Barrie Vernon-Roberts

Annular tears and disc degeneration in the lumbar spine. A post-mortem study of 135 discs

We studied 135 lumbar discs from 27 spines removed post-mortem from subjects of an average age of 31.5 years. Defects of the annulus fibrosus were classified as peripheral, circumferential or radiating; the nucleus pulposus as normal, moderately or severely degenerate. Peripheral tears were more frequent in the anterior annulus, except in the L5-S1 disc. Circumferential tears were equally distributed between the anterior and the posterior annulus. Almost all the radiating tears were in the posterior annulus, and closely related to the presence of severe nuclear degeneration. Histology suggested that peripheral tears were due to trauma rather than biochemical degradation, and that they developed independently of nuclear degeneration. The association of peripheral annular lesions with low back pain is uncertain but our study suggests that they may have a role in the pathogenesis of discogenic pain.

Discitis after discography

Infection after intradiscal injections has been recognised as a distinct entity, but discitis after discography has often been attributed to an aseptic process or a chemical reaction to the contrast material. We examined the hypothesis that discitis after discography is always due to infection, and report a clinical review and an experimental study. Part I. We reviewed the case records and radiographs of 432 patients who had undergone lumbar discography. When an 18-gauge needle without a stilette had been used, discitis was diagnosed in 2.7% of 222 patients but stiletted needles and a two-needle technique at each level reduced the incidence to 0.7%. Seven patients with discitis after discography had undergone anterior discectomy and fusion; in them the histopathological findings were of a chronic inflammatory response. Bacteria were isolated from the discs of three of the four patients who had open biopsy less than six weeks from the time of discography. These findings suggest that bacteria were initiators rather than promoters of the response. Part II. Multiple level lumbar discography was carried out in mature sheep, injecting contrast material with or without various concentrations of bacteria. Radiographs were taken and the discs and end-plates were examined histologically and cultured for bacteria at intervals after injection. None of the controls showed any evidence of discitis but all sheep injected with bacteria had typical radiological and histopathological changes by six weeks, though cultures were almost all negative. However, at one and two weeks after injection, but usually not after three weeks, bacteria could be isolated. We suggest that all cases of discitis after discography are initiated by infection, and that a very strict aseptic technique should be used for all injections into intervertebral discs.

The origin and fate of herniated lumbar intervertebral disc tissue.

Study Design In a clinicopathologic study, disc tissue collected from surgery and from cadaveric spines was examined to test an hypothesis about the pathogenesis of herniation. Objectives To determine the origin and fate of herniated lumbar intervertebral disc tissue. Summary of Background Data Previous studies have ascribed herniated disc tissue to the nucleus, anulus, or endplate, or combinations of the three. One study describes it as newly synthesized fibrocartilage. Regardless of its origin, peripheral neovascularization of disc fragments has been described and may be related to pain symptoms. Methods Disc tissue was collected after extrusion and was examined histologically to determine its origin and fate. To test the hypothesis that sequestration results from migration of isolated, degenerate fragments of nucleus pulposus through preexisting tears in the anulus fibrosus, cadaveric lumbar discs were examined in detail. Results Ninety‐eight percent of sequestrations contained some nuclear material indicating that nucleus pulposus is the principal substance extruded from the disc. None contained anulus alone. Although vascular repair was present in 89% of specimens, it did not correlate with several clinical parameters. Conclusions The autopsy study confirmed the model of nuclear fragmentation, migration, and extrusion along radiating anular clefts. Neovascularization of extruded fragments bore no relationship with duration of sciatic pain symptoms or clinical outcome.

Long-Term Exposure of Eμ-Pim1 Transgenic Mice to 898.4 MHz Microwaves does not Increase Lymphoma Incidence

Abstract Utteridge, T. D., Gebski, V., Finnie, J. W., Vernon-Roberts, B. and Kuchel, T. R. Long-Term Exposure of Eμ-Pim1 Transgenic Mice to 898.4 MHz Microwaves does not Increase Lymphoma Incidence. Radiat. Res. 158, 357–364 (2002). A total of 120 Eμ-Pim1 heterozygous mice and 120 wild-type mice were exposed for 1 h/day 5 days/week at each of the four exposure levels in “Ferris-wheel” exposure systems for up to 104 weeks to GSM-modulated 898.4 MHz radiation at SARs of 0.25, 1.0, 2.0 and 4.0 W/kg. In addition, 120 heterozygous and 120 wild-type mice were sham-exposed; there was also an unrestrained negative control group. Four exposure levels were used to investigate whether a dose–response effect could be detected. Independent verification confirmed that the exposures in the current study were nonthermal. There was no significant difference in the incidence of lymphomas between exposed and sham-exposed groups at any of the exposure levels. A dose–response effect was not detected. The findings showed that long-term exposures of lymphoma-prone mice to 898.4 MHz GSM radiofrequency (RF) radiation at SARs of 0.25, 1.0, 2.0 and 4.0 W/kg had no significant effects when compared to sham-irradiated animals. A previous study (Repacholi et al., Radiat. Res. 147, 631–640, 1997) reported that long-term exposure of lymphoma-prone mice to one exposure level of 900 MHz RF radiation significantly increased the incidence of non-lymphoblastic lymphomas when compared to sham-irradiated animals.

The natural history of age-related disc degeneration: The pathology and sequelae of tears

Study Design. A quasi 3-dimensional pathologic survey of tears in the L4–L5 disc. Objective. To seek accurate information on the pathogenesis and outcomes of tears to facilitate correlation with radiologic imaging and biomechanical testing; and to improve laboratory models for testing hypotheses of disc function and failure. Summary of Background Data. Tears are evidence of structural failure involving the anulus. There are substantial differences in the structure and function of the anterior and posterior anulus and the nonlamellar “nucleus” is much smaller than generally conceptualized and modeled. Method. Microscopy of sections prepared from 5-mm-thick parallel sagittal slices of 70 L4–L5 discs was used to construct maps of tears in each slice and record other features of interest. A template was used to classify data for analysis. Results. Multiple-level analysis detected 20% more tears than in a single disc section. Concentric, perinuclear, and radiating tears often appeared first in the posterior disc and were numerous throughout life. However, rim lesions, transdiscal tears, endplate separations, and Schmorls nodes were infrequent in young discs. Rim lesions and transdiscal tears markedly increased in the older discs while the other tears showed modest growth. In elderly discs, many tears acquired blood vessels accompanied by nerves capable of transmitting pain. Apart from about 15% of rim lesions, healing of tears by scar tissue was absent. Links between various types of tears result in complex discographic images from older discs and the cavitation of transdiscal tears lead to segmental instability. Conclusion. Tears in the L4–L5 disc show different patterns of incidence with aging, which can be explained by current biomechanical concepts. Tears may not only perturb disc function and cause segmental instability, but the frequency of neovascularization accompanied by neoinnervation indicates that pain originating within the degenerate disc should not be dismissed as the frequent evidence of bleeding into the tear lumen indicates the susceptibility of the vessels to trauma.

Early histologic changes in lower lumbar discs and facet joints and their correlation.

Abstract Biomechanical and histologic studies have highlighted the close functional relationship between lumbar discs and their associated facet joints, and it is conceivable that their degenerative changes are interdependent. However, separation of cause from effect remains controversial. Hitherto, no study in humans has correlated the changes histologically. The present study assessed histologic changes in lower lumbar discs and their associated facet joints in patients under the age of 40 years using classification systems developed for this investigation. A specific objective was to correlate changes in discs and facet joints. Data from 15 lower lumbar spine specimens were obtained. Three parasagittal sections per disc and one section per facet joint were graded histologically. The results were correlated with age, within the functional spinal unit (FSU), and with the adjacent level. Histologic changes were found in discs and facet joints from all FSUs. There was no correlation between the age of the subject and the degree of degeneration of the disc or facet joints at either level. The extent of disc degeneration at L4/5 correlated significantly with changes at L5/S1 (P < 0.01). There was no correlation between changes in discs and the associated facet joints at either level. The results of the study showed that microscopic changes are seen in the disc and facet joints from an early age and can be quite marked in some individuals before the age of 40 years. A correlation of degenerative changes within the FSU could not be established.

Changes in endplate vascularity after an outer anulus tear in the sheep

In 31 2-year-old sheep, a 5-mm deep cut was made parallel to the end plates in the left anterolateral anulus fibrosus of 3 randomly selected lumbar intervertebral discs. At 2 months, the area of the end plate occupied by blood vessels on the left (operated) side had increased significantly (P < 0.05) in the cranial end plate to 9.94%, and to 9.39% in the caudal and plate, compared with nonoperated values of 5.17% (cranial) and 5.87% (caudal). One year after opertion, these elevated values had diminished significantly (P < 0.05) to 7.92% (cranial) and 7.13% (caudal), and continued to decline progressively to 7.48% (cranial) and 6.88% (caudal) by 2 years. In contrast, no significant differences were found on the right (nonoperated) side of the discs. Thus, there was an early proliferation of vascular channels in the end plate in the vicinity of the experimental anular lesion, but not on the nonoperated side of the same disc. Thereafter, the end plate vascularity progressively diminished toward a normal level.

Iatrogenic discitis : the role of intravenous antibiotics in prevention and treatment. An experimental study

The role of antibiotics in the treatment of latrogenic discitis remains controversial. This study was carried out to assess the ability of cephazolln (a firstgeneration cephalosporin) to penetrate the intervertebral disc and to establish the role of intravenous antibiotics in the prevention and treatment of iatrogenlc discitis.1 Six sheep had 1 g of intravenous antibiotic administered between 30 minutes and 120 minutes before being killed. Two adjacent lumbar intervertebral discs were harvested and assayed for antibiotic concentration. Cephazolln could only be detected in the animals killed at 30 minutes. Intravenous cephazolin was administered 30 minutes before bacterial inoculation in 46 discs of nine sheep. In five animals, the bacterial suspension contained radlographic contrast and, in four sheep, reconstituted chymopapain. No evidence of discitis was found at any level at death. Eight sheep were treated with intravenous cephazolin commencing 1, 2, or 3 weeks after bacterial intradiscal inoculation and for periods of up to 21 days. All discs developed discitis, and the lesions appeared to be similar, irrespective of time between inoculation and the commencement, duration, and dosage of antibiotic therapy. Our study supports the use of a suitable broad-spectrum antibiotic during any surgical procedure that invades the Intervertebral disc. Antibiotics, however, are unable to arrest the progression of discitis once it is established.

Variation in cytokines induced by particles from different prosthetic materials.

Particles of prosthetic material stimulate macrophages to release cytokines, which may cause bone loss and loosening of the prosthesis. This study investigates the possibility that particles of different prosthetic materials may induce different cytokines and thus have different effects on bone remodeling. The in vitro response of human monocytes to particles of cast and forged cobalt chrome alloy, stainless steel, and titanium aluminum vanadium alloy were compared. There was no difference in the biologic response to cobalt-chrome particles derived from cast or forged material. Cobalt-chrome particles were toxic to the cells, but titanium aluminum vanadium particles did not affect cell viability. Stainless steel particles were approximately 10 times more toxic than were cobalt-chrome particles. All particles induced the release of tumor necrosis factor and interleukin 1 beta; stainless steel particles were the most potent stimulators of interleukin 1 beta; titanium aluminum vanadium particles were the strongest stimulators of interleukin 6 and prostaglandin 2. The study showed that particles derived from prosthetic materials of different metal compositions can elicit significantly different biologic responses. Understanding these different responses may help identify materials better suited for prostheses.

The synovial response to intraarticular cobalt-chrome wear particles.

The intraarticular effects of alloy wear particles similar in size to those present in the tissues around loose total joint prostheses were studied in rat knee joints injected with laboratory-prepared particulate cobalt-chrome. The particles induced rapid proliferation of macrophages and focal degeneration of synovial tissues similar to the response seen in the articular tissues around loose total joint prostheses in humans. Bacteriologic tests excluded infection as a factor. Wear particles may contribute to the changes in the tissues around total joint prostheses and may contribute to bone resorption resulting in prosthetic loosening. Experiments on animals provide useful information about the biocompatibility of materials used in the manufacture of total joint prostheses.