Clinical Article The Korean Journal of Sports Medicine 2016;34(2):132-138 pissn 1226-3729 eissn 2288-6028 https://doi.org/10.5763/kjsm.2016.34.2.132 소아야구견의견관절초음파소견 좋은삼선병원정형외과 구정회ㆍ조형래ㆍ진홍기ㆍ박기봉ㆍ신명지 Ultrasonographic Findings of Little Leaguer s Shoulder Jung Hoei Ku, Hyung Lae Cho, Hong Ki Jin, Ki Bong Park, Myung Ji Shin Department of Orthopaedic Surgery, Good Samsun Hospital, Busan, Korea The purpose of this study is to evaluate the ultrasonographic findings of little leaguer s shoulder among adolescent baseball players. Forty-two little leaguer s shoulder patients (age, 11 16 years; mean, 13.8 years; right, 39; left, 3), based on plain X-ray, were examined by bilateral shoulder ultrasonography. All patients were divided into groups on the basis of sonographic abnormalities and bilateral differences of physeal gap were measured in the cases of significant physeal widening. Sonographic abnormalities of dominant shoulder were physeal irregularity (45%), physeal fragmentation (21%), periosteal thickening (36%) and physeal widening (83%) that was the most common abnormalities. Seven of 42 patients (group A) had only physeal irregularity with minimal physeal widening, 26 patients (group B) had more than 1-mm physeal widening compared with nondominant shoulder. Nine patients (group C) had both physeal widening and fragmentation. Mean physeal gaps of the dominant and nondominant shoulders in 35 patients (group B and C) were 3.4±0.8 mm and 1.4±0.1 mm, respectively (p=0.013) and increased average physeal gap of dominant shoulder was 2.0±0.8 mm. Among three groups of patients, the duration of symptom was significant longer in group C (p=0.011). Physeal widening and fragmentation were associated with progression of the disease, but physeal irregularity was relatively early sonographic finding. Ultrasonography is a useful tool to evaluate the status of proximal humeral epiphysis and can aid early diagnosis of little leaguer s shoulder in the field. Keywords: Shoulder, Ultrasonography, Humerus 서 론 Received: September 29, 2016 Revised: October 31, 2016 Accepted: November 11, 2016 Correspondence: Hong Ki Jin Department of Orthopaedic Surgery, Good Samsun Hospital, 326 Gaya-daero, Sasang-gu, Busan 47007, Korea Tel: +82-51-310-9289, Fax: +82-51-310-9348 E-mail: hongiroom@naver.com Copyright 2016 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 (http://creativecommons.org/ licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 소아야구견은유소년기야구선수에서견관절통증과방사선소견상상완골근위부골단판간격의확대를보이는질환이다 1-3). 투구동작시반복되는견관절의과도한회전력으로인해발생하며질환초기에는동통이미미하여특별한치료없이운동을지속하는경우가많으나지속적인통증이나운동제한이발생하여병원을방문할경우는이미질환이진행되어재활과복귀에상당한시간을요하는경우가많아조기진단이중요하다. 견관절초음파검사는견관절주변의건, 근육, 인대, 점액낭과같은연부조직의성질뿐아니라 132 대한스포츠의학회지
구정회외. 소아야구견의견관절초음파소견 소아에서상완골근위골단판의상태에관한정보도얻을수있으며, 노트북크기의휴대용초음파기기를사용하면각종스포츠현장에직접방문하여간편하게즉각적인검사를시행함으로써유소년야구선수의현장검진에활용할수있다 4-6). 또한방사선노출의위험없이반복적으로사용가능하고건측과비교가가능하다는장점이있다. 본연구의목적은유소년학생야구선수에서단순방사선상진단된소아야구견환자의상완골근위골단판의초음파검사소견에대해알아보고이를건측과비교하고자한다. 연구방법 1. 연구대상 2013년 8월부터 2015년 2월까지단순방사선상에서소아아구견으로진단된유소년야구선수 42명을대상으로하였다. 평균신장은 161.8±10.9 cm, 평균체중은 57.2±11.3 kg, 평균 body mass index (BMI) 는 21.7±2.8 kg/m 2 이었다. 단순방사선상근위상완골골단판주위의경화, 골단판주위의골편형성, 골단판외측부또는골단판전체의확대가있는경우소아야구견으로진단하였다. 평균연령은 13.8세 ( 범위, 11 16세 ; standard deviation [SD], ±2.5세 ) 이며모두우세수에발생하였고 Table 1. Demographic characteristics of the patients (n=42) Characteristics Value Age (yr) 13.8±2.5 Height (cm) 161.8±10.9 Weight (kg) 57.2±11.3 Body mass index (kg/m 2 ) 21.7±2.8 Training history (yr) 3.4±2.9 Symptom duration (mo) 2.3±2.2 Dominant (right:left) 39:3 Position Pitcher Pitcher only 8 (19) Pitcher or fielder 12 (29) Fielder Catcher 6 (14) In-fielder 10 (24) Out-fielder 6 (14) Pitch count/wk* 550±80.5 Values are presented as mean±standard deviation or number (%). *Pitch counts for pitchers. 우측이 39명, 좌측이 3명이었다. 포지션별로는투수가 8명 (19%), 투 / 야수 12명 (29%), 포수 6명 (14%), 내야수 10명 (24%), 외야수 6명 (14%) 이었다. 포지션분류상투 / 야수겸용선수 12명은투수로분류하였고포수및내ㆍ외야수는야수로분류하였다. 투수 ( 투 / 야수겸용포함 ) 20명의주당평균투구수는 550±80.5회이었다. 야구를시작한기간은평균 3.4년 ( 범위, 1.5 5.3년 ; SD, ±2.9년 ) 이었다. 전예에서투구시우세수인환측견관절동통이있었으며, 이학적검사상견관절후방연부조직의구축을시사하는복합외전검사와수평내전검사에서양성을보였다. 증상발현시기는평균 2.3개월 ( 범위, 1.3 8.3개월 ; SD, ±2.2개월 ) 의만성손상이었고이전에소아야구견으로진단되어재활을받은환자나환측및건측견관절에수술을시행한선수는없었다 (Table 1). 2. 초음파검사방법초음파기기는 SonoAce X8 (Samsung Medison, Seoul, Korea) 를이용하였고전예에서 10 MHz의선형변환기 (probe) 로스포츠의학을전공한한명의정형외과의사 (H.L.C.) 가검사를시행하였다. 초음파검사전지원자한명에게 3차원컴퓨터단층촬영을시행하여견갑골과근위상완골간의위치관계를파악하였는데, 양측견관절검사시일정한검사위치선정을위하여비교적촉지가쉬운견봉의전외측모서리를골성표식자 (bony landmark) 로이용하였다 (Fig. 1A). 피검자는좌위에서견관절을 0 o 외전, 회전중립위를유지하고견봉전외측모서리를촉지한후상완장축과평행하게가상의선을그리고이선의후방에상완장축과평행하도록변환기를위치시켰다 (Fig. 1B). 상완골근위성장판의종축영상을얻어골단판의이상여부와골단판주위의골과연부조직의이상을건측과비교하였다 (Fig. 1C). 또한근위상완골골단판간격은골간단부와골단사이의간격을측정하여이를건측과비교하였다 (Fig. 2). 측정된양측상완골근위골단판간격수치는관찰자내오차를줄이기위해초음파화면상 2회측정하여평균값을사용하였다. 3. 자료의분석과통계초음파검사상 1 mm 이상의골단판확대가관찰되는환자의건측과환측의골단판간격의평균값은 Student t-test를이용하여비교하였고, 초음파소견에따라질환의정도를세그룹으로분류하여각분류별신체적이학적검사상의특징및포지션, 야구력, 투구수, 이환기간을일원배치분산분석을통해비교하였다. 모든통계학적자료의분석은 SPSS ver. 제 34 권제 2 호 2016 133
JH Ku, et al. Ultrasonographic Findings of Little Leaguer s Shoulder Fig. 1. Scanning technique and corresponding sonographic images of both shoulder in a little leaguer shoulder player. (A) Three-dimensional computed tomography of shoulder shows anatomical relationship between anterolateral corner of acromion (arrow) and proximal humeral epiphysis (dotted box indicates the location of the transducer). (B) Transducer is placed on lateral aspect of shoulder behind vertical imaginary line from acromion to upper arm. (C) Longitudinal images of both shoulders show hyperechoic irregular growth plate with bony fragmentation and widening of proximal humeral growth plate (asterisks indicate periosteum). D: deltoid muscle, E: proximal humeral epiphysis, M: proximal humeral metaphysis. Fig. 2. Bilateral measurement of physeal gap in right little leaguer shoulder player. Increased physeal gap (d1 d2=1.9 mm) is noted as right throwing side and nonthrowing side, 3.8 mm and 1.9 mm, respectively. M: proximal humeral metaphysis, E: proximal humeral epiphysis. 16.0 (SPSS Inc., Chicago, IL, USA)을 사용하였으며 p-value가 0.05 미만일 때 통계학적 의의가 있는 것으로 판정하였다. 결 과 초음파 검사상 건측 견관절과 비교하여 환측 골단판의 불규 칙성(19/42, 45%), 골단판 확대(35/42, 83%), 골단판의 골편 Table 2. Abnormal sonographic findings (n=42) Variable Physeal irregularity Physeal widening ( 1 mm) Physeal fragmentation Periosteal thickening No. (%) 19 35 9 15 (45) (83) (21) (36) The values in parentheses were used to calculate percentages of sonographic abnormalities. 형성(9/42, 21%), 골막 비후(15/42, 36%)가 관찰되었으며, 이 중 골단판 확대가 가장 흔한 소견이었다(Table 2, Fig. 3). 초음파 B군에서 8명(8/26, 31%), C군에서는 7명(7/9, 79%)이 관찰되었 검사상 질환의 진행 정도에 따라 골단판 확대가 없거나 1 다. 1 mm 이상의 골단판 확대를 보이는 35명(B군과 C군)의 mm 미만으로 미미한 단순 골단판의 불규칙성을 보이는 경우 환측과 건측의 평균 골단판 간격은 각각 3.4±0.8 mm, 1.4±0.1 가 7명(A군, 7/42, 17%), 건측 대비 1 mm 이상의 골단판 확대를 mm (p=0.013)로 환측이 건측보다 2.0±0.8 mm의 골단판 확대를 보이는 경우가 26명(B군, 26/42, 62%), 골단판 확대와 함께 보였다. B군의 경우 환측과 건측의 평균 골단판 간격은 각각 골편 형성을 함께 보이는 경우가 9명(C군, 9/42, 21%)이였다 3.1±0.3 mm, 1.4±0.2 mm (p=0.002)였고, C군의 환측과 건측의 (Table 3, Fig. 4). 골막 비후 소견은 A군에서는 관찰되지 않았고, 평균 골단판 간격은 각각 4.5±0.6 mm, 1.4±0.9 mm (p=0.016)이 134 대한스포츠의학회지
구정회외. 소아야구견의견관절초음파소견 Fig. 3. Various sonographic abnormalities of proximal humeral physes in throwing side of little leaguer shoulder players. (A) Irregular physis and minimal increased physeal gap, (B) widening of physeal gap more than 1 mm and physeal irregularity, (C) fragmentation of physis (arrow) and (D) periosteal thickening (asterisks indicate periosteum). M: proximal humeral metaphysis, E: proximal humeral epiphysis. Fig. 4. Classification of group of little leaguer shoulder players according to sonographic images. (A) Only physeal irregularity with minimal increased gap (<1 mm). (B) Physeal widening with or without physeal irregularity and (C) physeal widening and fragmentation of physis. M: proximal humeral metaphysis, E: proximal humeral epiphysis. Table 3. Sonographic classification of little league shoulder players (n=42) Sonographic abnormalities No. (%) Group A: only physeal irregularity with minimal physeal widening (<1 mm) Group B: physeal widening ( 1 mm) compared with the uninjured shoulder Group C: physeal widening with fragmentation 7 (17) 26 (62) 9 (21) 었다. B군과 C군의환측과건측의골단판간격차이는각각 1.7±0.6 mm, 3.0±0.4 mm이었다 (Table 4). 세군중골단판확대와골편형성을보인경우 (C군) 가상대적으로이환기간이길었으며 (p=0.011), 야구력, 포지션, 투구수 ( 투수의경우 ), 신체적검사상의특성과는의미있는차이가없었다 (p>0.05) (Table 5). 제 34 권제 2 호 2016 135
JH Ku, et al. Ultrasonographic Findings of Little Leaguer s Shoulder Table 4. Bilateral proximal humeral physeal gap in players with group B and C Variable Group B & C (n=35) Group B (n=26) Group C (n=9) Injured shoulder (mm) 3.4±0.8 3.1±0.3 4.5±0.6 Uninjured shoulder (mm) 1.4±0.1 1.4±0.2 1.4±0.9 Difference (mm) 2.0±0.8 1.7±0.6 3.0±0.4 p-value* 0.013 0.002 0.016 Values are presented as mean±standard deviation. *Statistically significant difference (p<0.05) between injured and uninjured shoulder in physeal widening players. Table 5. Demographic comparison among groups Variable Group A (n=7) Group B (n=26) Group C (n=9) p-value Height (cm) 160.7±8.9 161.7±9.7 161.8±7.5 0.224 Weight (kg) 57.6±9.3 57.2±10.2 58.6±11.7 0.364 Body mass index (kg/m 2 ) 22.3±1.5 21.8±1.7 22.3±1.8 0.473 Training history (yr) 3.2±1.6 3.4±1.5 3.2±1.7 0.238 Symptom duration (mo) 1.1±2.3 2.2±3.3 4.2±2.1 0.011* Position (pitcher :fielder ) 4:3 (57) 12:14 (46) 4:5 (44) 0.066 Pitch count/wk 560±70.8 550±57.5 570±76.4 0.243 Values are presented as mean±standard deviation. *Statistically significant difference among groups (p<0.05); Number of pitchers including pitchers or fielders; Fielders including catchers, percentage of pitcher in parenthesis; Pitch counts for pitchers. 고찰소아야구견은투구동작시상완골근위골단판의과도한회전성염전력으로인해발생한다고알려져있으며골단판의피로골절로해석되고있다 3). 해부학적으로회전근개건은골단판근위부에부착하고대흉근, 삼각근, 상완삼두근은골단판원위부에부착하는데투구를위해견관절외전, 외회전상태에서반복적인내전, 내회전동작으로인해생역학적으로약한상완골근위골단판이손상을쉽게받게된다 7). 투구량이많던지, 투구전후의스트레칭이나컨디셔닝부족, 전신적인운동사슬의부조화가소아야구견을유발하는인자로알려져있다 8,9). 투구단계중감속기와 follow through기에편심성수축을하는견관절후방근육과후하방관절낭이상지의견인력에저항하게되는데, 반복적투구로인한이들의손상은근육의단축과관절낭의비후및구축을유발한다 10,11). 본연구에서단순방사선소견상소아야구견으로진단된환자의전예에서수평내전검사나복합외전검사에서견관절후방연부조직의긴장이나구축이관찰되었다. 성장기골단판연골은일회성외상이나반복적미세외상에취약한구조물이다. 5 12세소아에서근위상완골의골절은골단판보다는골간부나골간단부위에서발생하나 13 16 세소아에서는골단판에서활발한성장이일어나는시기이므 로골단판이외상에더욱취약하여골절이골단판을통하여발생하는경우가많아골단판의피로골절로생각되는소아야구견이자주발생한다 12). 상완골근위골단판의급성골절과는달리만성골단판손상인소아야구견에서의방사선소견은탈무기질화 (demineralization), 골경화 (sclerosis), 골편형성 (fragmentation) 이관찰되며골단판의만성스트레스부하로인해골단판의성장세포가과증식하여골단판간격의확대를보이게된다 13). 저자들의초음파소견상에서도건측견관절과비교하여골단판의불규칙성, 골단판확대, 골단판의골편화, 골막비후가관찰되었으며이중소아야구견의진단의중심이되는골단판확대가 83% 로가장흔히관찰되었다. 저자들은임상적증상과함께단순방사선소견상에서골단판확대와같은이상을보이는환자를소아야구견으로진단하고이들의근위상완골초음파소견을분석하여초음파검사를이용한소아야구견진단에활용하고자하였다. 특히선수나지도자들의질환에대한이해부족이나심리적또는시간적이유로견관절통증이있어도병원에방문하지않고운동을지속하는경우가적지않으므로소아야구견에서보이는초음파상의이상소견은휴대용초음파장비를이용한현장방문검진시유용할것으로생각한다. 단순방사선상에서진단된 42예의소아야구견증례중초음파소견상골단판의확대가거의없거나단순골단판의 136 대한스포츠의학회지
구정회외. 소아야구견의견관절초음파소견 불규칙성을보인경우가 7예 (17%) 이었으므로초음파검사에서골단판확대를보이지않더라도골단판의불규칙성이관찰될경우 (group A) 는소아야구견의가능성이있을것으로판단된다. 골단판의확대를보이는 35예환자의초음파상평균골단판간격은건측에비해평균 2.0 mm의확대를보이며, 단순골단판확대만있는경우 (group B, 26예, 62%) 는건측대비평균 1.7 mm 질환이진행되었고, 골편형성이발생한경우 (group C, 9예, 27%) 는건측대비평균 3.0 mm의골단판확대를보였다. 소아야구견환자의진단에서단순방사선이나컴퓨터단층촬영, 자기공명영상과같은영상의학적방법으로골단판간격이건측보다확대되어있다는문헌은있으나 14,15), 환측골단판주위의이상소견만을기술하고있으며본연구와같이양측골단판의이상을비교하고골단판간격을수치상으로측정한연구는없다. 특히근골격계질환의영상검사로간편하게사용할수있는초음파를이용한연구또한보고된바가없어저자들의연구는소아야구견의보조적진단에참고자료로활용할수있을것으로생각한다. 저자들은초음파상질환의정도에따라세군으로분류하여각군들의역학적특성에대해서도비교하였는데질환의정도와신체적특징, 야구력, 포지션과는유의한차이를발견할수없었다. 그러나본연구에서는질환의정도에따라견관절통증과같은증상의이환기간에는유의한차이가있었는데, 전체환자는평균 2.3개월의이환기간을보였으며 A, B, C 각군의평균이환기간이각각 1.1개월, 2.2개월, 4.2개월로시간의경과에따라질환이진행되는것을알수있었다. 또한초음파소견상상완골근위골단판의골막비후나골편형성은소아야구견이비교적진행되었음을의미하며, 초기에조기발견하여적절한휴식과재활을시행하면질환의진행을막을수있을것으로생각된다. 소아야구견의발병의위험인자로는나이, 키, 체중과같은신체적조건과반복적투구동작으로인한신체의과사용, 운동역학과관련된투구폼이나운동사슬의이상을들수있다 8,9). Lyman 등 16) 은 9 12세야구선수에서나이가많고, 키가작으며체중이무거운선수들이견주관절손상의위험이더높다고하였으나, Olsen 등 8) 은 14 20세선수를대상으로견주관절손상을가진선수는키가 4 cm 더크고체중이 5 kg 더무겁다고하여신체조건에따른소아야구견질환의발생위험성은논란의여지가있다. 소아야구견은투구동작을많이하는야구선수에자주발생하는질환으로특히투수에서많이발생하는것으로알려져있으며 17,18) 본연구에서도약 1년 6개월간소아야구견으로진단된환자는투수 ( 투야수겸용포함 ) 가 48% 로가장많았고내야수 (24%), 포수또는외야수 (14%) 순이었다. 그러나질환의정도에따른분류상에서는투수가차지하는비율이 A군에서는 57%, 가장많은환자군인 B군에서는 46%, C군에서는 44% 로 A군에서는투수가많은경향은있었으나각군간의유의한차이는발견되지않았으며투수의경우투구수또한각군의유의한차이는없었다. 대상환자군이적은점은있으나저자들의결과는소아야구견의발생위험인자를단순히투구의양만으로는결정하기어려우며선수의투구역학이나운동사슬의이상과같은전신유연성부족과도관련이있을것으로생각한다. 본연구의단점으로는대상환자의수가적은후향적연구이며, 대조군이없고, 초음파소견과단순방사선검사의일치여부를판정하지못한점을들수있어단순방사선검사와의비교분석이나초음파검사의정확도와관련하여서는추가적인연구가필요할것으로생각된다. 그러나초음파검사는단순방사선에서볼수없는골막비후와같은연부조직의변화도관찰할수있으며, 스포츠현장에서즉각적으로이용이가능한장점이있고본연구는초음파검사시의참고치가되는기준을제시했다는데의미를둘수있다. 또한본연구는한명의관찰자에의해이루어져오차분석이없는점을단점으로들수있는데, Bica 등 19) 의연구에의하면경험있는단일검사자에의해시행된초음파검사의급내상관계수는 0.75 0.94의비교적우수한신뢰도와정확도를가지므로적절한검사술기획득이필수적이라할수있다. 저자들은본연구를통하여소아야구견의초음파검사상골단판확대가가장흔한소견이며건측대비평균 2.0 mm의골단판확대를보이는것을확인할수있었다. 질환이진행할수록골단판간격증가와함께골막비후및골편형성이일어나며골단판의불규칙성은비교적초기에관찰되는소견으로초음파검사를현장검진에활용하면질환의조기진단에유용한검사방법이될것으로생각한다. Conflict of Interest No potential conflict of interest relevant to this article was reported. References 1. Adams JE. Little league shoulder: osteochondrosis of the proximal humeral epiphysis in boy baseball pitchers. Calif Med 1966;105:22-5. 2. Albert MJ, Drvaric DM. Little League shoulder: case report. 제 34 권제 2 호 2016 137
JH Ku, et al. Ultrasonographic Findings of Little Leaguer s Shoulder Orthopedics 1990;13:779-81. 3. Barnett LS. Little League shoulder syndrome: proximal humeral epiphyseolysis in adolescent baseball pitchers. A case report. J Bone Joint Surg Am 1985;67:495-6. 4. Ocguder DA, Tosun O, Bektaser B, Cicek N, Ipek A, Bozkurt M. Ultrasonographic evaluation of the shoulder in asymptomatic overhead athletes. Acta Orthop Belg 2010;76: 456-61. 5. Wang HK, Lin JJ, Pan SL, Wang TG. Sonographic evaluations in elite college baseball athletes. Scand J Med Sci Sports 2005;15:29-35. 6. Brasseur JL, Lucidarme O, Tardieu M, et al. Ultrasonographic rotator-cuff changes in veteran tennis players: the effect of hand dominance and comparison with clinical findings. Eur Radiol 2004;14:857-64. 7. Gainor BJ, Piotrowski G, Puhl J, Allen WC, Hagen R. The throw: biomechanics and acute injury. Am J Sports Med 1980;8:114-8. 8. Olsen SJ 2nd, Fleisig GS, Dun S, Loftice J, Andrews JR. Risk factors for shoulder and elbow injuries in adolescent baseball pitchers. Am J Sports Med 2006;34:905-12. 9. Lyman S, Fleisig GS, Andrews JR, Osinski ED. Effect of pitch type, pitch count, and pitching mechanics on risk of elbow and shoulder pain in youth baseball pitchers. Am J Sports Med 2002;30:463-8. 10. Pappas AM, Zawacki RM, McCarthy CF. Rehabilitation of the pitching shoulder. Am J Sports Med 1985;13:223-35. 11. Burkhart SS, Morgan CD, Kibler WB. The disabled throwing shoulder: spectrum of pathology. Part I. pathoanatomy and biomechanics. Arthroscopy 2003;19:404-20. 12. Dameron TB Jr, Reibel DB. Fractures involving the proximal humeral epiphyseal plate. J Bone Joint Surg Am 1969;51: 289-97. 13. Mariscalco MW, Saluan P. Upper extremity injuries in the adolescent athlete. Sports Med Arthrosc 2011;19:17-26. 14. Obembe OO, Gaskin CM, Taffoni MJ, Anderson MW. Little Leaguer's shoulder (proximal humeral epiphysiolysis): MRI findings in four boys. Pediatr Radiol 2007;37:885-9. 15. Song JC, Lazarus ML, Song AP. MRI findings in Little Leaguer's shoulder. Skeletal Radiol 2006;35:107-9. 16. Lyman S, Fleisig GS, Waterbor JW, et al. Longitudinal study of elbow and shoulder pain in youth baseball pitchers. Med Sci Sports Exerc 2001;33:1803-10. 17. Zaremski JL, Krabak BJ. Shoulder injuries in the skeletally immature baseball pitcher and recommendations for the prevention of injury. PM R 2012;4:509-16. 18. Frush TJ, Lindenfeld TN. Peri-epiphyseal and overuse injuries in adolescent athletes. Sports Health 2009;1:201-11. 19. Bica D, Armen J, Kulas AS, Youngs K, Womack Z. Reliability and precision of stress sonography of the ulnar collateral ligament. J Ultrasound Med 2015;34:371-6. 138 대한스포츠의학회지