Masatsune Yamagata

Sensory Innervation of the Dorsal Portion of the Lumbar Intervertebral Disc in Rats

STUDY DESIGN The vertebral levels of dorsal root ganglia innervating the dorsal portion of the L5-L6 intervertebral disc were investigated in rats using a retrograde transport method. The pathways and functions of nerve fibers supplying the dorsal portion of the disc were determined by denervation and immunohistochemistry. OBJECTIVES The dorsal portion of the lumbar intervertebral disc has been reported to be innervated segmentally, but anesthetic block of the paravertebral sympathetic trunks and the L2 spinal nerve can relieve discogenic low back pain. In the current study, the sensory innervation of the dorsal portion of the L5-L6 intervertebral disc was investigated, because the disc anatomically corresponds to the L4-L5 disc in humans, and the dorsal portion of the human L4-L5 disc is frequently subject to injury that causes low back pain. METHODS A retrograde transport of Fluoro-Gold (F-G; Fluorochrome, Denver, CO) was used. Subjects included nontreated control (n = 32) and sympathectomized rats in which paravertebral sympathetic trunks were removed from L2 to L3 (n = 9). In a ventral approach, Fluoro-Gold crystals were placed on the dorsal portion of the L5-L6 disc, and labeled neurons in the bilateral dorsal root ganglia from T10 to L6 were counted. RESULTS Fluoro-Gold crystals did not leak from the dorsal portion of the L5-L6 disc in 14 of the 32 nontreated rats and in 5 of the 9 sympathectomized rats. These rats were used for analysis. Fluro-Gold-labeled neurons were found in dorsal root ganglia from T13 to L6 in the 14 control rats but only from L2 to L6 in the 5 sympathectomized rats. CONCLUSION The dorsal portion of the L5-L6 disc of rats was shown to be multisegmentally innervated by the T13 to L6 dorsal root ganglia. The sensory fibers from T13, L1, and L2 dorsal root ganglia were shown to innervate the dorsal portion of the L5-L6 disc through the paravertebral sympathetic trunks. In contrast, those from the L3-L6 dorsal root ganglia may innervate the dorsal portion of the L5-L6 disc through the sinuvertebral nerves.

MECHANICAL STABILITY OF THE PEDICLE SCREW FIXATION SYSTEMS FOR THE LUMBAR SPINE

Five different pedicle screw systems: AO Fixator Interne, VSP Steffee plate, Luque ISF, modified Zielke, and Chibatype plate screw system (experimental device), were evaluated for biomechanical strength. A fatigue test for the screw, compressive, and torsional tests for the pedicle screw systems and a pull-out test of the pedicle screw were done. Even the Schanz screw, which showed the highest endurance limit, may be broken under the continuous loading condition in the body. The AO Fixator Interne and Steffee plate system themselves are rigid and are indicated for injuries that need reduction. The Luque ISF, modified Zielke, and Chiba-type plate screw systems, however, are indicated for degenerative lumbar disease requiring in situ fusion. There was a linear positive correlation between the bone mineral density of the vertebral body and the pull-out strength of the pedicle screw (correlation coefficient, 0.68). The fixation strength of the pedicle screw to the bone decreased remarkably in osteoporosis.

Shock wave application to rat skin induces degeneration and reinnervation of sensory nerve fibres.

There have been several reports on the use of extracorporeal shock waves in the treatment of pseudarthrosis, calcifying tendinitis, and tendinopathies of the elbow. However, the pathomechanism of pain relief has not been clarified. To investigate the analgesic properties of shock wave application, we analyzed whether it produces morphologic changes in cutaneous nerve fibres. In normal rat skin, the epidermis is heavily innervated by nerve fibres immunoreactive for protein gene product (PGP) 9.5 and by some fibres immunoreactive for calcitonin gene-related peptide (CGRP). There was nearly complete degeneration of epidermal nerve fibres in the shock wave-treated skin, as indicated by the loss of immunoreactivity for PGP 9.5 or CGRP. Reinnervation of the epidermis occurred 2 weeks after treatment. These data show that relief of pain after shock wave application to the skin results from rapid degeneration of the intracutaneous nerve fibres.

Three-dimensional motion analysis of the cervical spine with special reference to the axial rotation.

The purpose of this study is to obtain basic data on the rotational motion of the cervical spine. Twenty normal men aged 25 to 31 years were investigated. Biplanar roentgenograms of the neck with the head held in neutral and maximally rotated positions were taken in a reference frame. Three sets of x-ray films were measured using a three-dimensional analysis system composed of a digitizer and a personal computer. Total axial rotation was 105° on an average between the occiput and the C7 vertebra. Seventy percent of the total axial rotation occurred between the occiput and the C2 vertebra. Each motion segment between the C2 and C7 vertebrae showed from 4° to 8° rotation on an average. When the head was rotated, lateral bending occurred by coupling in the same direction as rotation at each segment below the C3-C4 level, and in the opposite direction above the C2-C3 level. At the same time, flexion took place by coupling at each segment below the C5-C6 level, and extension above the C4-C5 level.

Long-term results of anterior interbody fusion for treatment of degenerative spondylolisthesis

Thirty-nine patients, 34 women and five men, underwent anterior decompression and interbody fusion for degenerative spondylolisthesis between February 1958 and August 1988. Their average age at surgery was 51 years (range, 34-74 years), and their average follow-up period was 12 years 7 months (range, 6 months to 30 years). Clinical evaluation was done by the score rating system of the Japanese Orthopaedic Association (JOA Score). Patients with JOA scores of 25 points or more were rated as “satisfactory.” Survivorship was analyzed by the method of Kaplan and Meier to determine the cumulative percentage of patients with satisfactory results. The following results were obtained: Seventy-six percent of the patients had satisfactory results for 10 years after the anterior interbody fusion, 60% for 20 years, and 52% for 30 years. Irrespective of their age at surgery, the patients generally maintained satisfactory results up to 65 years of age.

Sensory innervation to the anterior portion of lumbar intervertebral disc

Study Design The level of dorsal root ganglia that receives sensory afferent nerves from the anterior portion of the lower lumbar intervertebral disc was investigated in rats using a retrograde transport method. Objectives Sometimes patients with lower lumbar disc lesions complain of inguinal pain that does not correspond to the dermatome of the injured nerve roots. To investigate the origin of the pain, the authors studied the sensory innervation to the anterior portion of the lumbar intervertebral disc. Summary of Background Data The innervation to the posterior portion of the lumbar disc has been extensively investigated and has been reported to be segmental. However, little is known about the nerve supply to the anterior portion of the lumbar disc. Methods The retrograde transport method was used in rats. As tracers, horseradish peroxidase and choleratoxin B subunit were used. Horseradish peroxidase crystals were placed on the anterior portion of the L5‐L6 disc, and choleratoxin B subunit was injected into the L5‐L6 disc. The bilateral dorsal root ganglia were histologically examined. Results Labeling of L1 and L2 dorsal root ganglia neurons was recognized. No neurons were labeled in dorsal root ganglia of other levels, including the segmentally corresponding L5. Conclusions Using the retrograde transport method, the authors demonstrated that the anterior portion of the L5‐L6 lumbar intervertebral disc was innervated from L1 or L2 spinal nerves in rats. These results appear to explain the reason why patients with lower lumbar disc lesions sometimes complain of inguinal pain corresponding to the L1‐L2 dermatome.

Using cineradiography for continuous dynamic-motion analysis of the lumbar spine.

Study Design. Cineradiography was used to analyze continuous dynamic motion in the lumbar spine. Objectives. To identify motion patterns of the lumbar spine in asymptomatic volunteers and symptomatic patients with L4 degenerative spondylolisthesis, and to use the findings to discuss segmental instability in this disorder. Summary of Background Data. The use of radiographic findings to assess lumbar spine instability remains controversial. Although some studies have reported on lumbar kinematics during actual movement, the motion patterns in asymptomatic volunteers and symptomatic patients with L4 degenerative spondylolisthesis have not been fully clarified. Methods. While asymptomatic volunteers (n=20; mean age, 27; control group) and symptomatic patients with L4 degenerative spondylolisthesis (n=41; mean age, 63; degenerative spondylolisthesis [DS] group) flexed from a sitting neutral position and back to the neutral position (flexion course), cineradiography was used to record lateral segmental lumbar motions. Twelve frames were selected during the flexion course, and flexion-extension angle (f-e angle) and translation in the sagittal plane were measured at each motion segment (L2–L3, L3–L4, L4–L5, and L5–S1). The DS group was classified into 2 subgroups according to percentage of slip: DS group I, with a slip equal to or less than 15%; and DS group II, with a slip of more than 15%. The motion pattern was compared between the groups. Results. In the control group, f-e angle and translation at the L2–L3, L3–L4, and L4–L5 segments moved simultaneously, although the L5–S1 segment showed an initial delay. The amount of f-e angle and translation changed almost symmetrically. In both f-e angle and translation, the L4–L5 segment showed a large motion pattern. In DS group I (n=21), the L4–L5 segment showed a large motion pattern in f-e angle and an intermediate motion pattern in translation. In DS group II (n=20), the L4–L5 segment showed an intermediate motion pattern in f-e angle, and a small motion pattern in translation. The relative range of f-e angle at the L4–L5 segment had the largest range in DS group I, and the relative translation showed a serial decrease from the control group through DS group II. A significant correlation between f-e angle and translation (harmonious motion pattern) was noted at the L2–L3, L3–L4, and L4–L5 segments in the control group. The harmonious motion pattern at the L4–L5 segment was significantly less in the DS group than in the control group. The loss of harmonious motion pattern (disordered motion pattern) at L4–L5 was well-revealed in the DS group II. Conclusions. Motion analyses using cineradiography helped to explain the phenomena of lumbar spine kinematics. Based on continuous dynamic-motion analysis with cineradiography, large f-e angle and disordered motion pattern during the flexion-backward course in the DS group I was considered to be caused by segmental instability. The decreased translation and disordered motion pattern throughout the flexion course in the DS group II was considered to be caused by restabilization.

The Anatomy of the Lateral Femoral Cutaneous Nerve, with Special Reference to the Harvesting of Iliac Bone Graft*

Autogenous bone graft is frequently obtained from the anterior part of the ilium; however, many studies have shown that the harvesting of autogenous iliac bone graft carries the risk of meralgia paresthetica2,4-6,8,9. Although the lateral femoral cutaneous nerve usually emerges from the lateral border of the psoas major muscle and crosses the ilium as it runs toward the anterior superior iliac spine, its course can vary1,3,7. We investigated the anatomy of the lateral femoral cutaneous nerve, particularly as it relates to the harvesting of autogenous anterior iliac bone graft. The position of the lateral femoral cutaneous nerve was identified on both sides of the pelvis in 108 formalin-embalmed cadavera from Japanese individuals (sixty-four men and forty-four women) who had been sixty to ninety-seven years old at the time of death. Eleven of …

Results of surgery for discogenic low back pain: a randomized study using discography versus discoblock for diagnosis.

Study Design. Randomized, controlled study. Objective. To evaluate the diagnosis of discogenic low back pain (LBP) with discography and discoblock. Summary of Background Data. Discogenic LBP is usually diagnosed by magnetic resonance imaging and discography. However, the reliability of discography is controversial. Previously, we reported the usefulness of discoblock with bupivacaine for diagnosis, and discoblock improved the results of anterior interbody fusion surgery. However, that study was not a randomized, controlled study. Therefore, the purpose of the current study was to compare the results of surgery after diagnosis of LBP by discography and discoblock. Methods. Patients (n = 42) with severe LBP showing L4–L5 or L5–S1 disc degeneration on magnetic resonance imaging were evaluated by discography (1.5 mL of contrast medium) or discoblock (intradisc injection of 0.75 mL of 0.5% bupivacaine). We randomized the patients in turn. Anterior discectomy and interbody fusion were performed in patients who responded to the diagnostic procedures. The visual analogue scale score (0, no pain; 100, worst pain), Japanese Orthopedic Association Score (0, worst pain; 3, no pain), Oswestry Disability Index, and patient satisfaction before and 3 years after surgery were recorded and compared between groups. Results. Twelve patients did not show pain provocation by discography or pain relief by discoblock and were excluded. Fifteen patients who showed pain provocation by discography and 15 patients who experienced pain relief with discoblock were evaluated. Rates of improvement in the visual analogue scale score, Japanese Orthopedic Association Score, and Oswestry Disability Index score in the discoblock group were significantly higher than those in the discography group (P < 0.05) from baseline to 3 years after surgery. Three patients were dissatisfied with surgery after discography compared with one patient after discoblock. Conclusion. Pain relief after injection of a small amount of bupivacaine into the painful disc was a useful tool for the diagnosis of discogenic LBP compared with discography.

Sensory nerve fibres from lumbar intervertebral discs pass through rami communicantes: A possible pathway for discogenic low back pain

It has been thought that lumbar intervertebral discs were innervated segmentally. We have previously shown that the L5-L6 intervertebral disc in the rat is innervated bilaterally from the L1 and L2 dorsal root ganglia through the paravertebral sympathetic trunks, but the pathways between the disc and the paravertebral sympathetic trunks were unknown. We have now studied the spines of 17 rats to elucidate the exact pathways. We examined serial sections of the lumbar spine using immunohistochemistry for calcitonin gene-related peptide, a sensory nerve marker. We showed that these nerve fibres from the intervertebral disc ran through the sinuvertebral nerve into the rami communicantes, not into the corresponding segmental spinal nerve. In the rat, sensory information from the lumbar intervertebral discs is conducted through rami communicantes. If this innervation pattern applies to man, simple decompression of the corresponding nerve root will not relieve discogenic pain. Anterior interbody fusion, with the denervation of rami communicantes, may be effective for such low back pain.