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Biomedical subjects

D Greg Anderson

Publications and source records attributed to D Greg Anderson.

48 records · Page 3Linked to original sources
PubMed2003

Cervical sprains, disc herniations, minor fractures, and other cervical injuries in the athlete.

In today's health-conscious society, more people are participating in athletic endeavors. As participation increases, so does the incidence of cervical injuries. Fortunately, most of the cervical injuries seen in sports are minor and can be treated successfully with minimal morbidity. It is important, however, to accurately assess the patient sustaining a cervical injury to rule out the presence of a more severe cervical injury. When practitioners understand the pathophysiology and treatment of common injuries, including sprains, strains, contusions, disc herniations, and simple fractures, most athletes can be returned to full function.

Athletic Injuries↗
PubMed2002

Recombinant human osteogenic protein-1 (bone morphogenetic protein-7) as an osteoinductive agent in spinal fusion.

STUDY DESIGN: The data related to spinal applications of osteogenic protein-1 presented at national meetings or published in peer-reviewed literature are reviewed. OBJECTIVES: To review the available data related to the use of osteogenic protein-1 for spinal arthrodesis. REVIEW OF BACKGROUND DATA: Osteogenic protein-1 (bone morphogenetic protein-7) is a member of the bone morphogenetic protein family and has shown strong osteoinductivity in vivo. METHODS: The background related to osteogenic protein-1 for spinal applications and the known studies presented at national meetings or published in the peer-reviewed literature are reviewed. RESULTS: Osteogenic protein-1 is able to achieve solid bony fusion of the spine in both the anterior and posterolateral environments in animal studies and has a good safety profile. Early human trials appear to be promising. CONCLUSIONS: Animal studies support the ability of osteogenic protein-1 to enhance or replace autograft for spinal arthrodesis in both the posterolateral and interbody environment. Human trials ultimately will provide data to clarify the optimal role of osteogenic protein-1 in human spinal surgery.

Animals↗
PubMed2002

Pedicle screws with high electrical resistance: a potential source of error with stimulus-evoked EMG.

STUDY DESIGN: Clinically relevant aspects of pedicle screws were subjected to electrical resistance testing. OBJECTIVES: To catalog commonly used pedicle screws in terms of electrical resistance, and to determine whether polyaxial-type pedicle screws have the potential to create a high-resistance circuit during stimulus-evoked electromyographic testing. SUMMARY OF BACKGROUND DATA: Although stimulus-evoked electromyography is commonly used to confirm the accuracy of pedicle screw placement, no studies have documented the electrical resistance of commonly used pedicle screws. METHODS: Resistance measurements were obtained from eight pedicle screw varieties (5 screws of each type) across the screw shank and between the shank and regions of the screw that would be clinically accessible to stimulus-evoked electromyographic testing with a screw implanted in a pedicle. To determine measurement variability, resistance was measured three times at each site and with the crown of the polyaxial-type screw in three random positions. RESULTS: Resistance across the screw shank ranged from 0 to 36.4 ohms, whereas resistance across the length of the monoaxial-type screws ranged from 0.1 to 31.8 ohms. Resistance between the hexagonal port and shank of polyaxial-type screws ranged from 0 to 25 ohms. In contrast, resistance between the mobile crown and shank of polyaxial-type screws varied widely, ranging from 0.1 ohms to an open circuit (no electrical conduction). Polyaxial-type screws demonstrated an open circuit in 28 of 75 measurements (37%) and a high-resistance circuit (exceeding 1000 ohms) in 5 of 75 measurements (7%). CONCLUSIONS: Polyaxial-type pedicle screws have the potential for high electrical resistance between the mobile crown and shank, and therefore may fail to demonstrate an electromyographic response during stimulus-evoked electromyographic testing in the setting of a pedicle breech. To avoid false-negative stimulus-evoked electromyographic testing, the cathode stimulator probe should be applied to the hexagonal port or directly to the screw shank, and not to the mobile crown.

Alloys↗
PubMed2002

Comparative gene expression profiling of normal and degenerative discs: analysis of a rabbit annular laceration model.

STUDY DESIGN: A rabbit annular laceration model was used to investigate intervertebral disc gene expression in normal and lacerated discs. OBJECTIVES: To determine and compare the pattern of expression of potentially important genes in normal and lacerated discs and to determine if the changes in gene expression were similar to human degenerative discs. SUMMARY OF BACKGROUND DATA: Little is known regarding gene expression in normal or degenerating disc tissue. METHODS: Eighteen rabbits were subjected to annular laceration of the L1-L2 and L2-L3 discs while two rabbits served as sham controls. Control and lacerated discs were harvested 1 week, 3 weeks, and 6 weeks following surgery and subjected to histologic examination and gene expression analysis using the reverse transcription-polymerase chain reaction (RT-PCR). The genes studied included collagen Type I (Col I), collagen Type II (Col II), decorin, fibronectin (FN), interleukin-1a (IL-1alpha), bone morphogenetic protein 2 (BMP-2), Fas, matrix metalloproteinase 1 (MMP-1), matrix metalloproteinase 9 (MMP-9), matrix metalloproteinase 13 (MMP-13), and tumor necrosis factor (TNF). Expression levels of each gene were normalized to that of glyceraldehyde-3-phosphate dehydrogenase (GADPH), a constitutively expressed gene. RESULTS: Histology confirmed progressive degeneration of the discs over the 6-week study period. Different patterns of gene expression were observed in control and lesioned discs. Annular laceration caused a marked upregulation (two- to eightfold) of the expression of Col I, Col II, FN, MMP-1, MMP-9, MMP-13, and Fas genes, whereas that of BMP-2, IL-1alpha, and TNF genes was unaffected. Expression of the decorin gene was downregulated approximately sixfold after annular laceration. CONCLUSION: Annular laceration in this animal model resulted in marked changes in gene expression. Upregulation of gene expression was observed for some molecules found at high concentration in human degenerated discs, suggesting similarities to human disc degeneration at the molecular level. This supports the need for further study of the genes found to be activated by annular laceration.

Animals↗
PubMed2002

Bone grafting, implants, and plating options for anterior cervical fusions.

The basic principles of cervical spine surgery continue to include adequate decompression, provision of a structurally competent, biologically functional bone graft, and creation of a stable construct to allow for solid fusion. In recent years, the options to achieve these goals have expanded significantly. Bone banking and bone graft substitutes yield increasingly viable alternatives to autogenous bone graft. New prosthetic implants and cages are currently under investigation. The science of bone growth factors seems to be promising and is expected to revolutionize the approach to spinal arthrodesis. Various plating systems are available to provide internal stability to cervical spine constructs. It is important to understand the biomechanics of plating systems so that the optimal system may be used in a given situation. Long constructs place significant loads on SGs and anterior plates. It is important to consider the use of additional fixation, such as posterior segmental fixation in long constructs, which may be prone to failure using only anterior plate fixation. Anterior cervical plating for single-level ACDF remains controversial, whereas plating has been shown to improve the results of multilevel ACDF. Plating may provide a useful salvage option for a cervical nonunion, especially if deformity or neurologic compression dictates an anterior approach. Hardware failures may occur with anterior cervical plating, but most remain asymptomatic and do not require operative intervention.

Bone Plates↗
PubMed2002

Advances in surgical management of lumbar degenerative disease.

The past several years have seen many advances in spine technology. Some of these advances have improved the quality of life of patients suffering from disabling low back pain from degenerative disk disease. Traditional fusion procedures are trending toward less invasive approaches with less iatrogenic soft-tissue morbidity. The diversity of bone graft substitutes is increasing with the potential for significant improvements in fusion success with the future introduction of several well tested bone morphogenic proteins to the spinal market. Biologic solutions to modify the natural history of disk degeneration are being investigated. Recently, electrothermal modulation of the posterior annulus fibrosis has been published as a semi-invasive technique to relieve low back pain generated by fissures in the outer annulus and ingrowing nociceptors (intradiskal electrothermal therapy, and intradiskal electrothermal annuloplasty). Initial results are promising, however, prospective randomized studies comparing this technique with conservative therapy are still lacking. The same is true for artificial nucleus pulposus replacement using hydrogel cushions implanted in the intervertebral space after removal of the nucleus pulposus posterior or through an anterior approach. Intervertebral disk prostheses are presently being studied in small prospective patient cohorts. As with all new developments, careful prospective, long-term trials are needed to fully define the role of these technologies in the management of symptomatic lumbar degenerative disk disease.

Biomechanical Phenomena↗
PubMedDate not supplied

Analysis of patient variables affecting neurologic outcome after traumatic cervical facet dislocation.

BACKGROUND CONTEXT: Traumatic cervical facet dislocation accounts for a disproportionate rate of neurologic disability. The relative importance of patient and management variables, including the timing of spinal reduction, in ultimate neurologic outcome has not been well defined. PURPOSE: To analyze data from a cohort of patients sustaining traumatic cervical facet dislocation to determine the relative importance of several patient and management variables in neurologic recovery after injury. STUDY DESIGN/SETTING: A retrospective study was conducted at a major referral center for spinal-cord-injured patients. PATIENT SAMPLE: Forty-five patients sustaining traumatic cervical facet dislocation. OUTCOME MEASURES: Using improvement in American Spinal Injury Association (ASIA) motor score as the primary outcome measure, patient data were used to construct a statistical model allowing the analysis of several clinically relevant variables. METHODS: The records of patients sustaining a traumatic cervical facet dislocation over a 5-year period were reviewed. Clinical data were collected for all patients with adequate follow-up. The data were used to construct a statistical model designed to analyze the contribution of the variables age, gender, time to reduction of the spine and initial motor score to neurologic improvement (the outcome measure). In addition, the effect of variable interaction was studied. RESULTS: Most patients demonstrated neurologic improvement over the course of follow-up after cervical facet dislocation. For this data set, the variables age and initial motor score were significantly associated with neurologic improvement. However, time to reduction of the spine did not demonstrate a significant independent relationship to neurologic outcome. No significant interaction was found between patient age or gender and the time to reduction with regard to predicting neurologic recovery. CONCLUSION: The present study uses a statistical model to determine the relative importance of clinically relevant variables for a population of patients after traumatic cervical facet dislocation. This model confirms the clinical impression that younger patients with lesser degrees of neurologic injury tend to achieve the best neurologic recovery after a traumatic facet dislocation. Although a strong benefit from earlier spinal column reduction did not emerge from the present data set, additional study is needed to define those patients who would benefit from immediate reduction of the spinal column.

Adult↗
PubMedDate not supplied

Molecular basis of intervertebral disc degeneration.

This review will acquaint the reader with normal development, structure, and function of the intervertebral disc. The disc is composed of the vertebral endplate, nucleus pulposus, and annulus fibrosus. These three functional components all serve important purposes for health and function of the disc. Nutrition and biomechanics are also discussed. The molecular basis of disc degeneration is reviewed so that biologic approaches to the reversal and or treatment of disc degeneration may be better understood.

Biomechanical Phenomena↗
PubMedDate not supplied

Molecular pathogenic factors in symptomatic disc degeneration.

BACKGROUND CONTEXT: Although symptomatic disc degeneration is thought to be the leading cause of chronic low back pain, no available biologic therapy is yet available to treat this highly prevalent condition. PURPOSE: In this article, the cellular, biomechanical and molecular alterations that occur during disc degeneration are reviewed to provide a better understanding of this pathologic process. STUDY DESIGN: The cellular and molecular aspects of disc degeneration are reviewed. METHODS: The available studies detailing the molecular and cellular changes during disc degeneration are reviewed in an effort to provide a basis for understanding the biologic strategies for disc repair. RESULTS: Disc degeneration begins early in life and involves a cascade of changes at the cellular and molecular level that results in degradation of the extracellular matrix of the disc, leading to biomechanical failure of this complex structure. CONCLUSION: With a thorough understanding of the cellular and molecular events causing degeneration of the intervertebral disc, rational strategies for disc repair can be understood and evaluated. It appears that biologic disc repair will be feasible in the future although challenges remain in this blossoming field.

Adult↗
PubMedDate not supplied

Cell-based therapy for disc repair.

BACKGROUND CONTEXT: One of the most promising therapies for symptomatic disc degeneration involves the implantation of therapeutic cells into the degenerative disc. PURPOSE: In this article, the rationale and approaches for cell-based tissue engineering of the intervertebral disc are discussed. STUDY DESIGN: The scientific literature related to cell-based tissue engineering of the intervertebral disc is reviewed. METHODS: A variety of cell types have been used in various research models to affect matrix repair of the intervertebral disc. The use of cellular scaffolds and growth factors or genes also appears promising for achieving meaningful tissue repair of the intervertebral disc. RESULTS: Disc tissue engineering is a promising approach for achieving repair of the intervertebral disc. Using cell-based approaches, various research models suggest that improvements in the complex matrix of the disc may be achieved. CONCLUSION: A cell-based approach to repair of the intervertebral disc appears promising. More research is needed to define the optimal cell type, cellular scaffold and mixture of growth factors that may allow meaningful repair of the human symptomatic degenerative disc.

Animals↗
PubMedDate not supplied

Management of postprocedural discitis.

BACKGROUND CONTEXT: Fortunately, the incidence of postprocedural discitis is relatively uncommon. The paucity of physical examination findings behooves the spine care practitioner to have a high index of suspicion in any patient presenting with increasing back pain after an invasive spinal procedure. The diagnosis can often be established in a timely fashion based on the history, physical examination, laboratory studies (erythrocyte sedimentation rate, C-reactive protein and blood cultures) and imaging studies (plain radiographs, magnetic resonance imaging, computed tomography and radionuclide scanning). PURPOSE: To review the English literature on the subject of postprocedural discitis. The incidence, pathophysiology, laboratory markers and imaging findings are discussed. Recommendations on treatment strategies are presented along with long-term clinical outcomes of this postprocedure complication. METHODS: A contemporary English literature search of MEDLINE and PubMed on the topic of postoperative discitis was performed. RESULTS: The incidence of postprocedural discitis is approximately 0.2%. The most common etiologic agent is Staphylococcus aureus. The C-reactive protein is the most sensitive clinical laboratory marker to assess the presence of infection and effectiveness of treatment response. Magnetic resonance imaging is the imaging modality of choice in the diagnosis of spinal infection. The majority of patients are managed adequately with organism-specific antibiotics and spinal immobilization with good long-term outcomes. Operative intervention (open biopsy followed by antibiotic treatment and spinal immobilization or debridement and reconstruction) in patients who fail to respond to nonoperative treatment or in the presence of neurologic worsening has been demonstrated. CONCLUSION: Postprocedural discitis is a rare complication after any invasive spinal procedure. It is imperative for the treating surgeon to maintain a high index of suspicion. Appropriate laboratory and imaging studies are invaluable in establishing a timely diagnosis. In the majority of patients, antibiotic treatment along with spinal immobilization has been shown to produce good long-term outcomes. Operative intervention is rarely necessary in patients failing conservative treatment.

Anti-Bacterial Agents↗