Search PubMed⌕ Search

Biomedical subjects

Frank M Phillips

Publications and source records attributed to Frank M Phillips.

34 records · Page 2Linked to original sources
PubMed2003

Biologic treatment for intervertebral disc degeneration: summary statement.

In past decades, the biomechanics of intervertebral disc degeneration have received much attention. More recent research efforts have focused on understanding the biology of the disc degenerative process. The ability to manipulate disc architecture and biology by direct application of growth factors or by gene therapy techniques may present an opportunity to halt or slow disc degeneration. Preliminary studies using these strategies have confirmed their ability to replenish essential disc matrix components that are known to decrease with disc degeneration.

Aging↗
PubMed2003

Potential use of Sox9 gene therapy for intervertebral degenerative disc disease.

STUDY DESIGN: A new recombinant adenoviral vector expressing Sox9, a chondrocyte-specific transcription factor, was tested in a chondroblastic cell line and primary human intervertebral disc cells in vitro. Direct infection of intervertebral disc cells then was assessed in a rabbit model. OBJECTIVES: To deliver a potentially therapeutic viral vector expressing Sox9 to degenerative human and rabbit intervertebral discs cells, and to assess the effect of Sox9 expression on Type 2 collagen production. SUMMARY OF THE BACKGROUND DATA: The concentration of competent Type 2 collagen, an essential constituent of the healthy nucleus pulposus, declines with intervertebral disc degeneration. Recent studies suggest that Sox9 upregulates Type 2 collagen production. Interventions that augment Type 2 collagen production by intervertebral disc cells may represent a novel therapeutic method for patients with degenerative disc disease. METHODS: Adenoviral delivery vectors expressing Sox9 and green fluorescent protein were constructed using the AdEasy system. The chondroblastic cell line, HTB-94, and cultured human degenerated intervertebral disc cells were infected with the vectors. Reverse transcriptase-polymerase chain reaction and immunohistochemical analyses were performed to document increased Type 2 collagen expression. The AdSox9 virus then was injected directly into the intervertebral discs of three rabbits. After 5 weeks, the injected discs were evaluated histologically. RESULTS: The AdSox9 virus efficiently transduced HTB-94 cells and degenerated human disc cells. Western blot analysis confirmed increased Sox9 production. Increased Type 2 collagen production was demonstrated in infected HTB-94 and human disc cells using both reverse transcriptase-polymerase chain reaction and immunohistochemical staining. In the rabbit model, cells infected with AdSox9 maintained a chondrocytic phenotype, and the architecture of the nucleus pulposus was preserved over a 5-week study period compared to control discs. CONCLUSIONS: A novel adenoviral vector efficiently increased Sox9 and Type 2 collagen synthesis in cultured chondroblastic cells and human degenerated disc cells. In a rabbit model, sustained Sox9 production preserved the histologic appearance of the nucleus pulposus cells in vivo. These findings suggest a potential role for Sox9 gene therapy in the treatment of human degenerative disc disease.

Adenoviridae↗
PubMed2003

Osteogenic activity of the fourteen types of human bone morphogenetic proteins (BMPs).

BACKGROUND: Bone morphogenic proteins (BMPs) are known to promote osteogenesis, and clinical trials are currently underway to evaluate the ability of certain BMPs to promote fracture-healing and spinal fusion. The optimal BMPs to be used in different clinical applications have not been elucidated, and a comprehensive evaluation of the relative osteogenic activity of different BMPs is lacking. METHODS: To identify the BMPs that may possess the most osteoinductive activity, we analyzed the osteogenic activity of BMPs in mesenchymal progenitor and osteoblastic cells. Recombinant adenoviruses expressing fourteen human BMPs (BMP-2 to BMP-15) were constructed to infect pluripotent mesenchymal progenitor C3H10T1/2 cells, preosteoblastic C2C12 cells, and osteoblastic TE-85 cells. Osteogenic activity was determined by measuring the induction of alkaline phosphatase, osteocalcin, and matrix mineralization upon BMP stimulation. RESULTS: BMP-2, 6, and 9 significantly induced alkaline phosphatase activity in pluripotential C3H10T1/2 cells, while BMP-2, 4, 6, 7, and 9 significantly induced alkaline phosphatase activity in preosteoblastic C2C12 cells. In TE-85 osteoblastic cells, most BMPs (except BMP-3 and 12) were able to induce alkaline phosphatase activity. The results of alkaline phosphatase histochemical staining assays were consistent with those of alkaline phosphatase colorimetric assays. Furthermore, BMP-2, 6, and 9 (as well as BMP-4 and, to a lesser extent, BMP-7) significantly induced osteocalcin expression in C3H10T1/2 cells. In C2C12 cells, osteocalcin expression was strongly induced by BMP-2, 4, 6, 7, and 9. Mineralized nodules were readily detected in C3H10T1/2 cells infected with BMP-2, 6, and 9 (and, to a lesser extent, those infected with BMP-4 and 7). CONCLUSIONS: A comprehensive analysis of the osteogenic activity of fourteen types of BMPs in osteoblastic progenitor cells was conducted. Our results suggest an osteogenic hierarchical model in which BMP-2, 6, and 9 may play an important role in inducing osteoblast differentiation of mesenchymal stem cells. In contrast, most BMPs are able to stimulate osteogenesis in mature osteoblasts.

Adenoviridae↗
PubMed2003

Compressive preload improves the stability of anterior lumbar interbody fusion cage constructs.

BACKGROUND: Insertion of an anterior lumbar interbody fusion cage has been shown to reduce motion in a human spine segment in all loading directions except extension. The "stand-alone" cages depend on compressive preload produced by anular pretensioning and muscle forces for initial stabilization. However, the effect that the in vivo compressive preload generated during activities of daily living has on the construct is not fully understood. This study tested the hypothesis that the ability of the cages to reduce the segmental motions in flexion and extension is significantly affected by the magnitude of the externally applied compressive preload. METHODS: Fourteen specimens from human lumbar spines were tested intact and after insertion of two threaded cylindrical cages at level L5-Sl. They were subjected to flexion and extension moments under progressively increasing magnitudes of externally applied compressive follower preload from 0 to 1200 N. The range of motion at level L5-S1 after cage insertion was compared with the value achieved in the intact specimens at each compressive preload magnitude. RESULTS: The cages significantly reduced the L5-S1 flexion motion at all preloads (p < 0.05). They decreased flexion motion by 29% to 43% of that of the intact specimens for low preloads (0 to 400 N) and by 69% to 79% of that of the intact specimens under preloads of 800 to 1200 N. In extension, in the absence of an externally applied preload, the cages permitted 24% more motion than the intact segment (p < 0.05). In contrast, they reduced the extension motion at preloads from 200 to 1200 N. Under preloads of 800 to 1200 N, the reduction in extension motion after cage placement was 42% to 48% of that of the intact segment (p < 0.05). The reduction of motion in both flexion and extension after cage placement was significantly greater at preloads of 800 to 1200 N compared with the motion reductions at preloads of < or =400 N (p < 0.05). CONCLUSIONS: In contrast to the observed extension instability under anular tension preload only, the two-cage construct exerted a stabilizing effect on the motion segment (a reduction in segmental motion) in flexion as well as extension under externally applied compressive preloads of physiologic magnitudes. The external compressive preload significantly affected the stabilization provided by the cages. The cages provided substantially more stabilization, both in flexion and in extension, at larger preloads than at smaller preloads. CLINICAL RELEVANCE: The study suggests that the segment treated with an anterior lumbar interbody fusion cage is relatively less stable under conditions of low external compressive preload. The magnitude of preload required to achieve stabilization with stand-alone cages may be only partially achieved by anular pretensioning. Since the magnitude of the preload across the disc space due to muscle activity can vary with activities of daily living, supplemental stabilization of the cage construct may provide a more predictably stable environment for lumbar spine fusion.

Aged↗
PubMed2003

Minimally invasive treatments of osteoporotic vertebral compression fractures: vertebroplasty and kyphoplasty.

Although nonsurgical treatment of osteoporotic vertebral compression fractures, including medication, exercise, bracing, and bed rest, have been reasonably effective, vertebroplasty and kyphoplasty have evolved as valuable adjunctive treatment options. Over the past decade, vertebroplasty, which involves the percutaneous injection of bone cement directly into the fractured vertebral body, has been used as a treatment for painful osteoporotic vertebral body compression fractures, a leading cause of morbidity in the elderly. Kyphoplasty, another minimally invasive procedure that allows for correction of spinal deformity and for controlled cement filling of the fractured vertebral body, involves the percutaneous cannulation of the vertebral body followed by the placement of an inflatable bone tamp. Reported results for both vertebroplasty and kyphoplasty suggest rapid improvement in pain and physical functioning in patients with osteoporotic vertebral compression fractures. Kyphoplasty allows for low-pressure cement injection and affords the opportunity to correct spinal deformity. Further study is required to define the precise indications, timing, and relative merits of these techniques.

Contraindications↗
PubMed2002

Managing chronic pain of spinal origin after lumbar surgery: the role of decompressive surgery.

STUDY DESIGN: A literature review was conducted. OBJECTIVE: To provide an evidence-based approach for patients with neurogenic symptoms after lumbar surgery. SUMMARY OF BACKGROUND DATA: Patients may present with chronic pain of spinal origin after lumbar surgery. Failure to decompress the involved neural structures adequately or progression of the underlying degenerative condition may lead to neurologic symptoms. METHODS: A literature search of peer-reviewed publications that investigate etiologies and treatments for neurogenic pain in patients who have undergone previous spinal surgery was conducted. RESULTS: In the absence of profound or progressive neurologic deficits, most patients with chronic back and leg pain who have undergone previous spinal surgery should be treated nonoperatively. Additional decompressive surgical intervention may be justified in patients with well-defined, discrete pathology amenable to surgical correction who have been refractory to conservative care. The surgery typically will include meticulous decompression of the affected neural structures and may include arthrodesis to address any deformity or instability. CONCLUSIONS: In a patient presenting with neurogenic symptoms after lumbar surgery, a meticulous workup is required to elucidate the source of these symptoms. Surgical indications are similar to those for primary lumbar spinal surgery and include a well-defined anatomic source of neural compression that is amenable to a surgical solution.

Back Pain↗
PubMed2002

Intradiscal electrothermal therapy used to manage chronic discogenic low back pain: new directions and interventions.

STUDY DESIGN: Retrospective literature review. OBJECTIVES: To review the data on the clinical efficacy of intradiscal electrothermal annuloplasty found at this writing in the peer-reviewed literature to date, to discuss the methodologic strengths and flaws of the studies, to discuss the pitfalls of clinical study designs, to emphasize the need for prospective randomized studies and for increased basic science investigation. SUMMARY OF BACKGROUND DATA: Studies published or presented at peer-reviewed societies concerning the clinical efficacy of intradiscal electrothermal annuloplasty are reviewed, including background studies on deafferentation and application of thermal energy to alter biomechanical and structural properties. A proposal for future investigations is presented. METHODS: Background data from intracapsular annuloplasty highlighting the safety and efficacy of intradiscal electrothermal annuloplasty are presented. Current studies on this procedure, including those in the National Registry are reviewed. All the studies share a common study design: prospective cohort with historical or noninterventional groups used as controls. The patients reviewed are similar. All have nonradicular low back pain of at least 3 months duration, failed conservative care, normal neurologic examination, and MRI showing only nondegenerative disc disease and positive concordant discography. All the patients underwent intradiscal electrothermal annuloplasty lesion at one or two levels according to standard protocols. Follow-up evaluation was performed at various intervals up to 2 years. All the studies used data from a visual analog scale, with most using the Short Form 36 (SF-36) as outcome instruments. RESULTS: The reported follow-up periods for the studies ranged from 6 months to 2 years. Three published studies, one with a 6-month follow-up period and two with a 1-year follow-up period, were published in the peer-reviewed literature. Two recent reports presented to the North American Spine Society were reviewed: a study of patients on a manufacturer-sponsored registry with a 1-year follow-up period and a multicenter prospective cohort study of 75 patients in an intent-to-treat group, with a 1-year follow-up period. Using the 7-point criteria of Deyo et al, all the studies suggested a positive effect of treatment, with a decrease in visual analog scale ratings and improvement in SF-36 scales, particularly those for physical function and bodily pain. CONCLUSIONS: The studies published so far suggest that the pain resulting from lumbar disc disease may be diminished by intradiscal electrothermal annuloplasty. All these studies project a positive therapeutic effect. However, all the studies suffer from the same methodologic flaws. A prospective cohort design or a nonrandomized prospective design is used with a biased control. The scientific validity of various study designs is discussed, and a randomized prospective study is recommended. Additionally, more investigation into the basic science of the action of intradiscal electrothermal annuloplasty is required.

Chronic Disease↗
PubMed2002

An in vivo comparison of the potential for extravertebral cement leak after vertebroplasty and kyphoplasty.

STUDY DESIGN: A prospective in vivo study was conducted during the performance of kyphoplasty for the treatment of osteoporotic vertebral compression fractures, comparing extravertebral contrast extravasation with kyphoplasty and vertebroplasty. OBJECTIVE: To determine the frequency and pattern of extravertebral contrast extravasation after intravertebral injection during kyphoplasty and vertebroplasty, which have implications for cement leakage during these procedures. SUMMARY OF BACKGROUND DATA: Vertebroplasty involves the injection of cement directly into the cancellous bone of a fractured vertebral body in an attempt to stabilize the fracture. High rates of extravertebral cement leakage have been noted. Injection of contrast into the vertebral body under fluoroscopy has been recommended in an attempt to predict and minimize cement leakage. An alternative procedure, balloon kyphoplasty, involves the percutaneous placement of an inflatable bone tamp into the fractured vertebral body. As the tamp is inflated, vertebral body height is restored and a cavity is created within the vertebral body, allowing for low-pressure cement filling of the cavity. METHODS: During 20 kyphoplasty surgeries for vertebral compression fractures, contrast studies were performed. Immediately after positioning of an 11-gauge biopsy needle within the midvertebral body, 5 mL of Omnipaque was injected, mimicking vertebroplasty injection. Cinefluoroscopic images were obtained during injection. After bilateral fracture reduction and intravertebral cavity creation using inflatable bone tamps (kyphoplasty), contrast was injected again, mimicking cement injection during kyphoplasty. Scoring of the extravertebral contrast leakage was based on filling of the inferior vena cava and epidural vessels, as well as direct contrast extension through the vertebral cortex. RESULTS: The mean contrast leak scores for vertebroplasty- and kyphoplasty-stage injections were, respectively, 4.3 and 0.8 of 6 (P = 0.0001). The scores for epidural vessel and inferior vena cava filling and transcortical contrast leak each was significantly lower for kyphoplasty- than for vertebroplasty-stage injections (P = 0.0001 each). CONCLUSIONS: The findings showed less vascular and transcortical extravasation of injected contrast with kyphoplasty than with vertebroplasty. Although leakage of contrast may not correlate precisely with polymethylmethacrylate leakage, the authors believe this study highlights the relative safety of these procedures.

Aged↗
PubMed2002

Intertransverse lumbar interbody fusion.

STUDY DESIGN: Cadaver dissection and case reports were used to describe a novel technique of lumbar interbody arthrodesis that accesses the intervertebral disc through a posterolateral intertransverse process approach. OBJECTIVES: To describe the surgical approach and technique required in performing an intertransverse lumbar interbody fusion. The clinical results in two patients with 2-year follow-up evaluation after intertransverse lumbar interbody fusion are reported. SUMMARY OF BACKGROUND DATA: Many of the complications of lumbar interbody arthrodesis are associated with the surgical approach to the disc space. During an anterior approach, intraabdominal or retroperitoneal structures are at risk, whereas during a posterior approach, the cauda equina and spinal stabilizers may be jeopardized. A minimally invasive posterolateral discectomy for the treatment of herniated lumbar discs has been described. The authors hypothesized that a posterolateral approach might be used for achieving interbody arthrodesis. METHODS: Cadaver studies were performed to determine the feasibility and define the anatomy of a posterolateral, intertransverse process approach used to achieve lumbar interbody arthrodesis. These studies confirmed that this approach is feasible at L3-L4 and L4-L5. In two patients with discogenic low back pain, an intertransverse lumbar interbody fusion was performed using structural allograft bone wedges with supplemental translaminar facet screws. RESULTS: In two patients, an intertransverse lumbar interbody fusion was successfully performed without any complication. Both patients demonstrated good surgical outcomes 2 years after surgery, and radiographic assessment showed stable interbody grafts without motion on flexion-extension studies. CONCLUSIONS: This preliminary report suggests that lumbar interbody arthrodesis can be accomplished with a posterolateral intertransverse process approach. To the authors' knowledge, this is the first published report describing this approach for performing an interbody arthrodesis. The intertransverse lumbar interbody fusion (ILIF) approach avoids the need for either intraabdominal dissection or violation of the spinal canal-neural foramen in accessing the disc. This technique may therefore present an opportunity to accomplish a minimally invasive approach to lumbar fusion.

Adult↗
PubMedDate not supplied

Radiographic criteria for placement of translaminar facet screws.

BACKGROUND CONTEXT: Screw fixation of the facet joint has been reported to stabilize the lumbar spine and facilitate spinal fusion. Accurate placement of translaminar facet screws (TLFSs) requires identification of the posterior spinal elements, and the facet joints in particular, which may be facilitated by intra-operative fluoroscopy. PURPOSE: The purpose of this study was to define the radiographic parameters that will allow for successful placement of TLFSs. STUDY DESIGN: Eighteen TLFSs were placed in three human cadaver spines using fluoroscopic guidance, with screws placed from L3-L4 to L5-S1 bilaterally. After screw placement, the spines were dissected and examined for accuracy of screw placement. METHODS: In the first cadaver spine, TLFSs were placed with direct visualization of the posterior lumbar spine, during which a fluoroscopic image intensifier was used to define the appropriate radiographic parameters for safe placement of the screws. Bilateral TLFSs were then placed percutaneously using the radiographic parameters developed, after which the spines were dissected to examine the positions of the screws. RESULTS: The radiographic views identified to achieve proper TLFS placement were a true lateral, anteroposterior (AP), a 45-degree oblique and an AP view with the X-ray bean at 30- to 45-degree cephalad angle ("spinal outlet" view). Using these views and the defined radiographic criteria, proper positioning of percutaneously placed TLFSs was achieved, with no spinal canal breaches found. CONCLUSIONS: This study defines intra-operative radiographic criteria that will assist in placement of TLFSs. The use of this technique may allow for screw placement with less extensive exposure of the posterior spine.

Adult↗
PubMedDate not supplied

Restoring geometric and loading alignment of the thoracic spine with a vertebral compression fracture: effects of balloon (bone tamp) inflation and spinal extension.

BACKGROUND CONTEXT: In patients with osteoporosis, changes in spinal alignment after a vertebral compression fracture (VCF) are believed to increase the risk of fracture of the adjacent vertebrae. The alterations in spinal biomechanics as a result of osteoporotic VCF and the effects of deformity correction on the loads in the adjacent vertebral bodies are not fully understood. PURPOSE: To measure 1) the effect of thoracic VCFs on kyphosis (geometric alignment) and the shift of the physiologic compressive load path (loading alignment), 2) the effect of fracture reduction by balloon (bone tamp) inflation in restoring normal geometric and loading alignment and 3) the effect of spinal extension alone on fracture reduction and restoration of normal geometric and loading alignment. STUDY DESIGN/SETTING: A biomechanical study using six fresh human thoracic specimens, each consisting of three adjacent vertebrae with all soft tissues and bony structures intact. METHODS: In order to reliably create fracture, cancellous bone in the middle vertebral body was disrupted by inflation of bone tamps. After removal of the bone tamps, the specimen was compressed using bilateral loading cables until a fracture was observed with anterior vertebral body height loss of >/=25%. Fracture reduction was performed under a compressive preload of 250 N first under the application of extension moments, and then using inflatable bone tamps. The vertebral body heights, kyphotic deformity of the fractured vertebra and adjacent segments and location of compressive load (cable) path in the fractured and adjacent vertebral bodies were measured on video-fluoroscopic images. RESULTS: The VCF caused anterior wall height loss of 37+/-15%, middle-height loss of 34+/-16%, segmental kyphosis increase of 14+/-7.0 degrees and vertebral kyphosis increase of 13+/-5.5 degrees (p<.05). The compressive load path shifted anteriorly by about 20% of anteroposterior end plate width in the fractured and adjacent vertebrae (p=.008). Bone tamp inflation restored the anterior wall height to 91+/-8.9%, middle-height to 91+/-14% and segmental kyphosis to within 5.6+/-5.9 degrees of prefracture values. The compressive load path returned posteriorly relative to the postfracture location in all three vertebrae (p=.004): the load path remained anterior to the prefracture location by about 9% to 11% of the anteroposterior end plate width. With application of extension moment (6.3+/-2.2 Nm) until segmental kyphosis and compressive load path were fully restored, anterior vertebral body heights were improved to 85+/-8.6% of prefracture values. However, the middle vertebral body height was not restored and vertebral kyphotic deformity remained significantly larger than the prefracture values (p<.05). CONCLUSIONS: The anterior shift of the compressive load path in vertebral bodies adjacent to VCF can induce additional flexion moments on these vertebrae. This eccentric loading may contribute to the increased risk of new fractures in osteoporotic vertebrae adjacent to an uncorrected VCF deformity. Bone tamp inflation under a physiologic preload significantly reduced the VCF deformity (anterior and middle vertebral body heights, segmental and vertebral kyphosis) and returned the compressive load path posteriorly, approaching the prefracture alignment. Application of extension moments also was effective in restoring the prefracture geometric and loading alignment of adjacent segments, but the middle height of the fractured vertebra and vertebral kyphotic deformity were not restored with spinal extension alone.

Aged↗
PubMedDate not supplied

Gene therapy for spinal fusion.

Spinal fusion will continue to be an important part of the surgical treatment of spinal pathology for the foreseeable future. Traditional challenges to successful spinal fusion surgery include autograft donor site morbidity and pseudoarthrosis. Recent advances in the understanding of the biology of bone formation have allowed the development of therapeutic biologics. Although recombinant bone morphogenetic proteins delivered to the arthrodesis site will stimulate fusion, these proteins have been less successful in more challenging fusion situations (posterolateral), require supraphysiologic doses to promote fusion in humans, and are quite expensive. Gene therapy may represent the easiest method for the application of bone-forming biologic agents to promote spinal fusion. Both in vivo and ex vivo techniques of delivery of therapeutic genes have been used effectively to promote fusion in lower animals. Considerable research is required to identify gene therapy techniques and vectors with acceptable safety profiles and high fusion rates.

Animals↗
PubMedDate not supplied

Congenital lumbar spinal stenosis: a prospective, control-matched, cohort radiographic analysis.

BACKGROUND CONTEXT: Degenerative lumbar spinal stenosis manifests primarily after the sixth decade of life as a result of facet hypertrophy and degenerative disc disease. Congenital stenosis, on the other hand, presents earlier in age with similar clinical findings but with multilevel involvement and fewer degenerative changes. These patients may have subtle anatomic variations of the lumbar spine that may increase the likelihood of thecal sac compression. However, to the authors' knowledge, no quantitative studies have addressed various radiographic parameters of symptomatic, congenitally stenotic individuals to normal subjects. PURPOSE: To radiographically quantify and compare the anatomy of the lumbar spine in symptomatic, congenitally stenotic individuals to age- and sex-matched, asymptomatic, nonstenotic controlled individuals. STUDY DESIGN/SETTING: A prospective, control-matched, cohort radiographic analysis. PATIENT SAMPLE: Axial and sagittal magnetic resonance imaging (MRI) and lateral, lumbar, plain radiographs of 20 surgically treated patients who were given a clinical diagnosis of congenital lumbar stenosis by the senior author were randomized with images of 20, asymptomatic age- and sex-matched subjects. OUTCOME MEASURES: MRIs and lateral, lumbar, plain radiographs were independently quantitatively assessed by two individuals. Measurements obtained from the axial MRIs included: midline anterior-posterior (AP) vertebral body diameter, vertebral body width, midline AP canal diameter, canal width, spinal canal cross-sectional area, pedicle length, and pedicle width. From the sagittal MRIs, the following measurements were calculated: AP vertebral body diameter, vertebral body height, and AP canal diameter at the mid-vertebral level. On the lateral, lumbar, plain radiograph (L3 level), the AP diameters of the vertebral body spinal canal were measured. METHODS: The images of these 40 individuals were then randomized and distributed in a blinded fashion to five separate spine surgeons who graded the presence and severity of congenital stenosis utilizing a five-tier scale. Images consisting of 15 symptomatic individuals, graded definitely congenitally stenotic (mean age, 51.7 years; range, 43-65 years), and 15 asymptomatic individuals, graded definitely not stenotic (mean age, 50.7 years; range, 41-55 years), were age- and sex-matched and included for further review. From these 30 patients, a lateral, lumbar, plain radiograph and axial and sagittal MRIs (T1/T2 weighted) from L2-L5 were quantitatively analyzed. Rater reliability was assessed by Kappa coefficient testing. RESULTS: The cross-sectional area of the canal was significantly smaller in the congenitally stenotic patients at all lumbar levels measured (L2: 176 mm(2) vs. 259 mm(2), L3: 177 mm(2) vs. 275 mm(2), L4: 183 mm(2) vs. 283 mm(2), L5: 213 mm(2) vs. 323 mm(2), p<.05). Pedicle length was markedly shorter in the stenosis group at each lumbar level (L2: 5.9 mm vs. 8.9 mm, L3: 6.0 mm vs. 8.8 mm, L4: 6.5 mm vs. 9.2 mm, L5: 5.8 mm vs. 9.1 mm, p<.05). Furthermore, midline, axial AP canal diameter, vertebral body width, and sagittal AP canal diameter were all significantly smaller than the control patients (p<.05). A ratio of the AP diameter of the pedicle length to the vertebral body was also noted to be statistically significant on both the lateral plain radiographs (L3: 0.426 vs. 0.704) and sagittal MRI (L2: 0.343 vs. 0.461, L3: 0.361 vs. 0.461, L4: 0.362 vs. 0.481, L5: 0.354 vs. 0.452, p<.05). No difference was noted comparing the AP diameter of the vertebral body (axial and sagittal images), vertebral body height, canal width, and pedicle width. Kappa testing coefficient indicated a strong rater reliability (k=0.81, 95% confidence interval: 0.62-0.94). CONCLUSIONS: Congenital lumbar stenosis has not been clearly defined radiographically. Clinically, congenitally stenotic patients present at a younger age with fewer degenerative changes and multiple levels of involvement. Radiographically, these patients have a shorter pedicular length and as a result a smaller cross-sectional spinal canal area (mean critical values of 6.5 mm and 213 mm(2) were observed, respectively). The mean critical ratios were 0.43 (2:1 AP vertebral body: pedicle length) on the lateral lumbar radiograph and 0.36 on the sagittal MRI. The altered canal anatomy resulting from a decreased pedicle length may anatomically predispose these patients to earlier complaints of symptomatic neurogenic claudication. Identification of the presence of congenital stenosis should increase the treating surgeon's awareness of the potential need for multilevel treatment.

Adult↗
PubMedDate not supplied

Biomechanics of posterior dynamic stabilizing device (DIAM) after facetectomy and discectomy.

BACKGROUND CONTEXT: Lumbar fusion has been associated with inconsistent clinical outcomes and significant complications. Posterior dynamic devices have been developed to stabilize painful diseased lumbar motion segments while avoiding fusion. The Device for Intervertebral Assisted Motion (DIAM) is a silicone interspinous process "bumper" that is being clinically implanted for varied indications. PURPOSE: We analyzed the effects of the DIAM device on the biomechanical response of the lumbar spine in flexion-extension, lateral bending, and axial rotation after partial facetectomy and discectomy; the clinical situations in which its use might be considered. STUDY DESIGN/SETTING: A biomechanical study was performed using whole lumbar spine specimens (L1-sacrum). Surgical interventions were simulated at the L4-L5 level, and motions were measured at the operated and adjacent segments. PATIENT SAMPLE: Six fresh human lumbar spine specimens were used. METHODS: The lumbar spines were subjected to moments in flexion-extension (+/-6 Nm), lateral bending (+/-5 Nm), and axial rotation (+/-4 Nm). The specimens were tested under the following conditions: 1) intact; 2) after unilateral hemifacetectomy at L4-L5; 3) #2 and discectomy; and 4) #3 with DIAM. The angular motion values at the operated and adjacent segments were analyzed using analysis of variance and multiple comparisons with Bonferroni correction. RESULTS: Unilateral hemifacetectomy did not increase angular motion. Subsequent discectomy increased L4-L5 angular motion (degrees) from 9.2+/-1.6 to 11.7+/-2.0 in flexion-extension (p=.01), from 6.7+/-1.1 to 8.5+/-1.5 in lateral bending (p=.01), and from 2.6+/-0.7 to 3.8+/-0.8 in axial rotation (p=.00). Insertion of the DIAM device after discectomy restored the angular motion to below the level of the intact segment in flexion-extension (6.7+/-0.7 vs. 9.2+/-1.6, p=.02). In lateral bending, DIAM reduced the increased motion induced by discectomy (7.8+/-1.0 vs. 8.5+/-1.5, p<.05), but not to the intact level (7.8+/-1.0 vs. 6.7+/-1.1, p=.05). DIAM insertion did not reduce the increased axial rotation induced by discectomy, and the axial rotation remained larger than the intact value (4.1+/-0.6 vs. 2.6+/-0.7, p=.00). CONCLUSIONS: The DIAM device is effective in stabilizing the unstable segment, reducing the increased segmental flexion-extension and lateral bending motions observed after discectomy. In flexion-extension the DIAM restored postdiscectomy motion to below the intact values (p<.05). Interestingly, the DIAM device did not reduce the increased axial rotation motion observed after discectomy. These biomechanical effects must be considered when evaluating the clinical applications of the DIAM.

Aged↗