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Jonathan N Grauer

Publications and source records attributed to Jonathan N Grauer.

30 records · Page 2Linked to original sources
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↗
PubMedDate not supplied

Animal models for spinal fusion.

Animal models for spinal fusion are essential for preclinical testing of new fusion methods and adjuncts. They allow for control of individual variables and quantification of outcome measures. Model characteristics are considered. Preclinical experiments to evaluate proof of concept, feasibility, and efficacy are generally studied in an orderly progression from smaller to larger animal models with an evolving cascade of evidence which has become known as the "burden of proof". Methods of fusion analysis include manual palpation, radiographs, computed tomography, histology, biomechanical testing, and molecular analysis. Models which have been developed in specific species are reviewed. This sets the stage for the interpretation of studies evaluating bone graft materials such as allograft, demineralized bone matrices, bone morphogenetic proteins, ceramics, and others with consideration of the variables affecting their success. As evidence accumulates, clinical trials and applications are defined.

Animals↗
PubMedDate not supplied

Effect of daily parathyroid hormone (1-34) on lumbar fusion in a rat model.

BACKGROUND CONTEXT: Despite numerous studies evaluating the anabolic effects of intermittent administration of parathyroid hormone (PTH) on bone, there are no published studies examining its effect on spinal fusion outcomes. PURPOSE: To determine the effect of daily injection of human recombinant PTH(1-34) on posterolateral lumbar fusions in a rat model. STUDY DESIGN: Prospective, case-controlled, preclinical animal study. OUTCOME MEASURES: Manual palpation and serum osteocalcin. METHODS: Single-level, intertransverse process spinal fusions were performed with iliac crest autograft in 56 Sprague-Dawley rats. Animals received daily injections of placebo or PTH(1-34). At 6 weeks, fusion masses were assessed by manual palpation. Serum osteocalcin levels were assessed in a subset of the animals. RESULTS: Manual palpation revealed the control group to have a fusion rate of 37% (10/27) and the PTH(1-34)-treated group to have a fusion rate of 52% (15/29). Mean serum osteocalcin levels were 59.8 and 88.6 ng/L for the control and PTH(1-34) groups, respectively. CONCLUSIONS: There was a trend towards greater fusion rate in the PTH(1-34) group as compared with the placebo group. Further, PTH(1-34) administration was associated with a significant increase in osteocalcin levels. Certainly, further investigations are warranted, as an injectable agent capable of increasing fusion rates would be of great clinical value.

Animals↗