Yuichi Kasai

Metal concentrations in the serum and hair of patients with titanium alloy spinal implants.

Study Design. A retrospective study of serum and hair metal concentrations in patients with titanium alloy spinal implants was performed. Objective. To determine the incidence and possible causes of abnormal metal concentrations. Summary of Background Data. Several studies have demonstrated that metal debris are present in the tissues surrounding titanium alloy spinal implants. However, few studies suggest that metals dissolve, circulate in the body fluid, and accumulate in remote organs. Methods. Titanium, aluminum, and vanadium concentrations in serum and hair were measured after surgery in 46 patients with titanium alloy spinal implants (12 patients in the implant failure group and 34 patients in the no implant failure group) and 20 patients without spinal implants (control group). All the subjects were examined again 1 year after the first examination or implant removal. Results. Of the 46 patients with titanium alloy spinal implants, 16 patients (34.8%) exhibited abnormal serum metal concentrations and 11 patients (23.9%) exhibited abnormal hair metal concentrations. In the control group, three patients (15%) exhibited only abnormal serum and metal aluminum concentrations at the first examination. In both of the two patients who exhibited abnormal serum titanium concentrations and then had their spinal implants removed, the serum and hair titanium levels decreased to beneath the reference value limit in 1 year after the removal. Comparison of the implant failure and no implant failure groups showed no significant differences in the incidence of abnormal serum concentrations of titanium, aluminum, or both metals. Therefore, serum metal concentrations did not seem to be a useful indicator of hardware loosening or implant failure. Conclusions. Approximately one third of patients with titanium alloy spinal implants exhibited abnormal serum or hair metal concentrations at a mean time of mean 5.1 years after surgery. Titanium or aluminum may travel to distant organs after dissolution of metals from the spinal implants.

Effect of autologous platelet-rich plasma-releasate on intervertebral disc degeneration in the rabbit anular puncture model: a preclinical study

IntroductionPlatelet-rich plasma (PRP) is a fraction of plasma in which several growth factors are concentrated at high levels. The active soluble releasate isolated following platelet activation of PRP (PRP-releasate) has been demonstrated to stimulate the metabolism of IVD cells in vitro. The in vivo effect of PRP-releasate on degenerated IVD remains unknown. The purpose of this study was to determine the reparative effects of autologous PRP-releasate on degenerated intervertebral discs (IVDs).MethodsTo induce disc degeneration, New Zealand white rabbits (n = 12) received anular puncture in two noncontiguous discs. Autologous PRP and PPP (platelet-poor plasma) were isolated from fresh blood using two centrifugation techniques. Four weeks after the initial puncture, releasate isolated from clotted PPP or PRP (PPP- or PRP-releasate), or phosphate-buffered saline (PBS; control) was injected into the punctured discs. Disc height, magnetic resonance imaging (MRI) T2-mapping and histology were assessed.ResultsAnular puncture produced a consistent disc narrowing within four weeks. PRP-releasate induced a statistically significant restoration of disc height (PRP vs. PPP and PBS, P<0.05). In T2-quantification, the mean T2-values of the nucleus pulposus (NP) and anulus fibrosus (AF) of the discs were not significantly different among the three treatment groups. Histologically, the number of chondrocyte-like cells was significantly higher in the discs injected with PRP-releasate compared to that with PBS.ConclusionsThe administration of active PRP-releasate induced a reparative effect on rabbit degenerated IVDs. The results of this study suggest that the use of autologous PRP-releasate is safe and can lead to a clinical application for IVD degeneration.

A New Evaluation Method for Lumbar Spinal Instability: Passive Lumbar Extension Test

Background and Purpose. Although many studies have described clinical examination measures for the diagnosis of lumbar spinal instability, few of them have investigated the sensitivity and specificity of the measures that were used. The authors devised a passive lumbar extension (PLE) test for assessing lumbar spinal instability. The purpose of this study was to investigate the sensitivity, specificity, and positive likelihood ratio of this test. Subjects and Methods. The PLE test as well as the instability catch sign, painful catch sign, and apprehension sign tests were done for 122 subjects with lumbar degenerative diseases. The subjects were divided into 2 groups—instability positive and instability negative—on the basis of findings on flexion-extension films of the lumbar spine. The sensitivity, specificity, predictive values, and positive likelihood ratio of each test were investigated. Results. The sensitivity and specificity of the PLE test were 84.2% and 90.4%, respectively. These values were higher than those of other signs. The positive likelihood ratio of the PLE test was 8.84 (95% confidence interval=4.51–17.33). Discussion and Conclusion. The PLE test is an effective method for examining patients for lumbar spinal instability and can be performed easily in an outpatient clinic.

Biomechanical study of the lumbar spine using a unilateral pedicle screw fixation system.

Lumbar fusion combined with unilateral pedicle screw fixation has received favourable clinical reports. However, there are very few reports about the biomechanical properties of this system. The purpose of this study was to compare the biomechanics of a unilateral pedicle screw system with a bilateral system. Two fresh lumbar vertebral columns from human cadavers were used. Seven models were prepared by the sequential damage and spinal instrumentation of each specimen. Bending and rotation tests were performed to clarify the range of motion for each model using a 6-axis material tester that we have developed. We showed that the unilateral pedicle screw system offers only uneven fixation. This results in dispersion of rigidity depending on the direction of bending and rotation. The bilateral pedicle screw system, however, allows excellent fixation in all directions.

Prevalence of osteoarthritis, osteoporotic vertebral fractures, and spondylolisthesis among the elderly in a Japanese village

Purpose. To study the prevalence of osteoarthritis, osteoporotic vertebral fractures, and spondylolisthesis among elderly residents of a Japanese village and to examine the correlation between radiographic evidence of abnormality and lower back pain. Methods. 205 men (mean age, 70.7 years) and 323 women (mean age, 70.5 years) in a Japanese village participated in this cross-sectional study. Plain lateral radiographs were taken from the lower thoracic spine to the sacral spine. They were evaluated by 3 independent orthopaedic surgeons for degree of osteoarthritis (using Weiner grading system) and the presence of osteoporotic vertebral fractures and spondylolisthesis. Results. The prevalence of osteoarthritis in elderly Japanese villagers was 38.3%, whereas that of osteoporotic vertebral fractures and spondylolisthesis was 17.8% and 8.9%, respectively. There was no significant difference in osteoarthritis between men and women, but osteoporotic vertebral fractures and spondylolisthesis were significantly more common in females (p<0.01). No significant correlation was observed between lower back pain and radiographic evidence of degenerative spinal disease. Conclusion. The prevalence of spondylolisthesis in elderly Japanese was much lower than that in whites or African Americans. The prevalence of osteoarthritis or osteoporotic vertebral fractures was comparable with other English or US studies. Radiographic evidence of osteoarthritis, osteoporotic vertebral fractures, and spondylolisthesis is not necessarily associated with lower back pain.

Mixture ratios of local bone to artificial bone in lumbar posterolateral fusion.

There have been no reports on the effects of the mixture ratio of local bone graft to artificial bone on the outcome of intervertebral bone fusion. The purpose of this study was to determine whether the mixture ratio of local bone removed from laminae and spinous processes to apatite- and wollastonite-containing glass ceramic (AWGC) granules affected fusion rates in spinal fusion. Posterolateral lumbar fusion at two levels without spinal instrumentation was performed in 35 patients who were diagnosed with lumbar spinal canal stenosis. The patients were randomly divided into three groups, each of which received a different mixture ratio of local bone to AWGC granules: 2:1, 1:1, and 1:2. The total mass of grafted bone was 20 g in all three groups. The fusion rate was approximately 80% in all three groups. Our results indicate that lumbar posterolateral fusion can be successfully achieved even when the mixture ratio of local bone graft to AWGC granules is 1:2.

Thoracic myelopathy with alkaptonuria.

Study Design. A case of thoracic myelopathy with alkaptonuria (ochronotic spondyloarthropathy) is presented. Objective. To present and review the first reported case of an alkaptonuric patient with concomitant thoracic myelopathy. Summary of Background Data. Alkaptonuria, a rare hereditary metabolic disease, is characterized by accumulation of homogentistic acid, ochronosis, and destruction of connective tissue resulting in degenerative spondylosis and arthritis. Despite the high incidence of intervertebral disc diseases among patients with alkaptonuria, neurologic symptoms caused by spinal disease are rare. Thoracic myelopathy in a patient with alkaptonuria has not been previously reported. Methods. The clinical course, radiologic features, pathology, and treatment outcome of an alkaptonuria patient with thoracic myelopathy was documented. Results. Myelopathy of the patient was caused by rupture of a thoracic intervertebral disc. The neurologic symptoms of the patient were markedly improved after surgery. Conclusion. We have reported for the first time, that an alkaptonuria patient showed thoracic myelopathy caused by rupture of a thoracic intervertebral disc. Decompression followed by the instrumented fusion of the thoracic spine was effective for improving the neurologic symptoms.

New evaluation method using preoperative magnetic resonance imaging for cervical spondylotic myelopathy.

Abstract A new method based on the score of preoperative magnetic resonance images (MRI) was devised to evaluate cervical spondylotic myelopathy and predict the results of cervical laminoplasty. On T1- and T2-weighted sagittal MRI, the intervertebral disc spaces at each level from the axis to the first thoracic spine were examined as to whether the anterior or posterior subarachnoid space would be maintained or not, and for the presence or absence of spinal cord deformity. The data were divided into six grades and rated, and the total score for all sites was regarded as the preoperative MRI cumulative score. In conclusion, our method was highly reliable and useful for a preoperative evaluation and prediction of results after cervical laminoplasty for cervical spondylotic myelopathy.

Changes in water content of intervertebral discs and paravertebral muscles before and after bed rest

BackgroundAlthough low back pain can be principally produced or increased during action, it may also be induced or enhanced in the morning after bed rest. During bed rest, tissue edema (increased water content) may occur. In this study, we measured the changes in water content in the intervertebral disc and the paravertebral muscle before and after bed rest using a magnetization transfer magnetic resonance imaging (MT-MRI) technique that permits measuring water content in tissues.MethodsA total of 20 student volunteers were enrolled in this study. MT-MRI evaluation was performed before and after bed rest. To measure water content in the intervertebral disc and paravertebral muscle, two MRI sequences were performed using MT pulse-off and MT pulse-on. Based on the two images obtained, the equivalent cross-relaxation rate (ECR) was calculated.ResultsThe ECR for intervertebral discs was significantly lower after bed rest than before bed rest (P < 0.01). The ECR for paravertebral equivalent cross-relaxation rate muscles was significantly higher after bed rest than before bed rest (P < 0.05).ConclusionWe obtained results indicating that after bed rest the water content in the intervertebral disc and the paravertebral muscle was increased and decreased, respectively.

Porosity of β-tricalcium phosphate affects the results of lumbar posterolateral fusion.

Study Design: Clinical case-control and cross-sectional study. Objectives: To determine the influence of different porosities of &bgr;-tricalcium phosphate (&bgr;-TCP) as a bone substitute combined with local autograft bone obtained from decompression for lumbar posterolateral fusion (PLF). Summary of Background Data: Several reports have documented a high bone fusion rate using &bgr;-TCP as a bone substitute. &bgr;-TCP is increasingly used to supplement autograft in lumbar PLF, but the influence of different porosities of &bgr;-TCP for the lumbar PLF has not been reported. Methods: Sixty patients who were diagnosed with lumbar degenerative diseases and treated with 2-level noninstrumented lumbar PLF were divided into 2 groups. Thirty patients were treated with 75% porous &bgr;-TCP (&bgr;-TCP-75 group), and the others were treated with 60% porous &bgr;-TCP (&bgr;-TCP-60 group). The clinical and radiographic results of each patient were assessed at 2 years postoperatively. Results: Both the groups showed a good improvement rate of the Japanese Orthopaedic Association score (JOA score) at 2 years postoperatively, but there were no significant differences between them. The &bgr;-TCP-75 group represented a bone fusion rate of 70.0% (64.7% in men, 76.9% in women) and the &bgr;-TCP-60 group was 93.3% (87.5% in men, 100.0% in women). The latter exhibited a significantly better bone fusion rate than the &bgr;-TCP-75 group (P<0.05). Conclusions: In lumbar PLF, 60% porous &bgr;-TCP granules achieved a higher bone fusion rate than 75% porous &bgr;-TCP granules.