Review Article J. of Advanced Spine Surgery Volume 1, Number 2, pp JASS Posterior Dynamic Stabilization : Interspinous Devices Seong Son, M.D.,

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1 Review Article J. of Advanced Spine Surgery Volume 1, Number 2, pp JASS Posterior Dynamic Stabilization : Interspinous Devices Seong Son, M.D., Woo Kyung Kim, M.D., Sang Gu Lee, M.D., Chan Woo Park, M.D. Department of Neurosurgery, Gachon University, Gil Hospital, Incheon, South Korea Lumbar spinal stenosis is one of the degenerative diseases which have increasingly grown, as the nation is transitioning to an aging society. Even though medication is readily available as treatment for lumbar spinal stenosis, surgical treatments can be considered if symptoms are severe. The most basic operation, laminectomy and decompression, alone, can bring about improvements of symptoms by alleviating the pressure of the nerve root, however if instability is evident on the radiograph or during surgery, spinal fusion will be performed, and will yield favorable results. On the contrary, it is also common knowledge that spinal fusion can give rise to a variety of complications afterwards. New surgical procedures and apparatuses have been developed and used in clinical practices in order to overcome these complications. One of these new concepts is posterior dynamic stabilization. The purpose of posterior dynamic stabilization is to enable the spine to adjust so that, by limiting the movement to the direction which causes the pain, patients can feel at ease. Until recently, interspinous devices have been developed and applied in clinical practices in order to improve the symptoms of patients. The device is inserted after decompression of the nerve root in between the spinous processes of the lumbar part, where the symptom is present. By doing so, it not only limits the extension (without impacting flexion, axial rotation, and lateral bending) but also, alleviates the load on the facet joint by playing a role as a shock absorber. However, it is also true that the practice of this surgery has been limited due to the reports showing that; halo formed between the contact surface of the bone and the metal device might be the cause of pain; and according to a follow-up survey, fractures of the spinous process, breakaway of apparatus and post-operative complication such as kyphosis may be present. This paper will investigate the usefulness of these devices again by looking at the fundamental biomechanical effect of interspinous devices and analyzing the thesis which has been previously published. Key Words: Spinal stenosis, dynamic stabilization, interspinous device, Biomechanical study, Emerging technique 서론 지난수십여년동안, 퇴행성요추관협착증이나전방위전위증에의한요통및하지방사통을치료하는데있어, 척추경나사못고정술및추체간유합술을이용한유합술은불안정성 (instability) 의개념을바탕으로기본적인치료로시행되어왔다. 척추불안정증이굴곡-신전단순방사선촬영에서명확히보일때유합술은효과적일수있으나, 불안정증이없으면서통증을보이는환자에유합술을시행하는것은필요이상으로침습적인치료가될수있다. 게다가, 요통이분절의비정상적운동보다는비정상적하중전달 (load transmission) 에의한것이라는 개념이대두되었고, 유합술은인접분절에생체역학적인 부담을가져오게되고, 인접분절퇴행성변화 (adjacent segment degeneration) 등을야기할수있다고알려져 왔다 23). 이에유합술을대체하는치료방법이고안된바, 역동성척추안정화 (dynamic stabilization) 의개념 이고안되었는데, 분절의융합을목적으로하지않으면 서, 분절의운동및하중전달을바람직한방향으로변화 Corresponding author: Woo-Kyung Kim, M.D., Ph.D. Department of Neurosurgery, Gachon University, Gil Hospital, 1198 block, Guweol-Dong, Namdong-Gu, Incheon, South Korea, TEL: , FAX : wkkim@gilhospital.com 64 Copyright 2011 Korean Society for the Advancement of Spine Surgery

2 시키는것 을목적으로한다 25). 그것은척추분절의운동 성을유지하면서, 감압수술후발생할수있는불안정성 을보완하거나, 분절운동의하중부담 (load bearing) 형 태를변화시켜인접분절의부하를감소시키는것을의 미한다 24). 일반적으로역동성척추안정화시스템이란전디 스크치환술 (total disc replacement), 요추수핵치환 술 (nucleus replacement), 후방역동성안정화시스템 (posterior dynamic stabilization) 을포함한다. 여기서는 이들중, 후방역동성안정화시스템, 특히극돌기간장치 (interspinous devices) 에대해서다루고자한다. 본론 1. 생역학적근거정상추간판은콜라겐 (collagen) 과프로테오글라이칸 (proteoglycan) 의균등질겔 (homogeneous gel) 로구성되 어있어, 하중이추간판을가로질러균일하게전달되는 것이가능한등방성 (isotrophic) 구조이다 12,17,18). 이러한 구조적특성이굴곡, 신전, 측만운동시, 하중을동일하게 분배시켜적절한균형을유지하게한다. 그런데, 나이가 들어감에따라추간판의탈수화 (dehydration) 및붕괴 (collapse) 가생기고, 이는추간판을비균등질한구조로 만들어등방성의특성이소실된다 2,20). 그러므로추간판을 통과하는하중의전달이균일하게되지않으며, 이는척 추종판의소실, 후관절비대등의퇴행성변화를거쳐요 추의불균형 (imbalance) 을초래하고, 그로인해후관절, 척추종판 (end plate), 추간판섬유륜, 척추골막, 주변지 지연조직등에비정상적하중전달을야기한다 4,8,9). 이처 럼균형이깨진퇴행성척추에서는특정자세가통증을 유발시킬수있으며, 실제, 많은환자들이요추의불안정 증이없으면서, 위치 (position) 또는자세 (posture) 에관련 된통증을호소한다. 이는통증의원인이불안정증이아 닌비정상적하중전달과관련이있다는것을의미한다 21,22,26). 객관적근거를가지는불안정증에의한요통환자 들은상대적으로적다는것과최근들어기구및수술기 술의진보로인해골유합성공률이높아졌음에도환자의 임상적만족도는그에상응하지않다는사실은이러한 이론을뒷받침해준다 5,6,10). 유합술은수술후인접분절의퇴행성변화와같은주요 변형들의발생과관련이되어왔다. 게다가단단한후측 방나사못고정술도추간판에의하중은막을수없으며, Table 1. 극돌기간장치의적응증 Spinal stenosis Degenerative spondylolisthesis (Grade I) Discogenic low back pain Nontraumatic instability Lumbar disc herniation Facet syndrome 병변분절의하중전달의형태를변형시키더라도, 오히려 정상적인하중이일어나는분절의척추운동을방해할 수있다. 반면, 후방역동성안정화시스템은유합술과달 리, 비정상적부하가일어날수있는자세로되는것을막 을수있는동시에, 제한된운동을허용함으로써시상균 형 (sagittal balance) 에미치는해로운영향을없앨수있 다 13). 즉, 퇴행성추간판의부하를덜어줘서통증을줄일 수있고, 인접분절의부하를감소시켜인접분절의퇴행 성변화를예방할수있다. 생역학적으로, 후방역동성안 정화시스템은통증을야기하는방향으로의운동은제한 하면서그렇지않은모든범위의운동은허용하여, 보다 생리학적하중을전달하며정상적인척추운동에가깝게 유지한다 11,28). 2. 적응증후방역동성척추안정화시스템은주로척추관협착 증 (spinal stenosis), 퇴행성추간판 (degenerative disc disease) 및초기단계의척추전위증 (spondylolisthesis) 에적용되어왔다. 특히, 극돌기간장치는다음과같은경우에적용할수 있다 (Table 1). 좀더자세한예를들자면, 첫째, 퇴행성후관절및추간 판질환에서후관절과추간판을손상시킬수있는운동 을제한하여염증반응을감소시키거나자가 - 회복기전 을가능하게한다. 둘째, 골다공증이있는고령환자에서 나사못고정술은오히려해가될수있으며, 보다부드러 운안정화기술이필요할수있다 22). 셋째, 보존적인치료 에도불구하고지속적인신경인성파행이나요통이있고, 해부학적으로경계부위 (borderline) 정도의협착증이있 는환자들에시행할수있다. 넷째, 침습적인유합술을하 기어려운, 내과적금기증을가지거나전신상태가좋지 않은환자들과같은경우에도좋은역할을기대할수있 다. 65

3 3. 후방역동성안정화장치의분류 1980 년대중반이후다양한생역학적이론들을바탕 으로, 많은후방역동성안정화장치들이시도되어사용 되어왔고, 이들을다양하게분류해왔다. 보편적으로크 게 1) interspinous spacer device, 2) pedicle screw-based device ( 예, Graf system, Dynesys, dynamic rod & screw systems) 3) total facet replacement system 의세가지종 류로분류하며, 이중, 극돌기간장치에대해고찰해보고 자한다. 극돌기간장치는퇴행성추간판및후관절병변에기인 한요통및신경인성파행 (neurogenic claudication) 에대 한대체적인치료법으로서고안되었다. 이장치들은후방 인대를절제하여인접한극돌기들사이에삽입하여고정 하며, 척추를약간굴곡상태로유지함으로써, 요추관및 추간공의직경을증가시켜간접적신경감압을유도한다. 게다가, 척추의다른방향의운동은유지하면서신전운 동은제한하여후관절의하중을덜어, 후관절병변에의 한통증을줄일수있다. 이장치들은유합술에비해작은 조직절개와최소침습술기로신경감압이가능하고, 경 막외유착및뇌척수액유출등의위험을줄일수있다. 한편, 극돌기사이에이렇게 spacer 를사용하는대신긴 장밴드 (tension band) 를이용한 Elastic ligament, Loop system 과같은 interspinous ligament device 라고분류되 기도하는장치들이있으나, 장치에대한정보및임상 적인문헌보고가드문실정으로, 최근에는 interspinous device 로서 interspinous spacer device 가주로다루어진 다. 1) Coflex (Paradigm Spine, Wurmlingen, Germany) Interspinous U (Spine motion, Germany) 는 1994 년 Jacque Samani 27) 에의해처음소개된것으로, 감압술이후극돌기간인대와상극돌기인대를제거한후극돌기간사이에삽입하는 U 형태의티타늄기구로, 안정성유지및추간공확장효과를가져온다고알려져있다. Coflex 는이전에 Interspinous U 로불렸던것으로, 현재유럽등에서사용되고있지만아직 FDA 승인은받지못했다 (Fig 1). 수술술기는다음과같다. 1. 일반적인미세현미경감압술을시행한다. 2. 극돌기간인대 (interspinous ligament) 및극상인대 (supraspinous ligament) 를모두제거하고, implant 삽입을방해할수있는 bony overgrowth 를제거한다. 3. 적절한 implant size 를정하기위해 trial 을사용하며, 이때 distraction 시키는정도도고려된다. 적절한깊이는 dura 로부터약 3-4 mm 떨어져있는것이며, implant 를삽입한후, tip probe 를이용하여확인한다. 지금까지몇몇보고들이 Coflex 의임상적효용성을보고했다 년, 임효주등 15 ) 은 20명의환자에삽입하고, 5.9개월추적관찰하여 80% 의성공률을보고했고, 2006 년, 이숙인등 14) 은 65명의환자에삽입하고, 14개월추적관찰하여 85% 의성공률로긍정적인결과를얻었다. 그러나 2008 년, 윤성민등 29) 은 48명의환자에삽입하여, 22개월추적관찰한결과, 15명 (31%) 에서골미란 (bony erosion) 에의한미세한불안정증 (minor instability) 및불만족스러운임상결과를보였다고보고했다. 또한 2008 년, 배용식등 3) 은 19명에삽입하고, 38개월추적관찰하여만족할만한임상결과를얻었으나, 추간판제거술을한분절은통계적으로유의한추간판높이감소를보였다고보고했다. Fig 1. (A) Coflex 의전체모습. (B) 수술후전후면및측면단순방사선사진. 66

2) DIAM (Medtronic Sofamor Danek, Memphis, TN, USA) (Fig. 2) DIAM 의 core 는실리콘 (silicone) 으로만들어졌으며, 외부는폴리에틸렌 (polyethylene) 으로코팅되어있는데, 이는탄성물질이어서인접분절의부하를줄이고, 충격- 흡수역할을하게된다 6).

현재이장치는 FDA 승인을위한임상시험중에있다. Fig. 2. DIAM 의전체모습 3) Wallis (Abbott Spine, Bordeaux, France) (Fig. 3) 1986 년에유럽에소개된최초의 interspinous device 로 Senegas 에의해개발되었고가장오래된역사를가지고있다.

이장치의가장중요한점은척추의생리학적모양에맞게 H 자로되어뼈의절제를최소화시키고뼈에충격을경감시킬수있는디자인이라는것이다 7). 4) X-STOP (St. Francis Medical Technologies, Alameda, USA) (Fig.

4 2) DIAM (Medtronic Sofamor Danek, Memphis, TN, USA) (Fig. 2) DIAM 의 core 는실리콘 (silicone) 으로만들어졌으며, 외부는폴리에틸렌 (polyethylene) 으로코팅되어있는데, 이는탄성물질이어서인접분절의부하를줄이고, 충격- 흡수역할을하게된다 6). 이충격-흡수장치가추간판내압력을감소시키고회전탈구 (rotatory dislocation) 를감소시킬수있다 19). 이는통증을유발하는분절을안정화시키면서도어느정도의척추운동성을허용함을의미한다. 이장치의효과에대한논문들은아직까지많지않은실정이고, 몇몇보고에서수술받은환자들의만족률이높게보고되기는했으나, 좀더장기간의추적관찰이필요하다 16). 현재이장치는 FDA 승인을위한임상시험중에있다. Fig. 2. DIAM 의전체모습 3) Wallis (Abbott Spine, Bordeaux, France) (Fig. 3) 1986 년에유럽에소개된최초의 interspinous device 로 Senegas 에의해개발되었고가장오래된역사를가지고있다. 이장치의초기디자인은인접극돌기들사이에삽입된티타늄블록의 spacer 와극돌기주위를감싸서안정성을제공하는편평한 Dacron cord 로구성되었다. 이러한 1세대장치가긍정적결과를보이자제 2세대가개발되었는데, 블록의재료를티타늄대신에더탄력성이있고덜단단한 PEEK(polyetheretherketone) 로바꾼것이었다. 이장치의가장중요한점은척추의생리학적모양에맞게 H 자로되어뼈의절제를최소화시키고뼈에충격을경감시킬수있는디자인이라는것이다 7). 4) X-STOP (St. Francis Medical Technologies, Alameda, USA) (Fig. 4) 이장치는현재 FDA 승인을받은 (2005 년 11월 ) 유일한극돌기간장치로서, 계란형의티타늄금속 spacer 이며, 두개의측면날개가있어, 인접극돌기사이에고정되도록고안되었다. Implant 는어떠한골구조물에도고정되지않더라도, 뒤쪽으로는극상인대, 앞쪽으로는후궁, 머리쪽및다리쪽으로는극돌기들, 양옆으로는이장치의날개 (wing) 들에의해이동이제한된다 30). X-stop에대해여러임상연구들이시행되어왔는데, 요추협착증에의한신경인성파행을치료하는데에있어이장치의효용성을보여주고있다. 임의추출식전향적통제다기관임상시험 (randomized Fig. 3. Wallis 의전체모습 Fig. 4. X-stop 의전체모습. 67

5 prospective controlled multicenter trials) 과후향적연구 (retrospective study) 에서보존적인치료만을한군과비교했을때, 이장치를가진군에서더좋은결과를보였다고보고하였다 1,30,31). 결론 지금까지극돌기간장치를비롯한후방역동성안정화장치는꾸준히개발및개선되어왔고, 현재도활발히연구가진행되고있으나, 이러한장치들이해결해야할몇가지문제점들이있다. 첫째, 정확한생역학적분석과임상에의적용문제이다. 척추분절의운동을어느상황에서어느정도제한하는것이맞는지, 퇴행된구조물의하중을덜어주기위해얼마만큼의하중이분산되어야하는지생역학적으로분석하고, 또그결과가실제임상에서일관되게적용되도록고안이되어야하는데, 이는여느척추기구가그렇듯이아직풀지못한과제이다. 둘째, 아직장기간추적관찰이충분하지않다는것이다. 이론적으로는정상척추와비슷한운동성을가지면서통증을줄일수있다고하지만, 장기간삽입되어있어도일정한역할을하는지, 기구의손상이나, 불안정증의진행과같은다른부정적결과는없는지면밀히확인해야하며, 유합술같은다른술기와직접비교해봐야한다. 이론적으로많은이점들을가지고있음에도불구하고, 극돌기간장치가유합술보다우수하다는데에는논란이있으며, 임상적결과또한불확실하다고할수있다. 그러나현재, 신중히고려한적절한적응증에한해서는유합술을대체하는장치임에는이론적, 임상적근거가어느정도뒷받침되고있으며, 향후발전가능성도있다고사료된다. REFERENCES 1. Anderson PA, Tribus CB, Kitchel SH : Treatment of neurogenic claudication by interspinous decompression: application of the X STOP device in patients with lumbar degenerative spondylolisthesis. J Neurosurg Spine 4: , Ariga K, Miyamoto S, Nakase T, Okuda S, Meng W, Yonenobu K, at al. : The relationship between apoptosis of endplate chondrocytes and aging and degeneration of the intervertebral disc. Spine 26: , Bae YS, Ha Y, Ahn PG, Lee DY, Yi S, Kim KN, et al. : Interspinous implantation for degenerative lumbar spine : clinical and radiological outcome at 3-yr follow up. Kor J Spine 5(3): , Bogduk N : The innervations of the lumbar spine. Spine 8:286-93, Boos N, Webb JK : Pedicle screw fixation in spinal disorders: A European view. Eur Spine J 6:2-18, Caserta S, La Maida GA, Misaggi B, Peroni D, Pietrabissa R, Raimondi MT, et al. : Elastic stabilization alone or combined with rigid fusion in spinal surgery: A biomechanical study and clinical experience based on 82 cases. Eur Spine J 11:S , Christie SD, Song JK, Fessler RG : Dynamic interspinous process technology. Spine 30 Suppl 16: S73-S78, Fujiwara A, Lim TH, An HS, Tanaka N, Jeon CH, Andersson GB, et al. : The effect of disc degeneration and facet joint osteoarthritis on the segmental flexibility of the lumbar spine. Spine 25: , Fujiwara A, Tamai K, An HS, Kurihashi T, Lim TH, Yoshida H, at al. : The relationship between disc degeneration, facet joint osteoarthritis, and stability of the degenerative lumbar spine. J Spinal Disord 13:444-50, Gibson JN, Grant IC, Waddell G : The Cochrane review of surgery for lumbar disc prolapse and degenerative lumbar spondylosis. Spine 24: , Hartmann F, Dietz SO, Hely H, Rommens PM, Gercek E : Biomechanical effect of different interspinous devices on lumbar spinal range of motion under preload conditions. Arch Orthop Trauma Surg, Epub ahead of print, Hukins DW : A simple model for the function of proteoglycans and collagen in the response to compression of the intervertebral disc. Proc Biol Sci 249: , Korovessis P, Papazisis Z, Koureas G, Lambiris E : Rigid, semirigid versus dynamic instrumentation for degenerative lumbar spinal stenosis: a correlative radiological and clinical analysis of short-term results, Spine 29: , Lee SI, Kim WK, Yoo CJ, Lee SG, Park CW : Clinical experience of interspinous U device for degenerative spinal disease. Kor J spine 3: , Lim HJ, Rho SW, Jeon SR, Rhim SC : Early experience with interspinous U in the management of degenerative lumbar disease. Kor J Spine 1: , Mariottini A, Pieri S, Giachi S, Carangelo B, Zalaffi A, Muzii FV, et al. : Preliminary results of a soft novel lumbar intervertebral prothesis (DIAM) in the degenerative spinal pathology. Acta Neurochir Suppl 92: ,

6 17. McMillan DW, McNally DS, Garbutt G, Adams MA : Stress distributions inside intervertebral discs: the validity of experimental stress profilometry. Proc Inst Mech Eng H 210:81-87, McNally DS, Adams MA.: Internal intervertebral disc mechanics as revealed by stress profilometry. Spine 17:66-73, Minns RJ, Walsh WK : Preliminary design and experimental studies of a novel soft implant for correcting sagittal plane instability in the lumbar spine. Spine 22: , Moore RJ, Vernon-Roberts B, Fraser RD, Osti OL, Schembri M : The origin and fate of herniated lumbar intervertebral disc tissue. Spine 21: , Mulholland RC, Sengupta DK : Rationale, principles and experimental evaluation of the concept of soft stabilization. Eur Spine J 11 Suppl 2:S , Nachemson A : Towards a better ubderstanding of Low-back pain: a review of the mechanics of the lumbar disc. Rheumatol Rehabil 14: , Schlegel HD, Smith JA, Schleusener RL : Lumbar motion sequent pathology adjacent to thoracolumbar, lumbar and lumbosacral fusions. Spine 21: , Schmoelz W, Huber JF, Nydegger T, Dipl-Ing, Claes L, Wilke HJ : Dynamic stabilization of the lumbar spine and its effects on adjacent segments : an in vitro experiment. J Spinal Disord Tech 16; , 2003; 25. Sengupta DK : Dynamc stabilization devices in the treatment of low back pain. Orthop Clin North Am 35:43-56, Smith D, McMurray N, Disler P : Early intervention for acute back injury:can we finally develop an evidence-based approach? Clin Rehabil 16:1-11, Samani J : Study of a semi-rigid Interspinous U fixation system: 106 patients over 6 years. CD-Rom, Fixano, France, 2000, Wilke HJ, Drumm J, Häussler K, Mack C, Steudel WI, Kettler A : Biomechanical effect of different lumbar interspinous implants on flexibility and intradiscal pressure. Eur Spine J 17: , Yoon SM, Lee SG, Park CW, Yoo CJ, Kim DY, Kim WK : Late complications of single level interspinous U in lumbar spinal stenosis with mild segmental instability. Kor J Spine 5(2):89-94, Zucherman JF, Hsu KY, Hartjen CA, Mehalic TF, Implicito DA, Martin MJ, et al. : A multicenter, prospective, randomized trial evaluating the X STOP interspinous process decompression system for the treatment of neurogenic intermittent claudication: two-year follow-up results. Spine 30: , Zucherman JF, Hsu KY, Hartjen CA, Mehalic TF, Implicito DA, Martin MJ, et al. : A prospective randomized multi-center study for the treatment of lumbar spinal stenosis with the X STOP interspinous implant: 1-year results. Eur Spine J 13: 22 31, 2004 후방역동성안정화시스템 : 극돌기간기구 손성, 김우경, 이상구, 박찬우가천의과대학길병원신경외과 척추관협착증은인구의노령화가진행되면서점차증가하고있는대표적인퇴행성척추질환중하나이다. 약물치료를비롯한보존적치료가적절한치료법이될수있지만, 증상이심하거나보존적치료에도반응하지않는경우에는수술적치료가필요할수있다. 후궁절제술및감압술만으로신경근감압을통해증상을완화시킬수있지만, 척추불안정증이있을시에는척추유합술이필요하다. 이러한척추유합술은좋은결과를보이기도있지만, 반대로여러합병증을야기하기도한다. 이에척추유합술을대체하기위한다양한수술기법과기구가소개되었고, 그중하나가후방역동성안정화시스템이다. 후방역동성안정화시스템의목적은척추분절의통증을야기하는방향으로의운동은제한하는것이며, 극돌기간장치가임상에서많이활용되었다. 극돌기간장치는, 우선신경근감압술을한후에, 해당분절의극돌기사이에끼워넣는장치이다. 이것은신전을제한하고 ( 굴곡, 회전및편위는제한하지않음.), 충격흡수역할을하여후관절의하중을줄여줌으로써통증을줄일수있다. 그러나, 몇가지단점이있는바, 극돌기간장치와골조직사이에미란이생김으로써통증을조장할수있다는보고가있고, 추시관찰동안극돌기간장치의부러짐및이탈, 요추굴곡변성등의합병증이생길수있다는것이다. 이에극돌기간장치의유용성을생역학적관점에서재조명하고, 기존의연구들을토대로임상결과를고찰하고자한다. 색인단어 : 척추관협착증, 역동성안정화, 극돌기간장치, 생역학연구, 신기술 69

KISEP Clinical Article J Korean Neurosurg Soc , 2002 퇴행성요추질환환자에서척추유합술후발생한인접분절의퇴행성변화에대한수술적치료 * 김영수 구성욱 조용은 진병호 윤영설 진동규 Surgical Treatment of

KISEP Clinical Article J Korean Neurosurg Soc 32323-328, 2002 퇴행성요추질환환자에서척추유합술후발생한인접분절의퇴행성변화에대한수술적치료 * 김영수 구성욱 조용은 진병호 윤영설 진동규 Surgical Treatment of Adjacent Segment Degeneration after Spinal Fusion in