Journal of Korean Society of Spine Surgery Considerations for Surgical Treatment of Osteoporotic Spinal Fracture: Surgical Indication, Approach, Fixat

Journal of Korean Society of Spine Surgery Considerations for Surgical Treatment of Osteoporotic Spinal Fracture: Surgical Indication, Approach, Fixation, and Graft Material - Review Article - Hyoungmin Kim, M.D., Bong-Soon Chang, M.D., Choon-Ki Lee, M.D. J Korean Soc Spine Surg 2016 Mar;23(1):41-53. Originally published online March 31, 2016; http://dx.doi.org/10.4184/jkss.2016.23.1.41 Korean Society of Spine Surgery Department of Orthopedic Surgery, Gangnam Severance Spine Hospital, Yonsei University College of Medicine, 211 Eunju-ro, Gangnam-gu, Seoul, 06273, Korea Tel: 82-2-2019-3413 Fax: 82-2-573-5393 Copyright 2016 Korean Society of Spine Surgery pissn 2093-4378 eissn 2093-4386 The online version of this article, along with updated information and services, is located on the World Wide Web at: http://www.krspine.org/doix.php?id=10.4184/jkss.2016.23.1.41 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. www.krspine.org

Review Article J Korean Soc Spine Surg. 2016 Mar;23(1):41-53. http://dx.doi.org/10.4184/jkss.2016.23.1.41 Considerations for Surgical Treatment of Osteoporotic Spinal Fracture: Surgical Indication, Approach, Fixation, and Graft Material Hyoungmin Kim, M.D., Bong-Soon Chang, M.D., Choon-Ki Lee, M.D. Department of Orthopedic Surgery, Seoul National University College of Medicine, Seoul, Korea Study Design: A review of the literature. Objectives: To review the current evidence on the development of a viable surgical strategy for successful treatment of patients with osteoporotic vertebral fractures. Summary of Literature Review: Achieving rigid and stable spinal column reconstruction in elderly patients with osteoporosis is challenging because of the poor healing capacity and weak mechanical strength of their bones. Materials and Methods: A literature search of clinical and biomechanical studies on the issues of surgical treatment of patients with osteoporotic vertebral collapse was performed and reviewed in terms of the surgical approach, fixation, graft material, and medical considerations. Illustrative cases of the authors experiences were presented and reflected upon. Results: Posterior spinal fusion and vertebral augmentation showed shorter operating times, less bleeding, and fewer complications with comparable or superior clinical results than anterior corpectomy and fusion or a posterior closing wedge vertebral shortening procedure in multiple studies. Therefore, we recommend the former as a first-line surgical plan for patients with osteoporotic vertebral collapse. However, in some patients who suffer fixed kyphosis, or spinal cord compression by a retropulsed bony fragment or bone cement, or infected vertebroplasty, an anterior approach could be considered to remove the pertinent lesion and to restore anterior spinal column. For the enhancement of the purchasing strength of the screw in the osteoporotic vertebra (e), a technique of prefilled bone cement in the instrumented vertebra(e) or injection of bone cement through a fenestrated screw is useful. Further, preoperative assessment and correction of systemic and local factors that affect bone healing is required when spinal fusion surgery is considered in elderly osteoporotic patients. The selection of the graft material should be individualized according to the property among osteoconduction, osteoinduction, and ostegenesis, or structural support that is the most important for the successful bone healing of each patient. Conclusions: Comprehensive geriatric assessment and management of elderly patients before surgery and careful and meticulous surgical planning with respect to the surgical approach, instrumentation, and the graft material are important to achieve the best outcome of the surgical treatment of patients with osteoporotic vertebral collapse. Key words: Osteoporosis, Spine surgery, Surgical approach, Instrumentaion, Fixation, Graft choice 서론 고령환자에서골다공증과관련된척추의골절은매우흔하며, 이는고령환자의활동성, 삶의질, 생리적기능유지능력의심각한저하를초래한다. 제 2경추치상돌기 (odontoid process) 및천추날개 (sacral ala) 부위에도노령환자에서골다공증골절이드물지않게발생하지만, 가장흔히발생하는곳은흉요추부위이다. 흉요추부위골다공증성골절은대부분후방인대복합체손상을동반하지않고전방주손상만을동반하는압박골절이나안정형방출성골절형태로, 보존적치료에비교적좋은예후를보인다고알려져있고, 선택적으로경피적척추성형술등 Received: July 6, 2015 Revised: July 10, 2015 Accepted: November 18, 2015 Published Online: March 31, 2016 Corresponding author: Bong-Soon Chang, M.D., Ph.D. Department of Orthopedic Surgery, Seoul National University Hospital, 101 Deahak-ro, Jongno-gu, Seoul 110-744, South Korea TEL: +82-2-2072-3864, FAX: +82-2-764-2718 E-mail: bschang@snu.ac.kr Copyright 2016 Korean Society of Spine Surgery Journal of Korean Society of Spine Surgery. www.krspine.org. pissn 2093-4378 eissn 2093-4386 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. 41

Hyoungmin Kim et al Volume 23 Number 1 March 2016 의시술이통증의조기완화와환자의기능회복에도움을준다. 하지만보존적치료의실패로인한불유합, 함몰및변형, 신경압박등이발생하거나, 경피적척추성형술의합병증으로감염, 시멘트이탈 (PMMA dislodgement) 등이발생할경우에는수술적치료를요하는경우가많다. 고령환자의골다공증성척추골절의수술적치료를고려할때, 적응증, 외과적접근법, 기기고정술방법, 이식재료의선택, 또감압술및전방주지지 (anterior column support) 를시행여부와방법등이고민하게되는사항들이다. 수술의합병증을줄일수있으면서안정적인척주재건이가능한외과적접근법을선택하고, 물리적으로약하고골유합능력이저하되어있는 1,2) 골다공증성척추에서튼튼한고정과성공적인골유합을얻기위한최선의기기고정술및적절한골이식재료를선택하는것이수술적치료의성공을위한전략이다. 본연구에서는먼저골다공증성척추골절환자에서수술적치료가도움이되는적응증을살펴보고, 성공적인수술적치료를위해외과적접근법, 기기고정술, 이식재료선택그리고감압술과전방주지지여부및그방법에있어어떤고려가필요한지고찰하겠다. 대상및방법 문헌고찰을통하여골다공성척추골절이후수술적치료를시행할경우고려해야할사항들을수술적치료의적응증, 외과적접근법과그에따르는적절한감압술및전방지지술의시행방법, 기기고정술시고려할사항, 이식재료의선택, 그리고골치유에영향을미치는고령환자의내과적, 전신적인자측면에서최신지견을정리하고저자들의경험과증례에비추어고찰한다. 결과및고찰 수술적치료의적응증흉요추의골다공증성골절이후일차적보존적치료에실패하여지연성으로불유합, 후만변형, 척수압박등이발생하는경우가드물지않게발생한다. 1895 년독일의사 Hermann Kummell 은이러한환자에서척추체내의균열 (intravertebral cleft) 이단순방사선검사상확인되는것에초점을맞추고, rarefying vertebral osteitis( 연화성척추체골염 ) 이라는진단명을보고한이래, 골다공증성척추체골절이후보존적치료에도불구하고골절된척추체가 1) 불유합, 또는골괴사 (osteonecrosis, Kummell s disease), 2) 심한함몰 (collapse) 또는후만변형, 3) 척수압박을일으키는경우가일정부분의환자에서발생하는것 이알려져있다. 이세가지현상은각각독립적으로발생하는것이아니라척추체골절이후치유에실패하는상태를총칭하는것으로, 골다공증성척추골절의지연성함몰 (delayed collapse of osteoporotic vertebral fracture) 발생시보이는각각의임상적측면으로이해된다. 3) 이는심한통증, 변형, 신경학적이상등을야기하여고령환자의운동기능및일상생활유지능력에큰지장을초래하는것이알려져있으며, 자연경과에기대어호전을기대할수없으므로환자의내과적상태가허락한다면수술적치료를고려할것을권고한다. 한편, 초기보존적치료이후지속되는통증완화를위한고식적목적의경피적척추성형술이후감염, 시멘트의파손및이탈, 또는척수압박등의합병증도드물지만발생하고이때도역시수술적치료의선택이불가피한경우가많다. 4) 골다공증성척추골절환자에서수술적치료의목적은척추신경을감압하고척추의안정성을회복하여척주 (spinal column) 의체간균형유지기능및신경보호기능을회복시키는것이다 (Fig. 1, 2). 하지만많은경우이들은고령의나이와관련하여내과적, 생리적, 정신적으로취약하고, 전신마취하주요외과적처치를받고회복하는능력이저하되어있으며, 5) 무엇보다수술의대상이되는척추뼈가물리적으로도약하고창상및골치유능력도부실하여, 1,2) 수술한목적인척추안정성회복에실패하는경우가흔하다. 환자의고령과관련된생리적특성을잘이해하고, 동반된내과적질환및골다공증정도등을면밀하게파악하고적절한수술을계획하는것이수술의합병증을피하고치료목적을달성하는데매우중요하다. 환자의내과적, 생리적, 정신적취약성 (frailty) 을살피고이에대한적절한위험도평가및처치 (comprehensive geriatric assessment and management) 를병행할수있는노인의학 (geriatric medicine) 적접근이도움이된다. 5) 즉, 고령의골다공증성척추골절환자의수술적치료는척추골절문제가환자의건강및기능상태에미치는영향을통증, 마비, 그리고활동성제한정도에주안점을두고평가해서수술적치료에의한위험도를상회한다고판단될때진행하는것이바람직하며이에대한판단은내과및마취과전문의와의협진이권장된다. 외과적접근법과감압술및전방지지술의선택골다공증성척추골절로불유합및후만변형되어심한통증을호소하거나신경압박을동반하여하지마비가발생한환자에서주된병소는불유합또는함몰된척추체이다. 척추체는척수의전방에위치하고있어직접적인노출및감압을위해서는전방접근법이필요하며, 후방접근시에는척수에의해척추체가가리게되므로직접적인감압및전방지지를시행하는데제한이있다. 하지만후방접근에의해서도후궁절제술을통한간접적 42 www.krspine.org

Journal of Korean Society of Spine Surgery Osteoporotic Spine Reconstruction in the Elderly A B Fig. 1. Simple radiography and magnetic resonance image (MRI) of a patient with delayed osteoporotic vertebral collapse (A). Postoperative simple radiography (B) and computed tomography (C) images of a patient who underwent anterior corpectomy/decompression and reconstruction with a femoral shaft allograft and instrumentation with triangulated dual-screw fixation with a bicortical purchase for the treatment of spinal cord compression with delayed osteoporotic vertebral collapse. C 인감압을시행하면서척추성형술또는척추경을통한쐐기절골술을이용한척추체단축시키는방법으로전방지지를제공할수있다. 다음과같은수술방법이널리사용된다. 6-9) 1) 전방감압 ( 척추체제거 ) 및유합술 + 전방또는후방기기고정술 2) 후방감압 ( 후궁절제술 ) 및유합 / 기기고정술 + 척추성형술 3) 후방감압 / 척추경경유쐐기절골술 ( 추체단축술 ) 및후방유합 / 기기고정술각각의접근법및수술방법의장단점을살펴보고보고되어있는임상결과들을비교하겠다. 전방접근법 (Anterior approach): 전방접근법은병소의절제를통한직접적인감압술이가능하고, 삼면피질자가장골또는타이타늄메쉬케이지 (titanium mash cage) 와같은금속소재척추체대체이식물 (vertebral body replacement implant) 을사용 하여직접적인전방주재건 (anterior column reconstruction) 을할수있다. 따라서따라서후만변형의교정에있어서도유리한장점이있다 (Fig. 1). 6) 골다공증성척추골절불유합내지는함몰환자대부분의경우후방주또는후방인대복합체 (posterior ligament complex) 의손상이없는, 척주전방주의부전 (failure of anterior spinal column) 상태인것을고려하면, 개념적으로는가장이상적인척주재건방법 (spinal column reconstruction) 으로생각된다. 하지만심한골다공증환자에서는접촉면적이큰이식물을이용한다해도이식물의침강 (subsidence), 기기또는고정실패 (instrument failure) 을피할수없는단점이있다. 7) 그리고무엇보다도골다공증성골절의불유합이잘발생하는흉요추이행부 (thoracolumbar junction) 에전방접근하기위해서는횡경막을절제하고흉강과후복막강을통하여접근하는방법 (transpleural/retroperitoneal approach), 또는그보다조금원위부에서벽측흉막과흉벽근막사이공간을이용하는흉막 www.krspine.org 43

Hyoungmin Kim et al Volume 23 Number 1 March 2016 외 / 후복막접근법 (extrapleural/retroperitoneal approach) 8) 를시행하여야하는데척추외과의사들에게익숙하지않은접근법이라는큰단점이있고, 수술후호흡기관련합병증발생에주의를기울여야한다는문제점이있어그사용빈도가점점줄어들고있다. 그러나척추성형술이후감염이라던가시멘트 (polymethylmethacrylate, PMMA) 의이탈 (dislodgement) 또는파손 (fracture of PMMA) 등에의한척수압박이발생한경우등에서수술적인치료를요할경우, 문제가되는 PMMA 를직접제거하기위해서는전방접근법이척수에의해병소가가리게되는후방접근법보다유리한경우가많고, 또전방주지지와후방기기고정술과함께사용될경우 ( 전후방접근법 ) 기기고정실패를최소화할수있는장점이있다는연구도있어, 실패한수술적치료의재수술을위해서마지막으로고려할수있는방법이다. 9) 또, 후방의정상구조물손상없이척주재건을할수있다는전방접근만의장점이있어최소침습수술술기및기기의발전과함께발전의가능성이있다고할수있다. 10) 후방접근법 (Posterior approach): 골다공증성척추골절의불유합또는함몰에서척추관협착증이나전방전위증같은일반퇴행성척추질환에서와같이후궁절제술과척추경나사못을이용한기기고정술을이용한후방유합술만을시행할경우, 많은경우에서나사못고정실패 (screw loosening and pull-out) 가발생하는것으로알려져있다. 그이유는불유합된척추체에서기인하는불안정성 (intravertebral instability) 과이로인한척주의부하지탱능력 (load bearing capacity) 을회복시켜주지못하는상황에서, 골다공증으로인해척추경나사못고정력도충분히얻을수없으므로후방기기고정술을장분절에걸쳐시행해도실패하는경우가많기때문이다. 11) 또, 신경감압측면에서 도전방에서후방으로발생하는신경압박을후방감압술 ( 후궁절제술 ) 만으로적절히감압하지못할뿐만아니라, 감압술을위한후궁절제술을통해골다공증성골절대부분에서손상되지않은후방안정성을훼손시켜야한다는문제가있다. 하지만, 골다공증성척추골절불유합과동반된신경압박은불유합된척추체의불안정성에서기인하는동적인인자가직접적인압박보다더중요한역할을하는것이알려지면서전방접근법을통한직접적인감압술의필요성이줄어들었다. 12,13) 또, 후방접근수술시전방지지를제공하기위해후방기기고정술및유합술과함께척추성형술 (vertbroplasty) 을함께시행하는방법과, 불유합분절의척추경을통한절골술을시행하여불유합부위를폐쇄 (closing wedge shortening osteotomy) 하고유합을도모하는술식이소개되었다. 그중척추성형술을동시에시행하는방법은안전하고용이하며효율적인전방지지를제공하고, 단분절후방유합술만으로도좋은결과를얻을수있다는보고도있다 (Fig. 2). 7,9,15) 외과적접근법에따른임상결과의비교 : 후방접근법과전방접근법수술을비교한최근몇연구들을살펴보면, 후방접근수술과척추성형술을함께시행하였을때임상적, 방사선학적결과가전방접근법에의한수술과같거나못하지않으며, 합병증및수술시간, 출혈량등에있어오히려훨씬유리하다는결과가보고되어있다 (Table 1). 게다가후방접근법이실제많은척추외과의사에게훨씬익숙한술식이라는점을고려하면, 후방접근법에의한기기고정술및유합술과척추성형술을이용한전방지지수술법을불유합된골다공증성척추골절에서수술적치료를요할때가장일차적으로고려할만한술식으로권할만하다. 불유합과척추체내불안정성이뚜렷한경우에는복와위체위와후방기기고정술및척추성형술만으로상당한후만변형교정도 A B C D Fig. 2. Preoperative and postoperative simple radiography (A, C) and MRI (B, D) of a 68-year-old female patient who had dynamic spinal cord compression due to an intravertebral instability showing a spinal cord signal change on the MRI without a significant canal compromise in the supine position. She underwent posterior decompression and fusion combined with vertebral body augmentation with polymethylmethacrylate to provide anterior spinal column support for the treatment of the osteoporotic vertebral collapse of T12. 44 www.krspine.org

Journal of Korean Society of Spine Surgery Osteoporotic Spine Reconstruction in the Elderly Table 1. Comparative studies according to surgical approach for treatment of patient with osteoporotic vertebral collapse. Authors / year Group (n) conclusion (favored procedure) Rationale of conclusion 9 Nakashima et al. 2014 AP combined (25) vs posterior & VP(21) AP combined surgery less implant failure 7 Sudo et al. 2013 Anterior (32) vs posterior & VP (18) posterior & VP less blood loss less respiratory complications 15 Kashii et al. 2013 Anterior (27) vs posterior & VP (25) vs PSO (36) posterior & VP all similar clinical outcome but less blood loss and op time 16 Okuda et al. 2012 Anterior (26) vs PSO (14) anterior surgery less reoperation, less adjacent fracture 11 Uchida et al. 2010 Anterior (30) vs posterior & VP (28) vs posterior(no VP) (25) posterior & VP anterior surgery inferior result in posterior surgery (no VP) group 얻을수있다. 한편, 환자의증상을야기하는주된병변이척추체내불안정성 (intravertebral instability) 인환자에서는후방유합술없이척추성형술만으로도만족스러운임상결과를얻었다는보고도있다. 12) 그러나후만변형이체위에의해교정되는정도가크지않고척추체내불안정성이별로없는경우 ( 치유된상태에서척추관내골편이큰방출성골절이나후만변형이심한경우등 ) 에는후만변형교정및척추관내골편절제를통한직접적인신경관감압을위하여전방접근법을고려하는것이바람직하다. 전방접근법에제한이있거나익숙하지않은경우대안으로후방접근법시행시에척추경을통한척추체절골술 (transpedicular subtraction osteotomy or closing wedge shortening osteotomy) 을고려할수있지만 15) 전방접근법과비교한연구결과후만교정정도에있어서는전방접근법보다유리하지만교정소실정도도더크고기기고정실패등으로재수술을요하는경우가더많았다고한다. 16) 기기고정술시고려할사항 (Instrumentation and fixation issue) 골다공증은척추뼈의기계적 물리적인강도와생물학적골형성 골유합능력을감소시킨다. 1,2) 이는곧척추유합술의직접적인실패요인으로작용한다. 따라서골다공증이심한환자에서척추골절등의합병증에대한보존적치료의실패로수술적치료를고려해야하는상황에서, 그수술적치료역시성공하리라는보장이없다는것이가장큰문제이다. 수술적치료에서회복하고자하는척추의안정성은일차적으로내고정장치의튼튼한고정력을전제로하며골다공증이심한환자에서수술적치료의실패는역시일차적으로는내고정장치의고정력소실에서비롯된다. 따라서그동안골다공증환자에서고정력을높이기위해다음과같은다양한연구가이루어져왔으나아직만족할만 한수준에도달하였다고할수없으며앞으로도많은노력이필요하다. 기기고정술시고려할사항들에대하여, 나사못디자인, 나사못삽입술기, 나사못삽입척추성형술에대한항목별로지금까지발표된연구결과들을개괄적으로살펴보고, 이들연구결과의임상적인이용방안에대하여간략하게정리하고자한다. 17,18) 나사못디자인 (Screw design) 나사못직경및길이 : 일반적으로나사못의직경 (screw diameter) 이클수록 pull-out 에저항하는힘이증가하는것이알려져있다. 나사못의직경을 1 mm 증가시켰을때고정력이 9-39% 까지증가했다는보고가있으며, 2 mm 증가시켰을때는 18-46% 까지고정력이증가했다는보고가있다. 19,20) 그러나실제임상에서나사못의직경은환자의척추경크기를고려하여결정하여야한다. 과도하게큰직경의나사못을삽입시척추경골절발생할수있으며, 21) 그결과충분한고정력을얻을수없음을염두에두어야한다. 하지만나사못이길이는척추체길이의 80% 정도면충분한것으로알려져있으며그보다긴나사못을이용한다고 pull-out force 가증가하지는않는것으로알려져있다. 척추경나사못의경우고정력 60% 이상이척추경에서제공되며척추체에서기인하는부분이 15-20% 에지나지않기때문이다. 22) 한편, 골다공증이심한경우에는척추체길이의 50% 정도의나사못이나그보다긴나사못이나고정력의차이가더욱적은것으로알려져있다. 이는심한골다공증에서는척추체내해면골소실정도가심하기때문에척추체내나사못의길이가길어진다고더유리할것이없다. 긴나사못을이용해척추체전방피질골을통과시켜고정력을높이고자하는방법도있는데이에대해서는이후나사못삽입술기단락에서별도로언급하고자한다. www.krspine.org 45

Hyoungmin Kim et al Volume 23 Number 1 March 2016 원추형나사못 (Conical screw design): 나사못이직경을앞에서뒤방향으로점진적으로증가하도록디자인하면나사못이삽입되면서나사못주변의골조직 ( 해면골 ) 을밀어내는효과를얻을수있어좀더나은고정력을얻을수있을것이라는고안이다. 23,24) 10-48% 까지의고정력증가효과를확인했다는보고도있지만, 오히려 -16% 정도로고정력이약하다는보고도있다. 22,25) 골다공증환자의경우척추경내해면골양이감소되어있으므로원추형나사못디자인을통해부가적인고정력증가효과를얻기힘들것으로저자들은추정한다. 삽입한나사못의깊이를조정하기위해뒤로후퇴시킬경우고정력이소실된다는약점이있으나, 앞으로가면서직경이줄어드는척추경의해부학적특징과일치하는장점이있다. 원추형나사못과실린더형나사못의장점을결합하여코어는원추형으로나사산은실린더형으로디자인한스크류가기존실린더형나사못에비하여 23-27%, 기존원추형나사못보다는 10-21% 정도고정력이우수하다는보고가있다. 26) 나사산종류 (Tread type): 나사못의나사산 (thread) 모양도고정력에영향을주는것으로알려져있다. 나사산의크기 (size), 모양 (shape), 깊이 (depth), 피치 (pitch) 등이변수이다. 나사산모양과관련하여서는 V-type 이고정력이더욱좋다고알려져있다. 25) 기계조립시많이사용되는사각나사산은척추뼈에서고정력에이점이없는것으로알려져있다. 고정재료가충분히단단한경우작은피치가작을때접촉면적을늘릴수있고또고정력을높일수있지만, 무른재료의고정을위해서는깊고피치가큰나사산이이용된다. 무른재료에서피치사이에있는재료가파편처럼작용하므로충분한고정력을제공하지못하는것이다. 한편, 이중나사산디자인 ( 같은축상에다른모양의나사산을양쪽끝에만드는경우, 예. 앞쪽으로는피치가크고깊은나사산, 뒤쪽에는촘촘하고얕은나사산 ) 의경우일반적인디자인과비교하였을때노령환자에서고정력에있어큰차이가없었다. 26) 나사못재료 (Material): 뼈와탄성률이비슷하고생체적합성이좋은 (biocompatible) 타이타늄나사못이스테인레스나사못에비해보다나은고정력과임플란트와골융합 (osteointegration) 에있어더욱유용한것으로알려져있다. 27) 나사못삽입술기 (Insertion Technique) 내고정술 (internal fixation) 이익숙한정형외과의사는더강한고정력을얻기위해집착하는경향이있으며, 실제로내고정장치의강한고정력은다양한뼈수술 (bone surgery) 에서중요한성공요인중하나이다. 하지만이에대해서과학적인근거를 중심으로충분히기술되어있는교과서나문헌이없어많은오해나근거없는믿음이널리펴져있는것또한사실이다. 척추의대표적내고정장치인척추경나사못이삽입과관련된여러가지술기및믿음의과학적근거를살펴보고골다공증이흔히동반된노령척추환자의내고정술을고려할때도움이될수있는연구결과를살펴보았다. 나사못의고정력에관련된연구는대부분이 in vitro 실험을통해측정된결과인점을실제임상적적용에있어서는고려하여야한다. 척추경탐색구멍크기 (Pilot hole size): 나사못외직경의 71.5%(6.5 mm 직경나사못사용할경우 4.6 mm 정도 ) 크기로뚫었을때, 삽입시무리한힘이들지않으면서가장강한고정력을보인다는연구가있다. 28) 너무작을경우나사못이들어가면서척추경에골절이발생할가능성이있는문제가있으며너무구멍을크게낼경우나사못이충분한고정력을얻을수없는문제가있다. 나사산모양및내직경등이다양하므로이연구결과를문자의미그대로받아들일수는없으나참고할수있겠다. 탭핑 (Self-tapping screw VS pre-tapped hole): 다소상반된보고들이있지만대체적으로요추에대해서는나사못삽입전 tapping 은고정력을다소약화시키는것으로알려져있으며, 흉추에서는큰차이가없다는보고가있다. 29) Helgeson 등은골다공증이있는환자의경우 tapping 과정중의토크를측정하여가장적절한나사못직경을찾을수있다는연구도있는데, 2.5 inlbs의토크정도의 tap 이후그직경보다 1 mm 큰나사못을사용할경우강한고정력을얻었다고발표하였다. 30) 나사못삽입각도 (Insertion angle): 골다공증이심하지않은경우에는나사못장축에대해 10도정도방향으로작용하는 pullout force 에대한저항력이가장크지만, 골다공증이심할경우에는나사못장축에대하여 40도각도에대한저항력이가장크다는연구결과가있다. 31) 기기고정술시작용하는 pull out force 의방향을생각하여가능한많은각도를주는것이유리하다는결과이지만실제환자에서해부학적으로척추경손상없이줄수있는상향또는하향및수렴각도에제한이있는점을고려하여야한다. 이중피질골통과 (Bicortical purchase): 골다공증으로인해척추경나사못의고정력이약할것이염려될때에는척추체전방피질골을통과하도록긴나사못을사용하여고정력을 31-120% 까지향상시킬수있는것으로알려져있다. 30) 하지만피질골조차도충분한고정력을제공하지못할정도의심한골다공증환자에서는도움이되기어려우며, 척추체전방피질골을관통하 46 www.krspine.org

Journal of Korean Society of Spine Surgery Osteoporotic Spine Reconstruction in the Elderly 면서대혈관손상을일으킬위험이있는문제가있고또, 전방피질골을통과했음에도충분한고정력을얻는데실패하였을경우고정된나사못에가해지는부하에의한회전중심 (center of rotation) 이전방피질골쪽으로이동하면서척추경에보다큰골결손및척추경골절등을유발할수있는문제가있다. 32) Screw hubbing: 나사못의머리 (screw head) 를척추후궁후방피질골속에파묻힐정도로깊숙히박은것을 screw hubbing 또는 hubbed screw 라고한다. 일반적인척추경나사못에서는척추경이지레의받침점 (fulcrum) 으로작용하여나사못이척추체내에서시소같은움직임 (titter-totter effect) 을일으키면서고정실패, 해리 (loosening) 가발생하는데, screw hubbing 을통해 lever-arm 을줄이면이를예방하는데도움이될것이라는주장이있었고, hubbing 중증가하는 insertion torque 가강한고정력으로이어질것이라는생각도있었으며, 특히소아의경우뼈의탄성이성인보다좋으므로 screw hubbing 이나사못삽입강도를높이는데더욱유용할것이라는믿음이있었다. 하지만최근발표된연구에서흉요추에서 screw hubbing 시척추경, 횡돌기, 후궁등의골절을야기하기쉬우며골절시유의하게고정력이떨어진다는것이 in vitro 실험에서확인되었다. 33) 이는성인이나성장중인소아환자나차이없이확인되었으며, 경추의외측괴나사못삽입시에도역시 screw hubbing 이고정력을떨어뜨린다는보고가있으므로나사못삽입점의피질골보다깊숙이나사를박지않는것이바람직하다. 34) 즉, 이때는나사못삽입시 빡빡하게들어가는정도 를뜻하는 insertion torque 가항상강한고정력으로이어지지않는다는것을의미한다. 수록고정력이강하며, 양측피질골을다통과하는나사못을사용할경우 40% 이상고정력이강화되며, 척추체하나당 2개의나사못이수렴하는각도로 (triangulation) 삽입하는것이권장된다 (Fig. 1C). 36) 나사못삽입척추성형술 (Augmentation of implant-bone interface) 골다공증이심하여부실한나사못주변의뼈를보강하여나사못고정력을향상시키고자, PMMA 또는 Calcium Phosphate 같은골시멘트물질을이용하여척추경및척추체를충전한이후나사못을삽입할수있다. 골시멘트주입후나사못고정시골다공증이있는척추체에서고정력을 25-340% 까지향상시킬수있다는보고가있고, 비용이많지않으며쉽게사용할수있다는점에서매우유용하다고할수있다. 하지만 PMMA 의일반적인특성과척추체의해부학적특징을고려하여합병증이발생하지않도록주의하여야한다. PMMA 는주입과정중에혈관으로새어나갈경우폐색전증등이발생할수있으며, mono-mma 의독성으로인한혈압저하가나타날수있다. 또, polymerization 과정중에발열로인해주변조직의온도를 40-100 까지상승시킬수있는데이는인해주변의신경세포나 피질골경로나사못 (Cortical bone trajectory screw): 해부학적척추경축을따라삽입하는기존의척추경나사못과달리척추경의후방하부내측피질골과전방상부외측피질골을 screwbone interface 로이용하는나사못이다. 기존의척추경나사못과달리나사못괘도가하내측 (inferomedial) 에서상외측 (superolateral) 을향하므로 convergency 가요구되는기존의척추경나사못에비해이상적인나사못삽입각도를얻기위한절개창크기가줄어든다 (Fig. 3). 기존의척추경나사못에비하여짧을길이를사용하고도더강한고정력을얻을수있다는연구가있으며, 35) 해면골소실이심한골다공증환자에서는피질골을이용하여고정력을얻는다는점에서더유리할가능성이있으나아직임상적인결과는보고되지않았다. 전방기기고정술 (Anterior instrumentation): 전방접근법으로 내고정술까지시행하는경우 Kaneda instrument 류의기기가가 장널리사용된다. 연골하골 (subchondral bone) 가까이삽입할 A B Fig. 3. Simple radiography (A, B) showing cortical bone trajectory screw fixation for L5 S1 interbody fusion. www.krspine.org 47

Hyoungmin Kim et al Volume 23 Number 1 March 2016 골세포등의괴사가일어날수있는온도이며, 생체내에서분해되지않고이물질 (foreign body) 로평생남는물질이므로, 액체상태에서척추뼈내로주입된 PMMA 가해면골사이공간으로침투해딱딱하게굳어진이후에이를제거하는경우에서는매우심한골결손을야기할수있다. PMMA 의단점을보완하기위하여 Calcium Phosphate 시멘트 ( 이하 CaP) 를사용하기도한다. CaP는생체내에서분해되는물질이며, 신생골에의해대체되는것으로알려져있으며, 수화 (hydration) 에의해경화되며열을흡수하는반응이므로발열이없는장점이있다. 고정력은 PMMA 보다는다소약한것으로알려져있으나 30-60% 까지고정력이강해지는것으로알려져있으며, 특이하게수술직후보다수술후신생골에의해 CaP가대체되면서더욱고정력이강해지는것이동물실험에서확인되었다. 하지만마찬가지로액체상태로주입시 PMMA 와같이척추관내또는신경공내로새어나갈수있는문제는있으며, 이를피하기위하여입자형태의 CaP를나사못을박기위해뚫어논 pilot hole 에주입한이후나사못을삽입하는방법도있다. 술기 (Injection technique): 나사못의보다강한고정력을최대한안전한방법으로얻는것이관건이다. 대표적인방법으로나사못삽입을위한 pilot hole 에 PMMA 또는 CaP 시멘트를일정량주입한이후굳기전에일반적으로사용하는척추경나사못을삽입하는것이다 (prefilled augmentation technique). 이는특별한도구가필요없는장점이있지만, 시멘트가굳기전에나사못을적절하게삽입하지못한경우낭패를볼수있는단점이있으며, 나사못삽입시시멘트가새는것을조절할수없다는문제도있다. 이러한단점을보완하기위해 cannulated screw 에측면구멍 (side hole) 을뚫어서나사못삽입이후시멘트를주입할수있도록고안된나사못 (fenestrated screw) 을사용할수도있다 (screw injection technique). Fenestrated screw 의경우시멘트주입시압력이상당히많이필요한단점이있어충분한양을넣기전에시멘트가굳어버리는것을주의하여야하며, 마찬가지로시멘트가원하지않는곳으로새어나갈위험은있다. 골다공증성척추체에대한고정력을비교한연구에서, 나사못만고정하는경우에비해전자의방법은약 160%, 후자의방법은약 190% 정도 pullout strength 가증가되었다는연구가있고, 19) 또전자의방법이후자의방법보다 20-40% 가량고정력이우수하다는연구결과도있다. 38) 적정주입량 (Optimal volume): 많은양의시멘트를넣는것이더욱강한고정력을얻을것이라는예상과달리흉추에서는 1cc, 요추에서는 1.5cc 의 PMMA 시멘트를사용하였을때가장강한고정력 ( 흉추에서는 186%, 요추에서는 264% 로고정력향 상 ) 을얻었다는연구결과가있다. 37) 시멘트가새어나갈위험을 무릅쓰고무리하게많은양의시멘트를사용할것을고집할필 요가없다는뜻이기도하지만실제임상에서적용시에는수술 할환자환자개개인의조건을고려하여결정하는것이바람직 하겠다. 나사못위치조정 (Screw turnback in cement augmented vertebra): 골다공증이심한척추체에서더강한고정력을얻기 위하여시멘트 (PMMA, polymethylmethacrylate) 를척추경및 척추체에삽입한이후척추경나사못을삽입하기도한다. 이때 PMMA 가완전히굳은이후나사못을전진시킬경우나사못 과굳어진 PMMA 사이균열이발생하면서고정력이심각하게 줄어들며, 후퇴시킬경우는전진시키는경우에비해심각할정 도로고정력이줄어들지는않는것이확인되었고, 시멘트가굳 기전 (4 분이내 ) 나사못위치를조정하는것은고정력에있어큰 변화를주지않은것으로알려졌다. 24,38) 따라서시멘트를이용하 여나사못고정술을시행할경우에는가급적시멘트가굳기전 에적절한위치로조정하는것이바람직하며, 시멘트가굳은이 후앞으로나사못을더깊이전진시키는것은피하는것이바람 직하겠다. Table 2. Systemic factors influencing bone healing Positive factors Insulin Insulin-like growth factor and other somatomedin Testoterone Estrogen Growth hormone Thyroxine Parathyroid hormone Calcitonin Vitamin A Vitamin D Anabolic steroids Vitamin C Negative factors Corticosteroids Vitamin A intoxicaiton VItamin D deficiency Vitamin D intoxication Anemina; iron deficiency Negative nitrogen balance Calcium deficiency Non-steroidal anti-inflammatory durgs Adriamycin Methotrexate Rheumatoid arthritis Syndrome of inappropriate antidiuretic hormone Castration Tobacco Sepsis 48 www.krspine.org

Journal of Korean Society of Spine Surgery Osteoporotic Spine Reconstruction in the Elderly 고령환자의척추유합술시고려할사항및골이식재료의선택전신적인자 : 노령의척추질환환자들은내과적으로다양한상태에있으며또한전신에작용하는다양한약물을함께복용하고있는경우가많다. 일반적으로골유합에미치는전신적인인자의영향을정리하면 Table 2와같다. 이들은동물실험및일부임상연구에서확인된것들로척추의유합술결과에도유사한영향을미칠것으로추정된다. 비타민 D의경우과도한경우도부족한경우도골유합에부정적인영향을미치는것이알려져있다. 하지만, 다른인자들과마찬가지로각각에대하여정성적으로용량에따른반응의차이가잘알려져있지는않다. 불가피한인자들도있고, 모든인자를완벽하게조절하지못하더라도, 고령환자에서척추유합술을고려해야할경우가능한이들인자의영향을최적화할수있도록노력이필요하다. 실제적으로척추유합술의성공여부를결정하는가장중요한시기는수술후 3-7일정도로알려져있으므로, 이시기동안척추의유합에부정적인영향을미칠가능성이있는인자들중조절가능한것들 (NSAIDs, 흡연, 부신피질호르몬, 방사선치료, 항암치료등 ) 은피하는것이바람직하겠다. 다분절척추유합술이후성공적인골유합등의치유과정을거치기위해서는영양기능이매우중요하다. 다분적척추유합술받는환자들에서영양상태가수술전수준으로회복하는데 6-12 주가량필요한것으로알려져있다. 따라서, 술전에영양상태를반영하는키와체중, 질소균형상태, 혈중알부민농도, 피부항원검사, 림프구숫자등을확인하여수술적치료이후적절한치유반응을보이지못할것으로예상되는경우수술적치료여부를진행여부를재고할필요가있다. 최근의체중감소, 피부항원검사에대한무반응 (anergy to skin antigen test), 알부민농도 3.4 mg/dl 이하, 림프구숫자 1,500 개이하소견이있을경 우임상적인적색경보 (red flag) 로생각할수있으며면밀한영양학적평가및적극적인영양공급치료를고려하는것이권장된다. 39) 국소적인자 : 골다공증이있는고령환자에서는뼈의기계적강도만약해지는것이아니라골수기능또한저하된다. 즉, 골형성에기여하는세포 (osteogenic stem cells and progenitors) 의농도및생물학적능력이약화되는것으로알려져있다. 따라서고령의척추환자에서유합술을고려시성공적인수술적치료를위해서는기계적인고정력의확보뿐만아니라 Table 3과같은국소적생물학적인자들에대한고려가필요하며가능한인자에대해서는교정하기위한노력이필수적이다. 40) 골이식재료의선택 : 척추유합술시, 이상적인골이식재료는골형성능력 (osteogenic potential), 골유도능력 (osteoinductive potential), 골전도능력 (osteoinductive potential) 의세가지생물학적기능이필요하다. 지난수십년간골형성및치유와관련된생물학적, 임상적연구결과많은경우에있어서척추의퇴행성질환에대한유합술시행시자가장골이식 (autologous iliac bone grafting) 을대체할수있는재료들이개발되었지만, 아직도이세가지를가장이상적으로갖추고있는것은골수및골세포를충분히간직하고있는자가장골의해면골뿐이다. 하지만골다공증이심한노인환자에서는자가장골이식도만족스러운임상결과를보장하지못한다. 골다공증이심한환자에서는자가장골또한골수의기능이많이감소되어있으며해면골의양또한충분치못한단점이있고기계적강도가약해질경우삼면피질골을유지한형태 (tricortical strut graft) 로채취하더라도이식부위에서구조적지지에실패하여침강 (subsidence) 가일어 Table 3. Local factors influencing bone healing Positive factors Increased surface area (bone and viable local tissue) Local stem cell sources (eg., bone marrow, periosteum) Osteoconductive scaffold (eg., fibrin clot or other matrix material) Mechanical loading Mechanical stability Factors promoting recruitment, activation, and proliferation of osteoblastinc stem cells (eg., platelet degranulation products including PDGF, EGF) Osteoinductive factors (eg., BMPs) Factors promoting angiogenesis (eg., FGF, EGF, VEGF) Electrical stimulation Negative factors Osteoporosis - mechanical & biologic aspect Radiation scar Radiation Dennervation Tumor Marrow-packing disorder Infection Local bone disease Mechanical motion Bone wax (other materials inducing foreign body reaction) www.krspine.org 49

Hyoungmin Kim et al Volume 23 Number 1 March 2016 나는일이흔히보고되어있다. 따라서골다공증이어느정도진행된고령환자에서유합술시특히골결손부위가크다면구조적지지 (structural support) 를할수있는이식물 (implant) 또는대퇴골간부동종골 (allograft) 과같은구조물과함께골형성기능을제공하는 ( 자가장골또는전방접근시얻을수있는늑골 ) 등을사용하는것이권장된다. 전방지지물의선택시에는기계적으로이를감당할수있을정도로튼튼해야하며가능한접촉면적이넓을수록골유합측면에서도유리하고, 단위면적당부하를줄일수있어척추체종판의지지실패로인한골절, 침강발생을피할수있는점을고려하여야한다. 따라서, 현재로서는골다공증이있는고령환자의척추전방주재건술시행시에는자가장골해면골과충분한기계적지지를제공할수있는이식물을조합하여사용하는것이최선의선택으로판단된다. 후방유합술시에는동종골등의골이식재또는대체재를단독으로사용하기보다는자가장골해면골을함께이용하는것이유합술의실패를막을수있는최선의방법으로생각된다. 한편, 아직은그안정성및효과에대한검정이마무리되지는않았지만 teriparatide( 유전자재조합부갑상선호르몬 ) 을이용한골다공증의전신적치료 (systemic treatment) 및 rhbmp ( 유전자재조합골형성유도단백 ) 의국소적사용이추후심한골다공증환자의척추유합술결과를향상시키는데도움이될것으로기대된다. 41) 결론 고령의골다공증성척추골절환자의수술적치료시, 포괄적노인의학적평가를통하여수술적치료의득과실을면밀히살피고, 다양한수술방법과이식물의장단점을따져서최선의외과적접근법, 기기고정술, 이식재료등을선택하는것이성공적인치료를위하여중요하다. 후방접근수술과척추성형술을함께시행할경우할경우합병증및수술시간, 출혈량등에있어장점이있고, 많은척추외과의사에게훨씬익숙한술식이라는점에서불유합된골다공증성척추골절에서수술적치료를요할때가장일차적으로고려할만한술식으로권할만하다. 후만변형이복와위체위에의해교정되는정도가크지않고, 척수를압박하는골편이나시멘트가있거나감염된시멘트등병소를직접제거해야하는경우전방접근법을고려할수있다. 후방접근수술시복와위의체위에의한후만변형교정정도가충분하지않은경우쐐기절골척추체단축술 (closing wedge vertebral shortening) 술식을고려할수있다. 골다공증성척추의나사못고정술시행시충분한고정력을얻을수없는경우시멘트충전이후나사못삽입방법을이용할수있다. 아울러고령환자의생물학적내과적특성을고려하여영양상태등골유합에영향을 미칠수있는생물학적변수들을가능한최적의조건으로맞추기위한노력이필요하다. REFERENCES 1. Lill CA, Hesseln J, Schlegel U, et al. Biomechanical evaluation of healing in a non-critical defect in a large animal model of osteoporosis. J Orthop Res. 2003;21:836 42. 2. Peter Augat, Ulrich Simon, Astrid Liedert, et al. Mechanics and mechano-biology of fracture healing in normal and osteoporotic bone. Osteoporos Int. 2005;16:S36 S43. 3. Ito Y, Hasegawa Y, Toda K, et al. Pathogenesis and diagnosis of delayed vertebral collapse resulting from osteoporotic spinal fracture. Spine J. 2002;2:101-6. 4. Abdelrahman H, Siam AE, Shawky A, et al. Infection after vertebroplasty or kyphoplasty. A series of nine cases and review of literature. Spine J. 2013;13:1809-17. 5. Kim KI, Park KH, Koo KH, et al. Comprehensive geriatric assessment can predict postoperative morbidity and mortality in elderly patients undergoing elective surgery. Arch Gerontol Geriatr 2013;56:507-12. 6. Kanayama M, Ishida T, Hashimoto T, et al. Role of major spine surgery using Kaneda anterior instrumentation for osteoporotic vertebral collapse. J Spinal Disord Tech. 2010;23:53-6. 7. Sudo H, Ito M, Kaneda K, et al. Anterior decompression and strut graft versus posterior decompression and pedicle screw fixation with vertebroplasty for osteoporotic thoracolumbar vertebral collapse with neurologic deficits. Spine J. 2013;13:1726-32. 8. Moskovich R, Benson D, Zhang ZH, et al. Extracoelomic approach to the spine. J Bone Joint Surg Br. 1993;75:886-93. 9. Nakashima H, Imagama S, Yukawa Y, et al. Comparative study of 2 surgical procedures for osteoporotic delayed vertebral collapse: anterior and posterior combined surgery versus posterior spinal fusion with vertebroplasty.spine (Phila Pa 1976).2015;40:E120-6. 10. Ragel BT, Amini A, Schmidt MH. Thoracoscopic vertebral body replacement with an expandable cage after ventral spinal canal decompression. Neurosurgery. 2007;61:317-22. 11. Uchida K, Nakajima H, Yayama T, et al. Vertebroplasty- 50 www.krspine.org

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Review Article J Korean Soc Spine Surg. 2016 Mar;23(1):41-53. http://dx.doi.org/10.4184/jkss.2016.23.1.53 골다공증성척추골절환자의수술적치료시고려사항 : 외과적적응증, 접근방법, 고정방법, 이식재료의선택 김형민 장봉순 이춘기서울대학교의과대학정형외과학교실연구계획 : 종설목적 : 본연구에서는골다공증성척추골절환자에서성공적인수술적치료를위해외과적접근법, 기기고정술, 이식재료선택등에있어어떤고려가필요한지살펴보겠다. 선행문헌의요약 : 고령환자에서골다공증과관련된척추의골절에대한수술적치료는, 뼈의기계적 물리적강도가약하고, 골유합능력이저하되어있어튼튼한고정과성공적인골유합을얻는데실패하는경우가많다. 대상및방법 : 골다공성척추골절이후수술적치료를시행할경우고려해야할내과적, 일반적사항및외과적접근법, 기기고정술, 이식재료의선택에관한연구결과를보고한문헌을검색하여최신지견을정리하고저자들의경험에비추어고찰한다. 결과 : 후방접근수술과척추성형술을함께시행할경우할경우합병증및수술시간, 출혈량등에있어장점이있고, 많은척추외과의사에게훨씬익숙한술식이라는점에서불유합된골다공증성척추골절에서수술적치료를요할때가장일차적으로고려할만한술식으로권할만하다. 후만변형이복와위체위에의해교정되는정도가크지않고, 척수를압박하는골편이나시멘트가있거나감염된시멘트등병소를직접제거해야하는경우전방접근법을고려할수있다. 골다공증성척추의나사못고정술시행시충분한고정력을얻을수없는경우시멘트충전이후나사못삽입방법을이용할수있다. 아울러고령환자의생물학적내과적특성을고려하여영양상태등골유합에영향을미칠수있는생물학적변수들을가능한최적의조건으로맞추기위한노력이필요하다. 결론 : 고령의골다공증성척추골절환자의수술적치료시, 포괄적노인의학적평가를통하여수술적치료의득과실을면밀히살피고, 다양한수술방법과이식물의장단점을따져서최선의외과적접근법, 기기고정술, 이식재료등을선택하는것이성공적인치료를위하여중요하다. 색인단어 : 골다공증, 척추수술, 외과적접근법, 기기고정술, 골이식재 약칭제목 : 고령환자의골다공성척추수술 접수일 : 2015 년 7월 6일 수정일 : 2015 년 7월 10일 게재확정일 : 2015 년 11월 18일 교신저자 : 장봉순 서울시종로구대학로 101 서울대학교의과대학정형외과학교실 TEL: 02-2072-3864 FAX: 02-764-2718 E-mail: bschang@snu.ac.kr Copyright 2016 Korean Society of Spine Surgery Journal of Korean Society of Spine Surgery. www.krspine.org. pissn 2093-4378 eissn 2093-4386 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. 53