Long Segment Anterior Cervical Discectomy and Fusion, Including C2: Surgical Pearls and Review of Our Experience.

STUDY DESIGN: A retrospective study of thirteen patients undergoing 5-level anterior spinal surgery for cervical myelopathy. OBJECTIVE: While limited literature exists in reviewing the treatment of high cervical pathology extending caudally, we believe long segment surgery beginning at C2-3 can be accomplished with good success and is an option more patients may benefit from. We aim to describe the technique in accessing the C2-C3 disk space and efficacy of treating multilevel disease beginning at the C2 vertebral body. This includes an extensive technical report and surgical pearls. SUMMARY OF BACKGROUND DATA: Compression at the level of C2 can be daunting to access because of steep approach required. Few studies have described the technique in reaching the C2 level, with less information describing the efficacy of a 5-level anterior fusion starting at C2. METHODS: Patients who underwent surgery between 2000 and 2016 were identified utilizing the department billing database and ICD codes. Patients age, operative indications, levels treated, length of hospital stay, fusion outcome, and operative complications were explored. Independent analysis of fusion was performed. RESULTS: The average length of hospital stay was 3.9 days. Eight patients reported significant improvement of hand weakness, numbness, and/or gait at 6 months follow-up. The most frequent complication was dysphagia (23%). One patient experienced recurrent symptoms secondary to nonunion, and another patient suffered a postoperative neurological worsening because of anterior spinal artery syndrome. CONCLUSION: This retrospective review discusses the technique to visualize and fully decompress C2-C3 spinal segments. In addition, we explored the efficacy and perioperative risk in long segment anterior cervical discectomy and fusion.

The History of Neurosurgical Spinal Oncology: From Inception to Modern-Day Practices.

The neurosurgical management of spinal neoplasms has undergone immense development in parallel with advancements made in general spine surgery. Laminectomies were performed as the first surgical procedures used to treat spinal neoplasms. Since then, neurosurgical spinal oncology has started to incorporate techniques that have developed from recent advances in minimally invasive spine surgery. Neurosurgery has also integrated radiotherapy into the treatment of spine tumors. In this historical vignette, we present a vast timeline spanning from the Byzantine period to the current day and recount the major advancements in the management of spinal neoplasms.

Stabbing Injury of the Cervical Spinal Cord Resulting in Complete Loss of Bilateral Proprioception.

BACKGROUND: Direct penetrating trauma to the spinal cord as a result of stabbing is rare. The vertebral column is strongly suited to protecting the vital neural structures underneath, especially in the midline. CASE DESCRIPTION: A 25-year-old woman experienced a direct stabbing injury to her spinal cord, through the midline structures, resulting in bilateral dorsal column injury. She remained intact with regard to motor function despite bilateral sensory and proprioception loss. CONCLUSIONS: Owing to the strength of the protective elements of the osseous structures surrounding the spinal cord, direct stabbing injuries usually result in incomplete neurologic deficits. This is generally manifested as a Brown-Sequard syndrome because of the midline ligamentous structures and spinous processes deflecting injuries laterally. Our patient experienced a direct midline puncture, resulting in a unique case of bilateral dorsal column injury. These injuries are generally treated conservatively, in the absence of a retained foreign body. Spinal cord stabbing injuries are a rare entity with interesting clinical and anatomic correlations.

Stiffness Matters: Part II-The Effects of Plate Stiffness on Load-Sharing and the Progression of Fusion Following Anterior Cervical Discectomy and Fusion In Vivo.

STUDY DESIGN: Real time in vivo measurement of forces in the cervical spine of goats following anterior cervical discectomy and fusion (ACDF). OBJECTIVE: To measure interbody forces in the cervical spine during the time course of fusion following ACDF with plates of different stiffnesses. SUMMARY OF BACKGROUND DATA: Following ACDF, the biomechanics of the arthrodesis is largely dictated by the plate. The properties of the plate prescribe the extent of load-sharing through the disc space versus the extent of stress-shielding. Load-sharing promotes interbody bone formation and stress-shielding can inhibit maturation of bone. However, these principles have never been validated in vivo. Measuring in vivo biomechanics of the cervical spine is critical to understanding the complex relationships between implant design, interbody loading, load-sharing, and the progression of fusion. METHODS: Anterior cervical plates of distinct bending stiffnesses were placed surgically following ACDF in goats. A validated custom force-sensing interbody implant was placed in the disc space to measure load-sharing in the spine. Interbody loads were measured in vivo in real time during the course of fusion for each plate. RESULTS: Interbody forces during flexion/extension were highly dynamic. In animals that received high stiffness plates, maximum forces were in extension whereas in animals that received lower stiffness plates, maximum forces were in flexion. As fusion progressed, interbody load magnitude decreased. CONCLUSION: The magnitude of interbody forces in the cervical spine is dynamic and correlates to activity and posture of the head and neck. The magnitude and consistency of forces in the interbody space correlates to plate stiffness with more compliant plates resulting in more consistent load-sharing. The magnitude of interbody forces decreases as fusion matures suggesting that smart interbody implants may be used as a diagnostic tool to indicate the progression of interbody fusion. LEVEL OF EVIDENCE: N/A.

Load-sharing through elastic micro-motion accelerates bone formation and interbody fusion.

BACKGROUND CONTEXT: Achieving a successful spinal fusion requires the proper biological and biomechanical environment. Optimizing load-sharing in the interbody space can enhance bone formation. For anterior cervical discectomy and fusion (ACDF), loading and motion are largely dictated by the stiffness of the plate, which can facilitate a balance between stability and load-sharing. The advantages of load-sharing may be substantial for patients with comorbidities and in multilevel procedures where pseudarthrosis rates are significant. PURPOSE: We aimed to evaluate the efficacy of a novel elastically deformable, continuously load-sharing anterior cervical spinal plate for promotion of bone formation and interbody fusion relative to a translationally dynamic plate. STUDY DESIGN/SETTING: An in vivo animal model was used to evaluate the effects of an elastically deformable spinal plate on bone formation and spine fusion. METHODS: Fourteen goats underwent an ACDF and received either a translationally dynamic or elastically deformable plate. Animals were followed up until 18 weeks and were evaluated by plain x-ray, computed tomography scan, and undecalcified histology to evaluate the rate and quality of bone formation and interbody fusion. RESULTS: Animals treated with the elastically deformable plate demonstrated statistically significantly superior early bone formation relative to the translationally dynamic plate. Trends in the data from 8 to 18 weeks postoperatively suggest that the elastically deformable implant enhanced bony bridging and fusion, but these enhancements were not statistically significant. CONCLUSIONS: Load-sharing through elastic micro-motion accelerates bone formation in the challenging goat ACDF model. The elastically deformable implant used in this study may promote early bony bridging and increased rates of fusion, but future studies will be necessary to comprehensively characterize the advantages of load-sharing through micro-motion.

Effect of steroid use in anterior cervical discectomy and fusion: a randomized controlled trial.

OBJECT Anterior cervical discectomy and fusion (ACDF) is an effective procedure for the treatment of cervical radiculopathy and/or myelopathy; however, postoperative dysphagia is a significant concern. Dexamethasone, although potentially protective against perioperative dysphagia and airway compromise, could inhibit fusion, a generally proinflammatory process. The authors conducted a prospective, randomized, double-blinded, controlled study of the effects of steroids on swallowing, the airway, and arthrodesis related to multilevel anterior cervical reconstruction in patients who were undergoing ACDF at Albany Medical Center between 2008 and 2012. The objective of this study was to determine if perioperative steroid use improves perioperative dysphagia and airway edema. METHODS A total of 112 patients were enrolled and randomly assigned to receive saline or dexamethasone. Data gathered included demographics, functional status (including modified Japanese Orthopaedic Association myelopathy score, neck disability index, 12-Item Short-Form Health Survey score, and patient-reported visual analog scale score of axial and radiating pain), functional outcome swallowing scale score, interval postoperative imaging, fusion status, and complications/reoperations. Follow-up was performed at 1, 3, 6, 12, and 24 months, and CT was performed 6, 12, and 24 months after surgery for fusion assessment. RESULTS Baseline demographics were not significantly different between the 2 groups, indicating adequate randomization. In terms of patient-reported functional and pain-related outcomes, there were no differences in the steroid and placebo groups. However, the severity of dysphagia in the postoperative period up to 1 month proved to be significantly lower in the steroid group than in the placebo group (p = 0.027). Furthermore, airway difficulty and a need for intubation trended toward significance in the placebo group (p = 0.057). Last, fusion rates at 6 months proved to be significantly lower in the steroid group but lost significance at 12 months (p = 0.048 and 0.57, respectively). CONCLUSIONS Dexamethasone administered perioperatively significantly improved swallowing function and airway edema and shortened length of stay. It did not affect pain, functional outcomes, or long-term swallowing status. However, it significantly delayed fusion, but the long-term fusion rates remained unaffected. Clinical trial registration no.: NCT01065961 (clinicaltrials.gov).

Low rate loading-induced convection enhances net transport into the intervertebral disc in vivo.

BACKGROUND CONTEXT: The intervertebral disc primarily relies on trans-endplate diffusion for the uptake of nutrients and the clearance of byproducts. In degenerative discs, diffusion is often diminished by endplate sclerosis and reduced proteoglycan content. Mechanical loading-induced convection has the potential to augment diffusion and enhance net transport into the disc. The ability of convection to augment disc transport is controversial and has not been demonstrated in vivo. PURPOSE: To determine if loading-induced convection can enhance small molecule transport into the intervertebral disc in vivo. STUDY DESIGN: Net transport was quantified via postcontrast enhanced magnetic resonance imaging (MRI) into the discs of the New Zealand white rabbit lumbar spine subjected to in vivo cyclic low rate loading. METHODS: Animals were administered the MRI contrast agent gadodiamide intravenously and subjected to in vivo low rate loading (0.5 Hz, 200 N) via a custom external loading apparatus for either 2.5, 5, 10, 15, or 20 minutes. Animals were then euthanized and the lumbar spines imaged using postcontrast enhanced MRI. The T1 constants in the nucleus, annulus, and cartilage endplates were quantified as a measure of gadodiamide transport into the loaded discs compared with the adjacent unloaded discs. Microcomputed tomography was used to quantify subchondral bone density. RESULTS: Low rate loading caused the rapid uptake and clearance of gadodiamide in the nucleus compared with unloaded discs, which exhibited a slower rate of uptake. Relative to unloaded discs, low rate loading caused a maximum increase in transport into the nucleus of 16.8% after 5 minutes of loading. Low rate loading increased the concentration of gadodiamide in the cartilage endplates at each time point compared with unloaded levels. CONCLUSIONS: Results from this study indicate that forced convection accelerated small molecule uptake and clearance in the disc induced by low rate mechanical loading. Low rate loading may, therefore, be therapeutic to the disc as it may enhance the nutrient uptake and waste product clearance.

Multilevel anterior cervical fusion using a collagen-hydroxyapatite matrix with iliac crest bone marrow aspirate: an 18-month follow-up study.

OBJECTIVE: The pseudarthrosis rate after multisegment anterior cervical fusion is directly related to the number of levels surgically fused. The advent of osteobiological adjuvants offers an opportunity to reduce both the likelihood of failed arthrodesis and the need for posterior instrumentation. Collagen-hydroxyapatite matrix is osteoconductive and has been used with autogenous bone marrow aspirate (BMA) to promote fusion. We report our results of using collagen-hydroxyapatite matrix with BMA for multilevel anterior cervical discectomy and fusion and anterior cervical corpectomy and fusion (ACCF). METHODS: Sixty-six consecutively treated patients underwent a multilevel anterior cervical discectomy and fusion and/or ACCF during a period of 16 months. In all cases, a Smith-Robinson decompression was performed followed by allograft fibula strut grafting filled with collagen-hydroxyapatite matrix and BMA, and anterior semiconstrained cervical plating. A vacuum chamber was used to draw the BMA slowly through the collagen-hydroxyapatite sponges. No patient underwent simultaneous posterior instrumentation. Clinical outcome was determined by an independent observer who evaluated patients on the basis of symptom and neurological examination results. Radiographic fusion was determined by dynamic x-rays and computed tomographic scanning during an 18-month follow-up period. RESULTS: With the inclusion of discectomies performed in ACCF procedures, patients were fused between two and five disc levels (mean, 3.1 levels). Seventeen patients underwent one to four-level corpectomies (mean, two levels). Clinical improvement was observed in 49 patients. Conditions in nine patients remained unchanged, and two patients had radicular palsies. In all, 60 patients were followed and analyzed for radiographic fusion. All but two patients demonstrated successful radiographic fusion. CONCLUSION: Collagen-hydroxyapatite matrix with BMA can be a safe, effective adjuvant for promoting fusion in multilevel anterior cervical discectomy and fusion and ACCF. Although randomized, controlled studies are necessary to determine whether or not the fusion rates are superior to those obtained from using allograft alone, these results compare favorably to historical data in the literature.

Direct real-time measurement of in vivo forces in the lumbar spine.

BACKGROUND CONTEXT: Accurate knowledge of the mechanical loads in the lumbar spine is critical to understanding the causes of degenerative disc disease and to developing suitable treatment options and functional disc replacements. To date, only indirect methods have been used to measure the forces developed in the spine in vivo. These methods are fraught with error, and results have never been validated using direct experimental measurements. PURPOSE: The major aims of this study were to develop a methodology to directly measure, in real time, the in vivo loading in the lumbar spine, to determine if the forces developed in the lumbar spine are dependent on activity and/or posture and to assess the baboon as an animal model for human lumbar spine research based on in vivo mechanical loading. STUDY DESIGN: Real-time telemetered data were collected from sensor-imbedded implants that were placed in the interbody space of the lumbar spines of two baboons. METHODS: An interbody spinal implant was designed and instrumented with strain gauges to be used as a load cell. The implant was placed anteriorly in the lumbar spine of the baboon. Strain data were collected in vivo during normal activities and transmitted by means of a telemetry system to a receiver. The forces transmitted through the implant were calculated from the measured strain based on precalibration of the load cell. Measured forces were correlated to videotaped activities to elucidate trends in force level as a function of activity and posture over a 6-week period. The procedure was repeated in a second baboon, and data were recorded for similar activities. RESULTS: Implants measured in vivo forces developed in the lumbar spine with less than 10% error. Loads in the lumbar spine are dependent on activity and posture. The maximum loads developed in the lumbar spine during normal (baboon) activities exceeded four times body weight and were recorded while animals were sitting flexed. Force data indicate similar trends between the human lumbar spine and the baboon lumbar spine. CONCLUSIONS: It is possible to monitor the real-time forces present in the lumbar spine. Force data correlate well to trends previously reported for in vivo pressure data. Results also indicate that the baboon may be an appropriate animal model for study of the human lumbar spine.

A pilot study to evaluate the effectiveness of small intestinal submucosa used to repair spinal ligaments in the goat.

BACKGROUND CONTEXT: Destabilization of the lumbar spine results from sacrifice of the anterior longitudinal ligament and disc when removed for graft or cage placement. In a similar fashion, transection of the interspinous ligament during surgical approaches to the posterior spine may result in segmental instability. Such instability can cause abnormal motion or implant migration resulting in a higher incidence of pseudarthrosis. Small intestinal submucosa (SIS) is a naturally occurring extracellular collagen-based matrix, which is derived from porcine small intestine. SIS contains cytokines and growth factors and has been shown to act as a resorbable scaffold in vivo that promotes host soft tissue regeneration with little scar tissue formation. SIS can be manufactured in laminated sheets of various sizes and thicknesses for different indications. Successful applications of SIS in animals have included dural substitution, rotator cuff repair, vessel repair, abdominal and bladder wall repair, and others. However, SIS has not been investigated to determine its ability to facilitate regeneration of spinal ligaments. PURPOSE: The purpose of this pilot study was to evaluate the efficacy of SIS as a barrier to prevent interbody device migration, and to act as a scaffold for regeneration of the anterior longitudinal ligament (ALL) and posterior interspinous ligament (PISL) in a goat model. STUDY DESIGN/SETTING: The thoracolumbar spine of the goat was exposed surgically. After resection and removal of the ALL or PISL at alternating levels, either SIS was placed or no treatment was administered. New ligament formation and SIS resorption were monitored over a 12-week period. OUTCOME MEASURES: Plain film radiographs and histomorphometry were used to assess the progress of healing over a 12-week time period. METHODS: Four skeletally mature nubian-alpine crossbred goats were used in this study. Under general anesthesia, each T10 to L5 motion segment was exposed surgically. Both anterolateral and posterior approaches were performed simultaneously at each level. Anteriorly, alternating levels received either 1) anterior discectomy, sacrifice of ALL and placement of SIS (SIS group); 2) anterior discectomy, sacrifice of ALL and no SIS (surgical control group) or 3) no surgical intervention (nonoperative group). A solid interbody spacer was placed into the disc space after discectomy to deter spontaneous anterior interbody fusion. Posteriorly, alternating levels were treated with either 1) sacrifice of the PISL with placement of SIS (SIS group); 2) sacrifice of PISL and no SIS (surgical control group) or 3) no surgical intervention (nonoperative group). The SIS was secured to the adjacent superior and inferior spinous processes to create a tension-band effect. Animals were radiographed immediately postoperatively to confirm placement of interbody spacers and anchors and to serve as a baseline for monitoring interbody spacer positioning. After surgery, all animals were allowed unrestricted motion for 12 weeks. At the end of the 12-week period, animals were radiographed and euthanized. The lumbar spine was harvested en bloc and processed for decalcified histologic evaluation. The dorsal and ventral aspects of each motion segment were analyzed for signs of inflammation and scar tissue formation, residual SIS and regenerated ALL or PISL. RESULTS: All animals tolerated the surgical procedure well, and there were no intraoperative or anesthesia-related complications. Twelve-week radiographs showed some evidence of ventral migration of the interbody spacers in several animals. Fifty percent (two of four) of spacers in surgical control group levels had migrated more than 10 mm (resulting in complete migration out of the disc space), whereas no spacers migrated completely out of levels with SIS placed. Gross analysis at necropsy indicated iatrogenic scar formation at operated levels, the degree of which was not different from surgical control group to SIS levels. Histologic evaluation of areas where the ALL had been removed indicated formation of organized fibrilar collagenous tissue that spanned the disc space at some levels where the SIS was placed. In some cases, the newly formed tissue was approximately the thickness of the ALL at the nonoperative group levels. The newly formed collagenous tissue was accompanied by sparse focal areas of inflammation, with small fragments of residual SIS at some levels. At surgical control group levels, there was a varying degree of connective tissue that ranged from moderately organized to randomly oriented with no significant signs of inflammation. Similarly, histologic analysis of some levels where SIS was placed posteriorly showed formation of organized collagenous tissues where the PISL had been removed. CONCLUSIONS: In this model, the SIS patch was sufficient to prevent acute ventral migration of interbody spacers from the disc space. The extent of long-term healing and new tissue formation in the SIS group indicates that it may be efficacious as a reparative intervention for transected ligaments in the spine. Most SIS specimens showed formation of organized collagenous tissue, indicating a long-term potential for ligament formation. However, in this model, 12 weeks of postoperative healing is insufficient to assess the full potential of SIS as a spinal ligament repair. Further research that follows the healing process to a longer time point postoperatively may be necessary to fully understand the potential of SIS as a resorbable scaffold for tissue replacement.