Biomedical subjects

Alexander R Vaccaro

Publications and source records attributed to Alexander R Vaccaro.

At least 19 recordsLinked to original sources

PubMed2005

Failure of standard imaging to detect a cervical fracture in a patient with ankylosing spondylitis.

STUDY DESIGN: Retrospective case study of 38-year-old male with ankylosing spondylitis who presented with a Brown-Séquard syndrome following a fall and an occult fracture on initial spinal imaging studies. OBJECTIVE: To review the recommended imaging protocol in a patient with ankylosing spondylitis and a suspected cervical spine fracture. SUMMARY OF BACKGROUND DATA: Plain radiographic imaging using orthogonal views can detect the majority of spinal fractures. However, fracture identification is particularly difficult in patients with ankylosing spondylitis. Of the various contemporary imaging methods, [magnetic resonance imaging (MRI), computed tomography (CT), nuclear scanning] high-definition multidetector CT scanning is the most useful in identifying subtle fractures, but in metabolic bone diseases the utility of these methods is unknown. METHODS: Retrospective radiographic evaluation of imaging studies of ankylosing spondylitis patient with occult fracture by five spine surgeons and neuroradiologists, followed with detailed review and interpretation of literature concerning present radiology techniques and methods to isolate occult fractures. RESULTS: Initial imaging studies, including plain radiographs of the spinal axis, cervical and thoracic single-detector CT with reconstructed images, and MRI, were unremarkable in detecting an occult cervical spine fracture in a patient with ankylosing spondylitis and a spinal cord injury following a fall. The patient was placed empirically in a halo orthosis and a high definition multidetector CT scan was obtained. This study demonstrated a transverse fracture through the fused C6-C7 spinal level. CONCLUSION: Occult fractures in ankylosing spondylitis may not be apparent on routine plain radiographic and MRI studies. In the setting of ankylosing spondylitis, a high index of suspicion must be maintained in all patients presenting with spinal pain following even minor trauma. High-resolution multidetector CT imaging appears to be more sensitive and accurate in the diagnosis of fractures in this patient subgroup than other contemporary imaging methods.

Adult↗

PubMed2005

Industry support and correlation to study outcome for papers published in Spine.

STUDY DESIGN: Retrospective review of articles published in the journal Spine. OBJECTIVES: To evaluate potential correlations between research sponsorship and study outcome. SUMMARY OF BACKGROUND DATA: Industry sponsorship has traditionally been associated with more positive results than non-funded or peer-reviewed funded projects in other areas of medicine. The association of such sponsorship and study outcome has not been addressed previously in spine research. METHODS: Articles from the journal Spine from January 2002 to July 2003 were reviewed. These were examined for the subject evaluated, type of study design, funding source, and conclusion reached. RESULTS: Of 1143 articles, 527 met inclusion criteria of having abstract, materials/methods, and conclusion sections. Industry support was reported for 84 (15.9%), foundation support for 67 (12.7%), government support for 54 (10.2%), institution support for 17 (3.2%), and no funding was reported for 304 (57.9%). The odds ratio of industry funded reporting positive results was 3.3 times that of studies with any other funding sources (P < 0.001). CONCLUSIONS: Industry funded studies demonstrated a statistically greater likelihood to report positive results than studies with other funding sources. Potential explanations for this are biased study design, biased experimental technique, biased result interpretation, or publication bias. Although the expense of research and limited funding sources have forced an increased reliance on industry support for funding basic science and clinical spine research, this does introduce the potential for bias and must be recognized by the reader.

Bibliometrics↗

PubMed2005

Differences in the work-up and treatment of conditions associated with low back pain by patient gender and ethnic background.

STUDY DESIGN: Retrospective review comparing physician workup of degenerative lumbosacral pathologies between different genders and ethnic groups. OBJECTIVES: To investigate whether patient ethnicity and gender influence the workup and treatment of degenerative spinal pathologies. SUMMARY OF BACKGROUND DATA: Data from numerous studies suggest that patient gender and ethnicity play a role in medical decision-making, with white males receiving more frequent interventions than women and minorities. METHODS: Patients enrolled for an "initial visit" in the National Spine Network database with lumbosacral level degenerative diagnosis were reviewed. Variables included patient gender, ethnicity, age, duration of symptoms, patient-graded severity of symptoms, radicular symptom pattern, and work status. RESULTS: We identified 5690 patients with degenerative lumbosacral pathologies. Although females were more likely than males to have imaging tests ordered, male (18.5%) patients were significantly more likely to have surgery recommended than female (16.3%) patients (P < 0.031). Nonwhite females were 52% less likely to have surgery offered at initial visit, as compared to white males (P < 0.005). More imaging tests were ordered or reviewed among whites (76.6%) than among any other ethnic group (P = 0.162). White (18.3%) and Asian (22.5%) patients were significantly more likely to have surgery recommended or prescribed than black (11.1%) and Hispanic (14.5) patients (P < 0.0001). CONCLUSIONS: This study suggests that ethnicity and gender affect the workup and surgical management of degenerative spinal disorders. However, it should be noted that there are a number of confounding factors not identified in the database, including managed care and insurance status and cultural differences, which may affect both test ordering and treatment recommendations. Further study of bias in clinical decision-making is indicated to assure equal delivery of quality care.

Black or African American↗

PubMed2005

A 2-year follow-up pilot study evaluating the safety and efficacy of op-1 putty (rhbmp-7) as an adjunct to iliac crest autograft in posterolateral lumbar fusions.

The ability of bone morphogenetic proteins (BMPs) to induce bone formation has led to a multitude of investigations into their use as bone graft substitutes in spinal surgery. The purpose of this multi-center clinical pilot study was to evaluate the safety and efficacy of BMP-7 (osteogenic protein 1, OP-1), in the form of a putty, combined with autograft for intertransverse process fusion of the lumbar spine in patients with symptomatic spinal stenosis and degenerative spondylolisthesis following spinal decompression. Twelve patients with spinal stenosis and degenerative lumbar spondylolisthesis underwent a laminectomy and partial or complete medial facetectomy as required for decompression of the neural elements, followed by an intertransverse process fusion by placing iliac crest autograft and OP-1 putty between the decorticated transverse processes. No instrumentation was used. Patients were followed clinically using the Oswestry scale and SF-36 outcome forms, and radiographically using static and dynamic radiographs to assess their fusion status over a 2-year period. Independent and blinded radiologists assessed the films for the presence of bridging bone between the transverse processes and measured translation and angulation on dynamic films using digital calipers. Radiographic outcome was compared to a historical control (autograft alone fusion without instrumentation for the treatment of degenerative spondylolisthesis). All adverse events were recorded prospectively. The results showed eight of the nine evaluable patients (89%) obtained at least a 20% improvement in their preoperative Oswestry score, while five of ten patients (50%) with radiographic follow-up achieved a solid fusion by the criteria used in this study. Bridging bone on the anteroposterior film was observed in seven of the ten patients (70%). No systemic toxicity, ectopic bone formation, recurrent stenosis or other adverse events related to the OP-1 putty implant were observed. A successful fusion was observed in slightly over half the patients in this study, using stringent criteria without adjunctive spinal instrumentation. This study did not demonstrate the statistical superiority of OP-1 combined with autograft over an autograft alone historical control, in which the fusion rate was 45%. There were no adverse events related to the OP-1 putty implant in this study, which supports findings in other studies suggesting the safety of bone morphogenetic proteins in spinal surgery.

Aged↗

PubMed2005

Indications for surgery and stabilization techniques of the occipito-cervical junction.

Occipito-cervical (OC) instrumentation and fusion is indicated in traumatic atlanto-occipital dissociation and type III Anderson-Montesano occipital condyle fractures. The goals of surgery are to stabilize the mechanically compromised OC junction, correct deformity or displacement, and decompress compromised neural structures. The goals of instrumentation are to provide immediate stability, improve fusion rate, diminish the need for postoperative external immobilization, and decrease rehabilitation time. To successfully instrument the occipito-cervical spine, a working knowledge of the anatomy of the occipital-cervical junction is imperative. A wide variety of stabilization techniques and instrumentation systems are currently available, each with its own advantages and disadvantages. With familiarity of the constraints and benefits of the available instrumentation systems, the individual fixation needs of a clinical situation can be fulfilled and successful patient outcomes can be achieved.

Bone Plates↗

PubMed2005

Standard and minimally invasive approaches to the spine.

With the advent of minimally invasive surgical approaches to the spine, the ability to adequately expose the desired anatomic structures while minimizing the disadvantages of excessive soft tissue stripping, dissection, and prolonged retraction has become increasingly popular. A minimally invasive one- or two-level posterior exposure of the spine is now safely attainable with the latest minimal-access systems that exploit the biomechanics of an adjustable blade retractor. As the clinical use of these developing systems escalates, more outcomes data will become available to determine the safety and value of these minimally invasive procedures.

Cervical Vertebrae↗

PubMed2005

A critical analysis of the literature regarding surgical approach and outcome for adult low-grade isthmic spondylolisthesis.

OBJECTIVE: A systematic review of the radiographic and clinical outcomes of adult patients undergoing surgery for low-grade isthmic spondylolisthesis was performed to determine whether conclusions could be made regarding the optimal choice of surgically managing adult low-grade isthmic spondylolisthesis. METHODS: We tabulated the radiographic and clinical outcomes of patients who underwent a posterior procedure alone, an anterior procedure alone, or a combined anterior and posterior procedure. We also evaluated the influence of covariates such as laminectomy, spinal internal fixation, smoking, and secondary gain issues on these outcomes. Patients were pooled, and a chi analysis was performed to determine the relationship between surgical approach and patient outcome. A covariate analysis was performed to determine the influence of a laminectomy, spinal fixation, smoking, and secondary gain issues on these outcomes. RESULTS: The available literature consisted primarily of retrospective case series, with only 4 of 34 reports being prospective randomized controlled studies. Patients with combined anterior and posterior procedures were most likely to achieve a solid fusion and a successful clinical outcome. The use of spinal fixation also increased the chance of fusion and successful clinical outcome. CONCLUSIONS: A pooling of the surgical literature on adult low-grade spondylolisthesis indicates that a combined anterior and posterior procedure most reliably achieves fusion and a successful clinical outcome. The literature, however, is primarily retrospective and heterogeneous with respect to indications for surgery and methods of evaluating outcome, providing a compelling rationale for a prospective randomized controlled trial of the various surgical approaches to this problem.

Adult↗

PubMed2005

Assessment of two thoracolumbar fracture classification systems as used by multiple surgeons.

BACKGROUND: The reproducibility and repeatability of modern systems for classification of thoracolumbar injuries have not been sufficiently studied. We assessed the interobserver and intraobserver reproducibility of the AO (Arbeitsgemeinschaft für Osteosynthesefragen) classification and compared it with that of the Denis classification. Our purpose was to determine whether the newer, AO system had better reproducibility than the older, Denis classification. METHODS: Anteroposterior and lateral radiographs and computerized tomography scans (axial images and sagittal reconstructions) of thirty-one acute traumatic fractures of the thoracolumbar spine were presented to nineteen observers, all trained spine surgeons, who classified the fractures according to both the AO and the Denis classification systems. Three months later, the images of the thirty-one fractures were scrambled into a different order, and the observers repeated the classification. The Cohen kappa (kappa) test was used to determine interobserver and intraobserver agreement, which was measured with regard to the three basic classifications in the AO system (types A, B, and C) as well as the nine subtypes of that system. We also measured the agreement with regard to the four basic types in the Denis classification (compression, burst, seat-belt, and fracture-dislocation) and with regard to the sixteen subtypes of that system. RESULTS: The AO classification was fairly reproducible, with an average kappa of 0.475 (range, 0.389 to 0.598) for the agreement regarding the assignment of the three types and an average kappa of 0.537 for the agreement regarding the nine subtypes. The average kappa for the agreement regarding the assignment of the four Denis fracture types was 0.606 (range, 0.395 to 0.702), and it was 0.173 for agreement regarding the sixteen subtypes. The intraobserver agreement (repeatability) was 82% and 79% for the AO and Denis types, respectively, and 67% and 56%, for the AO and Denis subtypes, respectively. CONCLUSIONS: Both the Denis and the AO system for the classification of spine fractures had only moderate reliability and repeatability. The tendency for well-trained spine surgeons to classify the same fracture differently on repeat testing is a matter of some concern.

Adult↗

PubMed2005

Is wound drainage necessary after lumbar spinal fusion surgery?

BACKGROUND: Despite a lack of any evidence to support the utilization of closed-suction drainage after spinal surgery, it is a frequently utilized procedure. MATERIAL/METHODS: A retrospective evaluation of eighty-five consecutive posterior lumbar fusions at a single level for degenerative disease was performed during the six-year period between March of 1996 and February 2002 by a single surgeon. No patient had a drain placed at the conclusion of the surgical procedure. RESULTS: One patient developed a postoperative deep wound infection requiring debridements and intravenous antibiotics for six weeks. One patient developed a postoperative cellulitis that resolved with PO antibiotics. One patient who received intravenous Lovenox (Enoxaparin) for deep vein thrombosis prophylaxis in the immediate peri-operative period developed a hematoma that was surgically decompressed. No additional complications were noted. The results of this study compare favorably with similar well-matched historical controls using routine peri-operative lumbar wound drainage. CONCLUSIONS: Lumbar spinal fusion for degenerative disease without closed suction drainage in the immediate post-op period does not appear to increase the risks of wound related complications postoperatively as compared to historical controls. The routine use of postoperative closed-suction drainage following a single level posterior lumbar fusion for degenerative disease is not supported by the currently available literature. Such a conclusion is not applicable in nondegenerative pathologies such as metastatic disease following radiation where the risk of bleeding and wound complications may be much greater. In addition, individual patient subgroups with degenerative disease, such as those at risk for perioperative epidural bleeding, may benefit from the placement of a perisurgical drain.

Adult↗

PubMed2005

Whiplash: fact or fiction?

Cervical sprain/strain or whiplash injuries are a common cause of acute and chronic musculoskeletal impairments and are ubiquitous after rear-end automobile collisions. The diagnosis is largely subjective and the ideal treatment controversial. Unfortunately, the majority of compensated litigation claims are associated with whiplash-type injuries secondary to motor vehicle accidents. Fortunately, many recent advances have led to better understanding of the collision and injury biomechanics and to development of a prognostic classification system, objective diagnostic tests, an array of treatment modalities, and, most important, safer automobiles. These advances will undoubtedly lead to decreased incidence, a more accurate diagnosis, and a tailored management regimen resulting in improved outcomes and ultimately fewer legal proceedings.

Accidents, Traffic↗

PubMed2005

Stretch-associated injury in cervical spondylotic myelopathy: new concept and review.

The simple pathoanatomic concept that a narrowed spinal canal causes compression of the enclosed cord, leading to local tissue ischemia, injury, and neurological impairment, fails to explain the entire spectrum of clinical findings observed in cervical spondylotic myelopathy. A growing body of evidence indicates that spondylotic narrowing of the spinal canal and abnormal or excessive motion of the cervical spine results in increased strain and shear forces that cause localized axonal injury within the spinal cord. During normal motion, significant axial strains occur in the cervical spinal cord. At the cervicothoracic junction, where flexion is greatest, the spinal cord stretches 24% of its length. This causes local spinal cord strain. In the presence of pathological displacement, strain can exceed the material properties of the spinal cord and cause transient or permanent neurological injury. Stretch-associated injury is now widely accepted as the principal etiological factor of myelopathy in experimental models of neural injury, tethered cord syndrome, and diffuse axonal injury. Axonal injury reproducibly occurs at sites of maximal tensile loading in a well-defined sequence of intracellular events: myelin stretch injury, altered axolemmal permeability, calcium entry, cytoskeletal collapse, compaction of neurofilaments and microtubules, disruption of anterograde axonal transport, accumulation of organelles, axon retraction bulb formation, and secondary axotomy. Stretch and shear forces generated within the spinal cord seem to be important factors in the pathogenesis of cervical spondylotic myelopathy.

Biomechanical Phenomena↗

PubMed2005

The thoracolumbar injury severity score: a proposed treatment algorithm.

OBJECTIVE: Significant controversy exists regarding the optimal management of thoracolumbar injuries. This is in part due to the lack of understanding of the natural history of various injury subtypes and the absence of a universally accepted classification scheme that facilitates communication among care providers and assists in directing treatment. The Spine Trauma Study Group has developed an injury severity score based on three major variables: the mechanism of injury determined by radiographic appearance, the integrity of the posterior ligamentous complex, and the neurologic status of the patient. By systematically assigning specific point values within each category based on the severity of injury, a final severity score may be generated that can be used to help direct treatment. The goal of this work is to present a proposal of a detailed treatment algorithm to assist in the nonoperative or operative management of thoracolumbar injuries. METHODS: A detailed review of the world's spinal literature was performed to ascertain predictors of instability following thoracolumbar trauma. With use of known biomechanical and clinical outcome measures, an arbitrary assignment of point values to various injury descriptors was performed. The assessment of the validity of the severity score was compared retrospectively with a variety of selected cases representing the typical injury patterns under the three major injury groups: compression, translational/rotational, and distraction injuries. CONCLUSIONS: The proposed treatment algorithm is an attempt to assist physicians using best-evidence medicine in managing thoracolumbar spinal injuries. The final point flow chart with graduated treatment recommendations is only preliminary and needs to be validated through prospective cohort analysis. In addition, the importance of the chosen variables determining spinal stability must also be verified.

Algorithms↗

PubMed2004

Differentiation of mesenchymal stem cells towards a nucleus pulposus-like phenotype in vitro: implications for cell-based transplantation therapy.

OBJECTIVE: Because mesenchymal stem cells can differentiate into chondrocyte-like cells, we ask the question, can mesenchymal stem cells commit to the nucleus pulposus phenotype? BACKGROUND: Back pain, a significant source of morbidity in our society, is linked to degenerative changes of the intervertebral disc. Absence of suitable graft tissue limits therapeutic approaches for repair of disc tissue. For this reason, there is considerable interest in developing "tissue engineering" strategies for the regeneration of the nucleus pulposus. METHODS: Rat mesenchymal stem cells were immobilized in 3-dimensional alginate hydrogels and cultured in a medium containing transforming growth factor-beta1 under hypoxia (2% O2) and normoxia (20% O2). Mesenchymal stem cells were examined by confocal microscopy to evaluate their viability and metabolic status after labeling with Celltracker green, a thiol sensitive dye, and Mitotracker red, a dye sensitive to the mitochondrial membrane potential. Flow cytometry, semiquantitative reverse transcription polymerase chain reaction and Western blot analysis were carried out to evaluate phenotypic and biosynthetic activities and the signaling pathways involved in the differentiation process. RESULTS: Under hypoxic conditions, mesenchymal stem cells formed large aggregates and exhibited positive Celltracker and Mitotracker signals. Glucose transporter-3, matrix metalloproteinase-2, collagen type II and type XI, and aggrecan mRNA and protein expression was upregulated, whereas there was no change in the levels of decorin, biglycan, fibromodulin, and lumican. Hypoxia maintained the expression of CD44 (hyaluronan receptor), ALCAM (CD166), and endoglin (transforming growth factor-beta receptor). Likewise, expression of beta3 and alpha2 integrin was upregulated. Transforming growth factor-beta treatment increased MAPK activity and Sox-9, aggrecan, and collagen type II gene expression. Basal levels of the phosphorylated MAPK isoform ERK1/2, but not p38, were higher under hypoxic conditions than normoxia, and its activation was further augmented by treatment of cells with transforming growth factor-beta. In hypoxia, transforming growth factor-beta sustained phosphorylated p38 expression for an extended time period. Pharmacological inhibition of ERK1/2 and p38 enzymatic activity resulted in a decrease in Sox-9, aggrecan, and collagen type II mRNA levels. CONCLUSIONS: Our results indicate that hypoxia and transforming growth factor-beta drive mesenchymal stem cell differentiation towards a phenotype consistent with that of the nucleus pulposus. Measurement of selected signaling molecules and response to specific inhibitors suggest involvement of MAPK signaling pathways. It is concluded that mesenchymal stem cells could be used to repopulate the damaged or degenerate intervertebral disc.

Animals↗

PubMed2004

Cervical arthroplasty: material properties.

Discectomy, decompression, and fusion are traditionally used to manage cervical disc disease accompanied by neural element compression that is refractory to conservative management. Concerns regarding stress at levels adjacent to fusion and possible adjacent-level degeneration as well as a desire to maintain a more normal biomechanical environment have led to investigation of cervical disc replacement as an alternative to fusion procedures. Cervical disc prostheses currently under investigation are constructed of predominantly metal-on-polyethylene or metal-on-metal bearing surfaces, and use roughened titanium surfaces and osteoconductive coatings to facilitate fixation. The unique anatomy and biomechanics of the cervical spine must be considered when extrapolating from the experience of appendicular arthroplasty and lumbar disc replacement.

Arthroplasty↗

PubMed2004

A pilot study evaluating the safety and efficacy of OP-1 Putty (rhBMP-7) as a replacement for iliac crest autograft in posterolateral lumbar arthrodesis for degenerative spondylolisthesis.

STUDY DESIGN: A prospective, randomized, controlled, multicenter clinical study was conducted. OBJECTIVE: To compare the clinical and radiographic outcomes of patients treated with OP-1 (BMP-7) Putty to autogenous iliac crest bone graft for one-level uninstrumented posterolateral fusion of the lumbar spine following decompressive laminectomy for the treatment of symptomatic degenerative spondylolisthesis with spinal stenosis. BACKGROUND: Preclinical studies have demonstrated that osteoinductive recombinant human osteogenic protein 1 in the form of OP-1 Putty is successful at achieving a posterolateral fusion in rabbits and dogs without any significant safety concerns. METHODS: Thirty-six patients with degenerative lumbar spondylolisthesis and symptoms of neurogenic claudication were randomized (2:1) to either OP-1 Putty (3.5 mg of OP-1 per side) or autogenous iliac crest bone graft for one-level uninstrumented posterolateral fusion following a decompressive laminectomy. Enrollment in the study was complete when 24 OP-1 Putty patients and 12 autograft patients had been randomized and treated. A patient administered Oswestry scale and SF-36 scale were used to determine clinical outcomes. Independent, blinded neuroradiologists reviewed both static and dynamic radiographs to determine fusion status. RESULTS: At the 1-year follow-up, 32 patients were available for clinical analysis and 29 patients were available for radiographic review. Clinical success as measured on the Oswestry scale was achieved by 18 of 21 (86%) OP-1 Putty patients and 8 of 11 (73%) autograft patients. SF-36 pain index scores showed similar results. Fourteen of 19 (74%) OP-1 Putty patients and 6 of 10 (60%) autograft patients achieved a successful posterolateral fusion fulfilling all fusion criteria. Of the 29 evaluable patients, 15 were both clinical and radiographic successes, 5 were radiographic successes but were clinical failures, 1 patient was both a radiographic and clinical failure, and 8 patients were radiographic failures but were clinical successes. No systemic toxicity, ectopic bone formation, recurrent stenosis, or other adverse events related to the OP-1 Putty implant were observed. CONCLUSION: Although the posterolateral spine is a challenging fusion environment in patients with degenerative spondylolisthesis, successful radiographic fusion was obtained using OP-1 Putty at a rate that was similar to autograft given the number of patients in this study. Importantly, there were no apparent adverse consequences related to the use of the OP-1 Putty implant in this patient population.

Adult↗

PubMed2004

Development of a New Zealand white rabbit model of spinal pseudarthrosis repair and evaluation of the potential role of OP-1 to overcome pseudarthrosis.

STUDY DESIGN: Posterolateral lumbar fusions were performed in nicotine-exposed, New Zealand white rabbits. Animals that developed a pseudarthrosis were then regrafted with no graft, autograft, or osteogenic protein-1 (OP-1). OBJECTIVES: To establish a model of pseudarthrosis repair and to evaluate the ability of OP-1 to induce fusion in this model. SUMMARY OF BACKGROUND DATA: OP-1 has been shown to have a 100% fusion rate in an established rabbit fusion model, even in the presence of nicotine, which is known to inhibit fusion. METHODS: Forty-four New Zealand white rabbits underwent posterolateral lumbar fusion with iliac crest autograft. To maximize the incidence of pseudarthroses, nicotine was administered to all rabbits. At 5 weeks, the spines were explored, and all pseudarthroses were redecorticated and grafted with no graft, autograft, or OP-1. At 10 weeks, the rabbits were killed and fusions masses were assessed with manual palpation, radiography, computed tomography, and/or histology. RESULTS: Nine rabbits (20%) were lost to complications. Thirty-four (94%) had pseudarthroses on exploration at 5 weeks. By manual palpation at 10 weeks, 1 of 10 (10%) pseudarthroses that received no graft fused, 5 of 12 (42%) pseudarthroses that received autograft fused, and 9 of 11 (82%) pseudarthroses that received OP-1 fused. Computed tomography and histology further characterized the fusion masses. CONCLUSIONS: This study establishes a model for treatment of pseudarthroses. OP-1, which has previously been shown to have 100% fusion rate in animal models, outperformed autograft and induced fusion in 82% of rabbits.

Animals↗

PubMed2004

Conus medullaris and cauda equina syndrome as a result of traumatic injuries: management principles.

Conus medullaris syndrome (CMS) and cauda equina syndrome (CES) are complex neurological disorders that can be manifested through a variety of symptoms. Patients may present with back pain, unilateral or bilateral leg pain, paresthesias and weakness, perineum or saddle anesthesia, and rectal and/or urinary incontinence or dysfunction. Although patients typically present with acute disc herniations, traumatic injuries at the thoracolumbar junction at the terminal portion of the spinal cord and cauda equina are also common. Unfortunately, a precise understanding of the pathophysiology and optimal treatments, including the best timing of surgery, has yet to be elucidated for either traumatic CES or CMS. In this paper the authors review the current literature on traumatic conus medullaris and cauda equina injuries and available treatment options.

Adult↗

PubMed2004

Enhancement of stability following anterior cervical corpectomy: a biomechanical study.

STUDY DESIGN: An in vitro biomechanical study of various reconstructive techniques following decompression of the spondylotic cervical spine. OBJECTIVE.: To evaluate the biomechanical stability of anterior cervical plate fixation following three strategies of decompression for multilevel cervical spondylosis (three levels) of the cervical spine: three level discectomy, single corpectomy and discectomy, and a two-level corpectomy. SUMMARY OF BACKGROUND DATA: The main goals of surgical treatment for cervical myelopathy include adequate decompression and stabilization while maintaining or restoring cervical lordosis. Cervical decompression is often performed through a corpectomy followed by strut-graft reconstruction. An anterior cervical plate with end-fixation (two points of fixation) is then used to span the construct. The authors propose an alternative to multilevel corpectomy and long-segment end construct plate fixation. Often times, the cervical stenosis is confined to the area of the degenerative discs. As a result, the authors feel that either multilevel discectomy or a corpectomy combined with discectomy followed by segmental plate fixation may provide adequate decompression with increased biomechanical rigidity as compared to cervical plate-constructs with end-fixation only. METHODS: Seven human cadaveric fresh-frozen cervical spines from C1-T1 were utilized. Three-dimensional motion analysis with an optical tracking device was used to determine motion following various reconstruction methods. All seven cervical spines underwent testing in a randomized order. The end construct model consisted of a corpectomy at C4 and C5 with a polymethyl methacrylate strut graft and an anterior cervical PEAK (DePuy-AcroMed) plate. The two segmental constructs also utilized the PEAK plate with one construct undergoing discectomies at C3-C4, C4-C5, and C5-C6 with polymethyl methacrylate interbody grafts and the other segmental construct undergoing a discectomy at C3-C4 and a corpectomy of C5. All specimens underwent a pure moment application of 2 Nm with regards to flexion-extension, lateral bending, and axial rotation. RESULTS.: The three-level discectomy and combined one-level discectomy and corpectomy with segmental fixation was significantly more rigid in flexion-extension and lateral bending than the two-level corpectomy with end-construct plate fixation (P < 0.05). There was no increase in stability during extension between the end construct (two-level corpectomy) reconstruction model and the un-instrumented corpectomy and grafted specimen. No difference was noted between the segmental constructs and the end-construct with regards to axial rotation. CONCLUSIONS: Cervical myelopathy is traditionally treated with a multilevel corpectomy and an end-construct plate fixation spanning the strut graft. A large moment arm is generated at the ends of the construct, potentially leading to plate migration or dislodgment. Often times, adequate decompression can be achieved with either a multilevel discectomy or a combined discectomy and corpectomy with segmental plate fixation. This study clearly demonstrates that segmental plate fixation affords a more biomechanically rigid method of reconstruction with regards to flexion-extension and lateral bending than end-construct plate fixation. The increased rigidity afforded by segmental fixation may significantly decrease the likelihood of plate dislodgement in the setting of anterior instrumentation alone following anterior alone, long segment reconstruction procedures.

Biomechanical Phenomena↗