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Biomedical subjects

James T Robertson

Publications and source records attributed to James T Robertson.

10 recordsLinked to original sources
PubMed2005

Matrix remodeling expression in anulus cells subjected to increased compressive load.

STUDY DESIGN: Mechanobiology study of gene expression changes as a result of compressive overload of anular fibrochondrocytes. OBJECTIVE: To test hypotheses regarding phenotype shift in genes coding for representative extracellular matrix (ECM) proteins and matrix modulators. SUMMARY OF THE BACKGROUND DATA: In degenerative disc disease, the transfer of compressive load through the disc shifts largely from the nucleus onto the anulus. In vivo models simulating this condition have shown derangement of the collagenous ultrastructure in the anulus. In vitro models of cultured anulus cells subjected to static compressive stress generally suggest a down-regulation of synthesis. This study evaluated the expression of specific isomers of genes responsible for mechanical viability and metabolism of the disc under cyclic compressive loads. METHODS: Fibrochondrocytes were digested from the anuli of 3, 2-week-old pigs, embedded in 1.5% alginate gel, and hydrostatically compressed at 0.5 Hz for 3 hours to amplitudes of 10 and 30 atm. These levels represented nominal load transfer through the healthy disc and high load transfer through the degenerative disc. Ribonucleic acid was isolated, reverse transcribed, and evaluated by real-time polymerase chain reaction for expression of type I (C-I) and type II (C-II) collagen, aggrecan, the matrix metalloproteinase (MMP-1), and the transforming growth factor beta (TGFbeta-1). Results were expressed at percentages of uncompressed controls. RESULTS: The lower pressure of 10 atm resulted in up-regulation of all ECM protein genes. C-I and C-II both averaged 141%, and aggrecan 121% of controls (P < 0.05). MMP-1 and TGFbeta-1 were essentially unchanged. With the pressure increased to 30 atm, C-II remained approximately at the level expressed under lower pressure, but C-I was reduced to 42% of controls (P < 0.05), indicating a phenotype shift. MMP-1 and TGFbeta-1 also were down-regulated to 71% and 54% of controls, respectively (P < 0.05). CONCLUSIONS: The up-regulation of the ECM genes with nominal pressure highlights the mechanobiological importance of common activity in fibrocartilage homeostasis. Differential regulation of the 2 primary collagen types with high pressure indicates a capacity of the anulus to remodel according to pathomechanical conditions.

Aggrecans↗
PubMed2005

Assessment of adjacent-segment disease in patients treated with cervical fusion or arthroplasty: a prospective 2-year study.

OBJECT: The authors compared the incidence of radiologically documented changes and symptomatic adjacent-level cervical disc disease after single-level discectomy and subsequent cervical fusion or arthroplasty in two independent prospective clinical studies. METHODS: The patients were treated with the Affinity Anterior Cervical Cage System or the Bryan Artificial Cervical Disc. In each study the patients were required to undergo serial cervical radiography preoperatively and 24 months postoperatively, as well as serial clinical evaluations including documentation of adverse events, neurological status, and results of the 36-item Short Form Health Survey. All serial radiographs were reviewed prior to evaluating the clinical symptoms for development of increasing or new adjacent degenerative disc disease (DDD). Subsequently, the clinical data were analyzed. For various reasons of exclusion, the cases analyzed in the Bryan disc-treated cohort consisted of 74 patients and in the Affinity system-treated cohort there were 158 patients. New anterior osteophyte formation or enlargement, increased narrowing of an interspace, new DDD, and calcification of the anterior longitudinal ligament were the radiological findings indicative of adjacent-level disease. Fusion was associated with a significant increase in x-ray film-based changes of adjacent-disc disease (p = 0.009, odds ratio [OR] 2.44). In the cage fusion series, the incidence of symptomatic adjacent-level DDD was statistically greater than that in the group treated with the artificial disc (p = 0.018), and the patients required a statistically greater number of medical treatments related to episodic symptoms of neck, shoulder, and arm pain attributed to new disc disease (p = 0.001, OR 35.8). CONCLUSIONS: In comparing these prospective studies the authors demonstrated that maintaining motion rather than fusion will prevent symptomatic adjacent-disc disease and will decrease adjacent-level radiological indicators of disease at a 24-month postoperative interval.

Adult↗
PubMed2004

Long-term outcome after implantation of the Prestige I disc in an end-stage indication: 4-year results from a pilot study.

OBJECT: The long-term function of an artificial cervical disc device is critical to its clinical success. The Prestige I Cervical Disc System has been used clinically since June 1998, and long-term results can now begin to be assessed. The authors conducted clinical and radiographic examinations at 3 and 4 years postoperatively to evaluate the longterm performance of the Prestige I device. METHODS: A pilot trial was initiated in which the Prestige I disc was implanted in a cohort of patients with end-stage disease, who often had a history of multiple previous fusion procedures. All patients were followed according to a standardized clinical and radiographic protocol until 2 years postoperatively. Outcome measures included the Short Form-36 (SF-36) and Neck Disability Index (NDI) questionnaires, neurological status, and radiographic status. To evaluate the long-term function of the device, Ethics Committee approval was obtained to assess the patients at 3 and 4 years postoperatively. All patients were contacted, and after signing an additional informed consent document, were reevaluated according to the standardized protocol. Of the 17 patients in the original cohort, 13 were evaluated at 3 years and 14 were evaluated at 4 years postoperatively. Clinical outcome measures including the NDI and SF-36 showed good improvement, especially when the endstage nature of the disease is considered. Radiographic analysis showed that the Prestige I disc maintained motion at the treated segment at 3 and 4 years postoperatively. CONCLUSIONS: In this report the authors demonstrate the clinical viability of the Prestige I cervical disc system at long-term postoperative intervals, even in the more severe biomechanical environment of end-stage disease.

Adult↗
PubMed2004

Effect of laser shock peening on fatigue life and surface characteristics of stainless steel cortical bone screws.

OBJECTIVE: To investigate the effect of laser shock peening on the fatigue life and surface characteristics of 3.5-mm-diameter cortical bone screws. SAMPLE POPULATION: 32 stainless steel, 3.5-mm-diameter cortical bone screws. PROCEDURE: Screws were randomly assigned to an untreated control group or 2 power-density treatment groups, 6 gigawatts (GW)/cm2 and 8.5 GW/cm2, for laser shock peening. Number of cycles to failure and findings on scanning electron microscopy-assisted morphometric evaluation, including the mode of failure, surface debris, surface damage, and thread deformation, were compared between control and treated screws. RESULTS: The 6 GW/cm2 treated screws had a significant (11%) improvement in fatigue life, compared with untreated control screws. The 8.5 GW/cm2 treated screws had a significant (20%) decrease in fatigue life, compared with control screws. A mild but significant increase in thread deformation was evident in all treated screws, compared with control screws. The 8.5 GW/cm2 treated screws had significantly more surface irregularities (elevations and pits), compared with control or 6 GW/cm2 treated screws. CONCLUSION AND CLINICAL RELEVANCE: A modest positive increase in fatigue strength was produced by this design of laser shock peening on the midshaft of cortical bone screws. High laser shock peening power densities were detrimental, decreasing screw fatigue strength probably resulting from structural damage. Greater fatigue life of cortical bone screws can be generated with laser shock peening and could reduce screw breakage as a cause of implant failure; however, future studies will be necessary to address biocompatibility, alternative cleaning techniques, alterations in screw strength and pullout characteristics, and effects on susceptibility to corrosion.

Analysis of Variance↗
PubMed2003

Prevention of cerebrospinal fistulae and reduction of epidural scar with new surgical hemostat device in a porcine laminectomy model.

STUDY DESIGN: In a porcine laminectomy model, a standard dural/arachnoid incision was made and tested for cerebrospinal fluid leak after material application. Sites were graded for scar formation and healing response at 3 weeks. OBJECTIVE: This study compares effectiveness of CoStasis, Tissucol, and suture for prevention of cerebrospinal fluid leaks and epidural scar formation after spinal dural incisions. SUMMARY OF BACKGROUND DATA: Cerebrospinal fluid leaks following cranial and spinal surgery are potentially serious complications. Epidural scar formation is exacerbated by improper control of hemostasis. A hemostatic agent with dural sealant properties may be advantageous. METHODS: Total laminectomy was performed at three levels in seven pigs. At each level, a uniform 1.5 cm incision was made in the dura and arachnoid. A single suture was placed to approximate the edges and sites were treated with one of three methods: CoStasis, Tissucol, or no treatment. At sacrifice, 3 weeks later, epidural scar was graded, pressure testing of some sites was done, and tissue for histologic sections was harvested. RESULTS: CoStasis and Tissucol produced immediate dural sealing when the valsalva maneuver was applied. One suture-only site leaked. At sacrifice, all sites were sealed. CoStasis and Tissucol had less scar formation than control sites. Pressure testing results were similar at CoStasis and Tissucol sites. CONCLUSION: CoStasis and Tissucol have comparable effectiveness in sealing CSF leaks immediately and at 3 weeks after complete laminectomy. CoStasis demonstrated comparable performance to Tissucol with less epidural scar formation than primary suture alone.

Animals↗
PubMed2002

The new Frenchay artificial cervical joint: results from a two-year pilot study.

STUDY DESIGN: A clinical prospective observational cohort study of 15 patients undergoing cervical intervertebral disc replacement. OBJECTIVE: To assess the safety, clinical stability, and capacity of a newly designed cervical intervertebral disc replacement for preserving motion in the cervical spine of patients with degenerative disc disease. SUMMARY OF BACKGROUND DATA: Anterior cervical discectomy and interbody fusion results in loss of motion segments and there is evidence of accelerated degenerative changes occurring at adjacent levels. Intervertebral disc replacement may be a valid alternative to fusion. There is a need for cervical disc replacement to be evaluated in prospective studies before it can be adopted as an acceptable surgical technique. METHODS: The study enrolled 15 patients with cervical radiculopathy or myelopathy and radiologically confirmed cervical disc herniation or posterior vertebral body osteophytes. Eligibility for the study required that patients have either a previous adjacent-level surgical or congenital spinal fusion or radiologic evidence of adjacent-level degenerative disc disease. After decompressive surgery via an anterior approach, all 15 patients received the artificial joint. Follow-up visits were at set intervals and included clinical examination, radiologic assessment, and evaluation by patient-completed questionnaires. RESULTS: In all cases, the artificial joint maintained motion at the operative levels while reestablishing intervertebral height. The procedure was considered safe for experienced spine surgeons to perform, and the device was stable, with no dislocation of components or backing out of screws. Two screws broke, but without any consequence. Improvements in assessment scores were noted. CONCLUSIONS: Cervical intervertebral motion can be maintained with the new device, which is clinically stable. Meticulous attention must be paid to the surgical technique to maximize the chances of a good result. The pilot study was successful, although it has yet to be determined what conditions will benefit most from this technology.

Arthroplasty, Replacement↗
PubMed2002

Persistent low back pain and sciatica in the United States: treatment outcomes.

Patients with persistent low back pain (LBP) appear to be different in several important ways from patients who have traditionally been classified as patients with acute or chronic LBP, and data on the effectiveness of the treatments prescribed for them are lacking. The aim of the current study was to evaluate the short- and long-term effectiveness of the treatments currently prescribed for these patients. The data reported in this article were gathered as part of a multicenter, prospective, cross-sectional study of patients who were treated for persistent LBP by neurologic and orthopedic surgeons who are recognized specialists in spinal disorders. At enrollment, patients completed a baseline evaluation, and their physicians recorded relevant clinical and treatment data on standardized study forms. At 3, 6, 12, and 24 months after treatment, patients completed follow-up evaluations. Patients were divided into five treatment groups, and effectiveness was evaluated separately for each group using five patient-reported measures of outcome: pain severity, functional disability, psychologic distress, physical symptoms, and health care use. The data revealed that at the 2-year follow-up, the typical patient of the no-treatment group had improved slightly in terms of pain severity and health care use, but had experienced little or no improvement in functional disability, physical symptoms, and psychologic distress. The average patient in the conservative care group reported small improvements in pain severity, functional disability, physical symptoms, and health care use, with no change in psychologic distress. These small improvements occurred within the first 3 months after enrollment, with essentially no change thereafter. The average patient in the immediate surgical care group showed substantial improvement on all of the outcome measures. The observed improvements were evident shortly after treatment and were maintained for the duration of the study. Patients in the delayed surgical care group had outcomes that were less dramatic than those observed in the immediate surgery care group, but greater than those observed in the conservative care group. The patients who were treated surgically by physicians outside the study, outside surgical care group, did not improve over time. Patients with persistent LBP who received no treatment showed no spontaneous recovery. Conservative care treatments prescribed by surgeons who specialize in spinal disorders, did not appear to be any more effective than no treatment. The outcome of surgery for persistent LBP varied from dramatic for one subgroup of surgical patients, to poor for another subgroup of patients. Patients who were selected immediately for surgical treatment improved substantially. Those treated surgically later by study physicians or by physicians not associated with the study fared less well.

Adult↗
PubMed2002

The Brain Tumor Cooperative Group NIH Trial 87-01: a randomized comparison of surgery, external radiotherapy, and carmustine versus surgery, interstitial radiotherapy boost, external radiation therapy, and carmustine.

OBJECTIVE: The objective of the Brain Tumor Cooperative Group NIH Trial 87-01 trial was to investigate the effect of additional implanted radiation therapy in newly diagnosed patients with pathologically confirmed malignant gliomas. METHODS: The study involved a randomized comparison of surgery, external beam radiotherapy, and carmustine (BCNU) versus surgery, external beam therapy, interstitial radiotherapy boost, and BCNU in newly diagnosed malignant gliomas. (125)I was chosen as best suited for this effort because it allowed preimplantation planning and postimplantation quality assurance review. Two hundred ninety-nine patients met the eligibility criteria and were randomized into the two arms of the study between December 1987 and April 1994. Follow-up continued for an additional 3 years. Twenty-nine patients were identified as having committed protocol violations and were excluded, resulting in 270 subjects in the Valid Study Group. One hundred thirty-seven patients received external beam radiation and BCNU, and 133 underwent the (125)I implantation plus external beam radiation and BCNU therapy. RESULTS: The overall median survival for the Valid Study Group was 64.3 weeks. The median survival for patients receiving additional therapy of (125)I was 68.1 weeks, and median survival for those receiving only external beam radiation and BCNU was 58.8 weeks. The cumulative proportion surviving between the two treatment groups was not statistically significantly different (log-rank test, P = 0.101). As in other studies in the literature, age, Karnofsky score, and pathology were predictors of mortality. Additional analyses incorporating an adjustment for these prognostic variables, either in a stratified analysis or Cox proportional hazards model, did not result in statistically significant differences in the cumulative proportion of patients surviving between the two treatment groups. CONCLUSION: We conclude that there is no long-term survival advantage of increased radiation dose with (125)I seeds in newly diagnosed glioma patients.

Antineoplastic Agents, Alkylating↗
PubMedDate not supplied

Reduction of epidural fibrosis in lumbar surgery with Oxiplex adhesion barriers of carboxymethylcellulose and polyethylene oxide.

BACKGROUND CONTEXT: Postsurgical epidural adhesions and fibrosis after surgery for lumbar disc herniation are a consequence of normal wound healing. The presence of fibrosis renders reoperations risky, and in some patients fibrosis may lead to nerve root tethering. PURPOSE: One approach to minimizing the risk of developing epidural adhesions is to provide a barrier between the dural membrane and the healing connective tissues. The purpose of these studies was to evaluate such a barrier device. STUDY DESIGN/SETTING: In vivo investigation in an animal model at a university laboratory. PATIENT SAMPLE: Rabbit. OUTCOME MEASURES: Gross and histomorphic evaluation. METHODS: Barriers comprised of carboxymethylcellulose (CMC) and polyethylene oxide (PEO) (Oxiplex; FzioMed, Inc., San Luis Obispo, CA) were studied as devices to reduce epidural adhesion formation in rabbit laminotomy and laminectomy models. The barriers tested were either a gel alone (gel) or a gel covered with a film (gel/film combination). Two laminotomy or laminectomy sites (depending on the surgical method) were created in each rabbit at L4 and L6. One site was treated with a CMC/PEO gel, or CMC/PEO gel/film combination, and the other site served as a surgical control. Two surgical models that differed in the extent of adhesion formation at untreated injury sites and the method of injury generation were used. RESULTS: Model A, which did not incorporate dural abrasion, resulted in up to 40% adhesion-free laminectomy sites in controls. Model B, which did incorporate abrasion of the dural membrane, resulted in less than 10% adhesion-free laminotomy sites in controls. Compositions of CMC/PEO gels (2.5% to 10% PEO) and films (22.5% PEO) were tested in both models. Efficacy parameters included measuring the number of sites free of epidural fibrosis and reduction in the severity of fibrosis (adhesions). Both gels and gel/film combinations consistently reduced the frequency and the extent of epidural fibrosis in both models. Gels of CMC/PEO containing a higher content of PEO (10%) and a higher molecular weight of PEO (4.4 mD) were most effective in Model B and resulted in up to 84% laminotomy sites with minimal or no epidural fibrosis, whereas controls exhibited over 90% of the sites with epidural fibrosis. Histological evaluation of the surgical sites indicated that the reduction of epidural fibrosis was accompanied by normal bone healing. In addition, these experiments demonstrated that the gel/film combination provided no additional benefit to that obtained by the gel alone. CONCLUSIONS: Gels of CMC/PEO reduced epidural fibrosis and did not impair normal heal ing.

Animals↗