Sadaaki Nakai

Long-term follow-up study of posterior lumbar interbody fusion.

To see whether degenerative changes of the adjacent disks are accelerated by fixation of a lumbar segment, 48 patients who had undergone posterior lumbar interbody fusion (PLIF) more than 5 years previously were investigated radiographically and clinically. Narrowing of disk spaces was observed in 31% of the subjects, but it usually occurred at levels proximal to the fusion. The incidence of adjacent disk narrowing was not significantly higher after PLIF, compared with reports on degenerative changes of lumbar disks with aging. Some subjects showed narrowing of disks that were not adjacent to the fused level, suggesting that individual predisposition played a role in disk narrowing. Instability was not seen in any of the subjects. New development or elongation of the traction spurs at adjacent segments occurred at the disks proximal to the fusion. The clinical results were generally satisfactory, despite progression of degenerative changes on radiographs.

Anorectal and bladder function after sacrifice of the sacral nerves.

Study Design. The quantitative changes in anorectal and bladder functions after sacrifice of the sacral nerves were assessed. Objectives. To evaluate the bladder and anorectal functions before and after sacral nerve division in patients with sacral bone tumors. Summary of Background Data. The quantitative changes in bladder and anorectal functions after sacrifice of the sacral nerves have not been intensively studied. The purpose of this investigation was to measure the bladder and anorectal function before and after sacral nerve division using manometry and cystometry. Methods. Surgical resection of a sacral tumor was performed in five patients. The sacral nerves were sacrificed bilaterally in three patients and unilaterally in two patients. Anorectal function was evaluated on the basis of symptoms and physiologic tests. Micturition function was evaluated based on symptoms, and intravesical pressures were measured by cystometry. Results. The two patients with unilateral sacral nerve loss did not experience subjective problems with defecation or micturition, although the residual volume of urine was increased after surgery. Two of the three patients with bilateral sacral nerve loss had no urge to defecate, were unable to differentiate between feces and flatus, and experienced no urgency. Fecal incontinence was uncommon because of firm feces. It was possible to control defecation using enemas on alternate days. The third patient underwent colostomy because the maximum resting pressure, which is controlled by the hypogastric nerves, was affected before surgery. Conclusion. Unilateral sacrifice of sacral nerves results in little bladder or anorectal dysfunction.

Experimental Study on the Dynamics of Lumbosacral Nerve Root Circulation

Study Design. Experimental investigation of the dynamics of nerve root circulation. Objectives. To study the dynamics of lumbosacral nerve root circulation by using seriography in dogs. Summary of Background Data. The vascular distribution to the nerve root has been discussed mainly from the morphologic aspects, and no adequate elucidation has been presented concerning the kinetics of the blood supply to the nerve root. Methods. To investigate the direction of blood flow in the nerve roots, a series of photographs of the cauda equina were taken using a motor-driven camera immediately after 3 mL of india ink was injected through the aortic catheter manually. The changes in the blood flow direction caused by compression of the nerve root also were observed. After the dog was killed, the nerve roots were cleared by the Spalteholz technique to identify the vessels observed during the experiment. Results. The blood flow in the radicular arteries was descending in the proximal part and ascending in the distal part of the nerve roots. This observation supports the suggestion that there is a so-called watershed of the blood flow in the radicular arteries themselves. However, when the ascending radicular artery of the nerve root was cramped, the radicular blood flow on the proximal side was downward. The microangiograms also showed that there were abundant anastomoses of intrinsic vessels in the nerve roots. Conclusions. There is no relatively hypovascular region in the nerve root that is vulnerable in the course of degenerative changes in the lumbosacral spine. Therefore, it is unlikely that the watershed represents a weak point of the blood flow in the nerve root.

Anterior transvertebral herniotomy for cervical disk herniation.

This study analyzed the results of anterior transvertebral herniotomy for cervical disk herniation to assess the utility of this procedure. Anterior transvertebral herniotomy was performed in 24 patients who had cervical disk herniation without spinal canal stenosis. In most patients, a good result was obtained, but simultaneous or subsequent anterior intervertebral fusion was necessary in four patients. In one (4%) patient, the two adjacent vertebrae had fused spontaneously. The best indication for this treatment judging from the postoperative results is a large disk hernia associated with either myelopathy or radiculopathy, but without spinal canal stenosis.

Neurophysiological Changes of the Nerve Root Induced by Mechanical Compression

Physiological investigations of nerve root compression were performed experimentally using dog models. The blood flow, partial oxygen pressure, tissue pH, and action potential were more severely affected at the proximal side than at the distal side when the nerve root was compressed. When the clamp was released, the blood flow at the proximal side and the partial oxygen pressure at both sides were almost completely restored, whereas the blood flow at the distal side and the tissue pH at both sides after 60 g and 30 g force compression did not recover and persisted at the reduced level. These functional changes induced by compression not only can be caused by mechanical nerve fiber deformation, but also may be a consequence of changes in the microcirculation and endoneurial (cerebrospinal fluid) flow in the nerve root due to formation of intraradicular edema. This intraradicular edema may then lead to acidosis, with subsequent impairment of the nerve function. This suggests that intraradicular inflammatory reactions are critical factors in the development of pain associated with nerve root compression.

Propofol decreases the amplitude of motor-evoked potentials in a concetration-dependent manner

Masashi Uchida, Medicine, Makoto Nishio, Medicine, Syuntaro Hanamura, Medicine, Naoyuki Sizu, Medicine, Noriko Ikeda, Laboratory Medicine, Akihiro Yamauchi, Laboratory Medicine, Sadaaki Nakai, Medicine, Kiyoshi Takeda, PhD,Dr 1. Anesthesiology, Fujita Health University, Toyoake, Japan 2. Orthopaedic Surgery, Fujita Health University, Toyoake, Japan 3. Laboratory Medicine, Fujita Health University, Toyoake, Japan

Experimental study using diode laser in discs: the healing process in discs and adjacent vertebrae after laser irradiation

The direct and secondary changes following diode laser irradiation of intervertebral discs were studied in rabbits. A quartz fiber was inserted into the discs, and laser irradiation was applied. Subsequently, the lumbar vertebrae were extracted en bloc, and subjected to sagittal magnetic resonance (MR) imaging and histologic examination immediately after irradiation, and 3, 12, and 24 weeks after irradiation. MR images showed low signal intensity of the intervertebral discs on T2-weighted images 3 weeks after irradiation, which remained unchanged to 24 weeks. Although the signal intensity of the adjacent vertebral bodies remained unchanged on T1-weighted images, the intensity was high on T2-weighted images 3 weeks after irradiation, but had reverted to normal or was low 12 to 24 weeks after irradiation. On histologic examination, the inner layer of the annulus fibrosus was seen to protrude into the void created by vaporization of the nucleus pulposus 3 weeks after irradiation. Multinuclear chondrocytes were observed, as if the disc was being reconstructed. Fibrous tissue in the epiphysis and metaphysis was observed soon after irradiation but decreased over time and was replaced by normal bone marrow.

Experimental study using ER-YAG laser in discs: changes in glycosaminoglycan content and synthesis in discs

Changes in discs after Er-Yag laser irradiation are scarcely reported. We made an experimental study using white rabbits and Er-Yag laser. Under general anesthesia, Er-Yag laser was irradiated into lumbar discs. Three or 8 weeks after irradiation, rabbits were sacrificed, and these discs were extracted. The quantitative analysis of the glycosaminoglycan content in the annulus fibrosus, and the incorporation of 35S-sulfate in chondroitin 4 sulfate were measured. The results showed, the increased incorporation of 35S-sulfate in chondroitin 4 sulfate and chondroitin 6 sulfates in groups of laser irradiation may indicate Er-Yag laser irradiation in nucleus pulposus, accelerated glycosaminoglycan production, in the annulus fibrosus. But no difference of unsaturated isomers of chondroitin 4 sulfate, and chondroitin 6 sulfate, and no difference of saturated isomer of keratan sulfate indicate, the influence of Er-Yag laser irradiation was not so high, as to bring the quantitative changes of matrix of annulus fibrosus in term of 8 weeks.

Posterior Lumbar Interbody Fusion: With and Without Pedicle Screw Fixation

We are presently using posterior lumbar interbody fusion (PLIF) [1] for posterior decompression and simultaneous interbody fusion mainly in one or two segments in the lumbar and lumbosacral areas for selected intervertebral disk hernia cases, failed back cases, and various sorts of spondylolisthesis cases. Internal fixation with pedicle screw systems is also being conducted in selected cases so as to diminish pseudarthrosis, shorten postoperative bed rest, and reduce spondylolisthesis. In this paper we compare the results of simple PLIF and PLIF with pedicle screw fixation in order to investigate the differences between these two methods based on various parameters.