Yasumitsu Toribatake

Expansive midline T-saw laminoplasty (modified spinous process-splitting) for the management of cervical myelopathy.

Study Design. The authors developed a method of spinous process‐splitting laminoplasty using a threadwire saw in a prospective study of 25 patients with cervical myelopathy. This report describes the surgical technique and the results of the expansive midline laminoplasty performed with an threadwire saw. Objectives. To compare the efficacy of midline, threadwire‐saw laminoplasty with that of the original spinous process‐splitting laminoplasty. Summary of Background Data. The spinous process‐splitting laminoplasty was described by Kurokawa in 1982. Although the procedure has a number of theoretical and practical advantages, it has not been widely used because of technical difficulties. Methods. Twenty‐five patients who underwent expansive, midline, threadwire‐saw laminoplasty from C3 to C7 for cervical myelopathy were studied. The threadwire saw was used to split the spinous processes. The mean follow‐up period was 34 months. Neurologic results were evaluated with pre‐ and postoperative scores, and recovery rates were evaluated by methods described in previous reports using the Japanese Orthopaedic Association scoring system. Radiographic data analyzed included plain radiographs and computed tomography scans. The duration of surgery and the amount of blood lost during this procedure using the threadwire saw were compared with the duration and blood loss that occurred during the original Kurokawas procedure using a burr. Results. In all cases, good enlargement of the cervical canal was achieved. The mean increase in cervical cross‐sectional area was 36.1%, according to computed tomography scans. No dural tears occurred, and no patients experienced any decrease in neurologic function. The neurologic recovery rate was 72%, which was almost same as the neurologic recovery rate in the original procedure. Using the threadwire saw, the mean duration of surgery was 63 minutes shorter and the mean blood loss was 70 cc less than in procedures using burrs Conclusions. The application of the threadwire saw to split the spinous processes made Kurokawas procedure simpler, faster, and safer.

The effect of hydrostatic pressure on intervertebral disc metabolism.

STUDY DESIGN By the use of pressure vessels, hydrostatic pressure was applied to intervertebral disc cells cultured in an alginate. OBJECTIVE To test the hypothesis that hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells. SUMMARY OF BACKGROUND DATA The influence of compression (both hydrostatic and mechanical) on chondrocyte metabolism was examined in a number of earlier studies. However, in most of these studies, articular cartilage, not intervertebral disc, was used, and in none of these was hydrostatic pressure applied to intervertebral disc cells cultured in alginate. METHODS Fresh cells were harvested from the lumbar intervertebral discs of dogs. Before their suspension in an alginate gel system, the cells were plated and expanded until they reached confluence. Then, by use of the alginate gel system, the cells were exposed (for up to 9 days) to specific values of hydrostatic pressure inside two stainless steel pressure vessels. One vessel was kept at 1 MPa and the other at atmospheric pressure. The effects of 1 MPa were compared against atmospheric pressure by measuring the incorporation of [3H]-proline and [35S]-sulfate into collagen and proteoglycans, respectively, for the anulus cells and nucleus cells separately, and by determining whether this incorporation was reflected by changes in the levels of mRNA for aggrecan and Types I and II collagen. RESULTS Comparisons with atmospheric pressure yielded the following findings: 1) In the incorporation studies, the nucleus and anulus cells exhibited a differential response to a hydrostatic pressure of 1 MPa. Collagen and proteoglycan syntheses were stimulated in the nucleus cells and inhibited in the anulus cells. 2) There was no significant increase in cell proliferation, as measured by DNA content, at 1 MPa for either the anulus or nucleus cells. 3) The mRNA levels of collagen (Col 1A1 and Col 2A1) and aggrecan increased at 1 MPa in both the nucleus and anulus cells. CONCLUSIONS Hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells.

Total en bloc spondylectomy and circumspinal decompression for solitary spinal metastasis.

We have developed a new surgical technique, ‘total en bloc spondylectomy’ (TES), to treat a solitary metastasis in the thoracic or lumbar vertebra. This operation is designed as a local cure for the metastatic site and involves the radical resection of the affected vertebra with a wide margin. The spondylectomy consists of two steps: en bloc laminectomy with posterior spinal instruments for stabilisation (first step) and en bloc corporectomy and replacement using a vertebral prosthesis (second step). TES makes it possible to remove the affected vertebra extracompartmentally with its tumour barrier and accomplishes circumferential decompression of the spinal cord. Before clinical practice, we constructed experimental models using cats to examine spinal cord blood flow (SCBF) after ligation of the nerve roots and circumspinal decompression. The changes of SCBF were negligible, so it was proved that TES on one vertebra has little effect on spinal cord circulation. This method was used in 24 patients. Fourteen of the 18 patients with neurological deficits improved remarkably, and the 23 evaluable cases experienced pain relief. Impending paralysis was prevented in all six patients by this surgical intervention. There has been no recurrence of the local tumour after surgery. After a median follow up period of 14.1 months, 12 patients have survived. These data suggest that TES may have a significant clinical value in the treatment of spinal metastasis.

The effect of compressive force applied to the intervertebral disc in vivo. A study of proteoglycans and collagen

Study Design. Coil springs were stretched and attached to produce a compressive force across the lumbar intervertebral discs of dogs for up to 27 weeks. Objective. To test the hypothesis that a high compressive force applied over a period of time affects the production of proteoglycans and collagen by the intervertebral disc cells. Summary of Background Data. It is a commonly held belief that high forces applied to the intervertebral disc, and to joints in general, play a role in causing degeneration. Methods. Pairs of stainless steel coil springs were stretched and attached to produce a compressive force across the lumbar intervertebral discs (L1‐L2 and L3‐L4) of 16 dogs. Dogs were killed between 13 and 27 weeks after the springs were attached. The discs (L1‐L2 and L3‐L4) were excised and assessed using immunohistochemical analyses and enzyme‐linked immunosorbent assay; T13‐L1 and L4‐L5 were used as controls. Results. The main result relates to a group effect in the six dogs, assessed using enzyme‐linked immunosorbent assay, that were generally at the highest values of force for the greatest number of weeks. For the nucleus, but not the anulus, Spearman rank correlations revealed a strong correlation between increases in force and force‐weeks (force multiplied by number of weeks) and increases in collagen type I accompanied by decreases in proteoglycans, chondroitin sulfate, and collagen type II for both experimental discs (L1‐L2 and L3‐L4), as compared with corresponding values in the controls (T13‐L1 and L4‐L5). In other words, as either the force or the force‐weeks increased, the effect on the nucleus became greater. Conclusion. A high compressive force applied to the disc over a period of time initiates changes in proteoglycans and collagen.

Vascularization of the fusion mass in a posterolateral intertransverse process fusion

Study Design. A previously characterized rabbit model was used to study vascularization of the fusion mass in a posterolateral intertransverse process fusion. Objectives. To determine the interosseus origin of the new blood vessels in a posterolateral intertransverse process fusion mass and to test the hypothesis that bone incorporation and the extent of vascularization are closely related. Summary of Background Data. It has been reported that vascularization is essential for bone graft incorporation. There are, however, few reports dealing with vascularization of the spinal arthrodesis. Methods. Thirty‐one adult New Zealand White rabbits underwent bilateral intertransverse process fusion, using autogenous iliac crest bone graft. The rabbits were killed at 3 weeks (n = 6) and 6 weeks (n = 25) after surgery, and colored silicone was injected to fix the vasculature. A semiautomated image analysis system was used to assess the percentage of the area of vascularization in the fusion mass and the transverse processes. Results. The major interosseus blood supply for vascularization of the autogenous bone graft came from upper and lower transverse processes. There were three types of fusion mass observed at 6 weeks after surgery: solid type, solid type with cartilaginous cleft, and nonunion type. There was significantly less vascularization of the fusion mass and of the transverse processes in the nonunion type compared with that in the solid type and with that in the cartilaginous cleft type. Conclusions. There is a close correlation between bone incorporation and the extent of vascularization in a posterolateral intertransverse process fusion.

Guidelines to decortication in posterolateral spine fusion

Despite the development of innovative approaches and the general success that has been achieved with spinal fusion, the rate of nonunion in some studies has been reported as high as 35%. Decortication has been shown to promote the fusion process and provides not only a rich source of vascular supply from the underlying cancellous bone, but also access to pluripotent stem cells within the marrow. Although the blood supply to the lumbar spine has been described, little attention has been paid to relevant areas of the spine most affected by decortication during the posterolateral fusion process. To assess these areas of the spine and attribute some potential importance to spinal fusion outcome, a perfusion study was designed to delineate the vascular anatomy involved in a decortication procedure. Cadaver spines were perfused with a radiopaque contrast material, fixed, decalcified, and cleared en bloc by the method of Spalteholz. Transverse, sagittal, and coronal slabs were made and the vascular supply was documented. The dominant intraosseous architecture of the vertebra reflected a cancellous bone structure, characterized by marrow and a sinusoidal blood distribution within a trabecular matrix. A contrasting architecture could be differentiated in the pars interarticularis that was more consistent with dense, cortical bone. Matrix from this region typified haversian lamellar bone and exhibited parallel osteons that contained a central vascular component. The relevance of this variance could have multiple implications, given the differences between cortical and cancellous bone in function, formation, healing, and remodeling. In posterolateral intertransverse process arthrodesis, the transverse processes and lateral facets are good areas to be decorticated, whereas the pars interarticularis is less attractive.

Regulation of vasomotion of arterioles and capillaries in the cat spinal cord: role of α actin and endothelin-1

Ring-shaped vasoconstrictions of arterioles at their branching sites have often been reported in vascular corrosion casts of the brain and spinal cord in rats and cats. It is surmised that smooth muscle cells in arteriolar walls could regulate the blood flow by changing the diameter of the lumen (ie vasomotion). However, few reports have described vasomotion at the capillary (capillaries have no smooth muscle cells). Also, there have been no reports on endothelin-1 in the arterioles and capillaries of the spinal cord. This study was designed to determine (1) the electron microscopic architecture of vasomotion; (2) the immunohistochemical identification of α actin and endothelin-1 in the arterioles and capillaries of the spinal cord. Twenty-seven adult mongrel cats were used to study vascular corrosion casts at the lumbosacral spinal cord segments immunohistologically and through scanning electron microscopic observations. Sections of the spinal cord were stained with monoclonal anti-α actin and endothelin-1 antibodies. Vascular corrosion casts demonstrated two types of vasomotion: a sausage-like peristalsis and a ring-shaped vasoconstriction at the arteriole and capillary levels. In the immunohistological study, α actin and endothelin-1 were identifiable in the vascular wall at the bifurcation, and pericytes were found to contain microfilaments of α actin. The ring-shaped vasoconstriction might be regulated by smooth muscle cells in arterioles and by pericytes in capillaries by releasing endothelin-1.

The epiconus syndrome presenting with radicular-type neurological features.

We report 15 patients with an epiconus syndrome presenting with radicular-type clinical features involving the lower extremities and identify the vertebral level at which the spinal cord terminated. All patients, consisting of 10 men and five women, aged 37 to 71 years, presented with unilateral or bilateral leg muscle atrophy as well as sensory deficit. Unilateral or bilateral reduction or absence of deep tendon reflexes were present in 13 patients, while pathological reflexes were seen in three cases and bladder dysfunction in 10. Prior to presentation, five patients with the epiconus syndrome were mistakenly diagnosed as having different spinal diseases, which were treated surgically. The level of epiconus compromise detected on radiological examination ranged from the lower level of the T10 vertebra to T12-L1 intervertebral disc level, but most frequently at T11-12 disc level. The level of termination of the spinal cord was between T12 and L1-2 disc level, but most frequently at the middle portion of the L1 vertebra, which was on average 1.6±0.4 (mean±standard deviation) vertebrae distal to the epiconus lesions. The presence of different neurological features related to epiconus compromise should be carefully examined with reference to the level of termination of the spinal cord.

Symptomatic arachnoiditis ossificans of the thoracic spine. Case report

This report describes a man aged 65 years who developed spastic paraparesis secondary to arachnoiditis ossificans in the thoracic spine. Over 35 years previously, in Southeast Asia, the patient had received repeated lumbar punctures in the treatment of meningitis possibly associated with malarial fever. He had multiple arachnoidal ossifications located at levels from T6 to T9 dorsal to the spinal cord which were well delineated by computed tomography. The lesions were completely extirpated by dorsal route surgery, and the patient had marked neurological improvement after surgery. Histology confirmed that the lesions showed mature bone that formed with an osseous marrow and trabeculae, and the lesions exhibited clusters of arachnoidal cells as well as the proliferation of osteoblasts surrounding the ossified area. Early diagnosis and surgical intervention, however, are mandatory in such cases, if the patient is to attain an acceptable degree of recovery.

Differences in Gait Characteristics of Patients with Lumbar Spinal Canal Stenosis (L4 Radiculopathy) and Those with Osteoarthritis of the Hip.

It is important to differentially diagnose thigh pain from lumbar spinal stenosis (particularly lumbar fourth nerve root radiculopathy) and osteoarthritis of the hip. In this study, using a treadmill and a motion analysis method, gait characteristics were compared between these conditions. Patients with lumbar fourth nerve root radiculopathy had increased physiological knee flexion immediately after foot-ground contact, possibly owing to a slight decrease in the muscle strength of the quadriceps femoris muscle. Patients with osteoarthritis of the hip had decreased range of motion of the hip joint probably due to anatomically limited mobility as well as gait strategy to avoid pain resulting from increased internal pressure on the hip joint during its extension. Our facile and noninvasive method can be useful for the differential diagnosis of lumbar spinal canal stenosis from osteoarthritis of the hip.