Biomedical subjects

Jonathan N Grauer

Publications and source records attributed to Jonathan N Grauer.

14 recordsLinked to original sources

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↗

PubMed2004

Comparison of posterolateral lumbar fusion rates of Grafton Putty and OP-1 Putty in an athymic rat model.

STUDY DESIGN: Posterolateral lumbar spine fusions in athymic rats. OBJECTIVES: To compare spine fusion rates of two different osteoinductive products. SUMMARY OF BACKGROUND DATA: Many osteoinductive bone graft alternatives are available. Grafton (a demineralized bone matrix [DBM]) and Osteogenic Protein-1 (OP-1, an individual recombinant bone morphogenetic protein) are two such alternatives. The relative efficacy of products from these two classes has not been previously studied. The athymic rat spine fusion model has been validated and demonstrated useful to minimize inflammatory responses to xenogeneic or differentially expressed proteins such as those presented by DBMs of human etiology. METHODS: Single-level intertransverse process fusions were performed in 60 athymic nude rats with 2 cc/kg of Grafton or OP-1 Putty. Half of each study group was killed at 3 weeks and half at 6 weeks. Fusion masses were assessed by radiography, manual palpation, and histology. RESULTS: At 3 weeks, manual palpation revealed a 13% fusion rate with Grafton and a 100% fusion rate with OP-1 (P = 0.0001). At 6 weeks, manual palpation revealed a 39% fusion rate of with Grafton and a 100% fusion rate with OP-1 (P = 0.0007). Similar fusion rates were found by histology at 3 and 6 weeks. Of note, one or two adjacent levels were fused in all of the OP-1 animals and none of the Grafton animals. CONCLUSIONS: Significant differences between the ability of Grafton and OP-1 to induce bone formation in an athymic rat posterolateral lumbar spine fusion model were found.

Activin Receptors, Type I↗

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

Similarities and differences in the treatment of spine trauma between surgical specialties and location of practice.

STUDY DESIGN: Questionnaires administered to practicing orthopedic and neurosurgical spine surgeons from various regions of the United States and abroad. OBJECTIVES: To determine similarities and differences in the treatment of spinal trauma. SUMMARY OF BACKGROUND DATA: Spinal trauma is generally referred to subspecialists of orthopedic or neurosurgical training. Prior studies have suggested that there is significant variability in the management of such injuries. METHODS: Questionnaires based on eight clinical scenarios of commonly encountered cervical, thoracic, and lumbar injuries were administered to 35 experienced spinal surgeons. Surgeons completed profile information and answered approximately one dozen questions for each case. Data were analyzed with SPSS software to determine the levels of agreement and characteristics of respondents that might account for a lack of agreement on particular aspects of management. RESULTS: Of the 35 surgeons completing the questionnaire, 63% were orthopedists, 37% were neurosurgeons, and 80% had been in practice for more than 5 years. Considerable agreement was found in the majority of clinical decisions, including whether or not to operate and the timing of surgery. Of the differences noted, neurosurgeons were more likely to obtain a MRI, and orthopedists were more likely to use autograft as a sole graft material. Physicians from abroad were, in general, more likely to operate and to use an anterior approach during surgery than physicians from the northeastern United States. CONCLUSIONS: More commonalities were identified in the management of spinal trauma than previously reported. When found, variability in opinion was related to professional and regional differences.

Adult↗

PubMed2004

Morphologic evaluation of cervical spine anatomy with computed tomography: anterior cervical plate fixation considerations.

The computed tomography (CT) studies of the cervical spine from 50 males and 50 females were reviewed to provide morphometric data on a variety of anatomic parameters relevant to anterior cervical reconstruction and fixation. Measurements were made of the vertebral body width and midsagittal anteroposterior (AP) diameter and the distance between the medial borders of the longus coli muscles. Distances between adjacent endplates were also measured, both at their midpoint and at the anterior margin. Widths of the vertebral bodies measure 24.6 +/- 2.4 and 23.0 +/- 2.4 mm in males and females, respectively, with the narrowest measuring 17 and 14, respectively. The average midsagittal AP diameter of each vertebral body in males was approximately 17-18 mm, with the smallest AP diameter measured to be 13 mm. The average midsagittal AP diameter of each vertebral body in females was approximately 15-16 mm, with the smallest being 10 mm. CT scanning provides excellent osseous detail for the measurement of such parameters, and with its widespread use in the evaluation of cervical disorders, large numbers of patients can be reviewed.

Adult↗

PubMed2004

Evaluation of a novel pedicle probe for the placement of thoracic and lumbosacral pedicle screws.

BACKGROUND: Pedicle screw instrumentation is common in the lumbar spine and is gaining acceptance in the thoracic spine. The pedicle is generally cannulated with a gearshift probe or curette. SafePath (Mekanika, Boca Raton, FL) is an alternative pedicle probe designed for pedicle cannulation. This is a blunt-tipped, nonaggressive drill that seeks the cancellous portion of the pedicle. OBJECTIVE: The objective of this study was to evaluate the accuracy of this device in comparison with techniques commonly used for pedicle cannulation. METHODS: Four osteoligamentous fresh-frozen thoracic to sacral cadaveric spines were studied. The pedicles of one side of each cadaver were cannulated with the SafePath device. The contralateral pedicles were cannulated with either a gearshift probe or a 3-0 cervical curette. The accuracy of pedicle probe placement was evaluated by radiography, computed tomography (CT) scan, and direct observation via dissection. RESULTS: By direct observation, 51 of 128 pedicles were violated (40%). There were not significant differences between the results obtained with the gearshift probe or curette; there were 2 of 22 lumbosacral violations (9%) and 14 of 45 thoracic violations (33%). With the SafePath device, there were 0 of 22 lumbosacral violations (0%) and 34 of 45 thoracic violations (76%). SafePath performed significantly better in the lumbar spine and significantly worse in the thoracic spine. The accuracy for determining pedicle violation was 88% for radiography and 85% for CT. CONCLUSIONS: The results of this in vitro study suggest that the SafePath device may represent an alternative to traditional pedicle cannulation techniques in the lumbosacral spine. However, the opposite is true in the thoracic spine, where SafePath performed significantly worse than traditional techniques.

Bone Screws↗

PubMed2004

Predictors of paralysis in the rheumatoid cervical spine in patients undergoing total joint arthroplasty.

BACKGROUND: Rheumatoid arthritis is sometimes associated with radiographic evidence of instability of the cervical spine, most commonly an abnormal subluxation between vertebrae. When this instability compromises the space that is available for the spinal cord, it may be predictive of paralysis. However, the prevalence of radiographic signs of instability that are predictive of paralysis among patients with nonspinal orthopaedic manifestations of rheumatoid arthritis is unknown. METHODS: Radiographs of the cervical spine of patients with rheumatoid arthritis who had undergone total joint arthroplasty over a five-year period were retrospectively reviewed. The radiographs were evaluated for predictors of paralysis (a posterior atlantodental interval of <14 mm or a subaxial space available for the cord measuring <14 mm) and were compared with traditional parameters of instability (an anterior atlantodental interval of >3 mm or subaxial subluxation of >3 mm). RESULTS: Forty-nine of the sixty-five patients who were identified had flexion and extension lateral radiographs available for review. Only one of these patients had a posterior atlantodental interval of <14 mm, and only three had a space available for the cord that measured <14 mm at one level or more. In comparison, twenty patients had radiographic evidence of instability on the basis of traditional parameters. CONCLUSIONS: Although nearly one-half of the patients in the present study had radiographic evidence of cervical instability on the basis of traditional measurements, only four patients (8%) had a radiographic finding that was predictive of paralysis. Thus, while radiographic evidence of cervical instability was not infrequent in this population of patients who underwent total joint arthroplasty for rheumatoid arthritis, radiographic predictors of paralysis were much less common.

Adult↗

PubMed2003

Indications, techniques, and outcomes of posterior surgery for chronic low back pain.

This article summarizes a number of issues surrounding the diagnosis, indications, and techniques of posterior lumbar spine surgery for chronic low back pain. It would not be entirely unjustified for a spine surgeon to adhere to a totally avoidant approach to chronic low back pain, rationalized by a reasonably legitimate nihilism regarding the presently available means of diagnosing and surgically managing low back pain [64]. Judging by the number of lumbar fusions performed in North America and the tremendous intellectual and financial investment currently being made in technologies to enhance spinal fusion, such an approach is evidently not achieving wide-spread acceptance on this continent. A rationale approach is therefore required for the many low back pain sufferers with degenerative disk disease who arrive in the office having exhausted almost every imaginable form of nonoperative therapy. Every effort should be made to establish a pathoanatomic etiology of the back pain with a combination of diagnostic modalities. Surgical intervention should be approached cautiously and only after extensive dialog with the patient to establish realistic goals and expectations. Posteriorly performed interbody fusion procedures may provide a high fusion rate and satisfactory clinical outcomes for this challenging problem, although further research is necessary to determine more conclusively the role of surgery and the relative effectiveness of the various arthrodesis techniques.

Chronic Disease↗

PubMed2003

Radiographic analysis of transforaminal lumbar interbody fusion for the treatment of adult isthmic spondylolisthesis.

The radiographs of 35 consecutive adult patients with isthmic spondylolisthesis who underwent a transforaminal lumbar interbody fusion (TLIF) with one or two Brantigan carbon fiber cages and pedicle screw instrumentation were evaluated. Anterolisthesis, disk space height, and slip angle were measured in preoperative and postoperative standing neutral radiographs. Anterolisthesis was reduced and disk space height was increased with the TLIF procedure. Average slip angle, however, was not significantly altered. The restoration of lordosis across the listhetic disk space correlated with a more anterior placement of the interbody cage within the disk space. The TLIF technique, performed with the Brantigan cage and pedicle screw instrumentation, appears to be able to restore disk height and reduce forward translation in patients with isthmic spondylolisthesis, but improvement in sagittal alignment is dependent upon anterior placement of the interbody device.

Adult↗

PubMed2003

Bone graft alternatives for spinal fusion.

Bone grafting to achieve fusion is frequently performed in spinal surgery. Autograft is the gold standard bone graft material. However, due to limitations of supply and morbidity associated with the harvest of autograft, alternatives are being considered. Osteoconductive matrices, such as allograft, calcium or ceramic preparations are one such class of potential bone graft alternatives, but generally they lack osteoinductive properties. Recent attention has focused on osteoinductive materials such as demineralised bone matrix, recombinant bone morphogenetic proteins and bone marrow aspirates or blood product concentrates. These products may be combined with osteoconductive carriers and are clearly finding a place in the clinical arena.

Animals↗

PubMedDate not supplied

Pathophysiology and pharmacologic treatment of acute spinal cord injury.

BACKGROUND CONTEXT: The past three decades have witnessed increasing interest in strategies to improve neurologic function after spinal cord injury. As progress is made in our understanding of the pathophysiologic events that occur after acute spinal cord injury, neuroprotective agents are being developed. PURPOSE: Clinicians who treat acute spinal cord injuries should have a basic understanding of the pathophysiologic processes that are initiated after the spinal cord has been injured. A familiarity with the literature on which the current use of methylprednisolone is based is also essential. STUDY DESIGN/SETTING: Literature review. METHODS: Literature review of animal data on pathophysiologic mechanisms, and of both animal and human trials of neuroprotective agents. RESULTS: The mechanical forces imparted to the spinal cord cause primary damage to the neural tissue, but a complex cascade of pathophysiologic processes that imperil adjacent, initially spared tissue to secondary damage rapidly follows this. Attenuating this secondary damage with neuroprotective strategies requires an understanding of these pathophysiologic processes. Many researchers are investigating the role of such processes as ischemia, inflammation, ionic homeostasis and apoptotic cell death in the secondary injury cascade, with hopes of developing specific therapies to diminish their injurious effects. Beyond methylprednisolone, a number of other pharmacologic treatments have been investigated for the acute treatment of spinal cord injury, and even more are on the horizon as potential therapies. CONCLUSIONS: This review summarizes some of the important pathophysiologic processes involved in secondary damage after spinal cord injury and discusses a number of pharmacologic therapies that have either been studied or have future potential for this devastating injury.

Acute Disease↗

PubMedDate not supplied

Posterolateral lumbar fusions in athymic rats: characterization of a model.

BACKGROUND CONTEXT: The athymic rat has been used to study the role of osteoinductive products in spinal fusions. This small animal model has been advocated to minimize potential inflammatory responses to allogeneic or xenogenic proteins. Despite past experience, this model has not yet been well characterized. PURPOSE: To further define and validate a posterolateral lumbar fusion model in the athymic rat. STUDY DESIGN/SETTING: Comparison of fusions after animal survival surgery. PATIENT SAMPLE: Forty athymic and 20 normothymic rats. OUTCOME MEASURES: Manual palpation, radiography and histology at 3 and 6 weeks. METHODS: Single-level intertransverse fusions were performed at the L4-L5 level of 40 athymic rats. Twenty rats were implanted with autograft (athymic/autograft), and 20 had no graft placed (athymic/no graft). An additional 20 autograft fusions were performed on normothymic rats (normothymic/autograft). Half were sacrificed at 3 weeks; half were sacrificed at 6 weeks. RESULTS: At 3 weeks, 0% of the athymic/no graft rats fused, 20% of the athymic/autograft rats fused and 20% of the normothymic/autograft rats fused by manual palpation. At 6 weeks, 0% of the athymic/no graft rats fused, 30% of the athymic/autograft rats fused and 40% of the normothymic/autograft rats fused by manual palpation. Radiographs were of limited utility in determining fusion, and histology results were roughly concordant with those of manual palpation. CONCLUSIONS: This work further characterizes the athymic rat posterolateral lumbar fusion model. The absence of a thymus does not appear to affect autograft fusion rates, and no spontaneous fusions were seen when no graft was placed.

Animals↗

PubMedDate not supplied

Material considerations for intervertebral disc replacement implants.

Cervical and lumbar disc replacements are being performed with increasing frequency. Much of the background for the development for these implants is drawn from the literature of other joint replacements that have been in evolution and use for decades. Important variables for the function and longevity of such disc arthroplasty implants are clearly defined by the material properties of the components used for their production. The most frequently considered materials are cobalt-chrome alloys, titanium alloys, stainless steels, polyethylene, polyurethane and ceramics. In addition to implant materials, the interfaces of such materials must be considered. The bearing surfaces of an implant, in particular, are at risk of wear and failure. Overall, successful, long-term total disc arthroplasty requires a thorough understanding of biomaterials and how they can be used to achieve their desired goals.

Arthroplasty, Replacement↗

PubMedDate not supplied

Proposal of a modified, treatment-oriented classification of odontoid fractures.

BACKGROUND CONTEXT: The classification scheme of odontoid fractures described by Anderson and D'Alonzo is the one most commonly used. However, uncertainty exists in the distinction between Type II and "shallow" Type III fractures. Moreover, fractures at the base of the odontoid (Anderson and D'Alonzo Type II) include a spectrum of injury patterns. PURPOSE: To modify the Anderson and D'Alonzo classification of odontoid fractures based on current clinical treatment options. STUDY DESIGN: Proposal of a modified classification system for odontoid fractures. METHODS: A more precise distinction between Type II and III fractures based on the presence/absence of C1-C2 facet involvement is proposed. A modified classification of Type II fractures based on fracture line obliquity, displacement and comminution is then proposed, because these are factors deemed to influence management. To evaluate the reproducibility of this classification, 52 odontoid fractures were reviewed and classified by four attending spine surgeons and three spine fellows. RESULTS: There was substantial agreement (at least five of seven respondents) in 70% of cases. The overall kappa value for the modified classification system was 0.48, indicating moderate agreement, and there were no differences in kappa values between attending spine surgeons and fellows. CONCLUSIONS: The reproducibility of this system was demonstrated by the moderate agreement observed when applied to odontoid fractures at our institution. The proposed utility of this system is its ability to guide clinical decision making in the treatment of odontoid fractures. Prospective application of this modified classification system and suggested treatment options is now required.

Classification↗