Biomedical subjects

Kiyoshi Kaneda

Publications and source records attributed to Kiyoshi Kaneda.

At least 19 recordsLinked to original sources

PubMed2006

Comparative study of radiographic disc height changes using two different interbody devices for transforaminal lumbar interbody fusion: open box vs. fenestrated tube interbody cage.

STUDY DESIGN: Retrospective comparative study of the postoperative subsidence of two interbody devices following posterior or transforaminal lumbar interbody fusion (PLIF/TLIF) for degenerative spondylolisthesis of the lumbar spine. OBJECTIVE: To assess certain radiograph characteristics of PLIF/TLIF using two interbody fusion devices at L4-L5. SUMMARY OF BACKGROUND DATA: PLIF can achieve spinal stabilization with vertebral body support and direct neural decompression. Although various interbody devices have been used in PLIF procedures, no radiographic studies have compared the load-bearing capabilities of open box and fenestrated tube interbody cages. METHODS: Seventy-five patients who underwent one-level PLIF in the L4-L5 [corrected] segment for degenerative spondylolisthesis were retrospectively reviewed with a minimum 2-year follow-up. Fenestrated tube (Group FT: n = 30 [corrected]) or open box (Group OB: n = 45 [corrected]) cages were used for the PLIF procedure. The following radiographic parameters were evaluated to compare the load-bearing capabilities: disc space height (DH); percent increase and decrease of disc height (% IDH and % DDH, respectively); and percent coverage of the cage on the endplate (% CC). RESULTS: There were no significant differences in the baseline data, including age, segmental instability and osteoporotic status, between the two groups. Anterior %IDH and % CC were significantly higher in Group OB than in Group FT (% IDH: 69.4% vs. 57.3%; % OC: 24.5% vs. 12.9%), and anterior and posterior % DDH were significantly higher in Group FT than in Group OB (anterior: -2.9% vs. -.1%; posterior: -6.6% vs. -.3%). Although the restored DH gradually reduced over time in both groups, significant reduction to the preoperative level only occurred in Group FT. CONCLUSIONS: The load-bearing capabilities of the open box cage are superior to those of the fenestrated tube cage. Since there were no significant differences between the baseline status of the two groups, the larger cross-sectional area and stable framework design of the open box cage appears to bring about a greater load-bearing capability. Therefore, the open box cage seems to be biomechanically more advantageous as an interbody device for PLIF than the fenestrated tube cage.

Aged↗

PubMed2006

Radiological risk factors of pseudoarthrosis and/or instrument breakage after PLF with the pedicle screw system in isthmic spondylolisthesis.

OBJECTIVE: Several studies have reported favorable results of posterolateral fusion (PLF) with pedicle screw systems (PSs) for isthmic spondylolisthesis. However, the best indication and limitations of this method still remain unclear. The present study aimed to analyze the radiological risk factors of pseudoarthrosis and/or instrumentation failure after PLF with PSs in isthmic spondylolisthesis, and to determine the limitations of this method. METHODS: The study group comprised of 101 patients with isthmic spondylolisthesis who underwent PLF with PSs. Follow-up was performed for more than 5 years. Statistical analyses with multivariate logistic regression models were used to identify risk factors of pseudoarthrosis and/or instrument failures associated with PLF with PSs. RESULTS: Average follow-up was 8 years. Fusion rate was 95%. There were instrument breakage in 6 patients, and pseudoarthrosis in 5. Statistical analysis with a logistic regression model revealed that preoperative % disc height (odds ratio: 3.60 per 10%, P<0.01) and slip angle (odds ratio: 4.48 per 10 degrees kyphosis, P<0.05) were the most crucial risk factors of pseudoarthrosis and/or instrument breakage when performing PLF for isthmic spondylolisthesis. CONCLUSIONS: In conclusion, PLF with PSs provided satisfactory results with high fusion rate. However, there were complications including pseudoarthrosis or instrument breakage in specific conditions. Preserved disc height and presence of segmental kyphosis were risk factors of these complications. Statistically, % disc height within 20% without segmental kyphosis was the best indication for PLF with PSs.

Adult↗

PubMed2006

Unilateral transforaminal lumbar interbody fusion and bilateral anterior-column fixation with two Brantigan I/F cages per level: clinical outcomes during a minimum 2-year follow-up period.

OBJECT: There are no published reports of unilateral transforaminal lumbar interbody fusion (TLIF) in which two Brantigan I/F cages were placed per level through a single portal to achieve bilateral anterior-column support. The authors describe such a surgical technique and evaluate the clinical outcomes of this procedure. METHODS: Data obtained in 86 (93.5%) of the first 92 consecutive patients who underwent the procedure were retrospectively reviewed; the minimum follow-up duration was 2 years. The clinical outcomes were evaluated using the Japanese Orthopaedic Association (JOA) scoring system. Disc height, disc angle, cage positioning in the axial plane, and fusion status were radiographically evaluated. The mean follow-up period was 33.8 months. The mean improvement in the JOA score was 77.2%. Fusion was successful in 93% of the cases. According to the Farfan method, the mean anterior and posterior disc heights increased from 20.2 and 16.9% preoperatively to 35.9 and 22.7% at follow up, respectively (p < 0.01). The mean disc angle increased from 4.8degrees preoperatively to 7.5degrees at last follow-up examination (p < 0.01). Two cages were correctly placed to achieve bilateral anterior-column support in greater than 85% of the cases. The following complications occurred: hardware migration in two patients and deep infection cured by intravenous antibiotic therapy in one patient. CONCLUSIONS: Unilateral TLIF involving the placement of two Brantigan cages per level led to good clinical results. Two Brantigan cages were adequately placed via a single portal, and reliable bilateral anterior-column support was achieved. Although the less invasive unilateral approach was used, the outcomes were as good as those in many reported series of posterior lumbar interbody fusion in which the Brantigan cages were placed via the bilateral approach.

Adult↗

PubMed2005

Traumatically induced vertebral artery occlusion associated with cervical spine injuries: prospective study using magnetic resonance angiography.

STUDY DESIGN: A prospective study using magnetic resonance angiography (MRA) on a consecutive cohort of patients with cervical spine injuries. OBJECTIVE: To investigate clinical and radiographic features of vertebral artery injury/occlusion associated with nonpenetrating cervical spine trauma. SUMMARY OF BACKGROUND DATA: With the popularization of MRA, vertebral artery injury has been a common complication of cervical spine trauma. However, detailed clinical features such as restoration of blood flow in occluded vessels and collateral circulation have not been fully evaluated. METHODS: During a 2-year period, 64 consecutive patients with cervical spine fractures and/or dislocations were prospectively evaluated for patency of the vertebral artery and collateral circulation. Extracranial and intracranial MRAs were conducted at initial injury and follow-up. RESULTS: Vertebral artery occlusion occurred in 11 patients, including 10 with unilateral and 1 with bilateral. Only the patient with bilateral occlusion was symptomatic but had no permanent neurologic deficit as a result of brain ischemia. He had complete circle of Willis, which provides sufficient collateral blood supply from anterior circulation. Follow-up MRAs revealed restoration of blood flow in occluded vessel(s) in 3 patients. All of them had compressive injuries. CONCLUSIONS: The incidence of traumatically induced vertebral artery occlusion was 17.2%. The potential for blood flow restoration was higher in compressive injuries than in distractive injuries. The mechanism of occlusion in compressive injuries is likely to be vasospasm or minor artery dissection, which may cause reversible occlusion because vessels are subjected to relatively minor stretching in compressive injuries. Vertebral artery occlusion was rarely symptomatic because of sufficient collateral blood supply through not only contralateral vertebral artery but also the circle of Willis.

Adult↗

PubMed2005

An investigational study on the healing process of anterior spinal arthrodesis using a bioactive ceramic spacer and the change in load-sharing of spinal instrumentation.

STUDY DESIGN: Ceramic anterior lumbar interbody arthrodesis was performed using an in vivo sheep model. Observations of fusion status and the load-sharing of spinal instrumentation were studied at sequential intervals for 1 year after surgery. OBJECTIVES: To elucidate the healing process of spinal arthrodesis performed with a bioactive ceramic spacer and the change in load-sharing of anterior spinal instrumentation. SUMMARY OF BACKGROUND DATA: With the improved development of spinal instrumentation, anterior spinal arthrodesis has become a standard spinal reconstruction technique; however, the mechanistic basis underlying the healing process is not well documented. Moreover, it remains unclear how load-distribution through the fusion mass and spinal instrumentation change throughout the healing process. METHODS: Using 24 sheep, a two-level anterior lumbar interbody fusion (L2-L3, L4-L5) was performed using a smooth surface and a porous surface-modified bioactive ceramic, with each segment instrumented using a one-rod anterior spinal instrumentation system. Four animals each were killed at 2, 4, 8, 12, 24, and 52 weeks after surgery. Postmortem analysis included quantification of anterior rod strain under multidirectional flexibility testing and radiographic and histologic analyses of the arthrodesed segments. RESULTS: From 0 to 8 weeks after surgery, the bending strain of the rod gradually decreased despite no obvious bone formation. From 8 to 24 weeks after surgery, the rod strain markedly decreased with the development of bridging trabeculated bone formation between vertebral bodies. After 24 weeks after surgery, minimal changes were observed in rod strain; however, the fusion mass volumetrically increased with corresponding facet joint atrophy. The porous surface-modification of ceramic did not influence the histologic healing process, despite the improvement of interface osseous union rate. CONCLUSIONS: In anterior spinal arthrodesis, spinal instrumentation is mainly exposed to bending stress, with decreased load-sharing with corresponding development of the spinal fusion. Continuous bone remodeling of the anterior fusion mass results in concurrent decreases in spinal instrumentation and posterior spinal element load-transmission. The principal healing mechanism of ceramic anterior interbody spinal fusion is not an osseous union between the ceramic and vertebral body, but bridging bone formation around the ceramic, which directly connects the vertebral bodies above and below the disc.

Animals↗

PubMed2004

Iliac crest reconstruction with a bioactive ceramic spacer.

This study aimed to investigate the long-term clinical results of the apatite wollastonite-containing glass ceramic (AWGC) iliac spacer and to discuss its efficacy in reconstruction of the bone graft donor site at the iliac crest. Thirty-one patients were studied for more than 10 years. All patients underwent anterior spinal fusion using autogenous tricortical iliac bone graft. After harvest of tricortical iliac bone graft, an AWGC iliac spacer ranging from 15 mm to 70 mm in length was press-fitted into the gap. Long-term clinical results were obtained from radiological and blood examinations. Thirty patients (97%) were satisfied with the spacer. There was new bone formation around the spacer on the radiograph. There was no abnormal silicon concentration in blood examinations. AWGC iliac spacer appears to be useful in the reconstruction of harvested iliac crest. New bone formation occurs, reducing the defect size.

Adolescent↗

PubMed2004

A biomechanical analysis of metastatic vertebral collapse of the thoracic spine: a sheep model study.

STUDY DESIGN: This is a biomechanical study using sheep thoracic spine to investigate the probability of mechanical failure of the thoracic spine with various sizes or locations of tumor metastasis. OBJECTIVE: The objectives of this study were to investigate biomechanical effects of not only tumor sizes within the thoracic vertebral body but also its involvement of other spinal components on the probability of mechanical failures of the thoracic spine. SUMMARY OF BACKGROUND DATA: There have been no experimental studies concerning mechanical influences of destruction of costovertebral joint or posterior elements as well as vertebral body on the load-bearing capacity of the thoracic spine. METHODS: Ninety-nine fresh sheep thoracic spine specimens with ribs were used (T7-T9, T10-T12). Within vertebral bodies of 39 specimens, only trabecular defects were created in different sizes. In other 48 specimens, not only vertebral body defects that were 40% to the cross-sectional area of the vertebral body but also additional destruction of costovertebral joint, pedicle, and facet joint were created. All specimens were subjected to destructive biomechanical testing. RESULTS: The failure load decreased as the defect size in the vertebral body increased. A negative linear correlation was observed between the failure load and the size of vertebral body defect (r = 0.782). With 40% cross-sectional defect in the vertebral body, additional costovertebral joint destruction brought 25% reduction of the failure load, which was statistically significant. CONCLUSION: The load-bearing capacity of metastasized vertebrae in the thoracic spine was proportionally decreased when the defect size in the vertebral body increased. Destruction of costovertebral joint significantly increased the probability of vertebral collapse.

Animals↗

PubMed2004

Alendronate reduced vertebral fracture risk in postmenopausal Japanese women with osteoporosis: a 3-year follow-up study.

The risk-reducing effect of alendronate on vertebral fractures has been consistently reported. In a 2-year, randomized, double-blind, active drug-controlled (1 microg alfacalcidol) double-dummy study, we also reported that alendronate (5.0 mg) had a fracture-reducing effect in Japanese patients with preexisting vertebral fractures. The present report describes the risk-reducing effect of alendronate (5.0 mg) for 3 years in postmenopausal osteoporotic patients. The 3-year treatment period consisted of the original 2-year double-blind study followed by a 1-year extension. A total of 170 postmenopausal female patients were involved in the third year; 90 received alendronate and 80 received alfacalcidol. Both efficacy and safety were analyzed in these 170 patients. Vertebral fracture was determined by quantitative morphometry, and vertebral bone mineral density (BMD) was measured by the DXA method (dual-energy X-ray absorptiometry). The primary efficacy endpoint was the incidence of vertebral fracture, excluding fracture cases that occurred in the first 6 months after treatment initiation. The cumulative incidence of vertebral fracture at 3 years was 7.8% (7/90) in the alendronate group and 18.8% (15/80) in the alfacalcidol group, indicating a significantly reduced risk of fractures in the alendronate group (relative risk = 0.41, 95% CI = 0.18-0.97). Lumbar spine BMD increased by 9.2% in the alendronate group (n = 26) and by 1.4% in the alfacalcidol group (n = 22) at 3 years. The safety profile of alendronate during 3 years of treatment was similar to that of alfacalcidol. The present study thus demonstrated that treatment with alendronate 5.0 mg for 3 years increased vertebral BMD and reduced the risk of vertebral fractures in Japanese, postmenopausal women with osteoporosis.

Aged↗

PubMed2004

A comparison of incidences of vertebral fracture in Japanese patients with involutional osteoporosis treated with risedronate and etidronate: a randomized, double-masked trial.

To demonstrate the clinical benefit of risedronate at 2.5 mg daily in the treatment of involutional osteoporosis, the effect of risedronate on incidence of vertebral fracture was compared with that of etidronate. A total of 547 patients with one to four vertebral fractures were randomized to receive either treatment with 2.5 mg/day of risedronate or intermittent treatment (treatment of 2 weeks and off period of 10 weeks) with 200 mg/day of etidronate for 96 weeks in a double-masked fashion. All patients received 200 mg calcium supplement daily. Lateral and anteroposterior thoracic and lumbar spine radiographs were obtained at baseline and at 24, 48, 72, and 96 weeks. Cumulative incidence rates of patients who had at least one new or worsening vertebral fracture during the 96-week period were 12.3% for risedronate and 14.2% for etidronate, and it was verified that the fracture prevention effect of risedronate was not inferior to that of etidronate. The incidence rates of fracture during the initial 24-week period were 8.8% for risedronate and 6.0% for etidronate, but the cumulative incidence rate of fracture from 24 to 96 weeks was lower in the risedronate group (3.9%) as compared to the etidronate group (8.7%). Height loss was significantly less in the risedronate group (-0.28 cm) than in the etidronate group (-0.70 cm) after 96 weeks. Decreases in bone resorption markers including urinary total deoxypyridinoline and NTX were significantly greater in the risedronate group than in the etidronate group throughout the treatment period. An improvement of patient QOL was observed in both groups. No significant difference in the incidence of adverse events was observed between the two treatments. Daily oral risedronate (2.5 mg) was shown to provide an effective therapy for involutional osteoporosis in Japanese patients with good tolerability.

Aged↗

PubMed2004

Two-year observation of artificial intervertebral disc replacement: results after supplemental ultra-high strength bioresorbable spinal stabilization.

OBJECT: This 2-year experimental study was conducted to investigate the efficacy of a bioactive three-dimensional (3D) fabric disc for lumbar intervertebral disc replacement. The authors used a bioresorbable spinal fixation rod consisting of a forged composite of particulate unsintered hydroxyapatite/poly-L-lactide acid (HA/PLLA) for stability augmentation. The biomechanical and histological alterations as well as possible device-related loosening were examined at 2 years postoperatively. METHODS: Two lumbar intervertebral discs (L2-3 and L4-5) were replaced with the 3D fabric discs, which were augmented by two titanium screws and a spanning bioresorbable rod (HA/PLLA). The segmental biomechanics and interface bone ingrowth were investigated at 6, 15, and 24 months postoperatively, and results were compared with the other two surgical groups (3D fabric disc alone; 3D fabric disc with additional anterior instrumentation stabilization). The 3D fabric disc and HA/PLLA-spinal segments demonstrated segmental mobility at 15 and 24 months; however, the range of motion (ROM) in flexion-extension decreased to 49 and 40%, respectively, despite statistically equivalent preserved torsional ROM. Histologically there was excellent osseous fusion at the 3D fabric disc surface-vertebral body interface. At 2 years posttreatment, no adverse tissue reaction nor aseptic loosening of the device was observed. CONCLUSIONS: Intervertebral disc replacement with the 3D fabric disc was viable and when used in conjunction with the bioresorbable HA/PLLA spinal augmentation. Further refinements of device design to create a stand-alone type are necessary to obviate the need for additional spinal stabilization.

Animals↗

PubMed2003

Static and dynamic analysis of five anterior instrumentation systems for thoracolumbar scoliosis.

STUDY DESIGN: A nondestructive biomechanical investigation among five anterior spinal instrumentation systems for scoliosis. OBJECTIVES: The purpose of this study is to analyze the static and dynamic biomechanical stability of five different systems. SUMMARY OF BACKGROUND DATA: Although a variety of anterior spinal instrumentation systems for scoliosis are available, very few attempts have been made at comparative biomechanical studies. METHODS: Thirty calf spines were underwent static biomechanical tests, including flexion-extension, axial rotation, and lateral bending loading modes in the multisegmental spinal model. Five anterior instrumentation systems included: 1) Texas Scottish Rite Hospital system; 2) Bad Wildungen Metz; 3) anterior ISOLA; 4) Cotrel-Dubousset Hoph; and 5) Kaneda Anterior Scoliosis System. The initial and postfatigue stability after a cyclic loading test were analyzed by measuring the range of motion at instrumented segments compared to the intact within the same specimen (% to intact). RESULTS: Two-rod systems showed a significant decrease in range of motion compared to one-rod systems in flexion-extension (P < 0.001) and axial rotation (P < 0.05). In lateral bending, all systems demonstrated a significant decrease in range of motion of less than 40% to the intact (P < 0.001). After cyclical loading test, all systems increased in range of motion. In flexion-extension, one-rod systems depicted a significant increase in range of motion, compared to two-rod systems (P < 0.05). CONCLUSIONS: In the initial stability analysis, two-rod systems are superior to one-rod systems. For one-rod systems, repeated physiologic loading may result in reduced stability in flexion-extension.

Analysis of Variance↗

PubMed2003

Local kyphosis reduces surgical outcomes of expansive open-door laminoplasty for cervical spondylotic myelopathy.

STUDY DESIGN: This retrospective study analyzed the effects of cervical alignment on surgical results of expansive laminoplasty (ELAP) for cervical spondylotic myelopathy (CSM). OBJECTIVE: To determine the limitation of posterior decompression by ELAP for CSM in the presence of local kyphosis. SUMMARY OF BACKGROUND DATA: Several studies have reported that cervical malalignment affected surgical outcomes of ELAP. However, there has been no report to demonstrate crucial determinants of surgical outcomes of ELAP for CSM in relation to cervical sagittal alignment. METHODS: The study group comprised 114 patients who underwent ELAP for CSM. All were followed up for more than 2 years. The Japanese Orthopedic Association (JOA) scoring system for cervical myelopathy (full score, 17 points) was used to evaluate surgical outcomes for each patient 2 years after surgery. Statistical analysis with multivariate logistic regression models was used to ascertain the risk factors affecting postoperative surgical outcomes. RESULTS: The average JOA scores were 9.9 points before surgery and 14 points 2 years after surgery. The recovery rate was 60.2%. Statistical analysis showed that signal intensity change on MRI and local kyphosis were the most crucial risk factors for poor surgical outcomes. Calculated with the logistic regression model, the highest risk of poor recovery was local kyphosis exceeding 13 degrees. CONCLUSIONS: The influence of cervical malalignment on neurologic recovery after ELAP for CSM was shown. When patients have local kyphosis exceeding 13 degrees, anterior decompression or posterior correction of kyphosis as well as ELAP should be considered. Expansive laminoplasty for CSM is best indicated for patients with local kyphosis less than 13 degrees.

Adult↗

PubMed2003

Bone ingrowth fixation of artificial intervertebral disc consisting of bioceramic-coated three-dimensional fabric.

STUDY DESIGN: The bone-bonding characteristic of the new artificial intervertebral disc consisting of bioceramic-coated three-dimensional fabric was evaluated mechanically and histologically in an in vivo sheep model. OBJECTIVES: To investigate the mechanical properties and the histologic appearance of the interface between the three-dimensional fabric disc and the vertebral body, and to evaluate these alterations in vivo under a spinal segmentally mobile condition. SUMMARY OF BACKGROUND DATA: Bone ingrowth to the bioceramic-coated three-dimensional fabric surface had been demonstrated already under a stable environment in preliminary animal studies. METHODS: For this study, 20 sheep underwent two-level lumbar intervertebral disc replacement with three-dimensional fabric discs (Group I) or bioceramic spacers as a comparative material (Group II). All operative segments were stabilized temporarily with spinal instrumentation for the initial ingrown phase. Four animals each were killed at 4, 6, 15, and 24 months in Group I and at 6 months in Group II, and the operative segments were subjected to either a detachment test or histologic evaluation. RESULTS: The interfacial tensile strength at 6 months was significantly higher in Group I than in Group II. No significant decrease in tensile strength was detected until 24 months after surgery in Group I. Histologically, bone ingrowth to the three-dimensional fabric surface was observed 4 months after surgery, and no aseptic loosening occurred until 24 months after surgery. CONCLUSIONS: The findings show that the three-dimensional fabric disc was firmly fixed to the vertebral body by bone ingrowth, and that this biologic fixation was preserved even under the spinal segmentally mobile condition.

Animals↗

PubMed2003

Diagnostic accuracy of magnetic resonance imaging for detecting posterior ligamentous complex injury associated with thoracic and lumbar fractures.

OBJECT: The posterior ligamentous complex (PLC) in the thoracic and lumbar spine is one of the region's important stabilizers. The precise diagnosis of PLC injury is required to evaluate the instability of the injured spine; however, the accuracy of magnetic resonance (MR) imaging for diagnosing PLC injury has remained unclear. In this study, the authors compared preoperative MR imaging findings with direct intraoperative observation of PLC injury, clarifying the former's diagnostic accuracy regarding detection of PLC injury associated with the thoracic and lumbar fractures. METHODS: Data obtained in 35 patients who sustained thoracic or lumbar injuries were reviewed. There were 17 burst fractures, six flexion-distraction injuries, and 12 fracture dislocations. Each patient underwent MR imaging examination within 3 weeks of injury. Three radiologists independently evaluated sagittal MR images in a blinded fashion. The PLC-related information was retrospectively collected from each operative record. The diagnostic accuracy of MR imaging was analyzed by comparing imaging-documented intraoperative findings. The PLC injuries were detected in 23 patients (65.7%) by direct observation during posterior spinal procedures. The diagnostic accuracy of MR imaging in detecting injury of the supraspinous ligament (SSL) and interspinous ligament (ISL) was 90.5 and 94.3%, respectively. The specificity of T1-weighted MR imaging alone for depicting the SSL was significantly greater than T2-weighted imaging alone (p < 0.05). The overall mean kappa coefficient for MR imaging findings of PLC injury was 0.803, which indicated excellent interobserver reliability; that for ISL (0.915) was significantly greater than that for SSL (0.69) (p < 0.05). CONCLUSIONS: This study clarified a high diagnostic accuracy and interobserver reliability of MR imaging for PLC injury. The precise diagnosis of PLC injury is essential to determine the mechanical instability of the injured thoracic and lumbar spine, especially in differentiating unstable (three-column) burst fractures from the relatively stable (two-column) type. The authors conclude that MR imaging is a powerful diagnostic tool to evaluate PLC injury associated with thoracic and lumbar fractures.

Humans↗

PubMed2002

Artificial intervertebral disc replacement using bioactive three-dimensional fabric: design, development, and preliminary animal study.

STUDY DESIGN: A new artificial intervertebral disc was developed, and its intrinsic biomechanical properties, bioactivity, and the effectiveness as a total disc replacement were evaluated in vitro and in vivo. OBJECTIVES: To introduce a new artificial intervertebral disc and to evaluate the in vitro mechanical properties, fusion capacity to bone, and segmental biomechanics in the total intervertebral disc replacement using a sheep lumbar spine. SUMMARY OF BACKGROUND DATA: The loss of biologic fusion at the bone-implant interface and prosthetic failures have been reported in previous artificial discs. There have been no clinically applicable discs with detailed experimental testing of in vivo mechanics and interface fusion capacity. METHODS: The artificial intervertebral disc consists of a triaxial three-dimensional fabric (3-DF) woven with an ultra-high molecular weight polyethylene fiber, and spray-coated bioactive ceramics on the disc surface. The arrangement of weave properties was designed to produce mechanical behavior nearly equivalent to the natural intervertebral disc. Total intervertebral disc replacement at L2-L3 and L4-L5 was performed using 3-DF disc with or without internal fixation in a sheep lumbar spine model. The segmental biomechanics and interface histology were evaluated after surgery at 4 and 6 months. RESULTS: The tensile-compressive and torsional properties of prototype 3-DF were nearly equivalent to those of human lumbar disc. The lumbar segments replaced with 3-DF disc alone showed a significant decrease of flexion-extension range of motion to 28% of control values as well as partial bony fusion at 6 months. However, the use of temporary fixation provided a nearly physiologic mobility of the spinal segment after implant removal as well as excellent bone-disc fusion at 6 months. CONCLUSION: An artificial intervertebral disc using a three-dimensional fabric demonstrated excellent in vitro and in vivo performance in both biomechanics and interface histology. There is a potential for future clinical application.

Animals↗

PubMed2002

Complications related to hydroxyapatite vertebral spacer in anterior cervical spine surgery.

STUDY DESIGN: This is a report of complications related to the hydroxyapatite vertebral spacer used for anterior cervical reconstructive surgery. Compression of the spinal cord by broken fragments of hydroxyapatite spacer as well as its surrounding radiolucent clear zone were observed in seven patients. OBJECTIVES: To report complications related to the use of hydroxyapatite vertebral spacer for anterior cervical reconstructive surgery and to discuss how to prevent these complications. SUMMARY OF BACKGROUND DATA: Despite previous articles reporting the clinical applications of hydroxyapatite vertebral spacer for the cervical spine, clinical reports regarding the long-term results of hydroxyapatite spacer for anterior cervical surgery and its complications have been limited. METHODS: The authors reviewed patients who underwent anterior reconstructive surgery using the hydroxyapatite spacer at other hospitals and had postoperative complications related to hydroxyapatite spacer. RESULTS: Seven patients previously treated by anterior cervical spine surgery using the hydroxyapatite vertebral spacer were referred to the authors because of unsatisfactory surgical outcomes. All the patients had a radiolucent clear zone around the spacer and experienced severe neck pain. Four had fracture of the hydroxyapatite spacer, and two had compression of the spinal cord by retropulsed fragments of broken hydroxyapatite spacers. CONCLUSIONS: Although hydroxyapatite has been used in many medical fields because of its bioactive characteristics, its mechanical properties should be improved to lessen the risks of breakage and subsequent spinal cord compression. Gentle insertion maneuvers are also important to avoid the production of cracks inside the spacer.

Aged↗

PubMed2002

An in vitro human cadaveric study investigating the biomechanical properties of the thoracic spine.

STUDY DESIGN: An in vitro human cadaveric study comparing the effects of anterior and posterior sequential destabilization conditions on thoracic functional unit mechanics was studied. OBJECTIVES: To investigate the biomechanical properties of the human thoracic spine. SUMMARY OF BACKGROUND DATA: Few studies have addressed the mechanical role of the costovertebral joints under torsion in the stability of the human thoracic spine. METHODS: Sixteen functional spinal units with intact costovertebral joints were obtained from six human cadavers and randomized into two groups based on destabilization procedures: Group 1, anterior to posterior sequential resection; and Group 2, posterior to anterior sequential destabilization. Biomechanical testing was performed after each destabilization procedure, and the range of motion under maximum load was calculated. RESULTS: Group 1: Under flexion-extension, lateral bending, and axial rotation loading, discectomy increased the range of motion by 193%, 74%, and 111%, respectively. Moreover, subsequent right rib head resection further increased the range of motion by 81%, 84%, and 72%, respectively. Group 2: Under all loading conditions laminectomy + medial facetectomy resulted in a 22-30% increase in range of motion. Subsequent total facetectomy led to an additional 15-28% increase in range of motion. CONCLUSION: The rib head joints serve as stabilizing structures to the human thoracic spine in the sagittal, coronal, and transverse planes. In anterior scoliosis surgery additional rib head resection after discectomy may achieve greater curve and rib hump correction. The lateral portion of the facet joints plays an important role in providing spinal stability and should be preserved to minimize postoperative kyphotic deformity and segmental instability when performing decompressive wide laminectomy.

Aged↗

PubMed2002

The correlation between bursoscopic and histologic findings of the acromion undersurface in patients with subacromial impingement syndrome.

PURPOSE: Ideally, decompression of the coracoacromial arch in patients with shoulder impingement syndrome should be done only at the site of impingement. However, it is very difficult to determine the exact site of impingement before acromioplasty. The objectives of this study were to investigate the relationship between findings and the histopathologic changes of the undersurface of the acromion in subacromial impingement syndrome and to evaluate the usefulness of bursoscopy in identifying the site of the impingement. TYPE OF STUDY: Case series. METHODS: We investigated the correlation between subacromial bursoscopic findings and histopathologic changes of the coracoacromial arch in 50 patients with subacromial impingement syndrome. The acromion and the coracoacromial ligaments removed during acromioplasty were fixed in 10% formalin, decalcified, embedded in paraffin, and cut into sections along the direction of the coracoacromial ligament. After staining with toluidine blue, the specimens were evaluated for pathology using an optical microscope. RESULTS: The pathologic changes were classified into 3 types according to the direction of proliferative fibrocartilaginous changes at the enthesis of the acromial insertion of the coracoacromial ligament. The bursoscopic findings were classified into 4 types. Subacromial abnormalities in the bursoscopy findings correlated with histopathologic changes at the undersurface of the acromion. On the other hand, cases with normal findings on the undersurface of the acromion on bursoscopy had hypertrophic changes of fibrocartilage at the insertion of the coracoacromial ligament to the acromion. These results suggest that, with normal findings on the undersurface of the acromion in patients with subacromial impingement syndrome, there is impingement at the coracoacromial ligament. CONCLUSIONS: Bursoscopy is a useful procedure to determine the impingement site in patients with subacromial impingement.

Acromion↗