Darryl J. DiRisio

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

BACKGROUND CONTEXTnDestabilization 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.nnnPURPOSEnThe 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.nnnSTUDY DESIGN/SETTINGnThe 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.nnnOUTCOME MEASURESnPlain film radiographs and histomorphometry were used to assess the progress of healing over a 12-week time period.nnnMETHODSnFour 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.nnnRESULTSnAll 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.nnnCONCLUSIONSnIn 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.

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).

MULTILEVEL ANTERIOR CERVICAL FUSION USING A COLLAGEN-HYDROXYAPATITE MATRIX WITH ILIAC CREST BONE MARROW ASPIRATE : AN 18-MONTH FOLLOW-UP STUDY. Commentary

OBJECTIVEThe 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). METHODSSixty-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. RESULTSWith 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. CONCLUSIONCollagen-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.

Nerve entrapment and calf atrophy caused by a Baker's cyst : case report

An unusual case of leg pain and atrophy in a patient with gastrocnemius due to tibial nerve branch compression by a Bakers cyst is presented. The clinical findings and electrodiagnostic studies were supportive of isolated medial gastrocnemius denervation. Treatment by synovectomy along with decompression of the branch of the posterior tibial nerve to the medial head of the gastrocnemius muscle resulted in clinical improvement. No other cases of such selective branch compression have been previously reported.

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

BACKGROUND CONTEXTnThe 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 inxa0vivo.nnnPURPOSEnTo determine if loading-induced convection can enhance small molecule transport into the intervertebral disc inxa0vivo.nnnSTUDY DESIGNnNet transport was quantified via postcontrast enhanced magnetic resonance imaging (MRI) into the discs of the New Zealand white rabbit lumbar spine subjected to inxa0vivo cyclic low rate loading.nnnMETHODSnAnimals were administered the MRI contrast agent gadodiamide intravenously and subjected to inxa0vivo 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.nnnRESULTSnLow 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.nnnCONCLUSIONSnResults 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.

4:25 The Raymedica PDN prosthetic disc nucleus device in the baboon lumbar spine

Abstract Purpose of study: The purpose of this study was to monitor the course of events after placement of PDN prosthetic disc nucleus devices in the lumbar spine of the baboon and to assess the baboon as a model for future testing. Methods used: Three baboons underwent a lateral surgical approach to the lumbar spine. After discectomy, one animal had two custom-sized PDN implants tethered together and placed using the recommended surgical technique. Two additional animals were implanted but, because of limitations of instrumentation, had a single custom implant placed. Radiographs and computed tomography scans were obtained at 2, 4, 12 and 26 weeks to assess implant movement, disc height and end plate morphology. At 26 weeks, segments were harvested, processed undecalcified and evaluated. of findings: The two animals receiving a single device experienced migration of the implant from the disc in the first 2 weeks. Revision procedures using a technique that disrupted the end plate were performed, and smaller tethered PDN devices were placed. In these two animals, from 2 to 26 weeks after revision, there was progressive loss in disc height, end plate degeneration, implant subsidence, circumferential lucency and increasing sclerosis at adjacent vertebrae. Osteophytes bridged the disc space by 26 weeks. Histology revealed mild inflammation almost completely encapsulating the implants. The animal that received a PDN device pair at the initial surgery showed no signs of implant movement from 2 to 26 weeks, no changes in end plate morphology, no sclerosis, no increase in osteophytosis and only mild focal inflammation. Relationship between findings and existing knowledge: The two animals whose clinical outcome was unfavorable had a primary and revision procedure with focal disruption of the end plate, a possible initiator of osteophytosis. It is unknown whether the outcome would have been favorable at these levels if standard surgical techniques had been employed, but under these conditions, the degenerative changes of the disc and inflammatory response to the PDN devices were significant. In contrast, the animal that underwent only the primary procedure resulted in a favorable clinical outcome. Clinically, there have been reports indicating that the PDN device may be efficacious. There have also been reports on potential complications. The favorable response of one baboon to the implants is similar to reported favorable clinical outcomes. Migration of the PDN device from the disc space has been reported clinically; migration occurred in two baboons. Although there are no known clinical reports on histopathology associated with the PDN device, lucency, subsidence and sclerosis have been reported for interbody fusion devices and disc replacements. Overall significance of findings: These results indicate that the baboon may be an appropriate animal model for intervertebral disc research not only because the anatomy and morphology are similar to humans, but also because the potential complications and degenerative pathology are similar to those reported clinically. Disclosures: Device or drug: PDN prosthetic disc nucleus. Status: investigational. Conflict of interest: Eric Ledet, institutional research grant.

Use of the Case Western Reserve/Veterans Administration neuroprosthesis for exercise, standing and transfers by a paraplegic subject

Functional electric stimulation (FES) is a technology that may allow patients with spinal cord injury (SCI) to transfer stand and walk. This paper reports upon the use of the Case Western Reserve Neuroprosthesis by a T6 ASIA B paraplegic subject. The subject was able to stand for two minutes and 50 seconds. He could walk 35 feet with a swing to gait. Measurement of energy consumption showed that metabolic demand was only 2.1 metabolic equivalent units. The factors that limited the use of the device that need to be improved to make the technology practical for household or community ambulation are speed (5.8 m/min) of ambulation and fatigue of the stimulated muscles. Implications for Rehabilitation I think that the article is worth publishing for at least three reasons. It demonstrates the use and limitations of use of functional electric stimulation (FES) for standing and transfers by a paraplegic patient. It implies that main limiting factor to current technology is not the stress on the cardiovascular and pulmonary systems but the stress on the muscles that are innervated by the device. It includes suggestions for and references to changes that need to be made and are in the process of being developed to improve the technology and bring it closer towards something that is more practical and beneficial for the spinal cord injured population. The authors hope that the introduction and the discussion will be interesting and informative to readers who are not familiar with this technology.

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

BACKGROUND CONTEXTnAchieving 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.nnnPURPOSEnWe 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.nnnSTUDY DESIGN/SETTINGnAn in vivo animal model was used to evaluate the effects of an elastically deformable spinal plate on bone formation and spine fusion.nnnMETHODSnFourteen 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.nnnRESULTSnAnimals 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.nnnCONCLUSIONSnLoad-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.

Management of Thoracic Spine Injuries Part I: Thoracic Spine Anatomy and Stability

This article is the first of two parts. Thoracic spinal column injuries, although relatively uncommon, often are associated with significant visceral injuries and a high incidence of complete spinal cord injuries. For the purpose of this article, thoracic spinal column injuries are defined as injuries occurring between T2 and T11, although we discuss the anatomy of the entire thoracic spine (T1–T12). We emphasize that the cervicothoracic and thoracolumbar junctions, while including thoracic spinal levels, have unique anatomic and biomechanical features that affect management decisions and are distinct from other thoracic vertebrae. Part I of this article addresses the epidemiology of thoracic spinal column and spinal cord injuries, the unique anatomic features of the thoracic spine, the biomechanics of the thoracic spine, and the initial evaluation of thoracic spine injury. Part II will address the evaluation of spinal stability, the surgical decision-making process, and an overview of thoracic spinal surgical approaches. Epidemiology of Injuries to the Thoracic Spinal Column and Spinal Cord The annual incidence of traumatic spinal cord injury in the United States is approximately 40 per 1 million population. Mortality following spinal cord injury is significant, with a reported fatality rate as high as 48%. Because of the severity of concomitant injuries, most deaths occur before the patient reaches the hospital. The most common modes of traumatic spinal cord injury are motor vehicle collisions, falls, workrelated accidents, and recreational activity-related accidents. The latter category is the fastest-growing group of spinal cord injuries. Spinal cord injuries occur four times more commonly in young, Caucasian men than in any other group. Spinal cord injuries are classified according to the patient’s level of functioning, which is defined as the last spinal cord segment with normal motor and sensory function. Accordingly, patients are considered paraplegic if they demonstrate neurologic dysfunction below the T1 level and quadriplegic if the neurologic deficit includes a segment at or above T1. Injuries also are classified as complete or incomplete. Complete injuries are defined by absence of any motor, sensory, or reflex function below the level of injury, whereas injuries in which the patient has preserved some function are defined as incomplete. Many thoracic spinal cord injuries are misclassified, because the initial assessment of patients with these injuries often is limited by the presence of concurrent multiorgan Management of Thoracic Spine Injuries