두, 수지굴곡건등 ), 타원형 ( 아킬레스건 ), 직사각형 ( 슬 개건 ) 모양을나타낸다. 건의초음파검사는일반적으로고해상도선형변환기를사용 하는것이좋으며검사시야 (field of view), 해상도, 초점거리등을 알맞게조절하여야한다. 먼저건의횡단면, 즉단축초음파영상 을촬영하여건의위치를확인하고이를기준으로종단면, 장축 초음파검사를시행하면관찰에보다용이하다. 건의초음파검 사에서가장주의할점은변환기를최대한관찰하고자하는부위 에수직으로위치하는것이다. 초음파가건에비스듬하게입사되 면이등방성 (anisotropy) 에의해정상적인에코가사라지게된다. 특히극상건같이건섬유의일부가사면으로뼈에부착되거나, Figure 5. Ultrasonography findings of tendinopathy. Long axis image of the extensor carpi radialis brevis tendon shows a focal hypoechoic area (arrows), small calcifications (arrowheads), and loss of fibrillary pattern. LE, lateral epicondyle; RH, radial head. 관절위를지나며굴곡진경우에더욱세심하게검사를하여야 한다 (Fig. 4). 건실질의이상은건의퇴행성변화로인한건증 (tendinosis), 3,4) 건의일부가단절된부분파열, 건단면의전체가단절된완전파 열등이있다. 건증의초음파소견은건의국소적인부종이나타 나기도하고, 건실질내에국소적인저에코의영역이보이거나 섬유모양의선이불분명해지거나, 선사이의간격이증가하기도 한다 (Fig. 5). 5-7) 부분파열의경우국소적인고에코의섬유모양의 선의결손이관찰되며, 완전파열의경우에는고에코의섬유모 양의선의완전한단절이관찰된다 (Fig. 6). 건내에석회가침착 되는석회화건염의경우에는침착된석회의성상에따라건내 의석회의경계가아주강한고에코의선으로보이기도하고경 계가불분명한고에코의덩어리로나타나기도하며후방음향음 영 (posterior acoustic shadowing) 이강하게혹은약하게나타난다
337 Figure 6. Ultrasonography (US) findings of rupture of tendon. Long axis (A) and short axis (B) US image of the supraspinatus shows a focal anechoic cleft (arrows). SSP, supraspinatus tendon. Figure 7. Ultrasonography findings of calcific tendinitis of the shoulder. (A) Type I calcification appears as an intratendinous hyperechoic focus (arrows) with well-defined posterior acoustic shadowing (arrowheads). (B) Type III calcification appears as a hyperechoic focus (arrowheads) with absence of posterior acoustic shadowing. (Fig. 7). 건의초음파검사에서는건실질내의음영의이상, 건섬유모양의상태, 건의윤곽등건자체의검사뿐아니라건의안정성을함께검사하여야한다. 특히역동적검사를통해서건의불안정성을쉽게진단할수있으며상완이두건장두, 8) 비골건, 9) 후경골건 10) 의불안정등이보고되고있다. 3. 뼈뼈의상태를관찰하기가장유용한영상진단법은단순방사선사진이며초음파로는피질골하방의영상을얻을수없는한계가있다. 정상적인피질골의초음파영상은균일하게고에코의선과하방의저명한음향그림자 (acoustic shadowing) 가특징적이다 (Fig. 8). 간혹아주밝은고에코의선하방으로몇개의연속적인고에코의선이반복적으로관찰되기도하는데, 이는해면골내의이상보다는반향 (reverberation) 에의한허상 (artifact) 으로생각하여야한다. 소아의경우에는골막이저에코의얇은선으로피질 Figure 8. Long axis ultrasonography image of diaphysis of the radius shows a continuous straight hyperechoic line (arrows) and a reverberation artifact (arrowheads) projecting in the shadow beyond the bone can be seen.
338 정웅교 이순혁 Figure 9. Plain radiographs and ultrasonography (US) findings of mid-clavicle fracture. (A) Plain radiographs of the right clavicle taken six weeks after injury show no callus formation (arrow). (B) US image shows hyperechoic ossified callus formation (arrowheads). Figure 10. Short axis ultrasonography image of the anterior elbow joint shows a superficial echogenic layer (dashed arrows) related to an acoustical impedance mismatch between cartilage (solid) and adjacent fluid (water), an intermediate hypoechoic band (arrowheads) due to the hyaline cartilage and a deep echogenic layer at the cartilagesubchondral bone interface (arrows). Figure 11. Long axis ultrasonography image of the posterior shoulder shows a triangular hyperechoic posterior labrum (L). H, humeral head; G, glenoid. 골의고에코의선바로위를따라관찰되기도한다. 뼈의초음파가유용한점은늑골골절, 소아골절과같이단순방사선영상에서골절을쉽게진단하기어려운경우에보다쉽게골절을진단할수있고, 11-13) 단순방사선사진보다조기에가골형성을관찰할수있어골유합을예측할수있다는점이다 (Fig. 9). 14,15) 또한역동적초음파검사를통해골절부위혹은견봉골 (Os acromiale) 등의불안정여부를판단할수있다. 16) 4. 활막관절인체에는다양한형태의관절이존재하지만가장많은부분을차지하는관절은활막관절 (synovial joint) 이다. 활막관절은관절면을이루는뼈, 관절막과인대, 활막및연골판, 관절순등의내부구조물로구성되어있으며뼈는초자연골로덮여있다. 정상적인윤활관절은연골세포와콜라겐과프로테오글리칸 (proteoglycan) 으로이루어진세포기질로구성되어있고초음파 Figure 12. Long axis ultrasonography image over the medial knee shows the normal medial collateral ligament as a thick fibrillar band (arrowheads). F, femur; T, tibia; M, medial meniscus.
339 Figure 13. Ultrasonography (US) findings of a normal median nerve. (A) Short axis US image shows well-circumscribed individual structures of different sizes separated by echogenic epineurium (arrowheads). (B) Long axis US image shows the nerve fascicles appearing as elongated hypoechoic bands (arrowheads) that run parallel to each other. The internal epineurium (arrows) separates them more clearly. M, median nerve; T, flexor tendon. 영상소견은두개의고에코선사이에저에코부분이관찰된다 (Fig. 10). 상부의고에코는관절액과초자연골사이의경계에서관찰되는선이고중간의저에코는연골차체의음영, 하방의고에코는연골하방에위치하는피질골에의해만들어지는선이다. 인체의대부분의활막관절은 7-12 MHz 정도의변환기를사용하여관찰할수있고특히수지관절이나족지관절같이아주작은관절은 hockey stick 형태의변환기를사용하면용이하게관절낭, 활막등을관찰할수있다. 하지만, 고관절같이심부에위치한관절이나비만한환자의경우에는보다낮은주파수의변환기를사용하여야적절한영상을얻을수있다. 초음파검사를통해관절내삼출액, 활막의비후, 골의미란등을관찰할수있다. 관절내에존재하는슬관절의반월상연골, 견관절의관절순같은섬유연골은균일한고에코의영상으로관찰되며주변의뼈혹은관절막과연결되어있다 (Fig. 11). 하지만대부분심부에위치하고있어초음파영상으로세밀한부분까지관찰하기에는한계가있다. 관절을보강하는인대의초음파소견은관절양측뼈를연결하는고에코의섬유모양의띠형태를띤다 (Fig. 12). 인대역시건과마찬가지로이등방성에취약한구조이므로초음파검사를할때변환기의각도가수직이되도록주의하여야한다. 인대파열의초음파소견은파열의급, 만성유무에따라다르게나타난다. 급성부분파열의경우에는인대의부종이나국소적인저에코의영역이관찰되나전체적인연결은끊어져있지않다. 또한주변부연부조직의부종으로인해인대의천부에무에코의띠가나타날수도있다. 17) 급성완전파열의경우에는인대실질가운데에저에코의단절부분이나타날수있고주변에혈종이관찰될수있다. 특히관절에부하를가하며초음파검사를하면인대파열에의한관절의불안정을보다정확하게진단할수있다. 만성부분파열의경우에는인대가정상보다두꺼워져있고, 인대내에고에코의석회성병변을관찰할수도있다. 18) 5. 신경신경은신경섬유와이를둘러싸고있는내막 (endoneurium) 이있 고몇개의신경섬유가모여다발 (fascicle) 을이루고있다. 이신경섬유다발들은신경주막 (epineurium) 에둘러싸여있고, 몇개의신경다발은작은혈관을포함한결체조직으로연결되어있고이는다시신경외막 (epineurium) 으로싸여있다. 신경의초음파소견은비교적일관된양상을나타낸다. 단축영상에서는마치벌집과같이고에코의배경안에군데군데저에코의점들이산재되어있는모습이고장축영상에서는고에코의띠로구분되는여러개의저에코의선으로보인다 (Fig. 13). 저에코는신경섬유다발에의한영상이고고에코는섬유다발사이의신경주막에의해나타나는현상이다. 수근관증후군, 주관증후군등신경의압박되는경우초음파는신경의모양과신경내부의초음파음영의변화가관찰될수있다. 신경이갑자가납작하게변하거나압박이있는근위부는부종으로인해직경이증가될수있다. 19) 또한척골신경같은경우는관절운동에따라신경의불안정성이관찰될수있으므로특히역동적검사를시행하여야한다. 결론 근골격계조직의초음파영상은이를구성하는조직의구조와성상에의해특징지어진다. 따라서, 초음파영상이구현되는원리를이해하면각조직의특징적인영상소견에익숙해지는데많은시간이소요되지는않을것이며, 또한병적소견의초음파영상소견역시병인과병리소견을기초로하면검사및판독에어려움이없을것이다. 초음파는근골격계조직의여러상태를간편하게진단하고치료에도이용할수있는등필수적인도구로자리매김하고있다. 또한정상적인조직과병적인상황에익숙한정형외과의사는근골격계초음파검사에비교적손쉽게익숙해질수있을것이다. REFERENCES 1. Moosmayer S, Smith HJ. Diagnostic ultrasound of the shoul-
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341 pissn : 1226-2102, eissn : 2005-8918 Instructional Course Lectures J Korean Orthop Assoc 2013; 48: 334-341 http://dx.doi.org/10.4055/jkoa.2013.48.5.334 www.jkoa.org 근골격계초음파입문 정웅교 이순혁 고려대학교의과대학정형외과학교실 근골격계조직의병변을정확하게진단하기위해서는골조직의이상뿐아니라, 다양한연부조직의상태를평가하는것이중요하다. 연부조직의상태를평가하기위해서자기공명영상이널리사용되어왔으나검사비용이비싸고, 실시간검사가불가능한단점이있다. 최근에는근골격계조직의평가를위해초음파검사가사용되고있고, 점차유용성이증가하고있다. 초음파영상은조직고유의음향저항등에따라음영이구현된다. 초음파가잘반사되는뼈, 석회, 인대, 건등은고음영으로, 반사가덜일어나는근육, 신경등은저음영으로표현된다. 색인단어 : 근골격계조직, 초음파 접수일 2013 년 8 월 9 일수정일 2013 년 9 월 9 일게재확정일 2013 년 9 월 13 일책임저자정웅교서울시성북구인촌로 73, 고려대학교안암병원정형외과 TEL 02-920-5924, FAX 02-924-2471, E-mail drshoulder@korea.ac.kr 대한정형외과학회지 : 제 48 권제 5 호 2013 Copyright 2013 by The Korean Orthopaedic Association This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.