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Biomedical subjects

Robert D Fraser

Publications and source records attributed to Robert D Fraser.

11 recordsLinked to original sources
PubMed2006

The International Society for the Study of the Lumbar Spine: research trends over time and publication rates.

STUDY DESIGN AND OBJECTIVES: A retrospective review was conducted to assess trends in research selected for podium presentation at ISSLS. SUMMARY OF BACKGROUND DATA: Abstracts of past papers presented to ISSLS provide quantified documentation of trends in research as well as insight into future directions. METHODS: A systematic review of abstracts of research presented was performed. Graphical plots in each category of research and aspects of study quality were used to identify any trends. Univariate and multivariate logistical regression analyses were used to identify factors related to eventual publication. RESULTS: A total of 43% of selected papers focused on the disc, representing the single largest area of research. There is a linear trend over time toward increased selection of basic science papers and decreased clinical papers. Experimental research design is becoming more frequently selected. In 1978, over 80% of papers were purely descriptive. By 2002, 42% of papers were descriptive, whereas 40% incorporated an experimental design. However, over the past decade, there has been a linear increase in the proportion of randomized controlled trials among clinical papers compared with basic science or biomechanical papers. A total of 54% of all abstracts presented recently went on to publication. Independent factors that were associated with significantly (P < 0.05) higher publication rates included use of blinded or independent observers (84.6%), experimental design (68.4%), basic science or biomechanical papers (62.3%), and statistically positive result (61.8%). CONCLUSION: Overall, the type of research selected for presentation at ISSLS has improved over the years in regards to greater use of experimental and randomized study design. The eventual publication rates compare favorably to other research societies. Factors related to publication have been identified and should be considered in future research.

Humans↗
PubMed2006

Magnetic resonance imaging 20 years after anterior lumbar interbody fusion.

STUDY DESIGN: A 20-year magnetic resonance imaging (MRI) and functional outcome follow-up study was performed on patients who had undergone anterior lumbar interbody fusion. OBJECTIVES: The objectives of the present study are to determine whether or not degeneration is related to adjacent level fusion and the clinical significance of this degeneration. SUMMARY OF BACKGROUND DATA: There are concerns that lumbar fusion leads to increase stress at the adjacent levels. However, the clinical significance of this remains unclear. METHODS: Thirty-nine patients who underwent lower lumbar anterior lumbar interbody fusion and who had normal preoperative discograms at the level adjacent level were evaluated with a minimum of a 20-year follow-up. MRI scans were performed and independently evaluated for any evidence of degeneration. Functional status was assessed using the Low Back Outcome Scale. RESULTS: Twenty-nine (74.3%) patients had some evidence of degeneration in their lumbar spine and advanced degeneration was identified in 12 (30.7%) patients. Nine (23.1%) patients had advanced degeneration isolated to the adjacent level and 7 (17.9%) patients had evidence of advanced degeneration with preservation at the level adjacent to the fusion. There was no association between function and radiographic degeneration. Only 3 patients required additional surgery as a result of adjacent level degeneration. CONCLUSION: The prevalence of degenerative changes is similar to other studies involving normal asymptomatic subjects. Furthermore, the majority of degenerative changes seen occurred over multiple levels or at levels not adjacent to the fusion, suggesting that changes seen may be more likely related to constitutional factors as opposed to the increased stresses arising from the original fusion.

Follow-Up Studies↗
PubMed2006

Supplementary stabilization with anterior lumbar intervertebral fusion--a radiologic review.

STUDY DESIGN: A radiologic assessment of the success of anterior lumbar interbody fusion (ALIF) using thin-section computerized tomography (CT) was performed. OBJECTIVE: To assess the effect of different types of posterior stabilization on the fusion rate of ALIF. SUMMARY OF BACKGROUND DATA: Thin-section CT has shown a higher rate of pseudarthrosis with ALIF than previously reported with standard radiologic methods. Cadaveric studies have shown that posterior stabilization would increase stiffness of the motion segment and is likely to enhance the rate of fusion with ALIF. To our knowledge, the results of thin-section CT of ALIF, with and without posterior stabilization, has not been reported previously. METHODS: Patients with discogenic back pain confirmed by diskography underwent ALIF surgery, either as a stand-alone procedure or with posterior stabilization, using translaminar, unilateral pedicle, or bilateral pedicle screws. The 4 cohorts were followed up prospectively, and thin-section CT was used to assess interbody fusion. RESULTS: The fusion rate for stand-alone ALIF was 51%, for patients with supplementary stabilization with translaminar screws 58%, with unilateral pedicle screws 89%, and with bilateral pedicle screws 88%. A significant difference in the fusion rate was found when ALIF was combined with pedicle screw stabilization (P < 0.01). CONCLUSION: The addition of pedicle screw fixation at ALIF produces a significant increase in the rate of interbody fusion.

Adult↗
PubMed2005

A randomized, double-blind, controlled trial: intradiscal electrothermal therapy versus placebo for the treatment of chronic discogenic low back pain.

STUDY DESIGN: A prospective, randomized, double-blind, placebo-controlled trial of intradiscal electrothermal therapy (IDET) for the treatment of chronic discogenic low back pain (CDLBP). OBJECTIVES: To test the safety and efficacy of IDET compared with a sham treatment (placebo). SUMMARY OF BACKGROUND DATA: In North America alone, more than 40,000 intradiscal catheters have been used to treat CDLBP. The evidence for efficacy of IDET is weak coming from retrospective and prospective cohort studies providing only Class II and Class III evidence. There is one study published with Class I evidence. This demonstrates statistically significant improvements following IDET; however, the clinical significance of these improvements is questionable. METHODS: Patients with CDLBP who failed to improve following conservative therapy were considered for this study. Inclusion criteria included the presence of one- or two-level symptomatic disc degeneration with posterior or posterolateral anular tears as determined by provocative computed tomography (CT) discography. Patients were excluded if there was greater than 50% loss of disc height or previous spinal surgery. Fifty-seven patients were randomized with a 2:1 ratio: 38 to IDET and 19 to sham procedure (placebo). In all cases, the IDET catheter was positioned to cover at least 75% of the annular tear as defined by the CT discography. An independent technician connected the catheter to the generator and then either delivered electrothermal energy (active group) or did not (sham group). Surgeon, patient, and independent outcome assessor were all blinded to the treatment. All patients followed a standard postprocedural rehabilitation program. Independent statistical analysis was performed. OUTCOME MEASURES: Low Back Outcome Score (LBOS), Oswestry Disability Index (ODI), Short Form 36 questionnaire (SF-36), Zung Depression Index (ZDI), and Modified Somatic Perceptions Questionnaire (MSPQ) were measured at baseline and 6 months. Successful outcome was defined as: no neurologic deficit, improvement in LBOS of greater then 7 points, and improvement in SF-36 subsets (physical function and bodily pain) of greater than 1 standard deviation. RESULTS: Baseline demographic data, initial LBOS, ODI, SF-36, ZDI, and MSPQ were similar for both groups. No neurologic deficits occurred. No subject in either arm showed improvement of greater than 7 points in LBOS or greater than 1 standard deviation in the specified domains of the SF-36. Mean ODI was 41.42 at baseline and 39.77 at 6 months for the IDET group, compared with 40.74 at baseline and 41.58 at 6 months for the placebo group. There was no significant change in ZDI or MSPQ scores for either group. CONCLUSIONS: The IDET procedure appeared safe with no permanent complications. No subject in either arm met criteria for successful outcome. Further detailed analyses showed no significant change in outcome measures in either group at 6 months. This study demonstrates no significant benefit from IDET over placebo.

Adult↗
PubMed2005

Effects of intervertebral disc infection on the developing ovine spine.

STUDY DESIGN: A prospective in vivo animal study. OBJECTIVES: To determine whether infection in the juvenile spine influences spinal development. SUMMARY OF BACKGROUND DATA: Discitis is thought to occur in children when blood-borne infection penetrates the highly vascular immature disc. The condition generally resolves without apparent complication, but little is known about the long-term effects on the growing spine. METHODS: Twenty-nine 6-week-old lambs underwent discography at multiple lumbar levels using radiographic contrast deliberately inoculated with Staphylococcus epidermidis. No antibiotics were given. Plain radiographs were taken at intervals up to 52 weeks after inoculation for morphometric analysis of the vertebral bodies and discs, and the lumbar spines were prepared for histology. RESULTS: Sixteen of 44 inoculated discs showed radiological evidence of discitis between 2 and 6 weeks after inoculation. Disc height and disc area were significantly reduced from 2 weeks, and did not recover during the study period. Vertebral body dimensions and overall lumbar spine length were not significantly affected. CONCLUSION: Infection of juvenile ovine discs impedes disc development but has no significant effect on vertebral body growth.

Animals↗
PubMed2003

Does intradiscal electrothermal therapy denervate and repair experimentally induced posterolateral annular tears in an animal model?

STUDY DESIGN: The effects of intradiscal electrothermal therapy (IDET) on intervertebral discs in sheep were studied experimentally. OBJECTIVES: Posterolateral annular lesions were experimentally induced and allowed to mature for 12 weeks in the intervertebral discs of sheep. IDET was performed in an attempt to denervate and repair the annular lesion. The histologic and immunohistochemical effects of IDET were studied. SUMMARY OF BACKGROUND DATA: IDET continues to be used as a minimally invasive treatment for chronic discogenic low back pain, with success rates reported in up to 70% of cases. The mechanism of action by which IDET exerts its effect is poorly understood. Proposed mechanisms include the contraction of collagen and the coagulation of annular nociceptors. An ovine model was used firstly to induce a posterolateral annular lesion, secondly to assess the innervation of such a lesion, and thirdly to assess the effect of IDET on this innervation. MATERIALS AND METHODS: Posterolateral annular incisions were made in 40 lumbar discs of 20 sheep. Twelve weeks were allowed for each annular lesion to mature. IDET was then performed in the disc with the posterolateral annular tear and in another control level. IDET was performed using a modified intradiscal catheter (Spine-CATH; Oratec Interventions, Menlo Park, CA). Temperatures were recorded in the nucleus (TN) and the posterior annulus (TPA). The spines were harvested at predetermined intervals up to 18 months. Histologic sections of the discs were graded for disc morphology to assess degeneration and immunohistochemical staining to assess potential denervation. RESULTS: Vascular granulation tissue consistent with a healing response was observed in the posterior annular tear of all incised discs from 12 weeks. Protein gene product 9.5 (PGP 9.5) positive nerve fibers were clearly identified in the adjacent periannular tissue and the outer few lamellae of the posterior annulus. During the IDET procedure, the mean maximum TPA was 63.6C and the mean maximum TN was 67.C.At sacrifice, the number of nerve fibers identified in the posterior annular tear was the same for those specimens that had undergone IDET and those that had not. From 6 weeks after IDET, there was evidence of thermal necrosisin the inner annulus and adjacent nucleus but sparing the periphery of the disc. CONCLUSIONS: Vascular granulation tissue and posterior annular neo-innervation was observed in the experimentally induced posterolateral annular lesion. IDET delivered at 90C in the sheep consistently heated the posterior annulus and the nucleus to a temperature normally associated with coagulation of nociceptors and collagen contraction. IDET did not denervate the posterior annular lesion. Thermal necrosis was observed within the inner annulus and adjacent nucleus from 6 weeks after IDET. The reported benefits from IDET appear to be related to factors other than denervation and repair.

Animals↗
PubMed2003

Radiologic assessment of interbody fusion using carbon fiber cages.

STUDY DESIGN: A comparative study investigated the use of plain static radiographs, flexion-extension radiographs, and thin-section helical computed tomography (CT) scanning in the assessment of anterior lumbar interbody fusion using carbon fiber cages. OBJECTIVE: To compare plain static radiographs, flexion-extension radiographs, and thin-section helical computed tomography scans in the assessment of lumbar interbody fusion using carbon fiber cages. SUMMARY OF BACKGROUND DATA: Lumbar interbody fusion has become a popular procedure for the treatment of discogenic back pain. However, there currently is no universally accepted radiologic assessment tool for determining fusion, and the definitive criteria for diagnosing a successful interbody fusion in the lumbar spine remains controversial. METHODS: Plain static radiographs, flexion-extension radiographs, and helical computed tomography scans were performed on 32 patients (49 levels) 5 years after anterior lumbar interbody fusion using carbon fiber cages and autologous bone. A radiologist assessed fusion using the Hutter method to detect movement, whereas a spinal surgeon measured movement in degrees using the Simmons method. Helical computed tomography scans were assessed for the presence of bridging trabecular bone. RESULTS: The fusion rate was 86% on plain radiographs and 84% with the Hutter method. The fusion rate was 74% with the 2 degrees cutoff, and 96% with the 5 degrees cutoff prescribed by the Food and Drug Administration. Fusion on helical computed tomography scans was observed in 65% of the patients. CONCLUSIONS: In the radiologic assessment of interbody fusion using carbon fiber cages, the use of plain radiographs and flexion-extension radiographs produced much higher fusion rates than assessment with thin-section helical computed tomography scans. The thin-section helical computed tomography studies clearly demonstrated the radiographic presence or absence of bridging bone, a property that was not seen with plain static radiographs or flexion-extension radiographs.

Adult↗
PubMed2002

The biologic response to particles from a lumbar disc prosthesis.

STUDY DESIGN: Particles of a proprietary polyolefin rubber compound used in a lumbar disc prosthesis were generated in vitro and tested for biocompatibility in two animal models. OBJECTIVE To characterize any tissue response to polyolefin rubber particles. SUMMARY OF BACKGROUND DATA: Intervertebral disc prostheses are emerging as alternatives to fusion techniques for the treatment of symptomatic disc degeneration. The biocompatibility of all novel components used in the construction of these devices must be verified before they can be considered for general use. METHODS: Laboratory-generated polyolefin rubber particles were either injected into dorsal subcutaneous air pouches of 30 rats or placed directly onto the lumbosacral dura and nerve roots of 9 sheep. Histologic sections of tissues from, and remote from, the site of implantation were examined for evidence of inflammation and wound-healing responses. RESULTS: Polyolefin rubber particle debris induced a tissue response that was consistent with a normal foreign body reaction to large particles. The response was not significantly greater than that seen with similar size particles of ultrahigh molecular weight polyethylene. There was no evidence of particle migration from the site of implantation, and there was no evidence of local or systemic toxic effects. CONCLUSION: Polyolefin rubber particles induce only localized tissue response that is consistent with a normal foreign body reaction to large nontoxic particles.

Animals↗
PubMed2002

Total disc replacement arthroplasty using the AcroFlex lumbar disc: a non-human primate model.

Using a non-human primate model, the current study was undertaken to investigate the efficacy of the AcroFlex lumbar disc as an intervertebral disc prosthesis, based on biomechanical, histopathologic and histomorphometric analyses. A total of 20 mature male baboons (Papio cynocephalus, mean weight 30 kg) were randomized into two equal groups based on post-operative time periods of 6 (n=10) and 12 months (n=10). Each animal underwent an anterior transperitoneal surgical approach to the lumbar spine, with intervertebral reconstructions performed at L3-L4 and L5-L6 using the following techniques: (1) tricortical iliac autograft and (2) AcroFlex lumbar disc. The two treatments were equally randomized between the non-contiguous operative lumbar levels. Post-mortem analysis included histopathologic assessment of the systemic reticuloendothelial tissues, multi-directional flexibility testing of the operative functional spinal units and quantitative histological analysis of trabecular bone coverage at the prosthesis endplates. Data were statistically compared using a one-way ANOVA with the Student-Newman-Keuls test. All animals survived the operative procedure and post-operative interval without significant intra- or peri-operative complications. Histopathologic analysis of the paraffin-embedded systemic reticuloendothelial tissues indicated no significant pathologic changes at the 6- or 12-month intervals. Plain film radiographic analysis showed no lucencies or loosening of any prosthetic vertebral endplate. Biomechanical testing of the 6-month autograft, reconstructions with AcroFlex lumbar disc and non-operative control (n=10) intact motion segments indicated no significant differences in peak range of motion (ROM) in axial compression. However, axial rotation produced significantly lower ROM for the autograft treatment compared to the intact and AcroFlex groups (P<0.05). The most significant differences in peak ROM were noted between all treatment groups under flexion/extension and lateral bending loading modalities (P<0.05). By 12 months, the intact condition indicated significantly more motion in all bending modes compared to the AcroFlex and autograft treatments, which were not statistically different from each other (P>0.05). Gross histopathologic analysis of the AcroFlex disc prosthesis demonstrated excellent ingrowth at the level of the implant-bone interface, without evidence of fibrous tissue or synovium. BioQuant histomorphometric analysis at the metal-bone interface (bone contact area/total endplate area) indicated the mean ingrowth was 54.59+/-13.24% at 6 months and 56.79+/-5.85% at 12 months. Radiographic analysis showed no lucencies or loosening of the AcroFlex vertebral endplate. Based on multi-directional flexibility testing, motion was preserved in axial rotation, but significantly diminished in the other bending modalities, particularly at the 12-month interval. This effect may be secondary to the limited surface area of device-vertebral endplate contact. Histomorphometric analysis of porous ingrowth coverage at the vertebral bone-metal interface was more favorable for total disc arthroplasty compared to historical reports of cementless femoral components. This project serves as the first comprehensive in vivo investigation into the AcroFlex disc prosthesis, and establishes an excellent research model in the evaluation of total disc replacement arthroplasty.

Animals↗
PubMedDate not supplied

AcroFlex design and results.

The AcroFlex prosthesis is unique when compared to other current devices, as it has an elastomeric core sandwiched between two titanium endplates. The purpose of this design was to optimize shock absorption qualities. This paper reviews the design of the AcroFlex Disc and relevant design and outcomes of two pilot studies carried out on 28 patients using the AcroFlex prosthesis. Although clinical outcomes of the pilot studies were successful, the pivotal randomized trial has not been carried out due to detection of mechanical failure of the elastomer on thin cut CT scans. The implications of this for the AcroFlex and other arthroplasties are discussed.

Adult↗