Posterior atlanto-axial fusion with the Olerud Cervical Fixation System for odontoid fractures and C1-C2 instability in rheumatoid arthritis.

In posterior C1-C2 fusion, traditional wire fixation gives poor stability. The bone quality is often insufficient to provide the competent structural bone graft that is required, and the introduction of sublaminar wires is somewhat dangerous. The stability is markedly improved by adding transarticular screws, but the drawbacks of structural bone graft and sublaminar wires remain. The C1 claw of the Olerud Cervical Fixation System improves C1-C2 fixation without relying on structural bone graft or compromising the spinal canal. The aim of this study was to evaluate radiological healing and possible complications in a consecutive series of C1-C2 fusions from our department operated with the C1 claw device. Twenty-six patients (14 women) with a mean age of 73 (range 37-93) years were included. The diagnoses were odontoid fracture in 18 patients, rheumatoid instability in 6, and odontoid non-union and os odontoideum in 1 each. The patients were followed clinically and with plain radiographs for an average of 15 (range 3-27) months. There were no neurological or vascular complications, and no secondary displacements or reoperations in the series. Twenty patients followed for 6-27 months were radiographically healed. Six patients died from unrelated causes 1-38 months postoperatively. Three of these patients had no radiographs later than the postoperative control, one had a healed odontoid fracture but resorbed bone graft at 8 months, while the remaining two patients were not healed, but showed no signs of healing disturbance at the time of death. On the basis of the findings of this study, posterior C1-C2 fusion with the Olerud Cervical Fixation System seems promising. No serious complications related to the surgical procedure were encountered. The stability of the implant obviates the use of a solid bone block as a graft and still allows a high frequency of fusion healing.

Nucleus pulposus-induced nerve root injury: effects of diclofenac and ketoprofen.

MAIN PROBLEM: Nucleus pulposus and/or chronic compression can induce spinal nerve root injury. Inflammation has been proposed as having major importance in the pathophysiologic mechanisms involved in the induction of such injuries. Corticosteroids, potent anti-inflammatory drugs, have been demonstrated to reduce nucleus pulposus-induced spinal nerve root injury. The aim of the present study was to assess the effects of two potent non-steroidal anti-inflammatory drugs (NSAIDs), diclofenac and ketoprofen, in experimental nucleus pulposus-induced spinal nerve root injury in a pig model. METHODS: Eighteen pigs were included in the study. Autologous nucleus pulposus was harvested from a lumbar disc and applied locally around the first sacral nerve root after a partial laminectomy of the first and second sacral vertebrae. Six pigs were treated with daily intramuscular injections of diclofenac, 3 mg/kg body weight, for 7 days. Six other pigs were treated with daily intramuscular injections of ketoprofen, 4 mg/kg body weight, for 7 days. As controls, six pigs received injections with physiologic saline. After 7 days, the pigs were reanesthetized and the nerve conduction velocity over the exposed nerve root area was determined. RESULTS: The nerve conduction velocity was significantly higher in pigs treated with diclofenac than in the saline-treated controls, (57 +/- 6 m/s vs 38 +/- 18 m/s, P<0.05, Student's t-test). The velocity in pigs treated with ketoprofen, 42 +/- 24 m/s, did not differ significantly from that of controls. CONCLUSIONS: This study of two potent NSAIDs indicates that nucleus pulposus-induced nerve root dysfunction may be reduced by diclofenac but not by ketoprofen. The reason for this difference is not known, but it might be related to the fact that ketoprofen and diclofenac belong to different NSAID subgroups and have a different selectivity for the two cyclo-oxygenases COX-1 and COX-2.

Effects of diclofenac and ketoprofen on nerve conduction velocity in experimental nerve root compression.

STUDY DESIGN: The effects of diclofenac and ketoprofen on nerve conduction velocity in experimental nerve root compression were evaluated in a setup using an established pig model. OBJECTIVE: To assess the effects of two potent nonsteroidal antiinflammatory drugs, diclofenac and ketoprofen, in experimental nerve root compression. SUMMARY OF BACKGROUND DATA: Compression of spinal nerve roots is recognized to be of major etiologic importance for several common spinal pain syndromes. Secondary inflammatory changes, induced by microvascular permeability changes and leakage of inflammatory mediators into the endoneural tissue, have been proposed as important for the induction of spinal nerve root injury by chronic compression. METHODS: This study involved 21 pigs. An ameroid constrictor was used to induce compression. Seven pigs were treated with daily intramuscular injections of diclofenac 3 mg/kg for 7 days. Seven other pigs were treated with daily intramuscular injections of ketoprofen 4 mg/kg. For a control, seven pigs did not receive any drug treatment. After 7 days, the pigs were reanesthetized, and the nerve conduction velocity in the compressed nerve root segments was determined. RESULTS: The nerve conduction velocity was significantly higher (P < 0.05, Student's t test) in the pigs treated with diclofenac (50 +/- 16 m/second) than in the untreated pigs (32 +/- 15 m/second). The nerve conduction velocity also was significantly higher (P < 0.05) in the pigs treated with ketoprofen (59 +/- 16 m/second) than in the untreated pigs. There were no significant differences in nerve conduction velocity between pigs treated with ketoprofen and those treated with diclofenac. CONCLUSIONS: The findings indicate that intramuscular administration of diclofenac or ketoprofen, both potent antiinflammatory drugs, may reduce nerve root dysfunction induced by compression of spinal nerve roots in an experimental pig model.

A long-term (4- to 12-year) follow-up study of surgical treatment of lumbar spinal stenosis.

Limited data are available about the long-term outcome of surgical treatment for lumbar spinal stenosis, and there is a wide variation in reported success rates. There is also a controversy regarding differences in long-term outcome between patients undergoing decompressive surgery alone and those undergoing both decompression and fusion. The aim of this study was to evaluate the long-term clinical outcome and possible complications of decompressive surgery, with special reference to possible differences between patients undergoing fusion, with or without instrumentation, and those undergoing decompression alone. All 124 patients undergoing first-time surgery for lumbar spinal stenosis between 1982 and 1991 at our department were included, and their medical records were reviewed retrospectively. Ninety-six of the patients were available for follow-up and were re-examined by an independent investigator and assessed with a questionnaire after a mean follow-up period of 7.1 (range 4.0-12.2) years. Sixty-five percent of all the patients at the follow-up were subjectively satisfied. Eighty-eight percent of the patients reported constant or daily leg pain preoperatively compared to 43% at follow-up. Constant or daily low back pain was reported by 83% of the patients preoperatively compared to 45% at follow-up. Improvement in walking capacity was found in most patients, and only 4% of the patients who had a preoperatively documented maximum walking distance reported a decreased walking capacity. Twenty-four (25%) of all patients used analgesics daily at the time of follow-up, 34 patients (35%) occasionally and 38 patients (40%) never. The patients with fusions, instrumented or non-instrumented, did not differ significantly from the unfused patients regarding any of the above-mentioned parameters. The results of the study showed that most patients demonstrated a considerable improvement in walking capacity at follow-up. This improvement was significant (P < 0.001) and of clinical importance. A significant improvement regarding both low back pain and leg pain was found postoperatively compared to preoperatively (P < 0.001). There were no statistical differences, judged by all the evaluated parameters, regarding the clinical outcome between patients who were fused and those who were not. Neither were any significant differences found between instrumented fusions compared to uninstrumented fusions. In accordance with most other long-term follow-up studies, about two-thirds (65%) of the patients claimed a satisfactory result at follow-up.

A model for chronic nerve root compression studies. Presentation of a porcine model for controlled, slow-onset compression with analyses of anatomic aspects, compression onset rate, and morphologic and neurophysiologic effects.

STUDY DESIGN: Compression onset rate, anatomic aspects, and morphologic and neurophysiologic effects in spinal nerve roots were studied in a nerve root compression model in pigs. OBJECTIVES: To analyze the compression onset rate by measuring the gradual reduction of the inner diameter of the constrictor, the motor nerve conduction velocity by electromyography, the morphologic changes by light microscopy, and the gross and vascular anatomy by dissection and ink injections, respectively, in a model for experimental chronic nerve root compression. SUMMARY OF BACKGROUND DATA: Chronic nerve root compression is recognized to be related to back pain syndromes, including sciatica. Various aspects of morphologic and physiologic changes have been studied previously in models for acute compression and chronic nerve root irritation, but a controlled, graded chronic nerve root compression model has not been described. METHODS: An ameroid constrictor was applied around a spinal nerve root just cranial to the dorsal root ganglion. The inner diameter of this constrictor gradually becomes reduced. After 1 week or 4 weeks, electromyographic measurements were performed, and tissue samples were harvested for histologic analyses. The gross and vascular anatomy of the pigs' spinal nerve roots were studied by dissection and ink injections. RESULTS: There was a statistically significant decrease in the nerve conduction velocity in compressed compared with noncompressed spinal nerve roots after 1 week and after 4 weeks. The ameroid constrictors induced nerve fiber damage, endoneural hyperemia, bleeding, and inflammation at the compression zone. There was often a severe reduction in the number of myelinated fibers after 4 weeks. CONCLUSION: A model for controlled, chronic, partial nerve root injury using a gradual compression-onset constrictor is presented. This model allows for induction of a controlled graded chronic nerve root injury and can be used for research on basic pathophysiologic mechanisms and on the effects of various interventions on nerve root injury development.

Mechanical and biochemical injury of spinal nerve roots: a morphological and neurophysiological study.

Compression may induce morphological and neurophysiological changes in nerve roots. However, it has also been demonstrated experimentally that nucleus pulposus, without any compression, may induce similar changes when applied epidurally. The present study was undertaken to examine the morphological and functional effects of autologous nucleus pulposus and the combination of nucleus pulposus and compression in a pig model. Nucleus pulposus from a lumbar disc in the same animal was applied epidurally around the first sacral nerve root in the pig, with or without a specially designed constrictor. After 1 week, nerve root conduction velocity was determined in the exposed and in the contralateral control nerve root by local electrical stimulation and EMG recordings in the back muscles. Nerve root specimens were processed for blinded light-microscopic evaluation. There was a significant reduction in nerve conduction velocity for all exposed nerve roots as well as contralateral control nerve roots when nucleus pulposus had been applied. There were no statistically significant differences between the nerve conduction velocities recorded following the combined application of nucleus pulposus and compression and those recorded after application of nucleus pulposus alone. The reductions were similar to the reduction induced by the constrictor per se, as seen in a previous study. In all series there was also a decrease in conduction velocity in the control nerve roots, in contrast to previous studies. Light microscopy demonstrated axonal changes only in nerve roots exposed to the constrictor. In conclusion, both epidural nucleus pulposus and compression may induce a significant reduction in nerve conduction velocity. The combination, however, of these two agents does not increase the magnitude of such dysfunction. The potency of nucleus pulposus to induce changes in nerve roots after epidural application was further indicated by the fact that reduction in nerve conduction velocity also occurred in the contralateral control nerve roots in this series. The histological data suggest that axonal injury can not alone explain the reduction in nerve conduction velocity, and that the morphological basis for the functional changes must be sought at the subcellular level.

Neuropeptide changes in compressed spinal nerve roots.

STUDY DESIGN: Compression-induced changes in the concentration of substance P and VIP (vasoactive intestinal polypeptide), in spinal nerve roots and dorsal root ganglia were studied in an experimental nerve root compression model in pigs. OBJECTIVES: To analyze by radioimmunoassay the concentration of the neuropeptides substance P and VIP in a model for experimental chronic nerve root compression. SUMMARY OF BACKGROUND DATA: Neuropeptides such as substance P and VIP seem to be involved in the transmission of pain and changes in the levels of these neuropeptides have been described in models where peripheral or spinal nerve injury was induced. METHODS: An ameroid constrictor was applied on a spinal nerve root just cranial to the dorsal root ganglion. The inner diameter of this constrictor is gradually reduced. After 1 or 4 weeks, tissue samples were taken from the nerve root cranial to the constrictor and from the dorsal root ganglion for measurement of substance P and VIP concentrations. RESULTS: There was a statistically significant increase in substance P concentrations in the compressed dorsal root ganglia when compared to the noncompressed dorsal root ganglia at both 1 and 4 weeks. Substance P concentration was also significantly increased in the nerve root after 1 but not after 4 weeks. The VIP levels were not significantly changed in either tissue. CONCLUSIONS: The results of the study indicates an increase in substance P levels in the dorsal root ganglion (after 1 and 4 weeks) and in the nerve root (after 1 week) in a model for chronic nerve root compression in pigs. There were no significant differences in the VIP concentrations. The study thus indicates that changes in substance P are related to experimental chronic nerve root compression.

Effects of methylprednisolone on nucleus pulposus-induced nerve root injury.

STUDY DESIGN: The effects of intervention by intravenous injection of methylprednisolone to reduce the nerve root injury after epidural application of autologous nucleus pulposus was studied in an experimental model on the pig cauda equina in 20 animals. METHODS: Nucleus pulposus was harvested from a lumbar disc. After lowering the pH of the nucleus pulposus to 3.5 it was placed onto the sacrococcygeal cauda equina. Fifteen of the pigs received a single intravenous injection of 30 mg/kg methylprednisolone, 5 minutes, 24 hours, or 48 hours, respectively, after the application. After 7 days, the nerve conduction velocity was determined, and biopsies of the cauda equina was examined by lightmicroscopy. RESULTS: In the five pigs that did not receive any methylprednisolone treatment, nerve conduction velocity was reduced, whereas it was normal in the pigs treated 5 minutes and 24 hours after nucleus pulposus application. In pigs treated after 48 hours, nerve conduction velocity was reduced only slightly. At the light microscopic level, significant changes occurred in all series. CONCLUSIONS: This study indicates that the nucleus pulposus-induced effects on nerve function in an experimental pig model may be reduced dramatically by high-dose methylprednisolone administration within 24-48 hours after epidural application of autologous nucleus pulposus. The light microscopic changes were probably not significant for the nerve function. Instead, a morphologic explanation on a subcellular level should probably be sought.

Local electrophysiologic stimulation in experimental double level cauda equina compression.

Double level compression of nerve roots has been known to exist for a long time, but only in recent years the clinical significance of such conditions has been discussed. In the current study, nerve root function in double level compression was analyzed by measurements of tail muscle electromyogram, after stimulations of 1) the intermediate segment between the compression sites and 2) cranial to the two compression sites in a pig model. The electromyogram-amplitudes were more reduced after intermediate, than cranial stimulation. This difference was suggested to be based on an additional increasing threshold to elicit an action potential within the intermediate segment due to a nutritional deficit at this location. The results further stress the importance of local changes within the intermediate segment in double level nerve root compression.