Hajime Murai

Stability of transpedicle screwing for the osteoporotic spine. An in vitro study of the mechanical stability.

The influence of bone mineral density on the stability of transpedicle screwing was studied in the human cadaveric lumbar vertebrae. The pull-out force correlated with bone mineral density. The tilting moment (load needed to tilt the screw 4 degrees cranially at the screw-plate junction) and the cut-up force (load needed to tip the end plate up by the screw) correlated with bone mineral density. A correlation was also found between the maximum insertion torque of the screw and bone mineral density. The maximum insertion torque correlated with the pull-out force, the tilting moment, and the cut-up force. In the cyclic tilting test (200 cycles), the mean value of the tilting moment at the 200th cycle was 67.4 +/- 6.1%, compared with the first cycle. The results suggest that preoperative measurement of BMD is necessary for transpedicle screwing in osteoporotic cases, and that the cyclic tilting motion decrease its mechanical stability. The authors have also concluded that the maximum insertion torque could predict the mechanical stability.

Surface strain distribution on thoracic and lumbar vertebrae under axial compression. The role in burst fractures.

STUDY DESIGN The surface strain distribution on the thoracic and lumbar vertebrae during axial compressive loading was examined. OBJECTIVES To examine the general mechanical behavior of the thoracic and lumbar vertebrae to evaluate their role in burst fractures. SUMMARY OF BACKGROUND DATA Burst fractures are generally characterized by injury to the middle column and fracturing of the superior endplate. However, results in previous biomechanical investigations have not shown how these fractures are initiated during compression. METHODS Twenty-one thoracic and lumbar vertebrae (5 T10, 10 L1, and 6 L4) with upper and lower vertebrae were studied. Three-axis rosette strain gauges were cemented to 11 sites on the vertebral surface. An axial compressive load was applied, and the strain was measured in each specimen. The strain recorded by each rosette gauge was converted into a tensile, compressive, and shear component. RESULTS The highest tensile and compressive strain was recorded at the base of the pedicle. Shear strain in the vertebral body was significantly higher than that in the lamina at all three spinal levels. At L1 and L4, the tensile strain at the superior vertebral rim was higher than that at the inferior rim. CONCLUSIONS The high tensile and compressive strains found at the base of the pedicle of T10, L1, and L4 indicate that the base of the pedicle is the site of fracture initiation. The higher tensile strain at the superior vertebral rim of L1 and L4 supports the clinical observation of the thoracolumbar burst fractures.

Inverse relation between osteoporosis and spondylosis in postmenopausal women as evaluated by bone mineral density and semiquantitative scoring of spinal degeneration

Study Design. The relation between bone mineral density and severity of spondylosis was evaluated in postmenopausal women. Objective. To examine the possible inverse relation between osteoporosis and spondylosis by evaluating the association between bone mineral density and osteophyte formation or intervertebral disc narrowing using a semiquantitative scoring system. Summary of Background Data. The literature contains studies demonstrating an inverse relation between osteoporosis and spondylosis as well as those documenting insufficient support for such a relation. However, in these studies, only limited-range grading systems (e.g., Grades 1–4) were used to evaluate the severity of spondylosis. Methods. In this study, 104 postmenopausal women older than 60 years underwent bone mineral density measurement of the lumbar spine (anteroposterior, lateral, and midlateral) and proximal femur (femoral neck, trochanter, and Ward’s triangle) using dual-energy x-ray absorptiometry. Raw data representing the semiquantitative osteophyte score and disc score as well as the number of vertebral fractures were obtained using spinal radiograph. Correlations between bone mineral density and the radiographic variable were then analyzed. Results. Significant negative correlations were found between all bone mineral density data and the number of vertebral fractures (−0.524 ≤r ≤ −0.347;P < 0.05). Marginal/moderate positive correlations were observed between the osteophyte score and the bone mineral density data (0.263 ≤ r ≤ 0.580, P < 0.05), and between the disc score and the bone mineral density data (0.233 ≤ r ≤ 0.570, P < 0.05). Conclusions. On the basis of the finding that spondylotic changes in postmenopausal women exhibit positive correlations not only with the lumbar bone mineral density, but also with the remote-site bone mineral density, this study supports the view that osteoporosis has an inverse relation with spondylosis.

Total spondylectomy for primary malignant, aggressive benign, and solitary metastatic bone tumors of the thoracolumbar spine.

The records of 14 patients with malignant or aggressive benign vertebral tumors of the thoracolumbar spine who underwent total spondylectomy (TS) were evaluated retrospectively. Total spondylectomy was performed by bisecting the affected vertebra through the pedicle using fine threadwire saws and removing the vertebra en bloc through the posterior procedure alone or the one-stage anteroposterior combined procedure. Remarkable pain relief and ambulation after surgery were achieved in all 14 patients. No serious complications occurred. Nerve roots were sacrificed in seven cases. A marginal surgical margin was achieved in 10 cases and an intralesional surgical margin was achieved in four. At the site of the osteotomized pedicle, the surgical margin was marginal, with the possibility of tumor-cell contamination in 10 cases. Local recurrence was found in three cases of posterior total spondylectomy at 0.3 to 3.5 years (mean, 3.2 years) follow-up evaluation at the other site of the osteotomized pedicle. These results suggest that this type of total spondylectomy is effective in controlling local recurrence without incurring major complications and is a clinically useful procedure.

Nontraumatic acute complete paraplegia resulting from cervical disc herniation: a case report.

Study Design. A case report of nontraumatic acute complete paraplegia resulting from cervical disc herniation. Objectives. To describe a rare case of nontraumatic paraplegia resulting from enlargement of a herniated disc in the cervical spine and to outline appropriate management of a patient with severe spinal cord compression secondary to disc herniation with developmental spinal canal stenosis. Summary of Background Data. Acute progression of myelopathy into complete paraplegia resulting from disc herniation is rare. There are only four reported cases of nontraumatic acute myelopathy secondary to cervical disc herniation. No other report has described magnetic resonance imaging findings noted before and after the onset of acute myelopathy. Methods. A cervical disc herniation at C6–C7 is reported in a 29-year-old man who had nontraumatic acute complete paraplegia. Neurologic and magnetic resonance imaging findings are evaluated and discussed. Results. Disc herniation at C6–C7 enlarged nontraumatically, resulting in complete paraplegia. Emergent anterior decompression followed by secondary posterior multilevel decompression was performed. Magnetic resonance imaging studies revealed localized high signal intensity change in the spinal cord. No neurologic recovery was achieved 3 years post-surgery. Conclusion. We emphasize that there is a possibility of acute, irreversible progression of paralysis secondary to nontraumatic enlargement of cervical disc herniation with canal stenosis. In these cases, immediate early decompressive surgery is crucial to the prevention of severe myelopathy.

Posterior-approach vertebral replacement with rectangular parallelepiped cages (PAVREC) for the treatment of osteoporotic vertebral collapse with neurological deficits.

Study Design: A retrospective clinical study. Objective: To assess the efficacy of a new spinal reconstruction technique (posterior-approach vertebral replacement with rectangular parallelepiped cages: PAVREC) for the treatment of osteoporotic late vertebral collapse with neurological deficits. Summary of Background Data: Poor bone quality and medically complicated situations obfuscate precise treatment for paraplegia caused by osteoporotic vertebral collapse. Recently, posterior-approach corpectomy and replacement with a cylindrical cage have been proposed. However, postoperative cage subsidence and kyphosis progression frequently occurs. Methods: Surgical invasiveness, perioperative complications, and clinical and radiographic outcomes in a total of 19 consecutive patients with osteoporosis (7 men and 12 women; mean age, 75 y) who underwent PAVREC with a mean follow-up period of 45.6 months (range, 16–79 mo) were reviewed. The affected vertebral levels ranged from T12–L4. The mean bone mineral density of the femoral neck was 0.611±0.077 g/cm2 (mean±SD). Results: Mean operative time was 261 minutes (range, 155–326 min). Mean blood loss was 664 mL (range, 197–1595 mL). There were no reported surgical complications. Neurological deficits evaluated with the Frankel grading score improved >1 grade after surgery in all patients. Mean preoperative visual analog scale scores for back or leg pain (7.2; range, 6–9) significantly improved after surgery (1.4; range, 0–2) (P<0.05). Local kyphosis improved from a mean of 24.6 degrees before surgery to a mean of 1.5 degrees after surgery (P<0.05), and it was maintained at a mean of 2.5 degrees at the final follow-up. Although screw loosening, cage subsidence, and subsequent vertebral fracture were seen in several cases, no additional surgeries were needed. Solid bony fusion was confirmed in all cases. Conclusions: PAVREC provided a satisfactory clinical and radiologic outcome without severe complications. This procedure can be a treatment option for osteoporotic vertebral collapse and an alternative to an anterior-approach or single posterior-approach reconstruction with a cylindrical cage.

Anterior Decompression and Shortening Reconstruction with a Titanium Mesh Cage through a Posterior Approach Alone for the Treatment of Lumbar Burst Fractures

Study Design A retrospective study. Purpose To examine the efficacy and safety for a posterior-approach circumferential decompression and shortening reconstruction with a titanium mesh cage for lumbar burst fractures. Overview of Literature Surgical decompression and reconstruction for severely unstable lumbar burst fractures requires an anterior or combined anteroposterior approach. Furthermore, anterior instrumentation for the lower lumbar is restricted through the presence of major vessels. Methods Three patients with an L1 burst fracture, one with an L3 and three with an L4 (5 men, 2 women; mean age, 65.0 years) who underwent circumferential decompression and shortening reconstruction with a titanium mesh cage through a posterior approach alone and a 4-year follow-up were evaluated regarding the clinical and radiological course. Results Mean operative time was 277 minutes. Mean blood loss was 471 ml. In 6 patients, the Frankel score improved more than one grade after surgery, and the remaining patient was at Frankel E both before and after surgery. Mean preoperative visual analogue scale was 7.0, improving to 0.7 postoperatively. Local kyphosis improved from 15.7° before surgery to -11.0° after surgery. In 3 cases regarding the mid to lower lumbar patients, local kyphosis increased more than 10° by 3 months following surgery, due to subsidence of the cages. One patient developed severe tilting and subsidence of the cage, requiring additional surgery. Conclusions The results concerning this small series suggest the feasibility, efficacy, and safety of this treatment for unstable lumbar burst fractures. This technique from a posterior approach alone offers several advantages over traditional anterior or combined anteroposterior approaches.

Measurement of vertebral body dimensions of the thoracic and lumbar spines of 242 healthy women

Abstract: To establish diagnostic criteria for osteoporosis using roentgenograms of vertebral bodies, the posterior margin, anterior margin, and central portion heights of 14 vertebral bodies in 242 healthy women were measured. It was demonstrated that the measurement of vertebral heights using a digitizer by one expert could be made with high accuracy, based on the results of comparison between roentgenograms on a 50% reduced scale and ordinary-scale roentgenograms as well as those of daily and day-to-day variations of the measured values. According to these measurements, the seventh thoracic vertebra showed the most marked tendency toward wedge formation and the fifth lumbar vertebra toward reverse-wedge formation. In the measurement of vertebral body heights, the accuracy decreased at vertebral levels where the images of thoracic vertebral bodies are superimposed upon by the shadows of cardiovascular organs. Because the variations in measurement values in Japanese were not significant in comparison with those in European and American persons, means minus 3 SD were almost the same as means minus 25% designated in Japan with respect to the ratio of anterior to posterior margin heights of vertebral bodies. Moreover, the means minus 3 SD were almost equal to means minus 20%, with respect to the ratio of central to posterior margin heights of vertebral bodies. Thus, our conclusion is that the definition of vertebral deformity as designated in Japan is sufficiently accurate for the diagnosis of osteoporosis.

Osteomyelitis of the spine caused by mycobacterium avium complex in an immunocompetent patient

Mycobacterium avium complex (MAC)-associated extrapulmonary infections, for example osteomyelitis, are relatively rare [1, 2], although they are among the most common opportunistic infections in patients with acquired immunodeficiency syndrome [3, 4]. Furthermore, abscess and fistula formation after surgical procedures are common in mycobacterium osteomyelitis [1, 5]. In this paper, we report a case of an immunocompetent patient who had multiple osteomyelitis and paraspinous abscess because of MAC infection. This case report is important for two reasons. First, we describe a rare clinical entity of disseminated osteomyelitis caused by MAC presenting primarily in an immunocompetent host without trauma. Second, as far as we are aware, this is the first reported case in which paraspinous abscess secondary to lumbar vertebral biopsy was successfully treated with computer tomography-guided percutaneous catheter drainage and intermittent irrigation with povidone–iodine solution. The patient was informed that his case report would be submitted for publication and he gave consent. Case report

Fusion of Multiple Segments Can Increase the Incidence of Sacroiliac Joint Pain After Lumbar or Lumbosacral Fusion.

Study Design. A retrospective study. Objective. To determine the risk factors for sacroiliac joint pain (SIJP) after lumbar or lumbosacral fusion. Summary of Background Data. Recently, the sacroiliac joint has gained increased attention as a source of pain after lumbar or lumbosacral fusion. We examined the factors related to the development of SIJP after lumbar or lumbosacral fusion. Methods. In total, 262 patients who underwent lumbar or lumbosacral fusion from June 2006 to June 2009 were included in this study. All patients who did not show SIJP clinically in the preoperative screening period were considered. Of these patients, 28 newly developed SIJP. We investigated whether development of SIJP after lumbar or lumbosacral fusion is related to the presence of fusion involving the sacrum (floating fusion vs. fixed fusion) and the number of fused segments. Results. The incidence of SIJP was higher with fixed fusion (13.1%) than with floating fusion (10.0%). With regard to the number of fused segments, the incidence of SIJP was 5.8% for one fused segment, 10.0% for two segments, 20.0% for three segments, 22.5% for at least four segments. Thus, the incidence was significantly higher when at least three segments were fused. Logistic regression analysis was performed to determine if the development of SIJP was related to the presence of fusion involving the sacrum or the number of fused segments. The analysis revealed that the number of fused segments was significantly associated with the development of SIJP. Conclusion. SIJP is a potential cause of low back pain after lumbar or lumbosacral fusion surgeries. Our study indicated that fusion of multiple segments (at least three) can increase the incidence of SIJP after lumbar or lumbosacral fusion. Level of Evidence: Level 3