Original Article J Korean Orthop Assoc 2012; 47: 178-184 http://dx.doi.org/10.4055/jkoa.2012.47.3.178 www.jkoa.org 소아및청소년의장골에서발생한고립성골낭종의유연성골수내정에의한치료효과 : 후향적증례분석 Outcomes from Treatment of Simple Bone Cyst in the Long Bones with Flexible Intramedullary Nailing in Children and Adolescents: A Retrospective Cases Series 차수민 신현대 김경천 황정모 김보건 * 충남대학교의학전문대학원정형외과학교실, * 동아대학교의과대학정형외과학교실 목적 : 소아및청소년의장골에서발생한고립성골낭종에대해유연성골수내정을이용하여치료한결과를후향적으로분석하고자한다. 대상및방법 : 2002년 4월부터 2007년 12월까지장골에고립성골낭종이발견된총 85예의환자를대상으로하였으며, 평균연령은 10.8세, 병적골절을동반한경우 13예, 동반하지않은경우가 72예였으며, 부위별로는상완골근위부 33예, 상완골간부 41예, 근위대퇴골 11예였다. 1군 ( 스테로이드주입 ) 21예, 2군 ( 소파술및동종골이식술 ) 18예, 3군 ( 유연성골수내정을이용한감압및고정술 ) 46예였다. Capanna 의분류에따라평가하였다. 결과 : 골낭종의흡수및치료에걸리는기간은 1군평균 18.4개월, 2군 10.6개월, 3군 5.8개월이었다. Capanna 분류의완전치유는 1군 67%, 2군 56%, 3군 78% 였다. 재발은 1군 1예 (5%), 2군 1예 (6%), 3군 1예 (2%) 에서있었고치료에반응하지않은예는 1군 2예 (9%), 2군 1 예 (6%) 에서보였다. 결론 : 소아및청소년의장골에서발생한고립성골낭종에서유연성골수내정은병변의치유효과가탁월하며치료기간도짧으며술후안정성을제공할수있는우수한방법으로생각한다. 색인단어 : 골낭종, 유연성골수내정 서론 고립성골낭종은진정한의미의골종양은아니지만임상적으로는골종양과유사하여다른골종양과감별진단이중요시되는질환으로 Jaffe와 Lichtenstein 1) 에의해 "unicameral" 이라는용어가사용되면서하나의독립된질환으로분류되었다. 고립성골낭종의병인에는여러가지학설이있으나아직까지정확한정설은밝혀져있지않고있으며, 1-4) 치료방법도보존적요법, 5) 수술적요법등다양하게보고되고있다. 수술적치료로는소파술, 소 접수일 2011 년 7 월 24 일수정일 2011 년 8 월 26 일게재확정일 2011 년 8 월 29 일교신저자신현대대전시중구문화로 282, 충남대학교의학전문대학원충남대학교병원정형외과학교실 TEL 042-280-7349, FAX 042-252-7098 E-mail hyunsd@cnu.ac.kr 파술및골이식술, 낭포막부분절제술및전절제술, 경피적개공술, 자가골수주사법등이이용되고있다. 6) 고립성낭종의치료는현재까지이견이많은상태이며, 재발등에대해서는저자들에따라큰차이를보이고있다. 한편, 2000년이후장골에발생한고립성골낭종에서유연성골수내정을이용한 " 지속적감압및고정 " 의치료개념및우수한결과에대한보고들이있었다. 7-12) 저자들의국내문헌고찰에서, 골수내정을이용한치료결과가보고된바가없으며, 이에저자들은소아및청소년의장골에서발생한고립성골낭종에대해유연성골수내정을이용하여우수한결과를얻었기에기존의방법들과후향적증례분석및문헌고찰을하고자한다. 대한정형외과학회지 : 제 47권제 3호 2012 Copyright 2012 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.
179 고립성골낭종의치료 대상및방법 1. 연구대상 2002년 4월부터 2007년 12월까지장골에고립성골낭종이발견된 85예의환자를대상으로하였다. 단순방사선소견상단발성의얇아진피질골에명확히구분되는중심성골결핍이장관골의성장판에인접하여발생하는경우, 다발성의소엽형태가성장판에서다소떨어져존재하는경우, 특히피질골조각이병소내에모여있는양상 (fallen fragment sign) 에대해 1인의종양전문의와 1 인의방사선과전문의의판독상단순골낭종으로일치되는경우로하였으며, 서로일치하지않는경우나동맥류성골낭종, 섬유이형성증등과의감별을요하는경우는자기공명영상 (magnetic resonance imaging) 촬영후방사선적진단을하였다. 평균연령은 10.8세 (4-16세) 였으며, 남자 67예, 여자 18예, 병적골절을동반한경우 13예, 동반하지않은경우가 72예였으며, 부위별로는상완골근위부 33예, 상완골간부 41예, 근위대퇴골 11예였다. 평균추시기간은 27.6개월 (25-41개월) 이었다. 2. 연구방법다음의 3가지치료군으로분류를하였다. 1) 1군, 단순스테로이드주입 (methylprednisolone 40-150 mg), 2) 2군, 소파술및동종골이식술 (curettage and synthetic bone graft), 3) 3군, 유연성골수내정을이용한감압및고정술 (continuous decompression with flexible intramedullary nail). 1군은 21예로 3예에서병적골절이동반되었고, 2군은 18예로 4예에서병적골절이동반되었고, 3군은 46 예로 6예에서병적골절이동반되었다 (Table 1). 모든시술은 1인의술자가시행하였다. 스테로이드주입은방사선소견상피질골막이얇은경우탐침을이용하여병변에도달하였으며피질골막이두꺼운경우에는천공술 (drilling) 을시행한후주사침을병변에삽입하였다. 영상증폭기확인하에주사침의위치를확인하고 2개의침을이용, 초기에출혈이멈춘후배액되는액체를확인하였다. 주입량은낭종의크기와환자의연령에따라차이를두어 40-150 mg로하였다. 소파술및동종골이식은전신마취하에앙와위상태에서영 Table 1. Summary of the Cases according to the Anatomical Location of the Cyst and Options for the Treatments Group I Group II Group III ( )* (+) ( )* (+) ( )* (+) Total Proximal humerus 4 2 4 1 20 2 33 Shaft of humerus 12 0 9 3 15 2 41 Proximal femur 2 1 1 0 5 2 11 Total 18 3 14 4 40 6 85 21 18 46 *Absence of pathologic fracture; Presence of pathologic fracture. Figure 1. (A) Pre-operative simple radiograph of a 12-year-old boy, who had simple bone cyst involving the metaphysis of proximal humerus, associated with pathologic fracture. (B, C) Post-operative radiographs show the inserted flexible intramedullary nails. (D) Cyst absorption and bone healing was achieved at post-operative 5 months.
180 차수민 신현대 김경천외 2 인 상증폭장치를이용하여병소부위를확인후골수생검용주사침을사용하여흡인되는낭액및낭벽의조직으로진단을확인하였다. 그다음골수생검용투관침이나큐렛을이용하여낭종의엷은내막을파괴시킴과동시에낭종의수가여러개일경우에는각각의낭종격벽을파괴하여단일낭종으로만들었다. 낭종조영술을시행하여격벽의파괴여부와단일낭종을확인하고생리식염수로낭종내를세척한후에골이식을위하여점점직경이큰도관 (catheter) 을이용하여피질골에직경이약 1 cm 정도되는창 (window) 을만들고, 동종골은합성망상골대체제로서단일종류를이용하였다 (pure beta-tricalcium phosphate substitute, ChronOS, Synthes, Oberdorf, Switzerland). 골수내정삽입역시, 술전경피적또는관혈적조직검사를시행하지않았고, 전형적방사선소견및시술시유출되는전형적액체 (fluid) 양상으로고립성골낭종을잠정적으로진단하였다. 상완골및대퇴골모두에서역행성 (retrograde) 의삽입을하였고, 정삽입후영상증폭기감시하에낭종병변과낭종병변의근, 원위골수강을모두관통하도록정을위치시켰다 (Fig. 1). 근, 원위의성장판은정에의해관통하지않도록보존하였다. 골수강내직경과병변의크기를고려하여정의크기및개수를달리하였으며, 3점고정이되도록하였다. 병적골절이동반된경우는전위를정복후정을삽입하였다. 46예전예에서골이식은시행하지않았다. 사용한골수강내금속정역시단일종류였다 (Synthes, Bettlach, Switzerland). 모든치료전에경피적또는관혈적조직검사는시행하지않았으며, 85예모두에서전형적인방사선소견및흡인액의양상을확인하였다. 3. 술후처치스테로이드주입후 3개월째방사선소견을기준으로낭종이잔존하는경우재주입을하였고최다 4회까지하였으며평균 2.7회 (1-4회) 를주입하였다. 재주입시의용량도 40-90 mg 범위로하였다. 스테로이드주입군과소파술및동종이식골주입의군에서는병적골절이동반되지않은경우추가적부목고정없이자유로 운관절운동을허용하였고상완골의병적골절이동반된경우는장상지반석고붕대 2주, 대퇴골의병적골절이동반된경우는비체중부하안정 2주후목발보행 (crutch walking) 2주를시행하였다. 골수내정을이용한군에서는병적골절유무에상관없이대퇴골에병변이있는경우비체중부하관절운동 1주후체중부하보행, 상완골에병변이존재하는경우별도의외부고정없이관절운동을허용하였다. 4. 평가수술직후, 술후 6주, 3개월 ( 이후 24개월까지 3개월간격 ), 24개월이후는 1년간격으로전후면및측면단순방사선촬영을하였고, 모든예에서최소 24개월을추시하였다. Capanna의분류 13) 에따라다음의 4가지로평가하였다. 1) 완전치유 (complete healing): 낭종내공간이신생골로완전히대치되었으며피질골경계부위가비후된것이확인, 2) 불완전치유 (healing with residual radiolucency): 낭종내공간이신생골로일부대치되었고일부방사선투과병변이존재, 3) 재발 (recurrence): 낭종이치유된소견이관찰된후다시낭종의투과음영의확인및피질골이얇아지는소견, 4) 치료효과없음 (no response): 치료에도불구하고병변의차이가없음. 완전치유와불완전치유에해당하는예를치료효과가있는것으로판단하였다. 방사선소견은 2인의관찰자가측정하였으며각각의관찰자는 2일간격으로동일사진에대해서재평가하였다. 관찰자간, 관찰자내의일치율에대한평가로는 Kappa 값을이용하였고 Fleiss의방법 14) 으로 Kappa 값이 0.75 이상이면우수일치 (excellent agreement), 0.4 이상 0.75 미만이면양호일치 (fair to good agreement), 0.4 미만이면불량일치 (poor agreement) 로판단하였다. 결과 골낭종의흡수및치료에걸리는기간은 steroid 주입시 (1군) 평균 18.4개월 (12-24개월), 소파술및골이식술시 (2군) 10.6개월 Table 2. Summary of the Outcomes of Each Group, using the Classification by Capanna Complete healing Incomplete healing Recurrence No response Total Group I ( )* 11 (52) 4 (19) 1 (5) 2 (9) 18 21 (+) 1 (5) 2 (10) 0 0 3 Group II ( )* 9 (50) 3 (17) 1 (6) 1 (6) 14 18 (+) 1 (6) 3 (17) 0 0 4 Group III ( )* 31 (70) 8 (17) 1 (2) 0 40 46 (+) 5 (11) 1 (2) 0 0 6 Values are presented as n (%). *Absence of pathologic fracture; Presence of pathologic fracture.
181 고립성골낭종의치료 (9-18개월) 이었으며, 유연성골수내정을이용한경우 (3군) 5.8개월 (3-12개월) 이었다. Capanna 분류 14) 의완전치유및불완전치유를치료효과가있는것으로간주하였을때 1군은 86%, 2군은 89%, 3군은 98% 에서효과가있었다. 완전한치유의결과는 1군 67%, 2군 56%, 3군 78% 였다. 1군의치료에반응하지않은 1예는스테로이드주입후 25개월째유연성골수정내삽입으로 4개월후완전치유를보였으며다른 1예는 28개월째유연성골수내정으로치료하였으며현재외래추시중이며, 2군 1예의경우역시유연성골수내정으로치료후 6개월째골낭종의흡수소견이관찰되었다. 3군의재발이관찰되었던 1예는골수내정삽입후 6개월째치유의소견이관찰되었으나다시낭종이커지면서피질골이얇아지는소견을보여골수내정을제거하지않은상태에서추시중이다. 3군의재발 1 예를제외하고는모두평균 15.1개월에금속물제거술을시행하였고단, 1예에서골수내정삽입부위의염증소견으로항생제치료를병행하였다. 1군의유연성골수내정으로재치료한후현재추시중인예, 3군의재발 1예를포함, 전예의최종방사선추시에서관상및시상면상 10도이상의각형성은없었다. 2명의관찰자에의한방사선소견의결정은 Kappa 값 0.93으로 " 우수 " 일치의결과를얻었다 (Table 2). 고찰 고립성골낭종의병인에대해서많은연구들이있었으나현재까지정확한병인및병태생리에대해서는알려진바가없다. 7,15-18) 가장널리알려진이론은성장과관련된골간단의재형성과정에서정맥계의폐쇄와이로인한골수강압력의상승및낭종크기의증가이다. 그러나, 골수강내압력과병변과의연관성을뒷받침할수있는연구는현재까지없으며, 가설로서받아들여지는정도이다. 특히, 골수강압력의상승은낭종벽의골성재흡수 (osseous re-absorption) 와삼출액의축적을일으키며특히, 이러한삼출액내의 interleukin 1, prostaglandins 및여러단백분해효소등이골성재흡수에결정적역할을한다고보고되고있다. 19,20) 1960년 Cohen 21) 에의해골낭종병변에대한배액및감압의개념이소개된후, 골낭종의해부학적위치에따라 K-wire 또는유관나사를이용한다발성천공술, 유연성골수내정을이용한감압술의결과가보고되면서 8,22) 다양한치료방법중의하나정도로받아들여졌다. 그러나, 특히최근 10여년간장골에서유연성정을이용한배액및감압의효과가 90-100% 에이르는우수한치유를나타낸문헌들이보고되면서다시주목받고있다. 7,8,11) 스테로이드주입법은 Scaglietti 등 23) 과 Scaglietti 등 24) 에의해알려진후, 90% 에달하는성공률을보고하였지만재발률역시많으며수차례주입을해야하는점이있다. 25,26) 또한, 성장판의무혈성괴사, 조골세포의활동감소로인한점진적인골조송증, 지연 성가골형성, 특발성골절등의합병증이있을수있다. 23,27) 또스테로이드주입후, 2-3개월사이에방사선상낭종내에골형성이시작된다고했고주입후 3년이지나야완전히골낭종의흡수가일어난다고하였다. 24) 저자들의경우평균 18개월에낭종의치료를관찰할수있었고 2예에서치료에반응을하지않았으며 1예에서재발을하였다. 금속정삽입시골성조직과금속정의탄성계수 (modulus of elasticity) 의차이로인해보행시발생하는금속정의경미한변형 (deformation) 으로, 금속정과접촉하는부분의신생골형성이방해를받게되며결과적으로금속정주변의느슨한결합조직층 (small layer of loose connective tissue) 이생성되는특징이있으며, 12) 작은피부절개로시술이가능하고수술중출혈이적으며병변주변의피질골에대한추가적조작이없어최대한보존이가능하며, 병변부위에보강된기계적안정성 (mechanical stability) 으로시술후재원기간이짧고일상으로의복귀가빠르다는장점들이있다. 또한, 필요하다면알려진다른수술방법들을병행할수도있다. 한편, 삽입된정을통한병변의감압과정에있어병변내의병적조직 (pathologic tissue) 이정상적인조직으로 " 파급 " 되어, 이로인해 " 재발 " 될가능성은사실입증된바없으며여러연구에서도이런가설을뒷받침할만한결과는없었다. 스테로이드주입, 소파술및동종골이식술은낭종의경화 (consolidation) 에효과가있음이여러문헌의연구에서입증이되었으나강도가약해진골에기계적안정성 (mechanical stability) 을부여하지는못한다. 13,15,23-25,27,28) 2000년대부터 Roposch 등, 8) Givon 등 11) 에의해우수한치유율이보고되었으며저자들의결과역시 98% 에이르는치유결과를얻었으며특히, 평균술후 5.8개월에방사선적치료효과가관찰되었다. Journeau와 Ciotlos 28) 는스테로이드와골수내정의비교에서치료기간에는별차이가없으나합병증이스테로이드치료군에서많았다고보고하였다. 저자들의경우는두군의비교에서는치료결과및치료기간에차이가있었고골수내정의경우추가적외고정이필요하지않았던장점이있었다. 이번연구는후향적연구 (level IV, cases series) 라는한계가있으며치료결과에영향을줄수있다고알려진예후인자인격막형성및격막의수에따른분류, 발생위치에따른치료방법에따른차이, 연령, 낭종의크기및활동성에대한고려, 낭종지수 (cyst index) 29) 등에대한고려는하지않았으며다른여러수술적방법들과비교를하지못한제한점역시있다. 그러나저자들의연구결과와최근의외국문헌들에대한고찰결과골수내정을이용한배액및감압술은골낭종의치유과정이명백히짧으며술후안정성을유지할수있으며이로인한조기체중부하의효과가있으며또한술후관리도쉬운우수한방법으로생각한다.
182 차수민 신현대 김경천외 2 인 결론 소아및청소년의장골에서발생한고립성골낭종에서유연성골수내정은병변의치유효과가탁월하며치료기간도짧으며술후안정성을제공할수있는우수한방법으로생각한다. 참고문헌 1. Jaffe HL, Lichtenstein L. Solitary unicameral bone cyst with emphasis on the roentgen picture. The pathologic apperance and pathogenesis. Arch Surg. 1942;44:1004-25. 2. Neer CS, Francis KC, Johnston AD, Kiernan HA Jr. Current concepts on the treatment of solitary unicameral bone cyst. Clin Orthop Relat Res. 1973;97:40-51. 3. Chigira M, Maehara S, Arita S, Udagawa E. The aetiology and treatment of simple bone cysts. J Bone Joint Surg Br. 1983;65:633-7. 4. Morton KS. The pathogenesis of unicameral bone cyst. Can J Surg. 1964;7:140-50. 5. Siegel IM. Brisement forcéwith controlled collapse in treatment of solitary unicameral bone cyst. Arch Surg. 1966;92:109-14. 6. Gartland JJ, Cole FL. Modern concepts in the treatment of unicameral bone cysts of the proximmal humerus. Orthop Clin North Am. 1975;6:487-98. 7. de Sanctis N, Andreacchio A. Elastic stable intramedullary nailing is the best treatment of unicameral bone cysts of the long bones in children?: prospective long-term follow-up study. J Pediatr Orthop. 2006;26:520-5. 8. Roposch A, Saraph V, Linhart WE. Flexible intramedullary nailing for the treatment of unicameral bone cysts in long bones. J Bone Joint Surg Am. 2000;82:1447-53. 9. Saraph V, Zwick EB, Maizen C, Schneider F, Linhart WE. Treatment of unicameral calcaneal bone cysts in children: review of literature and results using a cannulated screw for continuous decompression of the cyst. J Pediatr Orthop. 2004;24:568-73. 10. Kokavec M, Fristakova M, Polan P, Bialik GM. Surgical options for the treatment of simple bone cyst in children and adolescents. Isr Med Assoc J. 2010;12:87-90. 11. Givon U, Sher-Lurie N, Schindler A, Ganel A. Titanium elastic nail--a useful instrument for the treatment of simple bone cyst. J Pediatr Orthop. 2004;24:317-8. 12. Santori F, Ghera S, Castelli V. Treatment of solitary bone cysts with intramedullary nailing. Orthopedics. 1988;11:873-8. 13. Capanna R, Albisinni U, Caroli GC, Campanacci M. Contrast examination as a prognostic factor in the treatment of solitary bone cyst by cortisone injection. Skeletal Radiol. 1984;12:97-102. 14. Fleiss JL, Cohen J. The equivalence of weighted Kappa and the intraclass correlation coefficient as measures of reliability. Educ Psychol Meas. 1973;33:613-9. 15. Cohen J. Unicameral bone cysts. A current synthesis of reported cases. Orthop Clin North Am. 1977;8:715-36. 16. Neer CS 2nd, Francis KC, Marcove RC, Terz J, Carbonara PN. Treatment of unicameral bone cyst. A follow-up study of one hundred seventy-five cases. J Bone Joint Surg Am. 1966;48:731-45. 17. Bloodgood JC. I. Benign bone cysts, ostitis fibrosa, giant-cell sarcoma and bone aneurism of the long pipe bones: a clinical and pathological study with the conclusion that conservative treatment is justifiable. Ann Surg. 1910;52:145-85. 18. Komiya S, Tsuzuki K, Mangham DC, Sugiyama M, Inoue A. Oxygen scavengers in simple bone cysts. Clin Orthop Relat Res. 1994;(308):199-206. 19. Bumci I, Vlahović T. Significance of opening the medullar canal in surgical treatment of simple bone cyst. J Pediatr Orthop. 2002;22:125-9. 20. Shindell R, Connolly JF, Lippiello L. Prostaglandin levels in a unicameral bone cyst treated by corticosteroid injection. J Pediatr Orthop. 1987;7:210-2. 21. Cohen J. Simple bone cysts. Studies of cyst fluid in six cases with a theory of pathogenesis. J Bone Joint Surg Am. 1960;42:609-16. 22. Shinozaki T, Arita S, Watanabe H, Chigira M. Simple bone cysts treated by multiple drill-holes. 23 cysts followed 2-10 years. Acta Orthop Scand. 1996;67:288-90. 23. Scaglietti O, Marchetti PG, Bartolozzi P. The effects of methylprednisolone acetate in the treatment of bone cysts. Results of three years follow-up. J Bone Joint Surg Br. 1979;61:200-4. 24. Scaglietti O, Marchetti PG, Bartolozzi P. Final results obtained in the treatment of bone cysts with methylprednisolone acetate (depo-medrol) and a discussion of results achieved in other bone lesions. Clin Orthop Relat Res. 1982;(165):33-42. 25. Hashemi-Nejad A, Cole WG. Incomplete healing of simple bone cysts after steroid injections. J Bone Joint Surg Br. 1997;79:727-30. 26. Chang CH, Stanton RP, Glutting J. Unicameral bone cysts
183 고립성골낭종의치료 treated by injection of bone marrow or methylprednisolone. J Bone Joint Surg Br. 2002;84:407-12. 27. Campos OP. Treatment of bone cysts by intracavity injection of methylprednisolone acetate: a message to orthopedic surgeons. Clin Orthop Relat Res. 1982;(165):43-8. 28. Journeau P, Ciotlos D. Treatment of solitary bone cysts by intra-medullary nailing or steroid injection in children. Rev Chir Orthop Reparatrice Appar Mot. 2003;89:333-7. 29. Kaelin AJ, MacEwen GD. Unicameral bone cysts. Natural history and the risk of fracture. Int Orthop. 1989;13:275-82.
184 차수민 신현대 김경천외 2 인 Outcomes from Treatment of Simple Bone Cyst in the Long Bones with Flexible Intramedullary Nailing in Children and Adolescents: A Retrospective Cases Series Soo-Min Cha, M.D., Hyun-Dae Shin, M.D., Ph.D., Kyung-Cheon Kim, M.D., Ph.D., Jung-Mo Hwang, M.D., and Bo-Kun Kim, M.D.* Department of Orthopedic Surgery, Chungnam National University School of Medicine, Daejeon, *Dong-A University College of Medicine, Busan, Korea Purpose: A retrospective review of cases series about the outcomes of treatment for simple bone cyst in the long bones with flexible intramedullary nailing in children and adolescents. Materials and Methods: Eighty-fi ve cases with a simple bone cyst in the long bones diagnosed between April 2002 and December 2007 were enrolled in the study. The mean age of the patients was 10.8 years. Thirteen cases were accompanied by a pathological fracture, and 72 cases were not. Thirty-three cases had a simple bone cyst on the proximal humerus, 41 cases on the shaft of the humerus, and 11 cases on the proximal femur. Steroid injections were performed in 21 cases (group 1), curettage and a synthetic bone graft in 18 cases (group 2), and decompression and fi xation using fl exible intramedullary nailing in 46 cases (group 3). We followed up all cases for at least 24 months and evaluated the results according to the Capanna classification. Results: The mean duration for absorption and healing of bone cysts was 18.4 months in group 1, 10.6 months in group 2, and 5.8 months in group 3. The complete cure rate according to the Capanna classification was 67% in group 1, 56% in group 2, and 78% in group 3. There was one case of recurrence in group 1 (5%), one case in group 2 (6%), and one case in group 3 (2%), as well as two cases of no response to treatment in group 1 (9%) and one case in group 2 (6%). Conclusion: Flexible intramedullary nailing for simple bone cysts in children and adolescents is effective for healing cystic lesions with a short healing duration and for mechanical stability. Key words: bone cyst, flexible intramedullary nail Received July 24, 2011 Revised August 26, 2011 Accepted August 29, 2011 Correspondence to: Hyun-Dae Shin, M.D., Ph.D. Department of Orthopedic Surgery, Chungnam National University Hospital, Chungnam National University School of Medicine, 282, Munwha-ro, Jung-gu, Daejeon 301-721, Korea TEL: +82-42-280-7349 FAX: +82-42-252-7098 E-mail: hyunsd@cnu.ac.kr