Cervical Spine Deformity: Indications, Considerations, and Surgical Outcomes

Review Article Cervical Spine Deformity: Indications, Considerations, and Surgical Outcomes

Abstract Samuel K. Cho, MD Cervical spinal deformity (CSD) in adult patients is a relatively Scott Safir, MD uncommon yet debilitating condition with diverse etiologies and clinical manifestations. Similar to thoracolumbar deformity, CSD can Joseph M. Lombardi, MD be broadly divided into scoliosis and kyphosis. Severe forms of CSD Jun S. Kim, MD can lead to pain; neurologic deterioration, including myelopathy; and cervical spine–specific symptoms such as difficulty with horizontal gaze, dysphagia, and dyspnea. Recently, an increased interest is shown in systematically studying CSD with introduction of classification schemes and treatment algorithms. Both major and minor complications after surgical intervention have been analyzed and juxtaposed to patient-reported outcomes. An ongoing effort exists to From the Department of Orthopaedic better understand the relationship between cervical and Surgery (Dr. Cho and Dr. Kim), the thoracolumbar spinal alignment, most importantly in the sagittal Department of Vascular Surgery (Dr. Safir), Icahn School of Medicine at plane. Mount Sinai, and the Department of Orthopaedic Surgery (Dr. Lombardi), Columbia University Medical Center, New York, NY. ervical spinal deformity (CSD) Etiology Dr. Cho or an immediate family Cremains a moving target in member serves as a paid consultant the current spine literature. It is a to Corentec, Globus Medical, potentially debilitating condition Congenital Medtronic, and Zimmer Biomet; has Atlanto-occipital fusion, os received research or institutional with numerous etiologies, such as support from Zimmer Biomet; and iatrogenic, inflammatory arthropathy, odontoideum, and basilar invagi- serves as a board member, owner, spondylosis, congenital, neuromuscu- nation are atlas and axis anomalies officer, or committee member of the lar, traumatic, infectious, and neuro- thatcanleadtoCSD.Klippel-Feil American Academy of Orthopaedic syndrome, which causes most of the Surgeons, the American Orthopaedic muscular processes. Severe cervical Association, the AOSpine North instability or sagittal malalignment can subaxial cervical congenital defects, America, the Cervical Spine Research lead to pain; neurologic deterioration, involves fusion of cervical verte- Society, the North American Spine including myelopathy; and cervical brae (Figure 1). Achondroplasia, the Society, and the Scoliosis Research – common skeletal dysplasia, can lead Society. None of the following authors spine (CS) specific symptoms such as or any immediate family member has difficulty with horizontal gaze, dys- to posterior vertebral scalloping, short received anything of value from or has phagia, and dyspnea. Recent efforts pedicle canal stenosis, laminar thick- stock or stock options held in a have sought to classify CSD and for- ening, and widening of intervertebral commercial company or institution disks. Down syndrome is linked to related directly or indirectly to the mulate treatment algorithms. In this subject of this article: Dr. Safir, review, we discuss the anatomy, ligamentous laxity that causes cervical Dr. Lombardi, and Dr. Kim. pathophysiology, and common etiol- instability seen at both the atlanto- J Am Acad Orthop Surg 2019;27: ogies of CSD. We then describe pos- axial joint and occiput-C1 level. e555-e567 sible treatments, which are as myriad DOI: 10.5435/JAAOS-D-17-00546 as the etiologies of CSD. Finally, we discuss the outcomes of CSD in the Traumatic Copyright 2018 by the American Academy of Orthopaedic Surgeons. literature and its relationship to thor- CSD can result from instability sec- acolumbar deformity (TLD). ondary to trauma. Upper CS injuries

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Figure 1

A, Preoperative AP and lateral radiographs of the cervical spine demonstrating kyphoscoliosis in an adult patient with Klippel-Feil syndrome. B, MRI of the cervical spine showing stenosis. C, Postoperative AP and lateral radiographs of the cervical spine after C2-T3 circumferential reconstruction. include occipitocervical dislocation, posttraumatic CSD develops do so Spondylosis and occipital condyle fractures, atlas frac- because of nonunion, implant fail- Degenerative Disk Disease tures, atlanto-axial rotatory instability ure, Charcot joint, or technical Disk degeneration leads to increased (AAI), atlanto-dens instability, and error after surgery for the injury.1 mechanical stress at the cartilaginous odontoid fractures. Subaxial injuries Injuries involving the posterior end plates at the vertebral body (VB) include traumatic spondylolisthesis ligamentous structures, such as lip. Generally, spondylosis begins of axis (Hangman’s fracture), flexion advanced-staged burst flexion- injuries, vertical compression in- compression or flexion-distraction with intervertebral disk desiccation, juries, and subaxial extension in- injuries, are prone to deformity leading to bulging of the anulus fi- juries. Posttraumatic CSD develops overall (Figure 2), whereas lateral brosus, loss of height anteriorly, and a in most patients because of the compression or burst injuries can positive feedback loop of increased trauma itself, but interestingly, result in posttraumatic coronal or anterior weight bearing leading to a minority of patients in whom a scoliotic deformities.1 cervical kyphosis (CK)2 (Figure 3). e556 Journal of the American Academy of Orthopaedic Surgeons

Spondylosis is also associated with Figure 2 ossification of the posterior longitudinal ligament, which can contribute to ventral cord compression. This often leads to loss of lordosis in the subaxial spine and can negatively influence global sagittal alignment (GSA). Patients will often hyperextend through their high CS (occiput-C2) to compensate for the loss of subaxial segments. By contrast, pure scoliotic deformity is rarely from spondylosis.

Inflammatory Rheumatoid arthritis (RA) is the most common inflammatory disorder that can affect the CS. The prevalence of CS involvement in RA ranges from Chronic flexion-distraction injury leading to angular kyphotic deformity in the 25% to 80%, depending on the algo- subaxial cervical spine. This patient successfully underwent C2-T1 rithm used,3 with seropositivity as a circumferential spinal fusion with correction of deformity. major risk factor. The three typical RA deformities in the CS are, in order of decreasing frequency, AAI or posterior cervical muscles, causing Postoperative development of insta- subluxation, superior migration of atrophy, and disruption of facet bility because of removal of static and the odontoid process, and subaxial joints may lead to instability. dynamic stabilizing soft-tissue struc- subluxation. Removal of the posterior tension tures and facet violation is a well- Seronegative spondyloarthropathies band leads to worsening compres- known complication, and it was a include ankylosing spondylitis (AS), sive forces on the anterior VB, thus major stimulus to the use of laminec- Reiter’s syndrome, psoriatic arthritis, exacerbating sagittal deformity and tomy with instrumented fusion and and enteropathic arthritis. AS is the causing a kyphotic angulation.4 laminoplasty. The literature compar- most common of the seronegative The incidence of iatrogenic CSD is ing outcomes of laminoplasty versus disorders and will affect the CS later in difficult to measure because of hetero- laminectomy are disparate, likely sec- the disease course. Common mani- geneity of patient and case complexity. ondary to the heterogeneity between festations in the CS are CK and AAI. One case series demonstrated a 45% surgeon technique and patient as well Global spinal kyphosis progresses as a incidence in patients without any pre- as radiographic characteristics.9,10 It means to offload painful facet joints, operative instability.5 Contrarily, can be agreed on, however, that the and autofusion in this abnormal sag- postoperative kyphosis developed in progression of loss of lordosis to ittal alignment leads to a fixed flexion 10.6% of patients undergoing lam- kyphosis after laminoplasty appears deformity. Furthermore, susceptibility inoplasty for cervical spondylosis, to be dependent on the technique. to spinal fractures leads to frequent ossification of the posterior longitu- Invariably, the preservation of muscle and missed fractures that can worsen dinal ligament, and multilevel disk attachments has been shown to be the existing deformity. herniation.6 A retrospective analysis essential for maintaining sagittal cer- investigating the incidence and out- vical alignment. The posterior cervical Iatrogenic comes of kyphotic deformity after approach requires careful exposure Iatrogenic (postoperative) remains laminectomy for cervical spondylotic from C3 to C7 while taking care to the most common cause. Typically, myelopathy determined that kyphosis dissect in the avascular plane, or the postoperative CK is associated may develop in 21% of these patients.7 raphe, between the left and the right with a previous laminectomy or In the pediatric population, weaker paraspinal musculature. Additionally, laminoplasty and demonstrates a musculature, ligamentous elasticity, during exposure of the lateral masses, loss of sagittal alignment, shifting and greater horizontal facets have been facet capsule violation can lead to the weight-bearing axis anteriorly theorized to account for the greater accelerated spondylosis, axial neck (Figure 4). Surgery denervates the rates of postoperative kyphosis.8 pain, and loss of lordosis.

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Figure 3 cause deformity via the therapeutic approach used to manage them, certain entities exist which may engender malalignment and deformity even pre- operatively. Kawabata et al12 described their experience treating three patients with severe CK associated with neurofibromatosis (NF) and noted that a high risk of spinal cord injury, coex- isting spinal cord and paraspinal tumors, difficulties in placing anchors in dystrophic vertebrae, and difficulty in obtaining solid fusion all potentially complicate the treatment of their patients’ cervical disease.

Radiographic Definition

Lordosis/Kyphosis It is important to consider the influence of CSD on global spinal alignment as compensatory changes occur to maintain horizontal gaze. Unlike the thoracolumbar spine (TLS), the CS can be divided into anterior (VB and disks) and posterior (facet joints) columns. The cervical load-bearing axis lies posterior to the VB of C2-C7, with posterior structures bearing about 64% of the axial load. This balance An adult patient with severe spondylotic kyphosis (A). He is hyperlordosing his afforded by the stability of bony and lumbar spine to maintain horizontal gaze. C2-T4 posterior spinal fusion with C7 ligamentous anatomy maintains the pedicle subtraction osteotomy to correct the deformity (B). normal cervical curvature and maintains an upright head position13 PA and lateral radiographs should Infectious finding but can present more fre- be used to assess coronal and sagittal Though a small contributor to the quently if Mycobacterium tuberculosis alignment. Flexion-extension views overall causes of CSD, spinal in- is the etiologic agent. In addition, early allow for assessment of flexibility and fections represent a growing area, surgery for vertebral osteomyelitis has stability. The most common method given the use of illicit intravenous the benefit of improving stability and to evaluate cervical lordosis involves drugs in the younger population and reducing kyphotic deformity relative the use of Cobb angles. Similarly, the genitourinary surgery and intrave- to conservative management. Patients cervical curvature index (Ishihara) is nous access devices in the elderly. being treated with chemotherapy for an alternative method of assessing Infections may involve any part of the spinal tuberculosis have, on average, cervical spinal alignment numeri- ° spine including the VB, intervertebral an increase of 15 in deformity, and a cally and is highly correlated with the . ° disk, neural arch, or posterior ele- kyphosis of 60 develops in 3% to C2-C7 Cobb angle.14 Although the 11 ments, but most commonly it will 5% of patients. cervical Cobb angle is straightfor- affect the anterior and middle col- ward and has good interrater reli- umns. Given its rich vascular supply, Neoplastic ability,measurementssuchasthe the VB are a common destination Though tumors involving the spinal sagittal vertical axis (SVA) have for dissemination of hematogenous cord or surrounding structures in gained traction in recent years osteomyelitis. Kyphosis is often a late the CS are much more likely to (Figure 5). e558 Journal of the American Academy of Orthopaedic Surgeons

GSA can be defined in multiple Figure 4 ways. Numerous studies have analyzed the health-related quality of life scores in relationship to adult TLD. These concepts have been echoed in the cervical deformity literature. Global alignment can be assessed by the C7 plumb line and the differ- ence between the C2 and C7 SVA. The normal range of the C2–C7 SVA is reported to be 16.8 6 11.2 mm.15 Additionally, in a retrospective review of patients undergoing cervical laminoplasty, Oshima et al16 found that postoperative functional outcome scores were markedly lower in patients with C2-C7 SVA of .150 mm. If full-standing spinal radiographs are unavailable, T1 sagittal angle or T1 slope is useful in predicting overall sagittal balance. The incidence of CK is likely to be twice as high if a patient 17 has a higher T1 slope. Although the Post-laminectomy kyphosis. Patient required a long spinal fusion (C2-T1) to high T1 slope demands a greater correct the deformity. degree of cervical lordosis, patients may be unable to provide it, causing the pharyngeal space. The chin brow CS and femoral heads, standing PA progressive kyphosis. Cervical lor- vertebral axis (CBVA) is used to assess and lateral CS radiographs, modified dosis is also strongly linked with T1 horizontal gaze and is defined by the Japanese Orthopaedic Association slope in maintaining horizontal gaze, angle subtended between a line drawn (mJOA) scores, and a clinical photo- and patients with higher T1 slope from the patient’s chin to brow and a graph or radiograph that includes the show more kyphotic changes af- vertical line. To obtain this distance, a skull for measurement of CBVA. ter cervical laminoplasty at 2-year photograph must be taken with the follow-up.18 Lee et al18 demonstrated patient standing, with hips and knees that thoracic inlet alignment had Scoliosis extended and neck neutral or fixed. notable correlation with craniocervical Scoliosis, though infrequent, presents a Lafage et al20 reported on CBVA sagittal balance, similar to the ef- distinct challenge for the spine sur- thresholds for disability and found fect that the pelvic incidence has on geon. It is often found in association that CBVA of ,24.8° or .117.7° the lumbar spine. Thoracic inlet with congenital bony anomalies, correlated with an Oswestry Dis- angle, along with neck tilt, affects Klippel-Feil syndrome, and NF type 1. ability Index of .40. the alignment of the CS in that Preoperative CT and MRI are both the thoracic inlet angle must in- crucial, especially given the latter’s crease or decrease based on changes Ames Classification ability to detect spinal dysraphism, in T1 slope and cervical lordosis Only one comprehensive CSD classifi- which approaches a prevalence of to maintain neck tilt at roughly cation system exists, which was pro- 30% in patients with congenital spine 44° to minimize muscle energy posed by Ames et al;21 it is an deformity.22 Surgical approach of this expenditure.19 adaptation of the Scoliosis Research rare entity can be anterior, posterior, Measuring horizontal gaze is also a Society-Schwab classification for adult or combined (Figure 1). In a case crucial clinical data point because it TLD. The system involves a deformity series of 18 patients with isolated can occur with severe kyphosis and descriptor and five modifiers. cervical scoliosis, the Cobb angle lead to a mechanical dysfunction of The classification system requires a improved from 35.1° to 15.7°; swallowing. Swallow dysfunction full-length standing PA and lateral however, a complication rate of arises as a consequence of collapse of spine radiographs that include the 30.8% was related to surgery.23

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Figure 5

Cervical alignment, Ishihara index, and spinal sagittal alignment. C7S Beta = C7 tilt angle, c-SVA = cervical sagittal vertical axis, LS = lumbar lordosis, PI = pelvic incidence, PT = pelvic tilt, SS = sacral slope, SVA = sagittal vertical axis, TK = thoracic kyphosis. (Reproduced with permission from Endo K, Suzuki H, Sawaji Y, et al: Relationship among cervical, thoracic, and lumbopelvic sagittal alignment in healthy adults. J Orthop Surg (Hong Kong) 2016;24 [1]:92-96.)26

Cervical-Thoracic-Lumbar ing in increased sagittal deformity.26 T1 slope-cervical lordosis, cervical Relationship Ames et al27 analyzed spinal param- lordosis, cSVA, C2-T3 SVA, and eters in an asymptomatic population global SVA compared with patients Given the fact that CK may represent and found that pelvic incidence cor- with TLD who were not operated normal alignment in some patients, related with lumbar lordosis, lumbar on.28 These patients additionally often a close relationship exists lordosis correlated with TK, and TK have worse Oswestry Disability between cervical and thoracolumbar correlated with cervical lordosis. The Index and Scoliosis Research Society alignment.24 Smith et al25 found that relationship between these parame- activity at 1 and 2 years. Even after 53% of adult patients with TLD ters does not perfectly translate from controlling for magnitude of TLD, had a concomitant cervical defor- one spinal segment to the next. For cervical alignment has a direct effect mity. Furthermore, in patients with instance, the increase in cervical lor- on health measures.29 normal horizontal gaze, thor- dosis in response to TK may not be acolumbar alignment and thoracic enough to maintain the head over the kyphosis (TK) directly affect the pelvis but does allow the patient to 24 Pathophysiology cervical alignment. Patients with maintain horizontal gaze. poor sagittal alignment often develop The relationship between cervical Normal cervical lordosis is between painful compensatory alignment deformity and TLD has been analyzed 10° and 20° with an average of 14.4° changes to maintain upright posture before and after surgical treatment. (as measured by C2-C7 angle). Pres- including knee flexion, pelvic retro- In a study of 470 patients with TLD, a ervation of sagittal balance requires version, thoracic hypokyphosis, 53% prevalence of CSD and CSD was intact anterior and posterior struc- and cervical hyperlordosis. Diebo associated with C7-S1 SVA, pelvic tilt, tures. Anteriorly, the VB and inter- et al24 found that patients with SVA and pelvic incidence-lumbar lordosis, vertebral disks resist compression. of .50 mm require cervical lordosis suggesting that CSD should be inves- Posteriorly, the facet joints, posterior to maintain gaze. tigated in patients presenting with CS musculature, and interspinous In the presence of spondylotic other spine pathologies.25 ligaments act as a tension band. degenerative changes, loss of com- After correction of the TLD, pa- When the integrity of the posterior or pensatory mechanisms for positive tients tend to be more misaligned 2 anterior structures is compromised sagittal alignment may occur, result- years from surgery with worse TK, and kyphosis is present, deformity is e560 Journal of the American Academy of Orthopaedic Surgeons

Figure 6 Figure 7

A patient whose head is completely suspended in air because of rigid cervical kyphosis (head suspension test). more than likely to progress. Ulti- mately, the spinal cord may become draped and tensioned over the posterior aspects of the VB, thereby compromising vascular supply. In Algorithmic selection of cervical deformity based on flexibility. (Reproduced with this setting, myelopathic symptoms permission from Hann S, Chalouhi N, Madineni R, et al: An algorithmic strategy may develop in patients, which can for selecting a surgical approach in cervical deformity correction. Neurosurg 31 lead to stepwise and potentially irre- Focus 2014;36[5]:E5.) versible neurologic injury. having the patient suspend his/her The indications for corrective sur- Clinical Presentation and head in air when supine, the so-called gery in the setting of AS are intolerable Indications head suspension test (Figure 6). Pa- deformity, neurologic deficit, airway tients can also exhibit a chin-on-chest compromise, esophageal dysmotility, Initial evaluation of the patient deformity that is characteristic of AS. and instability associated with frac- should be tailored based on the sus- Iatrogenic deformities are unique in ture. The indications for surgery in the pected etiology of their deformity. their presentation, and each requires setting of iatrogenic deformity include Patients with AS often exhibit chronic their own corrective approach de- intolerable posture, neurologic deficit, deformity that is gradually and pro- pending on the plane of deformity and intractable pain. gressively debilitating. Alternatively, (sagittal, coronal, or both), the loca- in the setting of trauma, they can also tion of the fusion mass and instru- Preoperative Evaluation exhibit acute deformity secondary to mentation (anterior, posterior, or fracture, with sudden decompensa- both), bone quality, soft-tissue quality, Patients with cervical deformity tion in posture and evidence of neu- and the presence or absence of infec- whether AS or iatrogenic often have rologic deficit. Patients with cervical tion. In addition, patients with high other medical comorbidities that deformity and evidence of ankylosis to mid-cervical deformity may not increase the risk of morbidity and on imaging with sudden pain should present with an obvious abnormality mortality. A thorough preoperative be considered to have a fracture until on visual inspection (Figure 2). By medical evaluation should be per- proven otherwise. contrast, those with cervicothoracic formed and the patient optimized Examination of patients with AS deformity often have a kyphotic before surgery. Nutrition and smok- should comprise of the patient stand- appearance with difficulty raising the ingstatusshouldbeassessedinevery ing upright with the hips fully extended head and pain, similar to those suf- case. Osteotomies can lead to sub- and in the seated and supine positions. fering from flatback syndrome in the stantial blood loss, and thus, preop- Patients with cervical deformity often TLS (Figure 3). Revisions, especially in erative measures should be taken to exhibit persistent cervical flexion the setting of complex cervical defor- have blood prepared. despite lying flat. The rigidity of the mity, require the utmost attention to Radiographic evaluation should deformity can be often assessed by detail to minimize complications. include long-standing radiographs to

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° Figure 8 20 ) cervical alignment to allow the patient to be able to visualize the ground in front of him/her. Approaches to deformity correction canbebroadlycategorizedintoante- rior, posterior, and combined. The strategy for selecting a particular approach is often not straightforward. Hann et al31 attempted to delineate an algorithm for surgical approach selection based on fixed versus pas- sively correctable deformities. A detailed graphical summary of the article has been provided, delineating possible surgical approach and techniques for addressing various cervical deformities (Figure 7).

Care should be taken to identify the vertebral arteries on preoperative MRI and to protect them during surgery. For maximal mobilization and induction of lordosis, we recommend wide exposure to the lateral margin of the uncinates bilaterally (Figure 8). If a previous fusion had been present, a high-speed burr can be used to take down the fusion at Chin-on-chest kyphoscoliosis. This patient underwent C4-C7 anterior the original disk space to the level of osteotomies (with standalone cages and one screw fixation) combined with C2- T3 posterior spinal fusion with multilevel Smith-Petersen osteotomies. C2 has the posterior longitudinal ligament. two pars screws and one intralaminar screw as proximal anchors. Concomitant coronal deformity can be corrected with asymmetric resec- tion of the fusion mass. Prophylactic assess GSA and coronal alignment. A foraminotomies are performed to preoperative CT provides information Surgical Treatment prevent root injury with spine on existing implants, fusion masses, One of the keys to surgical success extension. Diverging distraction pins and osseous landmarks for planned is a thorough preoperative planning. can also be used so that distraction instrumentation. MRI should also be Ideally,theCSshouldbemadeper- recreates lordosis. Two pins can be part of the workup in the setting of an pendicular to the clavicles in the coro- used on each VB to distribute forces abnormal preoperative neurologic nal plane. Considerations in the sagittal if bone quality is poor. The head can examination, previous decompression be propped up with sheets initially surgery, or congenital anomalies. plane should include flexibility and and gently pushed down on the Surgical management of cervical assessment of occiput-C2 motion. We forehead with removal of the sheets deformity requires meticulous pre- prefer to align the posterior vertebral one at the time on completion of the operative planning to determine the line of C2 as close to the anterior ver- osteotomy to induce lordosis.32 approach and the degree of correc- tebral line of C7 as possible. This re- tion needed. Digital imaging software sults in a balanced cervical posture, can allow surgeons to plan their os- assuming the TLS is already well Posterior teotomies and provide insight into aligned. In the setting of a spine without the postoperative alignment that can mobile cervical segments, we attempt For posterior osteotomies, the patient be attained.30 correction to a minimally flexed (15° to is placed prone in a Jackson frame e562 Journal of the American Academy of Orthopaedic Surgeons

Copyright © the American Academy of Orthopaedic Surgeons. Unauthorized reproduction of this article is prohibited. Samuel K. Cho, MD, et al with maximum reverse Trendelenburg. Figure 9 The foot of the Jackson frame is placed in the lowest rung of bottom bracket, and the top of the frame is placed in the lowest rung of the top bracket. We recommend that the head is placed in Gardner-Wells tongs with bivector traction. Typi- cally, 15 pounds of weight is applied on the inline traction at the beginning of the procedure. This weight is then placed on the extension rope at the conclusion of the osteotomy to aid in correction. Blood pressure should be closely monitored by an arterial line or a well-placed blood pressure cuff. We prefer to keep the blood pressure relatively high (around 85 mm Hg) in the setting of myelopathy to ensure adequate spinal cord perfusion. Foley catheter placement is inserted to assess fluid balance. A warming blanket can prevent hypothermia and thereby coagulopathy. Hemostatic techniques (eg, hemostatic agents, intraoperative blood salvage) can be used to minimize blood loss. A posterior midline incision is Rigid cervical kyphosis after laminectomy and fusion (A). The patient underwent C2-T4 revision fusion with T2 pedicle subtraction osteotomy to correct the made. The raphe of the paraspinal deformity while avoiding C8 or T1 radiculopathy (B). muscles is identified and dissected to minimize blood loss during exposure. Previous posterior fusions traction osteotomy (PSO) at C7 was down into the thoracic spine inferior with a mobile anterior column are developed as a means of shortening to the level of the osteotomy. We amenable to correction with multiple the posterior column while leaving recommend that if any question of Smith-Petersen osteotomies. We the anterior column intact (Figure 3). bony purchase comes up, then the advise prophylactic foraminotomies We recommend that all available surgeon supplements the posterior to prevent nerve root entrapment points of fixation be used. In cases fixation with anterior plate fixation at with correction of the deformity. A where the occipital-cervical junction the level of the osteotomy. The tech- tension band construct can be used by is mobile, we leave this joint alone. In nical details of a cervical PSO have connecting available spinous pro- cases where the occipital-cervical been described in the literature.33 cesses with a cable. This is done to junction is autofused, good boney Recently, some surgeons have found help maintain the extension of the purchase can be made in the occipital C8 or T1 nerve root palsy with pro- spine and hold correction until rods protuberance. It is the author’s found intrinsic hand weakness after can be placed and tightened into preference to use C2 pedicle screws C7 or T1 PSO and recommend that position. over laminar screws because they the three-column osteotomy be per- The Simmons osteotomy was clas- allow for collinear rod attachment. formed at T2 or below (Figure 9). sically described as an opening wedge Pedicleorparsscrewsandlaminar osteotomy of the lower CS that screws can be used together, that is, compromises the anterior column three or four points of fixation at Complications opening by hinging on the posterior C2, in case of poor bone quality column. This was inherently unsta- resulting in poor fixation (Figure 8). Complications resulting from cervi- ble, and subsequently, pedicle sub- The fusion should be extended cal deformity surgery are numerous

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Table 1 Patient Outcomes Table Exploring Correction and HRQOL Measures Surgical Correction Preoperative Postoperative Study Approach Kyphosis Kyphosis Degree of Correction HRQOL Measures

Kim Group 1 (17): Anterior Lordosis Lordosis Group 1: 23.1° angular NDI et al36 cervical osteotomy w/ (P = 0.10) (P = 0.92) correction, 1.4 cm w/out posterior translational instrumentation correction Group 2 (21): Anterior Group 1: 18.8° Group 1: 25.0° Group 2: 32.4° angular Group 1: 26.3 / 25.5 osteotomy and correction, 3.7 cm SPOs w/posterior translational instrumentation correction (P = 0.15 and 0.03, respectively) Group 2: 29.3° Group 2: 24.7° Group 2: 20.8 / 19.7 (P = 0.56, P = 0.78, respectively) Du 43 pts CDM associated 8.4% (Ishihara 19.3% — VAS: 37.4 6 12.1 / 10.6 et al37 with kyphosis-enlarged index) (P , (Ishihara 6 5.3 (P , 0.001) laminectomy w/lateral 0.001) index) mass screw fixation (P , 0.001) — JOA: 6.2 6 1.9 / 14.9 6 1.4 (P , 0.001) Yeh 20 pts anterior fusion, 25.0° (cervical 9.3° (cervical — NDI: 39.9 6 6.1 / 22.4 6 et al38 EOLP, lateral mass or curvature) (P curvature) 3.8 pedicle screw , 0.001) (P , 0.001) (P , 0.001) instrumented fusion — Nurick scale: 2.6 6 0.7 / 0.4 6 0.9 (P = 0.001) — VAS: 6.2 6 0.8 / 2.0 6 1.3 (P = 0.118) — JOA: 10.1 6 1.6 / 15.7 6 1.8 (P , 0.001) Grosso 34/13/53 pts dorsal/ Focal 23.9° Focal 2.8° Focal 1.5° (SD 7.8°) mJOA change et al35 ventral/combined (SD 14.5°) (SD 7.4°) Global 17.2° Global 24.2° Global 1.3° (SD 5.6°) Dorsal: 1.42 (SD 14.0°) (SD 11.2°) Ventral: 2.37 Combined: 1.05 (P = 0.097) Yeh 109 pts EOLP and 7.7° (CC) 16.1° (CC) — VAS: 5.4 / 3.9 et al39 adjunct short-segment ACDF — Nurick scale: 2.7 / 0.3 — JOA: 10.9 / 15.8 Lau 100 pts sequential 5.7° 6 7.3° 6.7° 6 7.3° 12.4° 6 8.0° (P , Nurick grade: 1.4 6 1.5/ et al40 interbody dilation (P , 0.001) (P = 0.001) 0.001) 0.9 6 1.5 (P = 0.037) Neck VAS: 6.2 6 2.6/ 4.4 6 2.0 (P = 0.02) (continued) ACDF = anterior cervical, diskectomy and fusion, ATO = anterior osteotomy, CC = cervical curvature, CDM = cervical degenerative myelopathy, EOLP = expansive open door laminoplasty, HRQOL = health-related quality of life, JOA = Japanese Orthopaedic Association, mJOA = modified Japanese Orthopaedic Association, NA = not applicable, NDI = Neck Disability Index, PSO = pedicle subtraction osteotomy, SPO = Smith-Petersen osteotomy, VAS = visual analog scale

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Table 1 (continued) Patient Outcomes Table Exploring Correction and HRQOL Measures Surgical Correction Preoperative Postoperative Study Approach Kyphosis Kyphosis Degree of Correction HRQOL Measures

Kim Group 1 (31): Anterior Lordosis Lordosis Angular Translational NDI: (P = 0.99) et al41 osteotomy w/w/out (P = 0.73) (P = 0.03) (P = (P = 0.56) posterior 0.03) instrumentation Group 2 (4): PSO Group 1: 24.8° Group 1: 25.0° Group 1: Group 1: Group 1: 26.0 / 21.5 27.7° 1.8 cm Group 2: 4.3° Group 2: Group 2: Group 2: Group 2: 25.2 / 20.5 216.2° 48.8° 2.8 cm Kim 4 groups (61 total): Lordosis Lordosis Angular Translational NA et al42 SPO 13.8° 25.6° 19.4° 3.5 cm PSO 20.3° 216.2° 44.8° 2.8 cm ATO 13.9° 24.9° 22.4° 1.3 cm ATO 1 SPO 30.9° 24.8° 32.5 3.6 cm Mahesh 9 pts single-stage 6.33° (C2-C7 2° (C2-C7 — mJOA: 7.88 / 15 et al43 posterior Cobb angle) Cobb angle) decompression and deformity correction for multilevel cervical myelopathy w/ kyphosis 215.8% 23.6% — (Ishihara (Ishihara Index) Index)

ACDF = anterior cervical, diskectomy and fusion, ATO = anterior osteotomy, CC = cervical curvature, CDM = cervical degenerative myelopathy, EOLP = expansive open door laminoplasty, HRQOL = health-related quality of life, JOA = Japanese Orthopaedic Association, mJOA = modified Japanese Orthopaedic Association, NA = not applicable, NDI = Neck Disability Index, PSO = pedicle subtraction osteotomy, SPO = Smith-Petersen osteotomy, VAS = visual analog scale

and include implant displacement, deformity surgery found 52 early the effects of surgical correction on graft dislodgement, pseudarthrosis, complications (#30 days postop) degree of deformity and health-related dysphagia, hoarseness, wound infec- of 78 patients, with 28.2% of quality of life measures. tion, dural tear, pneumonia, neuro- patients having $1 minor complica- logic deficits, airway issues, and tion and 24.4% of patients having $1 vertebral artery injury.13 Complica- major complication.34 Of the three Summary tions can be divided into categories approaches (anterior, posterior, and based on the operative technique. combined), some have found the CSD is an uncommon but debilitating Anterior approaches are more likely combined approach to be most condition with myriad etiologies but to cause vocal cord palsy, tracheal/ fraught with complications at a rate of with iatrogenic-induced deformity esophageal injury, graft failure, and 40% versus 30% and 27% for ante- being the most common cause. De- infection or hematoma. The posterior and dorsal, respectively.35 pending on the severity of the defor- rior approach is associated with mity, the flexibility, and the surgical higher rates of spinal cord or nerve approach, the complication rate can root injury, hardware failure or Patient Outcomes be high. The relationship of CSD to fracture, nonunion, vertebral artery TLD has been studied; sagittal imbal- injury, and infection or hematoma. Patients undergoing surgery for ance in the lumbar spine can lead to Finally, osteotomies are likely to CSD can be analyzed postoperatively painful compensatory changes in the cause infectious, respiratory, and by examining the effects on the mag- CS. At this time, the subject of CSD cardiovascular morbidities. nitude of deformity and the function represents a moving target as our A review of a multicenter database and quality of life. Table 1 demon- understanding of cervical and thor- for adult patients undergoing cervical strates a series of studies that explored acolumbar alignment evolves.

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