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Justin K. Scheer, Jessica A. Tang, Justin S. Smith, Frank L. Acosta Jr., Themistocles S. Protopsaltis, Benjamin Blondel, Shay Bess, Christopher I. Shaffrey, Vedat Deviren, Virginie Lafage, Frank Schwab, Christopher P. Ames and the International Spine Study Group

This paper is a narrative review of normal cervical alignment, methods for quantifying alignment, and how alignment is associated with cervical deformity, myelopathy, and adjacent-segment disease (ASD), with discussions of health-related quality of life (HRQOL). Popular methods currently used to quantify cervical alignment are discussed including cervical lordosis, sagittal vertical axis, and horizontal gaze with the chin-brow to vertical angle. Cervical deformity is examined in detail as deformities localized to the cervical spine affect, and are affected by, other parameters of the spine in preserving global sagittal alignment. An evolving trend is defining cervical sagittal alignment. Evidence from a few recent studies suggests correlations between radiographic parameters in the cervical spine and HRQOL. Analysis of the cervical regional alignment with respect to overall spinal pelvic alignment is critical. The article details mechanisms by which cervical kyphotic deformity potentially leads to ASD and discusses previous studies that suggest how postoperative sagittal malalignment may promote ASD. Further clinical studies are needed to explore the relationship of cervical malalignment and the development of ASD. Sagittal alignment of the cervical spine may play a substantial role in the development of cervical myelopathy as cervical deformity can lead to spinal cord compression and cord tension. Surgical correction of cervical myelopathy should always take into consideration cervical sagittal alignment, as decompression alone may not decrease cord tension induced by kyphosis. Awareness of the development of postlaminectomy kyphosis is critical as it relates to cervical myelopathy. The future direction of cervical deformity correction should include a comprehensive approach in assessing global cervicalpelvic relationships. Just as understanding pelvic incidence as it relates to lumbar lordosis was crucial in building our knowledge of thoracolumbar deformities, T-1 incidence and cervical sagittal balance can further our understanding of cervical deformities. Other important parameters that account for the cervical-pelvic relationship are surveyed in detail, and it is recognized that all such parameters need to be validated in studies that correlate HRQOL outcomes following cervical deformity correction.

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Dueng-Yuan Hueng, Ming-Ying Liu and Hsin-I Ma

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Frank L. Acosta Jr., Jamal McClendon Jr., Brian A. O'Shaughnessy, Heiko Koller, Chris J. Neal, Oliver Meier, Christopher P. Ames, Tyler R. Koski and Stephen L. Ondra

Object

As the population continues to age, relatively older geriatric patients will present more frequently with complex spinal deformities that may require surgical intervention. To the authors' knowledge, no study has analyzed factors predictive of complications after major spinal deformity surgery in the very elderly (75 years and older). The authors' objective was to determine the rate of minor and major complications and predictive factors in patients 75 years of age and older who underwent major spinal deformity surgery requiring a minimum 5-level arthrodesis procedure.

Methods

Twenty-one patients who were 75 years of age or older and underwent thoracic and/or lumbar fixation and arthrodesis across 5 or more levels for spinal deformity were analyzed retrospectively. The medical and surgical records were reviewed in detail. Age, diagnosis, comorbidities, operative data, hospital data, major and minor complications, and deaths were recorded. Factors predictive of perioperative complications were identified by logistic regression analysis.

Results

The mean patient age was 77 years old (range 75–83 years). There were 14 women and 7 men. The mean follow-up was 41.2 months (range 24–81 months). Fifteen patients (71%) had at least 1 comorbidity. A mean of 10.5 levels were fused (range 5–15 levels). Thirteen patients (62%) had at least 1 perioperative complication, and 8 (38%) had at least one major complication for a total of 17 complications. There were no perioperative deaths. Increasing age was predictive of any perioperative complication (p = 0.03). However, major complications were not predicted by age or comorbidities as a whole. In a subset analysis of comorbidities, only hypertension was predictive of a major complication (OR 10, 95% CI 1.3–78; p = 0.02). Long-term postoperative complications occurred in 11 patients (52%), and revision fusion surgery was necessary in 3 (14%).

Conclusions

Patients 75 years and older undergoing major spinal deformity surgery have an overall perioperative complication rate of 62%, with older age increasing the likelihood of a complication, and a long-term postoperative complication rate of 52%. Patients in this age group with a history of hypertension are 10 times more likely to incur a major perioperative complication. However, the mortality risk for these patients is not increased.

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Jordan M. Cloyd, Frank L. Acosta Jr., Colleen Cloyd and Christopher P. Ames

Object

The elderly compose a substantial proportion of patients presenting with complex spinal pathology. Several recent studies have suggested that fusion of 4 or more levels increases the risk of perioperative complications in elderly patients. Therefore, the purpose of this study was to analyze the effects of age in persons undergoing multilevel (≥ 5 levels) thoracolumbar fusion surgery.

Methods

A retrospective review of all hospital records, operative reports, and clinic notes was conducted for 124 consecutive patients who underwent surgery between 2000 and 2007 with an average follow-up of 3.5 years and a minimum follow-up of 1.2 years. The most frequent preoperative diagnoses included scoliosis, tumor, osteomyelitis, vertebral fracture, and degenerative disc disease with stenosis. Complications were classified as intraoperative and major and minor postoperative as well as the need for revision surgery. Multivariate logistic regression analysis was used to determine the effects of age and other potentially prognostic factors.

Results

After controlling for other factors, increasing age was associated with an elevated risk for major postoperative complications (OR 1.04, 95% CI 1.00–1.10) as were increasing levels of fusion (OR 1.5, 95% CI 1.1–2.1) and male sex (OR 4.6, 95% CI 1.3–16.2). In patients 65 years of age or older, rates of intraoperative complications, major and minor postoperative complications, and reoperation were 14.1, 23.4, 29.7, and 26.6%, respectively. The number of comorbidities was associated with a greater risk for perioperative complications in elderly patients (OR 1.8, 95% CI 1.1–2.8).

Conclusions

Age is a positive risk factor for major postoperative complications in extensive thoracolumbar spinal fusion surgery. Complication rates in the elderly are high, and good clinical judgment and careful patient selection are needed before performing extensive thoracolumbar reconstruction in older persons.

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Frank L. Acosta Jr., Jenni M. Buckley, Zheng Xu, Jeffrey C. Lotz and Christopher P. Ames

Object

Increased structural stability is considered sufficient justification for higher-risk surgical procedures, such as circumferential fixation after severe spinal destabilization. However, there is little biomechanical evidence to support such claims, particularly after traumatic lumbar burst fracture. The authors sought out to compare the biomechanical performance of the following 3 fixation strategies for spinal reconstruction after decompression for an unstable thoracolumbar burst fracture: 1) short-segment anterolateral fixation; 2) circumferential fixation; and 3) extended anterolateral fixation.

Methods

Thoracolumbar spines (T10–L4) from 7 donors (mean age at death 64 ± 6 years; 1 female and 6 males) were tested in pure moment loading in flexion–extension, lateral bending, and axial rotation. Thoracolumbar burst fractures were surgically induced at L-1, and testing was repeated sequentially for each of the following fixation techniques: short-segment anterolateral, circumferential, and extended anterolateral. Primary and coupled 3D motions were measured across the instrumented site (T12–L2) and compared across treatment groups.

Results

Circumferential and extended anterolateral fixations were statistically equivalent for primary and off-axis range-of-motions in all loading directions, and short-segment anterolateral fixation offered significantly less rigidity than the other 2 methods.

Conclusions

The results of this study strongly suggest that extended anterolateral fixation is biomechanically comparable to circumferential fusion in the treatment of unstable thoracolumbar burst fractures with posterior column and posterior ligamentous injury. In cases in which an anterior procedure may be favored for load sharing or canal decompression, extension of the anterior instrumentation and fusion one level above and below the unstable segment can result in near equivalent stability to a 2-stage circumferential procedure.

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Henry E. Aryan, C. Benjamin Newman, Eric W. Nottmeier, Frank L. Acosta Jr., Vincent Y. Wang and Christopher P. Ames

Object

Stabilization of the atlantoaxial complex has proven to be very challenging. Because of the high mobility of the C1–2 motion segment, fusion rates at this level have been substantially lower than those at the subaxial spine. The set of potential surgical interventions is limited by the anatomy of this region. In 2001 Jürgen Harms described a novel technique for individual fixation of the C-1 lateral mass and the C-2 pedicle by using polyaxial screws and rods. This method has been shown to confer excellent stability in biomechanical studies. Cadaveric and radiographic analyses have indicated that it is safe with respect to osseous and vascular anatomy. Clinical outcome studies and fusion rates have been limited to small case series thus far. The authors reviewed the multicenter experience with 102 patients undergoing C1–2 fusion via the polyaxial screw/rod technique. They also describe a modification to the Harms technique.

Methods

One hundred two patients (60 female and 42 male) with an average age of 62 years were included in this analysis. The average follow-up was 16.4 months. Indications for surgery were instability at the C1–2 level, and a chronic Type II odontoid fracture was the most frequent underlying cause. All patients had evidence of instability on flexion and extension studies. All underwent posterior C-1 lateral mass to C-2 pedicle or pars screw fixation, according to the method of Harms. Thirty-nine patients also underwent distraction and placement of an allograft spacer into the C1–2 joint, the authors' modification of the Harms technique. None of the patients had supplemental sublaminar wiring.

Results

All but 2 patients with at least a 12-month follow-up had radiographic evidence of fusion or lack of motion on flexion and extension films. All patients with an allograft spacer demonstrated bridging bone across the joint space on plain x-ray films and computed tomography. The C-2 root was sacrificed bilaterally in all patients. A postoperative wound infection developed in 4 patients and was treated conservatively with antibiotics and local wound care. One patient required surgical debridement of the wound. No patient suffered a neurological injury. Unfavorable anatomy precluded the use of C-2 pedicle screws in 23 patients, and thus, they underwent placement of pars screws instead.

Conclusions

Fusion of C1–2 according to the Harms technique is a safe and effective treatment modality. It is suitable for a wide variety of fracture patterns, congenital abnormalities, or other causes of atlantoaxial instability. Modification of the Harms technique with distraction and placement of an allograft spacer in the joint space may restore C1–2 height and enhance radiographic detection of fusion by demonstrating a graft–bone interface on plain x-ray films, which is easier to visualize than the C1–2 joint.

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Henry E. Aryan, Daniel C. Lu, Frank L. Acosta Jr. and Christopher P. Ames

Object

The treatment of vertebral osteomyelitis includes antibiotics with or without surgical intervention. The decision to place instrumentation into an infected spinal column remains controversial. The use of recombinant human bone morphogenetic protein–2 (rhBMP-2) in patients with osteomyelitis is also extremely controversial. The authors review their experience in performing corpectomy and fusion with titanium cages and rhBMP-2 in patients with vertebral instability and/or neurological compromise due to vertebral osteomyelitis.

Methods

Data obtained in 15 patients treated between 2001 and 2005 were included in this analysis. Nine patients presented primarily with axial pain and six with radiculopathy or myelopathy. Seven patients had an associated epidural abscess. The cervical spine was affected in six patients, the thoracic spine in five, and the lumbar spine in four. All patients underwent corpectomy of the involved vertebral bodies; the authors then performed spinal reconstruction, placing a titanium cage–plate system with morcellized allograft/autograft and rhBMP-2. In 10 patients, supplemental posterolateral screw–rod fixation was conducted.

A one-level corpectomy was performed in one patient, a two-level corpectomy in 13, and a six-level corpectomy in one. A morcellized allograft and rhBMP-2–filled titanium cage was used in 10 patients, and an autograft and rhBMP-2–filled cage in five patients. The most common pathogen was Staphylococcus aureus. All patients received intravenous antibiotics for at least 6 weeks postoperatively, and life-long antibiotic therapy was required in three patients with coccidiomycoses, candida, and tuberculosis osteomyelitis, respectively. There were no recurrent infections. Radiography demonstrated evidence of fusion in all patients at the last follow-up examination. The mean follow-up period was 20 months.

Conclusions

Corpectomy followed by titanium cage–plate reconstruction and the placement of rhBMP-2 may be a safe and effective treatment for selected patients with vertebral osteomyelitis. This surgical therapy does not appear, at least based on preliminary results, to lead to recurrent hardware infections. Based on the results obtained in this limited series, the authors found that rhBMP-2 can be used in the setting of active infection with excellent fusion rates and without complication. The morbidity associated with the autograft donor site is avoided when using cages. Antibiotic therapy tailored to the specific organism should be continued for at least 6 weeks after surgery, and life-long therapy is required in cases of fungal or tuberculosis infections.

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Kurtis I. Auguste, Cynthia Chin, Frank L. Acosta and Christopher P. Ames

Object

Expandable cylindrical cages (ECCs) have been utilized successfully to reconstruct the thoracic and lumbar spine. Their advantages include ease of insertion, reduced endplate trauma, direct application/maintenance of interbody distraction force, and one-step kyphosis correction. The authors present their experience with ECCs in the reconstruction of the cervical spine in patients with various pathological conditions.

Methods

Data obtained in 22 patients were reviewed retrospectively. A standard anterior cervical corpectomy was performed in all cases. Local vertebral body bone was harvested for use as graft material. Patients underwent pre- and postoperative assessment involving the visual analog scale (VAS), Nurick grading system for determining myelopathy disability, and radiographic studies to determine cervical kyphosis/lordosis and cage subsidence. Fusion was defined as the absence of motion on flexion–extension x-ray films.

Sixteen patients presented with spondylotic myelopathy, two with osteomyelitis, two with fracture, one with tumor metastasis, and one with severe stenosis. Fourteen patients underwent supplemental posterior spinal fusion, seven underwent single-level corpectomy, and 15 patients underwent multilevel corpectomy. No perioperative complications occurred. The mean follow-up period was 22 months. In 11 patients with preexisting kyphosis (mean deformity +19°), the mean correction was 22°. There was no statistically significant difference in subsidence between single- and multilevel corpectomy or between 360º fusion and anterior fusion alone. The VAS scores improved by 35%, and the Nurick grade improved by 31%. The fusion rate was 100%.

Conclusions

The preliminary results support the use of ECCs in the cervical spine in the treatment of patients with various disease processes. No significant subsidence was noted, and pain and functional scores improved in all cases. Expandable cylindrical cages appear to be well suited for cervical reconstruction and for correcting sagittal malalignment.

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Biomechanical analysis of a newly designed bioabsorbable anterior cervical plate

Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2005

Christopher P. Ames, Frank L. Acosta Jr., Robert H. Chamberlain, Adolfo Espinoza Larios and Neil R. Crawford

Object. The authors present a biomechanical analysis of a newly designed bioabsorbable anterior cervical plate (ACP) for the treatment of one-level cervical degenerative disc disease. They studied anterior cervical discectomy and fusion (ACDF) in a human cadaveric model, comparing the stability of the cervical spine after placement of the bioabsorbable fusion plate, a bioabsorbable mesh, and a more traditional metallic ACP.

Methods. Seven human cadaveric specimens underwent a C6–7 fibular graft—assisted ACDF placement. A one-level resorbable ACP was then placed and secured with bioabsorbable screws. Flexibility testing was performed on both intact and instrumented specimens using a servohydraulic system to create flexion—extension, lateral bending, and axial rotation motions. After data analysis, three parameters were calculated: angular range of motion, lax zone, and stiff zone. The results were compared with those obtained in a previous study of a resorbable fusion mesh and with those acquired using metallic fusion ACPs. For all parameters studied, the resorbable plate consistently conferred greater stability than the resorbable mesh. Moreover, it offered comparable stability with that of metallic fusion ACPs.

Conclusions. Bioabsorbable plates provide better stability than resorbable mesh. Although the results of this study do not necessarily indicate that a resorbable plate confers equivalent stability to a metal plate, the resorbable ACP certainly yielded better results than the resorbable mesh. Bioabsorbable fusion ACPs should therefore be considered as alternatives to metal plates when a graft containment device is required.

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Frank L. Acosta Jr., Jeffrey Lotz and Christopher P. Ames

Low-back pain is the most common health problem for men and women between 20 and 50 years of age, resulting in 13 million doctor visits in the US annually, with significant costs to society in terms of lost time from work and direct and indirect medical expenses. Although the exact origin of most cases of low-back pain remains unknown, it is understood that degenerative damage to the intervertebral disc (IVD) plays a central role in the pathogenic mechanism leading to this disorder. Current treatment modalities for disc-related back pain (selective nerve root blocks, surgical discectomy and fusion) are costly procedures aimed only at alleviating symptoms. Consequently, there is growing interest in the development of novel technologies to repair or regenerate the degenerated IVD. Recently, mesenchymal stem cells (MSCs) have been found to possess the capacity to differentiate into nucleus pulposus–like cells capable of synthesizing a physiological, proteoglycan-rich extracellular matrix characteristic of healthy IVDs. In this article, the authors review the use of MSCs for repopulation of the degenerating IVD. Although important obstacles to the survival and proliferation of stem cells within the degenerating disc need to be overcome, the potential for MSC therapy to slow or reverse the degenerative process remains substantial.