Neurospine 2020;17(3):534-542. Neurospine https://doi.org/10.14245/ns.2040380.190 pISSN 2586-6583 eISSN 2586-6591 Review Article Anterior Reconstruction Techniques Corresponding Author for Cervical Spine Deformity Samuel K. Cho 1,2 1 1 1 https://orcid.org/0000-0001-7511-2486 Murray Echt , Christopher Mikhail , Steven J. Girdler , Samuel K. Cho 1Department of Orthopedics, Icahn School of Medicine at Mount Sinai, New York, NY, USA Department of Orthopaedics, Icahn 2 Department of Neurological Surgery, Montefiore Medical Center/Albert Einstein College of Medicine, Bronx, School of Medicine at Mount Sinai, 425 NY, USA West 59th Street, 5th Floor, New York, NY, USA E-mail: [email protected] Cervical spine deformity is an uncommon yet severely debilitating condition marked by its heterogeneity. Anterior reconstruction techniques represent a familiar approach with a range Received: June 24, 2020 of invasiveness and correction potential—including global or focal realignment in the sagit- Revised: August 5, 2020 tal and coronal planes. Meticulous preoperative planning is required to improve or prevent Accepted: August 17, 2020 neurologic deterioration and obtain satisfactory global spinal harmony. The ability to per- form anterior only reconstruction requires mobility of the opposite column to achieve cor- rection, unless a combined approach is planned. Anterior cervical discectomy and fusion has limited focal correction, but when applied over multiple levels there is a cumulative ef- fect with a correction of approximately 6° per level. Partial or complete corpectomy has the ability to correct sagittal deformity as well as decompress the spinal canal when there is an- terior compression behind the vertebral body. If pathoanatomy permits, a hybrid discecto- my-corpectomy construct is favored over multilevel corpectomies. The anterior cervical os- This is an Open Access article distributed under teotomy with bilateral complete uncinectomy may be necessary for angular correction of the terms of the Creative Commons Attribution fixed cervical kyphosis, and is particularly useful in the midcervical spine. A detailed un- Non-Commercial License (https://creativecom- mons.org/licenses/by-nc/4.0/) which permits derstanding of the patient’s local anatomy, careful attention to positioning, and avoiding unrestricted non-commercial use, distribution, long periods of retraction time will help prevent complications and iatrogenic injury. and reproduction in any medium, provided the original work is properly cited. Keywords: Cervical spine deformity, Anterior cervical reconstruction, Anterior cervical Copyright © 2020 by the Korean Spinal discectomy, Anterior cervical corpectomy, Anterior cervical osteotomy, Vertebral column Neurosurgery Society resection INTRODUCTION Cloward beginning in 1958. Now, it is one of the most familiar and popular procedures with spine surgeons utilizing an anteri- Cervical spine deformity (CSD) represents an uncommon or approach for more than 80% of cervical fusions.5 In the set- yet severely debilitating condition.1 It is further characterized ting of CSD, anterior reconstruction techniques represent a range by marked heterogeneity related to the various etiologies, dis- of options with potential for powerful global or focal correction tinct drivers of deformity, clinical manifestations, and dynamic in the sagittal and coronal plane. Here, we review anterior re- state being the most mobile region of the spine.2 As such, man- construction techniques for CSD including the preoperative agement and treatments demonstrate significant variation amon- planning necessary, complication care and avoidance, and post- gst treating surgeons with anterior vs. posterior vs. combined operative management. approaches, grades of osteotomy, and number of levels addre- ssed.3 Despite classification schemes and proposed treatment PREOPERATIVE PLANNING algorithms, the ultimate decisions will be dependent on patient and surgeon preference.4 CSD surgeries are technically demanding and require signifi- Anterior approaches to the cervical spine have been promot- cant preoperative planning based on presence of radiculopathy ed since introduction of the technique by Smith-Robinson and or myelopathy with anterior or posterior compression, driver of 534 www.e-neurospine.org Echt M, et al. Anterior Reconstruction for Cervical Deformity deformity including the apical level, rigidity or flexibility of the tion with posterior release and fixation. Compared to posterior- deformity, and patient’s local anatomy. Patterns may be appreci- only surgery, correction can be achieved with a lower complica- ated by understanding the interplay of primary drivers of the tion risk and decreased total number of levels fused.12 High-grade cervical deformity including compensatory mechanisms, asso- osteotomy and extension to the distal thoracic or upper lumbar ciated symptoms, and outcomes based on management. Addi- spine, which may be necessary in posterior-only surgery, is as- tional considerations include the patient’s bone quality, func- sociated with worse outcomes and may potentially be avoided tional status, and comorbidities. with anterior reconstruction techniques.13,14 Even after anterior When considering goals of surgery for CSD, the primary aim index procedures, revision cervical surgery can be safely per- must be to treat and prevent neurologic deterioration. Thus, the formed through an anterior approach with low complication magnetic resonance imaging must be evaluated for compres- risks—assuming the case is performed by an experienced sur- sion of the spinal cord or foraminal stenosis. If there is ventral geon in a specialized center.15 compression present in the setting of a kyphotic deformity, then Assessment of the rigidity or flexibility of the deformity is also an anterior approach will typically be necessary to achieve ade- crucial. A head suspension test should be performed in the of- quate decompression. Likewise, if there is foraminal stenosis fice to determine rigidity of kyphotic deformity. These patients present, then a posterior-only approach will risk cervical root typically require more extensive osteotomies, and in cases of neuropraxia with the performance of a posterior column short- rigid chin-on chest deformity require traction to aid intubation. ening osteotomy. Even with adequate foraminotomies, if there In extreme cases, anterior exposure may not be possible and a is loss of disc height and consequently shortened foraminal hei- posterior release is necessary as part of a staged back-front-back ght—a foraminotomy may not help when the cranial-caudal surgery. Full-length standing and dynamic x-rays are needed. dimensions are further encroached by compression and exten- Patients that demonstrate cervical malalignment on extension sion. Increased thoracic kyphosis may also result in decreased x-rays likely indicate a need for higher grade osteotomies.16 foraminal area in the lower cervical spine, and predispose the Computed tomography (CT) is also standard work-up to dif- patient to increased foraminal stenosis with further neck exten- ferentiate between rigid or fixed kyphosis, and to determine if sion.6 This can be avoided with the use of anterior interbody there is anterior, posterior, or complete ankylosis. History of devices providing adequate indirect decompression and incre- prior surgery is a clear factor, entailing identification of fusion asing the foraminal height prior to closing of a posteriorly-based vs. pseudarthrosis. The ability to perform either a single anteri- osteotomy. or or posterior-only approach requires mobility of the opposite The primary driver of the deformity and the level of apex fig- column to achieve correction. If both columns appear anky- ures heavily into preoperative planning within the framework losed, a 540˚ procedure may be necessary—typically in the se- of global spinal harmony.7 The Ames Cervical Spine Deformity quence of back-front-back. Unless, anterior overpowering of classification outlines types of CSD, including cervical origin, fused facets appears feasible, as part of an anteriorposterior se- cervical-thoracic junction (CTJ) origin, thoracic origin, coronal quence, depending on the extent and quality of the posterior deformity, and craniovertebral junction origin.8 Based on spinal fusion mass.17 region involved as the origin of the deformity and the level of Further considerations include the patient’s local anatomy. apex the utility of an anterior approach becomes apparent. Spe- This refers to identification of the course of the vertebral arter- cifically, when the apex of the deformity is at the CTJ or thorac- ies, especially if planning for a corpectomy or complete unci- ic spine, patients will be unlikely improve in deformity related nate joint resection. It also refers to evaluating for the presence quality of life if the apex is not treated.9 In other words, kypho- of degenerative changes at other levels, particularly the proxi- sis at the CTJ or the thoracic spine, such as due to proximal junc- mal/distal end vertebrae when selecting levels for fusion. Con- tional kyphosis after correction of thoraco-lumbar spinal defor- comitant coronal deformity must be accounted in order to be mity, requires a posterior approach aimed at reducing the T1 corrected with asymmetric resection of bone mass. Additional- tilt in order to more readily match C2–7 cervical lordosis.10,11 In ly, areas of prior fusion can be resected with a high-speed burr general, the osteotomy performed at