Lactose drives Enterococcus expansion to promote graft-versus-host disease.

Disruption of intestinal microbial communities appears to underlie many human illnesses, but the mechanisms that promote this dysbiosis and its adverse consequences are poorly understood. In patients who received allogeneic hematopoietic cell transplantation (allo-HCT), we describe a high incidence of enterococcal expansion, which was associated with graft-versus-host disease (GVHD) and mortality. We found that Enterococcus also expands in the mouse gastrointestinal tract after allo-HCT and exacerbates disease severity in gnotobiotic models. Enterococcus growth is dependent on the disaccharide lactose, and dietary lactose depletion attenuates Enterococcus outgrowth and reduces the severity of GVHD in mice. Allo-HCT patients carrying lactose-nonabsorber genotypes showed compromised clearance of postantibiotic Enterococcus domination. We report lactose as a common nutrient that drives expansion of a commensal bacterium that exacerbates an intestinal and systemic inflammatory disease.

U.S. laboratory and field trials of metofluthrin (SumiOne) emanators for reducing mosquito biting outdoors.

Metofluthrin (SumiOne is a novel, vapor-active pyrethroid that is highly effective against mosquitoes. Laboratory and field trials were conducted in the United States to evaluate the mosquito repellent activity of metofluthrin-treated paper substrates ("emanators"). Initial studies were conducted to evaluate the field performance of 900-cm(2) paper fan emanators impregnated with 160 mg metofluthrin, where Aedes canadensis was the predominant species. Emanators reduced landing rates on human volunteers by between 85% and 100% compared to untreated controls. Subsequent tests with 4,000-cm(2) paper strip emanators impregnated with 200 mg metofluthrin were conducted in a wind tunnel as a precursor to conducting field trials using human bait and laboratory-reared Aedes aegypti. Paper strips, which were pre-aged in a fume hood to determine duration of protection, gave 89-91% reductions in landing rates compared with controls. Similar reductions in biting activity were also noted. Following these tests, field trials to assess effect on landing rates were conducted with emanators positioned 1.22 m on either side of volunteers protected from biting by Tyvek suits, with pre- and posttreatment counts being made. In Florida (predominantly Ochlerotatus spp.) 91-95% reductions were noted 10-30 min after emanators were deployed, while in Washington State (mostly Aedes vexans) 95-97% reductions were observed. These results demonstrate that metofluthrin-treated emanators are highly effective at repelling mosquitoes.

Short fusion strategy for thoracolumbar and lumbar adolescent idiopathic scoliosis using anterior dual-rod instrumentation.

AIMS: A total of 30 patients with thoracolumbar/lumbar adolescent idiopathic scoliosis (AIS) treated between 1989 and 2000 with anterior correction and fusion surgery using dual-rod instrumentation were reviewed. PATIENTS AND METHODS: Radiographic parameters and clinical outcomes were compared among patients with lowest instrumented vertebra (LIV) at the lower end vertebra (LEV; EV group) (n = 13) and those treated by short fusion (S group), with LIV one level proximal to EV (n = 17 patients). RESULTS: The allocation of the surgical technique was determined by the flexibility of the TL/L curves and/or neutral vertebrae located one level above LEV as determined on preoperative radiographs. If these requirements were met a short fusion was performed. The mean follow-up period was 21.4 years (16 to 27). The mean correction rate at final follow-up was significantly lower in the S group (74 sd 11%) than in the EV group (88 sd 13%) (p = 0.004).Coronal and sagittal balance, thoracic kyphosis, lumbar lordosis, and clinical outcomes evaluated by the Scoliosis Research Society-22 questionnaire scores were equivalent between the two groups. CONCLUSION: Short fusion strategy, which uses LIV one level proximal to LEV can be considered as an alternative to the conventional strategy, which includes LEV in the fusion, when highly flexible TL/L curves are confirmed and/or neutral vertebrae are located one level above LEV in patients with thoracolumbar/lumbar AIS curves. TAKE HOME MESSAGE: Short fusion strategy can be considered as an alternative to the conventional strategy in patients with thoracolumbar/lumbar AIS curves undergoing anterior spinal fusion with dual-rod instrumentation. Cite this article: Bone Joint J 2016;98-B:402-9.

Regional measurement of resin-dentin bonding as an array.

During the development of the microtensile bond-testing method, large variations in bond strengths were noted among serial sections. The reason for these variations is unknown. The purpose of this work was to determine the consistency of resin-dentin bond strengths across the occlusal surface of coronal dentin by dividing composite resin buildups into an array of 1x1 mm beams, the top half consisting of composite resin, and the bottom half consisting of dentin. Extracted human third molars had the occlusal enamel removed as a single section by means of a diamond saw. Resin composite buildups were made after the dentin was bonded with either One-Step or MacBond. After being stored in 37 degrees C water for 1 day, the teeth were vertically sectioned at 1-mm increments into slabs of bonded teeth. Each slab was further subdivided by vertical sections into 1x1x8 mm beams. Each beam was assigned an x-y coordinate and tested for tensile bond strength. Two different clinicians (A and B) performed the same procedures using One-Step in a parallel study. Using One-Step, clinician A obtained a large number of zero bonds in superficial dentin but fewer in deep dentin. This resulted in a very large standard deviation in bond strengths (mean +/- SD of 22+/-20 MPa in superficial dentin and 27+/-14 MPa in deep dentin). Clinician B obtained much higher (p<0.001) and more uniform bond strengths with One-Step (56+/-13 MPa in superficial dentin and 57+/-12 MPa in deep dentin). With MacBond, there were no zero bonds and hence less variation, with a mean of 41+/-13 MPa in superficial dentin and 27+/-12 MPa (x +/- SD) in deep dentin. When pairs of Z100 resin composite cylinders were bonded together with One-Step and then sectioned into an array, there was little variation in regional bond strength (37 +/-1 MPa). Dividing bonded resin composite buildups into an array of 20 to 30 1x1x8 mm beams allows for the evaluation of uniformity of resin-dentin bonds. The method used in this study detected local regional differences in resin-dentin bond strengths. The largest differences were shown to be related to technique rather than to material. The results indicate that resin-dentin bonds may not be as homogenous as was previously thought.

Evaluation of MTX/5-FU sequential chemotherapy utilized MTT assay for gastrointestinal cancer.

Fresh human gastrointestinal cancer cells are more resistant to anticancer drugs compared to other cancer cells, and the selection of anticancer drugs for cancer chemotherapy is important. In the present study, it is demonstrated that MTX enhanced the chemosensitivity of 5-FU, especially, in the tumor cells with less than 70% inhibition ratio by the MTT assay. It has been reported that MTX/5-FU sequential chemotherapy was one of the effective chemotherapies against gastric cancer and colon cancer, and it is possible to anticipate the efficacy of MTX/5-FU sequential chemotherapy by the MTT assays.

Indirect posterior reduction and fusion of the traumatic herniated disc by using a cervical pedicle screw system.

OBJECT: In this study the authors retrospectively review 16 patients with traumatic disc herniation secondary to middle and lower cervical spine injuries who underwent a single posterior reduction and fusion procedure in which a cervical pedicle screw system was used. The study was undertaken to evaluate whether the procedure effectively reduced the disc herniation and whether it can be safely conducted without performing anterior decompressive surgery. METHODS: A total of 73 patients with middle and lower cervical spine injuries were identified. In 50 patients, pre- and postoperative magnetic resonance (MR) images were obtained, and disc herniation was defined as the presence of an extruded disc that deformed the thecal sac or nerve roots. Traumatic disc herniation was revealed in 16 patients (32%) who underwent a single posterior reduction/fusion procedure in which a cervical pedicle screw system was used. The average follow-up period was 4.25 years (2-6.25 years). In all patients the average kyphotic deformity was 18 degrees, which was corrected to 0.7 degrees lordosis postoperatively. Anterior translation was reduced from 8 to 0.7 mm. The preoperative disc height ratio of 63% (normal 100%) was improved to 104%. Preoperative MR images revealed traumatic disc herniation in all 16 patients; postsurgery, reduction or reversal of disc herniation was observed in all patients. Thecal sac and/or spinal cord compression had disappeared after indirect decompression was achieved using a posterior procedure. No additional decompressive procedures were required to remove residual herniated disc material. Preoperatively, four patients presented with cervical radiculopathy, 10 with myelopathy (eight incomplete and two complete), and two without neurological symptoms. At final follow up, complete recovery was observed in all four patients with radiculopathy and improvement of at least one Frankel grade was shown in six patients (60%) with myelopathy. There were no cases of neurological deterioration immediately after surgery or during the course of the follow-up period. In all patients solid bone union was demonstrated, and there were no implant-related complications. CONCLUSIONS: Traumatic disc herniation may occur frequently in association with injury of the cervical spine. The incidence of traumatic disc herniation in our series was 32%. The cervical pedicle screw system allowed three-dimensional reduction of the injured cervical segment and reduction or reversal of a disc herniation. After surgery, compression of the thecal sac and/or spinal cord had disappeared. The cervical pedicle screw system provides effective and safe fixation of the cervical spine injury-related traumatic disc herniation, and the surgery can be performed safely in a single posterior-approach procedure without need of additional anterior decompressive interventions.

One-stage posterior decompression and reconstruction of the cervical spine by using pedicle screw fixation systems.

OBJECT: This retrospective study was conducted to analyze the results of one-stage posterior decompression and reconstruction of the cervical spine by using pedicle screw fixation systems in 46 patients. METHODS: Causes of cervical myelopathy in these 46 patients included spondylosis or ossification of the posterior longitudinal ligament, rheumatoid arthritis, metastatic or primary vertebral tumors, cervical spinal injuries, and spinal cord tumor. Thirty-three patients underwent this one-stage procedure as primary surgery. In the remaining 13 patients who had previously undergone laminectomies, the one-stage procedure was performed as salvage surgery. Cervical pedicle screws were inserted into the pedicles after probing and tapping. Graft bone was placed on the bilateral lateral masses, and pedicle screws were interconnected longitudinally by either plates or rods. Postoperatively, 26 patients showed improved neurological status (at least one grade improvement on Frankel's functional classification). There were no cases of neurological deterioration postoperatively. Solid bony fusion was obtained in all patients, except in seven patients with metastatic tumor who did not receive bone grafts. Correction of kyphosis was satisfactory. Postoperative radiological evaluation revealed that 10 (5.3%) of 190 screws inserted into the cervical vertebrae had perforated the cortex of the pedicles; however, no neurovascular complications were caused by the perforations. CONCLUSIONS: The pedicle screw fixation procedure, which does not require the lamina to be used as a stabilizing anchor, has proven to be valuable when performing one-stage posterior decompressive and reconstructive surgery in the cervical spine. The risk to neurovascular structures in this procedure, however, cannot be completely eliminated. Thorough knowledge of local anatomy and application of established surgical techniques are essential for this procedure.

In vitro antitumor activity of 4'-O-tetrahydropyranyladriamycin on human gastric cancer cells.

The antitumor activity of 4'-O-tetrahydropyranyladriamycin (THP-ADM) was assessed in established gastric cancer cell lines, including MKN-28, moderately differentiated adenocarcinoma and KATO-III, signet ring cell carcinoma and freshly excised human gastric cancer cells, using the MTT assay. The inhibition rates of THP-ADM were identical to those of adriamycin (ADM) in established gastric cancer cell lines, and the chemosensitivity of MKN-28 was higher than KATO-III. In fresh human gastric cancer cells obtained from 27 patients the inhibition rates of THP-ADM were identical to those of ADM, and there was a significant correlation of inhibition rates ADM and THP-ADM. These results indicate that THP-ADM should be a potent candidate to replace ADM in cancer chemotherapy.

The effects of desferrioxamine on thrombus formation in injured microvessels of the rabbit ear.

We investigated the effects of the iron chelator desferrioxamine (DFX) on thrombus formation in the arterioles and venules of the rabbit ear chamber. Thrombi were induced by irradiation with filtered light in combination with a fluorescent dye. The occlusive thrombus formation time was significantly extended by DFX. The morphological composition of thrombi in the arterioles and venules was different. In the arterioles, the thrombi consisted of platelet aggregation, but in the venules, platelets and leukocytes accumulated on the endothelium. This suggest that hydroxyl radicals may be important mediators in this model, as DFX is known as a hydroxyl radical scavenger. Furthermore, the components of thrombi in the arterioles and venules in the skin microvascular system may be different.

A biomechanical analysis of decompression and reconstruction methods in the cervical spine. Emphasis on a carbon-fiber-composite cage.

Biomechanical analysis of three different patterns of instability--that created by fifth and sixth cervical anterior discectomy, that created by one-level (fifth cervical) anterior corpectomy, and that created by two-level (fourth and fifth cervical) corpectomy--was performed in eighteen calf spines. Three types of anterior reconstruction--anterior iliac strut bone-grafting, use of an anterior carbon-fiber-composite cage packed with cancellous bone graft, as well as use of polymethylmethacrylate anteriorly--were cyclically tested in axial compression, torsion, and flexion-extension. Each of these types of reconstruction was also tested with supplemental posterior wire stabilization (the triple-wire technique of Bohlman). Regardless of the type of anterior instability, the carbon-fiber-reinforced cage packed with cancellous bone graft was more rigid than the iliac bone graft alone. The cage resulted in good stiffness in the axial compression and rotation tests and was the most rigid construct in the flexion-extension tests. The superior aspect of the polymethylmethacrylate constructs loosened at the bone-cement interface in eight of the twelve specimens during flexion-extension testing. The addition of the supplemental posterior wiring to the anterior constructs provided additional rigidity in flexion-extension testing.

A biomechanical analysis of Zielke, Kaneda, and Cotrel-Dubousset instrumentations in thoracolumbar scoliosis. A calf spine model.

A biomechanical study was performed in order to evaluate the initial stability of three spinal instrumentation systems, applied to a scoliosis model. Five calf spines (T11-L2) were destabilized anteriorly, and, by inserting a wedge-shaped resin disc within each destabilized intervertebral space, a thoracolumbar scoliosis was created. Three spinal instrumentation systems (Zielke anterior instrumentation, Kaneda anterior multisegmental fixation device, and Cotrel-Dubousset posterior instrumentation) were applied to correct the simulated scoliotic condition. Mechanical nondestructive cyclical testing in axial compression, rotation, flexion, and extension was performed on each spinal construct. The Kaneda device was the most stable instrumentation in all four loading conditions. Zielke instrumentation failed to restore the stability to the level of the intact spine in rotation, and was the least rigid instrumentation in flexion and extension. The Cotrel-Dubousset instrumentation demonstrated favorable stability in flexion and extension, but became the least rigid instrumentation in axial compression and rotation. This study suggests that a one-stage procedure with Zielke instrumentation and a two-stage procedure (anterior release with bone graft and posterior stabilization) with Cotrel-Dubousset instrumentation applied for the correction of scoliosis, should be supplemented with additional external or internal supports. The Kaneda device may offer enough stability with an anterior procedure alone in the correction of scoliosis.

One-stage posterior hemivertebra resection and correction using segmental posterior instrumentation.

STUDY DESIGN: A retrospective study of 12 patients with congenital kyphoscoliosis caused by a single hemivertebra who underwent one-stage posterior hemivertebra resection and correction by posterior segmental instrumentation. OBJECTIVES: To evaluate the surgical outcomes of 12 patients with hemivertebra treated by hemivertebra resection by single posterior approach and correction with segmental posterior instrumentation. SUMMARY OF BACKGROUND DATA: Congenital scoliosis caused by hemivertebra causes extremely severe curves in some patients. Posterior fusion or posterior and anterior hemi-epiphysiodesis is performed to prevent progression of the deformity. The results of these procedures have been variable and not promising, especially in an adolescent patient with fixed kyphoscoliotic deformity. Hemivertebra resection offers more certain results and better correction of the deformity. To date, hemivertebra resection is performed by anterior and posterior approaches either by one-stage or two-stage operation. Few reports have been published describing a procedure consisting of one-stage posterior hemivertebra resection and correction of the deformity by segmental posterior instrumentation. METHODS: A total of 12 patients with a single hemivertebra between the ages 8-24 years who underwent operative treatment were evaluated for a minimum of 2 years. All patients had a single nonincarcerated hemivertebra [T9 (1 patient), T10 (2), T11 (2), T12 (4), and L1 (3)]. After posterior hemivertebra resection, segmental posterior instrumentation was used for correction of the kyphoscoliotic deformity [CD (4 patients), Kaneda SR (2), and ISOLA (6)]. Radiographic evaluations were conducted on the preoperative, postoperative, and follow-up standing posteroanterior and lateral radiographs. RESULTS: All 12 patients had kyphoscoliotic deformity. Preoperative scoliosis averaging 49 degrees was corrected to 18 degrees (correction rate, 64%). Preoperative kyphosis of 40 degrees was corrected to 17 degrees of kyphosis. Trunk shift of 23 mm was improved to 3 mm. Correction loss was 2 degrees in the frontal plane and 3 degrees in the sagittal plane, and no patients showed more than 5 degrees of correction loss. No intraoperative complications were noted. Solid fusion was obtained in all patients, and no implant failure was verified at the final radiographic evaluations. CONCLUSIONS: This study indicated that correction of kyphoscoliosis caused by a single hemivertebra can be effectively conducted by one-stage posterior hemivertebra resection and correction using segmental posterior instrumentation. The operation was safe, and no associated adverse complications were noted. This procedure is best indicated for adolescent patients with a structural kyphoscoliotic deformity caused by a thoracic or thoracolumbar single hemivertebra.

Experimental study of thoracolumbar burst fractures. A radiographic and biomechanical analysis of anterior and posterior instrumentation systems.

STUDY DESIGN: The efficacy of posterior instrumentations for treating thoracolumbar burst fractures to restore spinal alignment and indirectly reduce intracanal bone fragments was investigated. Also, a biomechanical study was performed to compare the mechanical stability of anterior and posterior instrumentations. METHODS: Twenty-four fresh human cadaveric thoracolumbar spine segments were used. After clinically identical L1 burst fractures were created, two posterior instrumentations were used to restore spinal alignment: 1) Harrington dual distraction rods with sleeves and 2) AO internal fixator. Radiographs and computed tomography scans were obtained to assess spinal alignment and canal dimensions. Biomechanical testing was performed in axial compression, rotation, and flexion-extension on all constructs, including anterior reconstruction with the Kaneda device. SUMMARY OF BACKGROUND DATA: Kyphosis averaged 14 degrees in the injured specimens and was corrected to 1 degree of lordosis after posterior reduction, and vertebral body height was restored to normal in most of the specimens. Reduction rate of canal compromise was 12.3% for Harrington instrumentation and 18.5% for AO internal fixator. Anterior reconstruction with the Kaneda device was more stable than the posterior instrumentation systems in all loading conditions. RESULTS: The posterior reduction and stabilization with posterior instrumentation provided effective restoration of the sagittal alignment. However, the reduction capability of the intracanal bone fragments was distinctly limited. CONCLUSIONS: The anterior reconstruction method permits effective decompression of the spinal canal and offers superior mechanical stability compared with the indirect decompression and stabilization of posterior instrumentation.

The pathomechanics of compression injuries in the cervical spine. Nondestructive and destructive investigative methods.

Biomechanical analysis using nondestructive and destructive investigative methods was performed to evaluate the mechanisms of cervical compression injuries. These injuries produce two basic modes of failure: 1) anterior dislocation; and 2) rupture of the anterior ligamentous complex of the vertebral body. Distribution of these two failure patterns was determined by the initial cervical spine position; translational alignment did not have a significant effect. Different results were observed between spines positioned in flexion and extension, indicating that the most important factor determining the mode of failure was rotational alignment in the sagittal plane.

Anterior correction of thoracic scoliosis with Kaneda anterior spinal system. A preliminary report.

STUDY DESIGN: Analysis of the clinical results of 20 patients with thoracic scoliosis treated by anterior procedure with Kaneda anterior spinal system. OBJECTIVES: To evaluate the efficacy of the anterior surgical correction procedure with a new anterior instrumentation in thoracic scoliosis. SUMMARY OF BACKGROUND DATA: Posterior correction and fusion with posterior instrumentation has been a main component of the surgical management of thoracic scoliosis. However, to the best of the authors' knowledge, no clinical results of anterior instrumentation surgery for thoracic scoliosis have been published in the English literature. METHODS: Anterior correction and fusion using Kaneda anterior spinal system was performed in 20 patients with thoracic scoliosis (3 patients with King Type II curve, 13 with Type III, and 4 with Type IV). The average follow-up was 3 years, with a range of 2 years, 3 months to 4 years, 1 month. There were 1B patients with idiopathic scoliosis (13 adolescents and 5 adults) and 2 patients with a single thoracic curve caused by other etiologies. All patients had correction of scoliosis by fusion within the major thoracic curve. Radiographic evaluations were performed to analyze frontal, sagittal, and rotational deformities of the spine. RESULTS: The average correction rate of scoliosis was 71%. Above the instrumented levels, the correction rate was 75%. Preoperative kyphosis of the instrumented levels of 7 degrees was corrected to 14 degrees of kyphosis. The trunk shift was improved from 17 mm before surgery to 9 mm at final follow-up evaluation. The average improvement of the tilt-angle in the lower and vertebra of fusion was 81%, and was 83% in the stable vertebra. Apical vertebral rotation showed correction rate of 15% in patients without performing resection of the rib head joints and rod rotation maneuver (n = 6). However, the correction rate was improved to 58% after introduction of the technique discussed (n = 14). The angle of tangential rib deformity (rib hump) showed a correction rate of 50%. There was 1.2 degrees of frontal plane and 1.0 degree of sagittal plane correction loss within the instrumented area at final follow-up evaluation. At final follow-up, nonunion at the uppermost segment of the fusion range developed in one patient, and decompensation in the lumbar spine was observed in one patient with Type II curve. CONCLUSIONS: Anterior correction with Kaneda anterior spinal system provides excellent correction of the frontal curvature and sagittal alignment by fusing within the range of the major curve, without a significant loss of correction and implant failure. Rigid rotational deformity of the thoracic scoliosis is effectively corrected by resection of the rib head joints and rod rotation maneuver. However, too much correction of the thoracic curve should be avoided, to prevent decompensation of the lumbar curve, especially in Type II curves.

New anterior instrumentation for the management of thoracolumbar and lumbar scoliosis. Application of the Kaneda two-rod system.

STUDY DESIGN: The Kaneda multisegmental instrumentation is a new anterior two-rod system for the correction of thoracolumbar and lumbar spine deformities. This system consists of a vertebral plate and two vertebral screws for individual vertebral bodies and two semirigid rods to interconnect the vertebral screws. Clinical results of 25 thoracolumbar and lumbar scoliosis patients treated with this new instrumentation were analyzed. OBJECTIVES: To evaluate the efficacy of the new anterior instrumentation in correction and stabilization of thoracolumbar and lumbar scoliosis. SUMMARY OF BACKGROUND DATA: Since Dwyer first introduced the concept of anterior spinal instrumentation and fusion for scoliosis, anterior surgery has gradually gained acceptance. In 1976, a useful modification for the anterior spinal instrumentation, which reportedly provided means of lordosation and vertebral body derotation, was described. However, some authors reported a high tendency of the implant breakage, loss of correction, progression of the kyphosis, and pseudoarthrosis as the major complications. To overcome the disadvantages of Zielke instrumentation, the authors have developed a new anterior spinal instrumentation (two-rod system) for the management of thoracolumbar and lumbar scoliosis. METHODS: Anterior correction and fusion using Kaneda multisegmental instrumentation was performed in 25 patients with thoracolumbar or lumbar scoliosis. The average follow-up period was 3 years, 1 month (range, 2 years to 4 years, 7 months). There were 20 patients with idiopathic scoliosis (13 adolescents and seven adults) and five patients with other types of scoliosis, including congenital and other etiologies. All patients had correction of scoliosis by fusion within the major curve, and for 16 of the 25 patients, the most distal end vertebra was not included in the fusion (short fusion). Radiographic evaluations were performed to analyze frontal and sagittal alignments of the spine. RESULTS: The average correction rate of scoliosis was 83%. Over the instrumented levels, the correction rate was 90%. Preoperative kyphosis of the instrumented levels of 7 degrees was corrected to 9 degrees of lordosis. Sagittal lordosis of the lumbosacral area beneath the fused segments averaged 51 degrees before surgery and was reduced to 34 degrees after surgery. The trunk shift was improved from 25 mm before surgery to 4 mm at final follow-up evaluation. The average improvement in the lower end vertebra tilt-angle was 97% in those patients whose lower end vertebra was included in the fusion and 83% in patients whose lower end vertebra was not included in the fusion. Apical vertebral rotation showed an average correction rate of 86%. At final follow-up evaluation, all patients demonstrated solid fusion without implant-related complications. There was 1.5 degrees of frontal plane and 1.5 degrees of sagittal plane correction loss within the instrumented area at final follow-up evaluation. CONCLUSIONS: New anterior two-rod system showed excellent correction of the frontal curvature and sagittal alignment with extremely high correction capability of rotational deformities. Furthermore, correction of thoracolumbar kyphosis to physiologic lordosis was achieved. This system provides flexibility of the implant for smooth application to the deformed spine and overall rigidity to correct the deformity and maintain the fixation without a significant loss of correction or implant failure compared with conventional one-rod instrumentation systems in anterior scoliosis correction.

Static and cyclical biomechanical analysis of pedicle screw spinal constructs.

Biomechanical evaluation of twelve different spinal devices in vitro employing pedicle screws was performed using static (n = 5) and cyclical testing (n = 3) parameters. In general, the rank order of implant failures was similar between static and cyclical tests, performed at 600 N compressive load, 5 Hz, and 1 million cycles. The mean number of cycles to failure was higher for spinal instrumentation systems employing longitudinal rods than those using plates (ANOVA F = 16.94, P < .001). At 600 N, the compact Cotrel-Dubousset, TSRH, and ISOLA rod systems demonstrated mean cycles to failure ranging from 200,000 to 800,000 cycles. The remaining devices including Dyna-lok, Kirschner plate, and VSP devices had failures ranging from 50,000 to 210,000 cycles. Polyethylene cylinders representing vertebral bodies were used to eliminate the problems of biologic deterioration encountered with cadaveric spines (a full cyclical test to 1 million cycles required 56 hours), and thus to provide analysis of the weak portion of each spinal system. The failure of eleven of the twelve spinal systems occurred by fracture of a pedicle screw, most commonly at the junction of the upper screw thread and the collar (Kirschner, AO fixator, standard CD, ISOLA, and TSRH). However, in Dynalok and VSP systems, fracture of the threaded portion of the screw just posterior to the integral nuts was the most common screw fracture location. The compact CD system was the only spinal implant that consistently failed by fracture of the longitudinal spinal member (rod). The fatigue life of rod based systems was longer than plate based systems. These studies confirm the importance of anterior column load sharing (vertebral body, corpectomy bone graft) as the mean bending strength demonstrated by these implant systems was not inordinately high using this "worst case scenario" model.

Effects of chondroitinase ABC and chymopapain on spinal motion segment biomechanics. An in vivo biomechanical, radiologic, and histologic canine study.

STUDY DESIGN: The biomechanical effects of chondroitinase ABC and chymopapain related to spinal segmental instability were investigated using a canine model, as well by as radiologic and histologic analyses. OBJECTIVES: To evaluate the biomechanical, radiologic, and histologic affects on the lumber intervertebral disc of chondroitinase ABC compared with chymopapain. SUMMARY OF BACKGROUND DATA: No study on the biomechanical effects of chondroitinase ABC has been reported. METHODS: Forty-eight lumbar intervertebral discs in eight beagles were randomly assigned to three groups and received one of three materials: chondroitinase ABC, chymopapain, or buffered saline, using a lateral percutaneous procedure. One week after injection, the animals were killed and the lumbar spinal motion segments were removed. Spinal segmental instability after chemonucleolysis was evaluated in spinal motion segments without posterior elements. Radiologic and histologic changes were also investigated. RESULTS: Spinal segmental instability and disc space narrowing were more greater in the chymopapain group than in the chondroitinase ABC group. Destruction of nucleus and anulus proteoglycans, indicated by loss of safranin-O staining, was less intense in chondroitinase ABC-injected discs. CONCLUSIONS: Chondroitinase ABC results in less spinal segmental instability, disc space narrowing, and destruction of proteoglycans in intervertebral disc matrix than chymopapain.

Biomechanical role of the posterior elements, costovertebral joints, and rib cage in the stability of the thoracic spine.

STUDY DESIGN: This is a biomechanical study of the thoracic spine. Various ligaments and joints were resected sequentially and nondestructive cyclic loading tests were performed. Effects of each resection were analyzed biomechanically. OBJECTIVES: To investigate the role of the posterior elements, costovertebral joints, and rib cage in the stability of the thoracic spine. SUMMARY OF BACKGROUND DATA: There have been no experimental studies concerning the mechanical interaction between the thoracic spine and rib cage. METHODS: Eight canine rib cage-thoracic spine complexes, consisting of the sixth to eighth ribs, sternum, and T5-T9 vertebrae, were used. Six pure moments along three axes were applied to the specimens, and angular deformation of T6-T7 was recorded. After testing the intact specimen, resection of the stabilizers was conducted incrementally in the following manner: 1) removal of the posterior elements at T6-T7, 2) resection of the bilateral seventh costovertebral joints, and finally, 3) destruction of the rib cage. The same loading tests were repeated at each stage. The ranges of motion and neutral zones were calculated by digitization. RESULTS: A large increase in the range of motion in flexion-extension was observed after resection of the posterior elements and in lateral bending and axial rotation after resection of the costovertebral joints. A significant increase in the neutral zone in lateral bending and axial rotation was observed after bilateral resection of the costovertebral joints and destruction of the rib cage. CONCLUSIONS: The costovertebral joints and rib cage play an important role in providing stability to the thoracic spine. The state of the costovertebral joints and rib cage should be assessed to evaluate the stability of the thoracic spine.

Biomechanical role of the intervertebral disc and costovertebral joint in stability of the thoracic spine. A canine model study.

STUDY DESIGN: Biomechanical evaluation was performed to investigate the stability of the thoracic spine. Unilateral resection of the intervertebral disc, the rib head joint, and the costotransverse joint were sequentially performed, and nondestructive cyclic loading tests were conducted at each injury stage to examine the roles of the intervertebral disc and the costovertebral joint of the thoracic spine. The effects of each resection were three-dimensionally analyzed as the main motion and the associated coupled motions. OBJECTIVE: To examine the role of the intervertebral disc and the costovertebral joint in stability of the thoracic spine. SUMMARY OF BACKGROUND DATA: The effects of unilateral resection of the intervertebral disc and the costovertebral joints in the thoracic spine with the rib cage have not been documented three-dimensionally in a biomechanical study. MATERIALS AND METHODS: Ten canine rib cage-thoracic spine complexes, consisting of the sixth to eighth ribs, the sternum and T5-T8 vertebrae, were used. Six pure moments along three axes, flexion-extension, lateral bending, and axial rotation, were applied to the specimen, and the angular deformation between T6-T7 was recorded by a stereophotogrammetric method. After the intact specimens were tested, staged resections were conducted in the following manner: partial resection of the T6-T7 intervertebral disc, performed as a resection of the anterior longitudinal ligament, the nucleus pulposus, and the annulus fibrosus on the approach side, leaving the posterior longitudinal ligament intact; resection of the right seventh rib head with the joint capsule; and resection of the right seventh costotransverse joint. At each stage, the main motion and associated coupled motions were determined three dimensionally. RESULTS: The ranges of motion (ROM) in flexion-extension, lateral bending, and axial rotation were significantly increased after partial discectomy (P < 0.01). Moreover, along with large increases in the ROM of the main motions in left axial rotation and right lateral bending, coupled motions, expressed by right lateral bending and left axial rotation, showed marked increases after resection of the rib head joint (P < 0.05). The neutral zones also increased in lateral bending, axial rotation, and flexion-extension after partial discectomy (P < 0.01). A further increase in the neutral zone was observed in lateral bending after resection of the right seventh rib head (P < 0.01). CONCLUSIONS: In this canine spine model, the intervertebral disc regulates the stability of the thoracic spine in flexion-extension, lateral bending, and axial rotation. Moreover, the articulation of the rib head with the vertebral bodies provides stability to the thoracic spine in lateral bending and axial rotation. Unilateral resection of the rib head joint after partial discectomy on the same side produces significant coupled motions in lateral bending and axial rotation, resulting in a significant decrease in thoracic spinal stability, and integrity.