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1 Clinical Article The Korean Journal of Sports Medicine 2014;32(2): Jones 골절에서유한요소해석을이용한골수강내나사고정술과양측피질골나사고정술의비교 - 예비보고 - 대구가톨릭대학교의공학과 1, 조선대학교의과대학정형외과학교실 2 이연수 1 ㆍ이준영 2 ㆍ박상수 2 ㆍ임채원 2 ㆍ권은지 1 A Comparison of Bicortical and Intramedullary Screw Fixations in Jones Fractures Using Finite Element Analysis - Preliminary Report - Yeon Soo Lee 1, Jun Young Lee 2, Sang Soo Park 2, Chae Won Lim 2, Eun Ji Kwon 1 1 Department of Biomedical Engineering, Catholic University of Daegu College of Medical Science, Daegu, 2 Department of Orthopaedic Surgery, Chosun University Hospital, Chosun University College of Medicine, Gwangju, Korea Intramedullary screw fixation and bicortical screw fixation are widely used operation methods in the surgical treatment of Jones fractures. The purpose of this study is to evaluate of mechnical stability in two kind of Jones fracture. Using Mimics, three-dimensional models of the fifth metatarsal were reconstructed form computed tomography images of a 23-year-old Korean healthy male. Normal and osteoporotic bone models were made by changing bone density or thickness of cortical and cancellous bone. Two kinds of fixation techniques, i.e., intramedullary and bicortical screw fixation models, were simulated and muscles forces related to the fifth metatarsal base were applied. Maximum contact pressure difference were measured as 20,818 MPa, 12,155 MPa in normal bone, 23,371 MPa, 13,765 MPa in 85% cancellous osteoporotic bone, 24,310 MPa and 14,264 MPa in 75% cancellos osteoporotic model, 21,337 MPa, 20,971 MPa in 0.5 mm cortical osteoporotic bone, 26,322 MPa and 36,153 MPa in 1 mm cortical osteoporotic model, respectively for intramedullary screw fixation and bicortical screw fixation. Displacements on fracture interface were mm, mm in normal bone while mm, mm in 85% cancellos osteoporotic model, mm, mm in 75% cancellos osteoporotic model, mm, mm in 0.5 mm cortical osteoporotic model, mm, mm in 1 mm cortical osteoporotic model, respectively for intramedullary screw fixation and bicortical screw fixation. Bicortical screw fixation is superior in mechanical stability than intramedullary screw fixation for normal bone quality Jones fractures. For cortical osteoporotic bone Jones fractures, however, intramedullary screw fixation can give a better mechanical stability than bicortical screw fixation. Keywords: Metatarsal bones, Fracture fixation, Finite element analysis Received: January 6, 2014 Revised: June 4, 2014 Accepted: June 9, 2014 Correspondence: Jun Young Lee Department of Orthopaedic Surgery, Chosun University Hospital, Chosun University College of Medicine, 365 Pilmun-daero, Dong-gu, Gwangju , Korea Tel: , Fax: , leejy88@chosun.ac.kr Copyright 2014 The Korean Society of Sports Medicine CC This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 제 32 권제 2 호

2 YS Lee, et al. Finite Element Analysis in Jones Fracture 서론 1902년 Jones 1) 가제5 중족골근위부골절에대해보고한이후 Jones 골절에대해여러저자가치료의적응증및치료방법에대해보고하였다. Clapper 등 2) 은 Jones 골절환자에서보존적치료를우선적으로시행하여우수한결과를보고한반면 Pietropaoli 등 3) 은사체를이용한생체역학연구를통해보존적치료방법보다는수술적치료방법이임상결과나예후측면에서결과가우수하다고보고하였다. Jones 골절은족관절의족저굴곡상태에서전족부의내전혹은내번시외측경계에장력이가해지면서발생하게되고, 스포츠활동이나운동선수에게서발생빈도가높다 4,5). 활동력이많은사람이거나운동선수가아닌일반인은단하지석고부목고정하에 6 8주간의비체중부하하면서보존적처치를우선고려하는것이 Jones 골절의일반적인치료이다. 운동선수등조기회복이필요한경우에서는수술적처치가시행되기도하는데그방법으로는골수강내나사고정술과양측피질골나사고정술이보편적으로시행되고있다. 두가지수술방법모두좋은결과를보고하고있으나 6,7) 대부분임상적추시에의한결과이다. 생역학적연구는 Husain 과 DeFronzo 8) 가모형뼈와사체실험을통한두가지수술방법에대한연구를하였고양측피질골나사의우수성을발표하였다. 하지만모형뼈와사체실험은완벽히동일한조건하에실험이진행될수없는단점이있다. 이에본연구는유한요소해석의방법으로제5중족골의생리적상태와유사한조건을설정하고 Jones 골절에대해골수강내나사고정술과양측피질골나사고정술을시행하는실험을통해서, 두가지수술방법의기계적안정성에대하여비교분석하였다. 뿐만아니라골다공증성골모델을설정하여골다공증골상태에서두가지수술법의기계적안정성에대해서도비교분석하여이에대한결과를예비보고하고자한다. 컴퓨터전산화단층촬영하였고 1 mm의단층간격으로얻어진영상으로부터 Mimics V15 (Materialise, Leuven, Belgium) 를이용하여연부조직과골조직의컴퓨터캐드모델삼차원이미지를재건하였다. 2. 나사고정모델 Mimics의치밀골의기준인 housefield unit은 662 1,988로설정하여제5중족골의피질골과해면골의경계를나누어모델링하였고 Jones 골절모델은 Rapidform (INUS Technology Inc., Seoul, Korea) 을이용하여경상돌기로부터 1.5 cm 원위부인제4 5중족관절외측부에서시작하여내측피질골을향하여사선방향의가상의골절면을갖도록설정하였다 9). 고정에사용한나사는 4.0 mm 유관나사 (Synthes Inc., Paoli, PA, USA) 를사용하였으며, 전체길이는 45 mm, 나사부길이는 14 mm 였다. 나사삽입방법은골수강내나사고정술의경우제5중족골의경상돌기하연으로부터 10 mm 상방지점과단비골근부착부의바로내측부위지점이만나는곳으로정하였다. 나사의삽입방향은족저부에평행한가상의선에대하여 7 o 의족저굴곡되는방향으로삽입하였으며, 나사가골절부위를충분히통과하지만경상돌기부분의피질골이외의피질골은통과하지않도록하였다 10). 양측피질골나사고정술의경우나사삽입시작점은족저근막와단비골근부착부사이로정하였고외측피질골에서시작하여골절면을통과하고내측피질골까지나사부위가충분히통과하도록하였다 (Fig. 1). 연구방법 1. 연구대상 족부의외상력이나이전의특별한병력이없었던 23.5세한국남성을대상으로하였고신장과체중은 175 cm, 69 kg 이고 body mass index 는 kg/cm 2 으로정상범위에속하였으며이중에너지 X선흡수계측법 (dual-energy X-ray absorptiometry) 으로측정한요추부골밀도는 T-score 0.3이었다. 우측발을 Fig. 1. Bicortical screw fixation (A), Intramedullary screw fixation (B) model. Rectangular grid is fracture plane. 80 대한스포츠의학회지

3 이연수외. Jones 골절에서유한요소해석을이용한골수강내나사고정술과양측피질골나사고정술의비교 - 예비보고 - 3. 유한요소모델재구성된제5중족골과나사모델로부터 tetrahedron 유한요소를생성하였고요소의최대모서리길이는 0.5 mm로정하고원래캐드모델의형상으로부터유한요소로변환중에허용된형상의오차는 0.01 mm 이하로제한하였다. 피질골과해면골의 Young s modulus는각각 15,000 MPa, 300 MPa 그리고공통적으로포아송비 (Poisson s ratio) 는 0.3을부가하였고, 나사의재질은티타늄합금으로가정하여 Young s modulus 는 96,000 MPa, 포아송비는 0.36으로설정하였다. 또한골다공증골모델은피질골감소연구인 Ritzel 등 11) 의연구와해면골감소연구인 Baroud 등 12) 의연구를참조하여, 정상골상태보다피질골의두께가 0.5 mm, 1 mm 감소한두가지모델과해면골의 bone mineral density가 85% 와 75% 감소한두가지모델을만들었고 85% 와 75% 감소모델의 Young s modulus 는각각 255 MPa, 225 MPa 그리고포아송비는 0.3으로동일하게설정하였다. 4. 경계조건및근육의작용경계조건은피질골과해면골사이는움직임이전혀없는완전결합 (bonded) 으로설정하였으며그외의나사와제5중족골사이, 골절면의접촉면은움직임이있지만접촉은유지되는상태인접촉유지미끄러짐 (no separation) 으로설정하였고 제5중족골두의관절면은제5중족지관절을고정하기위해완전고정 (fixed support) 로설정하였다 (Fig. 2). 생리적상태와유사한조건을만들기위해제5중족골기저부와관련되어있는근육인단비골근, 제삼비골근, 족배골간근, 족저골간근, 단소족지굴곡근의작용방향은해부학적으로설정하였다. 각근육에작용하는힘은 Rohr 등 13) 이기술하였던각각의근육의생리적단면적 (physiologic cross-sectional area) 을참조하였고생리적단면적에단위면적 (cm 2 ) 당 25 N을부과하여각근육의힘의크기를단비골근, 제삼비골근, 족배골간근, 족저골간근, 단소지굴근각각 N, 77.5 N 68.0 N, 34.5 N, 50.0 N으로설정하였다 (Table 1). 해석은유한요소해석소프트웨어인 ANSYS V14.5 (ANSYS Inc., Canonsburg, PA, USA) 를이용하여시행하였다. 5. 기계적안정성평가골수강내나사고정술모델과양측피질골나사고정술모델의기계적안정성은두가지기준으로평가하였다. 첫째, 골절면에서전위정도둘째, 골절면에서접촉응력의최대차이값을평가하였다. 골절면의전위정도는골절면외측피질골임의의지점을설정하여 x, y, z 축에대한각각의이동거리의합을측정하였다. 외측피질골을설정한이유는제5중족골기저부골절의손상기전이족관절족저굴곡상태에서전족부가내전혹은내번되면서외측피질골에장력이가해져발생하는것이므로외측피질골에작용하는외력이가장크기때문이다. 골절면에서접촉응력은나사고정술의기계적안정성이우수하다면같은조건에서더넓은접촉면적을유지할수있게되고, 따라서골절면에서의접촉응력이고르게분포하여접촉응력의차이값이낮게측정된다 (Fig. 3). 즉접촉응력의차이값이작다면기계적안정성이상대적으로우수함을의미한다. Fig. 2. Boundary condition. Interface between cortical and cancellous bone is bonded. Bonded: no movement, complete union state, Fracture site: interface between screw and bone are no separation, No separation: movement can occur but contact is maintained, Fixed support: fifth metatarsophalangeal joint is fixed state. 결과 1. 골절면에서전위정도골수강내나사고정술과양측피질골나사고정술각각의 Table 1. Magnitudes of the muscle forces related to the fifth metatarsal base Category Peroneus brevis Peroneus tertius Dorsal interosseous Plantar interosseous Flexor digiti minimi brevis PSCA (cm 2 ) Force (N) PSCA: physiologic cross-sectional area. A force generating capacity of 25 N/cm 2 was multiplied by PCSA to obtain the muscle forces. 제 32 권제 2 호

$YS Lee, et al. Finite Element Analysis in Jones Fracture Fig. 3. Contact pressure on fracture plane. Contact pressure distribution is displayed by gradation scale. (A) is displayed by similar color.$ $It means mechanical stable or unstable, respectively. Table 2. Contact pressure and displacement on fracture plane Category Normal bone Cortical osteoporotic bone Cancellous osteoporotic bone 0.$

4 YS Lee, et al. Finite Element Analysis in Jones Fracture Fig. 3. Contact pressure on fracture plane. Contact pressure distribution is displayed by gradation scale. (A) is displayed by similar color. But, (B) is displayed by various color (sharp contrast). In other words, (A) is more evenly distributed contact pressure and (B) is too concentrated or too little contact pressure. It means mechanical stable or unstable, respectively. Table 2. Contact pressure and displacement on fracture plane Category Normal bone Cortical osteoporotic bone Cancellous osteoporotic bone 0.5 mm 1 mm 85% 75% Maximum contact pressure difference (MPa) Intramedullary Bicortical p-value Displacement (mm) Intramedullary Bicortical p-value Data were analyzed by paired t-test. p-values are presented by comparison of measurements between Intramedullary and bicortical fixation at five bone conditions. 모델에제5중족골기저부와관련되어있는근육인단비골근, 제삼비골근, 족배골간근, 족저골간근, 단소족지굴곡근의힘의크기와작용방향을적용하고골절면의미끄러짐의정도를측정하였다. 정상골상태일때골수강내나사고정술모델의골절면의전위는 mm, 양측피질골나사고정술모델의전위는 mm으로측정되었다. 해면골 85% 의골다공증모델에서골수강내나사고정술모델과양측피질골나사고정술모델의전위는각각 mm, mm으로측정되었고해면골 75% 의골다공증모델에서는각각 mm, mm으로측정되었다. 0.5 mm 감소피질골골다공증모델에서는 mm, mm으로측정되었고 1 mm 감소피질골골다공증모델에서는 mm, mm으로측정되었다 (Table 2). 정상골과해면골감소모델, 0.5 mm 피질골감소 모델에서는양측피질골나사고정술이골수강내나사고정술에비해전위정도가적었고, 1 mm 피질골감소모델에서는골수강내나사고정술이양측피질골나사고정술에비해전위정도가적었다. 2. 골절면에서접촉응력차이의최대값골절면에서전위정도평가와동일한조건으로제5 중족골기저부근육의힘과작용방향을적용한뒤, 골수강내나사고정술과양측피질골나사고정술모델의골절면에서접촉응력을측정하고가장큰응력지점값과가장낮은응력지점값의차이를구하였다. 정상골상태일때골수강내나사고정술모델과양측피질골나사고정술의접촉응력차이의최대값은각각 20,818 MPa, 12,155 MPa으로측정되었고해면골 85% 의골다공 82 대한스포츠의학회지

5 이연수외. Jones 골절에서유한요소해석을이용한골수강내나사고정술과양측피질골나사고정술의비교 - 예비보고 - 증모델에서는각각 23,371 MPa, 13,765 MPa으로측정되었으며, 해면골 75% 의골다공증모델에서는각각 24,310 MPa, 14,264 MPa 로측정되었다. 0.5 mm 감소피질골감소골다공증모델에서는각각 21,337 MPa, 20,971 MPa으로측정되었고 1 mm 감소피질골감소골다공증모델에서는각각 26,322 MPa, 36,153 MPa으로측정되었다 (Table 2). 정상골과해면골감소모델, 0.5 mm 피질골감소모델에서는양측피질골나사고정술이골수강내나사고정술에비해접촉응력차이의최대값이적었고, 1 mm 피질골감소모델에서는골수강내나사고정술이양측피질골나사고정술에비해접촉응력차이의최대값이적었다. 고찰 Lawrence와 Botte 14) 는제5중족골기저부골절을 3부분으로구분하였는데, 가장근위부인제1구역은중족입방관절을포함하여단비골건, 족저근막의외측띠가부착하며이보다원위부에삼차비골건이부착한다. 제2구역은골간단골단의이행부로서흔히진성 Jones 골절이라칭하며전형적인골절양상은경상돌기에서부터 1.5 cm 원위부인제4 5중족관절외측부에서시작하여내측피질을향하여사선방향의골절선이관찰되고스포츠손상에서전족부가족저굴곡상태일때내전혹은내번력을받을때발생하게된다. 제3구역은스트레스골절로서주로운동선수에서반복적인외력에의해발생하는피로골절이다. 일반적으로제1구역경상돌기견열골절의경우보존적처치를시행해도우수한골유합및임상결과를기대할수있고 2) Jones 골절은제1구역골절보다는보존적처치가어렵고, 제3구역피로골절은보존적치료시지연유합이나불유합혹은재골절등의합병증으로수술적처치를시행해야하는경우가많다 15-17). 즉, 제1구역은보존적처치, 제3구역은수술적처치를시행하는것이일반적이고제2구역인 Jones 골절은단하지석고부목고정하에 6 8주간의비체중부하등의보존적처치를우선고려하고, 운동선수등조기회복이필요한환자혹은장기간의석고고정으로인해초래되는불편감이나때때로발생하는지연유합, 불유합의가능성때문에경우에따라서수술적처치를시행하기도한다 18). 이에저자들은제2구역인급성 Jones 골절에서일반적으로시행되는수술방법인골수강내나사고정술과양측피질골나사고정술 2가지의기계적안정성에대해비교분석해보고자하였다. 일반적으로나사고정술은골절부위를압박함으로서인대와근육부착부로부터발생하는장력에저항해서일차골유합을 촉진할수있는장점을갖는다. Portland 등 7) 은제5중족골급성골절에대해서 22예의환자에서유관나사를이용한수술적처치를시행하였고수술후평균 8.8주에방사선학적골유합을얻었고금속나사의자극으로인한동통을호소한 2예를제외하고만족할만한결과를보고하였다. 또한 Pietropaoli 등 3) 은사체를이용한생체역학적연구를통해서급성 Jones 골절에서보존적치료보다는골수강내나사고정술을시행함으로써더강력한고정력을얻을수있어골절부전위를방지하여양호한결과를기대할수있음을보고하였다. Stewart 19) 는나사내고정방법으로경상돌기기저부로삽입하여골절면을통과해서내측피질골까지관통하는양측피질골나사고정술에대하여기술하였고, Mahajan 등 6) 은전위가있는제5중족골기저부제1, 2형골절환자 23예에대해서양측피질골나사고정술을시행하였고수술후평균 6.3주에방사선학적골유합을얻었고평균미국족부족관절학회 (American Orthopaedic Foot & Ankle Society) 족부기능지수는 94점으로모두양호한결과를보고하였다. 이렇듯골수강내나사고정술과양측피질골나사고정술모두비교적우수한임상적결과를보고하고있다. 생역학적연구를살펴보면 Husain과 DeFronzo 8) 은모형뼈 (sawbones) 10 예, 사체 (cadaver) 9예를이용한생역학연구에서 2가지경우모두양측피질골나사고정술이골수강내나사고정술보다우수하다고하였다. 본연구에서도골밀도가감소하지않은정상골상태일때, 양측피질골나사고정술이골수강내나사고정술에비하여골절면의전위거리가짧고골절면에서균일한접촉응력을유지할수있어더우수한술식으로해석되었다. 하지만 Husain과 DeFronzo 8) 의연구는제5중족골기저부에작용하는외력을단비골근으로만한정해서실험하였고, 작용하는힘의방향도골절선에수직인단방향으로만적용하였다. 실제 Jones 골절은단비골근과제삼비골근의부착부사이에서발생하기때문에 Husain 등의연구는골절부에발생하는장력과비틀림의외력을적용하고해석하는데한계가있다 18). 본연구는실제인체의조건과유사하도록제5중족골기저부의 5개의근육 ( 단비골근, 제삼비골근, 족배골간근, 족저골간근, 단소족지굴곡근 ) 모두를기시부와부착부를고려하여힘의방향과크기를적용하였기때문에결과의해석이보다정확하고의의가있다고할수있다. 또한사체실험은사체개개인별로해부학적차이가있어각각의모델에공평한하중및운동조건을부가하는것이어렵고이로인한오차가발생할수있지만, 본연구는유한요소해석을이용하였기때문에이를배제할수있었다. 저자는골밀도가감소한골다공증상태에서발생한 Jones 골절에대해서도같은조건하에 2가지 제 32 권제 2 호

6 YS Lee, et al. Finite Element Analysis in Jones Fracture 수술법에대한유한요소해석을시행하였다. Chao 등 20) 은골절치료에사용되는내고정의안정성은피질골과해면골의구조와내고정물의재질에큰영향을받는다고하였다. 즉골다공증상태에서내고정물의안정성은정상골상태와변화하게된다. 본연구에서는골다공증이진행하여피질골의두께가 1 mm 이상감소한다면오히려골수강내나사고정술이양측피질골나사고정술보다기계적안정성이더우수함을확인하였다. 이는양측피질골나사고정술에서삽입된나사와족저부가이루는각도가골수강내나사고정술의그각도보다커서직립상태에서굽힘하중을더받기때문에피질골의두께에더민감하게영향을받는것으로생각된다. 본연구의제한점은실제급성 Jones 골절은다양한양상으로나타날수있으나사선방향의골절선을갖는한가지골절모델만을적용한점과골다공증은피질골과해면골모두동시에감소상태를유발하지만, 본연구에서골다공증모델생성시피질골감소모델과해면골감소모델로따로나누어분석을시행한점이다. 또한한명을대상으로한차례의컴퓨터전산화단층촬영후얻은자료 (data) 를사용하여시행한예비보고이므로대상수를늘려반복된실험을진행하고, 이 data를바탕으로한임상과의연계를통한추시연구가필요하겠다. 결론적으로정상인에서발생한 Jones 골절은양측피질골나사고정술이기계적안정성측면에서골수강내나사고정술보다더우수한술식이라할수있다. 하지만피질골두께가감소한골다공증상태에서는골수강내나사고정술이양측피질골나사고정술보다기계적안정성이더우수한술식이라할수있겠다. References 1. Jones R. Fracture of the base of the fifth metatarsal bone by indirect violence. Ann Surg 1902;35: Clapper MF, O'Brien TJ, Lyons PM. Fractures of the fifth metatarsal. Analysis of a fracture registry. Clin Orthop Relat Res 1995;(315): Pietropaoli MP, Wnorowski DC, Werner FW, Fortino MD. Intramedullary screw fixation of Jones fractures: a biomechanical study. Foot Ankle Int 1999;20: Dameron TB Jr. Fractures and anatomical variations of the proximal portion of the fifth metatarsal. J Bone Joint Surg Am 1975;57: Kavanaugh JH, Brower TD, Mann RV. The Jones fracture revisited. J Bone Joint Surg Am 1978;60: Mahajan V, Chung HW, Suh JS. Fractures of the proximal fifth metatarsal: percutaneous bicortical fixation. Clin Orthop Surg 2011;3: Portland G, Kelikian A, Kodros S. Acute surgical management of Jones' fractures. Foot Ankle Int 2003;24: Husain ZS, DeFronzo DJ. A comparison of bicortical and intramedullary screw fixations of Jones' fractures. J Foot Ankle Surg 2002;41: Bucholz RW, Heckman JD, Court-Brown CM. Rockwood & Green's fractures in adults. 6th ed. Philadelphia, USA: Lippincott Williams & Wilkins; Johnson JT, Labib SA, Fowler R. Intramedullary screw fixation of the fifth metatarsal: an anatomic study and improved technique. Foot Ankle Int 2004;25: Ritzel H, Amling M, Posl M, Hahn M, Delling G. The thickness of human vertebral cortical bone and its changes in aging and osteoporosis: a histomorphometric analysis of the complete spinal column from thirty-seven autopsy specimens. J Bone Miner Res 1997;12: Baroud G, Nemes J, Ferguson SJ, Steffen T. Material changes in osteoporotic human cancellous bone following infiltration with acrylic bone cement for a vertebral cement augmentation. Comput Methods Biomech Biomed Engin 2003;6: Rohr ES, Johnson JE, Zhao L, Harris GF. Three-dimensional finite element analysis of the fifth metatarsal jones fracture. In: Harris GF, Smith PA, Marks RM, editors. Foot and ankle motion analysis:clinical treatment and technology. Florida: Talyer & Francis; p Lawrence SJ, Botte MJ. Jones' fractures and related fractures of the proximal fifth metatarsal. Foot Ankle 1993;14: Josefsson PO, Karlsson M, Redlund-Johnell I, Wendeberg B. Jones fracture. Surgical versus nonsurgical treatment. Clin Orthop Relat Res 1994;(299): Quill GE Jr. Fractures of the proximal fifth metatarsal. Orthop Clin North Am 1995;26: Hatch RL, Alsobrook JA, Clugston JR. Diagnosis and management of metatarsal fractures. Am Fam Physician 2007;76: Vertullo CJ, Glisson RR, Nunley JA. Torsional strains in the proximal fifth metatarsal: implications for Jones and stress fracture management. Foot Ankle Int 2004;25: Stewart IM. Jones's fracture: fracture of base of fifth metatarsal. Clin Orthop 1960;16: Chao EY, Inoue N, Koo TK, Kim YH. Biomechanical considerations of fracture treatment and bone quality maintenance in elderly patients and patients with osteoporosis. Clin Orthop Relat Res 2004;(425): 대한스포츠의학회지

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00- 차례(15-4).hwp PSJHJOBM! BSUJDMF 대한족부족관절학회지 : 제 15 권제 4 호 2011 J Korean Foot Ankle Soc. Vol. 15. No. 4. pp.207-211, 2011 울산대학교의과대학서울아산병원정형외과, 차의과학대학교분당차병원정형외과 *, 울산대학교의과대학울산대학교병원정형외과, 가톨릭대학교의과대학대전성모병원정형외과 최영낙 최영락 * 서정호