Paradoxical motion in L5-S1 adult spondylolytic spondylolisthesis.

INTRODUCTION: In patients with spondylolisthesis, it is assumed that flexion accentuates anterior displacement, whereas extension causes some reduction. Paradoxical movement-where flexion causes reduction of spondylolisthesis and extension increases the anterior translation, is rarely described. In this study, we investigate the prevalence of paradoxical motion in patients with L5-S1 spondylolytic spondylolisthesis and why this abnormal motion occurs. MATERIALS AND METHODS: Flexion and extension radiographs of 41 patients with grade I and II spondylolytic spondylolisthesis of the L5-S1 segment were analysed. Patients who had previous lumbar spine surgery, recent lumbar spine trauma, those more than 50 years of age and those with poor quality radiographs were excluded. RESULTS: There were 24 male and 17 female patients. The average age was 32.7 years. Of the 41 patients, 29 (70.7%) showed no significant instability. Six (15%) patients showed anterolisthesis, where flexion accentuated the forward displacement, while further six (15%) patients showed paradoxical motion. Statistical analyses found that patients with paradoxical motion had a significantly higher slip angle. CONCLUSION: In this study, we have demonstrated that: (1) paradoxical motion in spondylolytic spondylolisthesis is more common than previously thought. (2) Patients without anterolisthesis during flexion in dynamic radiographs may still have (paradoxical) instability. (3) Paradoxical motion may be more common in patients with a low sacral slope and increased lumbosacral lordosis.

Preventing and treating discitis: cephazolin penetration in ovine lumbar intervertebral disc.

Infection can occur after any spinal procedure that violates the disc and although it is not common, the potential consequences are serious. Treatment of discitis is not always successful and the key to management is prevention. Intradiscal prophylaxis with antibiotic is routinely used in spinal surgery, but there is a limited understanding of how well antibiotics can enter the avascular disc after intravenous injection. An in vivo ovine study to optimise prophylactic and parenteral treatment of discitis is described to assess the effectiveness of cephazolin in preventing and treating infection. The concentration of cephazolin was measured in disc tissue from normal and degenerate sheep discs to determine if cephazolin can enter the disc and if disc degeneration affects antibiotic uptake. Fourteen sheep were deliberately inoculated with bacteria to induce discitis. Eight sheep ("prophylaxis" group) were given either a 0, 1, 2 or 3 g dose of prophylactic cephazolin before inoculation while the remaining sheep ("treatment" group) were treated with cephazolin commencing 7 days after inoculation for 21 days at a dose of 50 mg/kg/day. Histopathology and radiography were used to assess the effect of the different treatments. Cephazolin was given 30 min prior to sacrifice and the intradiscal concentration was measured by biochemistry. In the "prophylaxis" group all doses of antibiotic provided some protection against infection, although it was not dose dependent. In the "treatment" group discitis was confirmed radiologically and histologically in all animals from 2 weeks onwards. Biochemical assay confirmed that antibiotic is distributed throughout the disc but was present in higher concentration in the anulus fibrosus than the nucleus pulposus. This study demonstrated that whilst the incidence of iatrogenic discitis can be reduced by antibiotic prophylaxis, it could not be abolished in all incidences with a broad-spectrum antibiotic such as cephazolin. Furthermore, antibiotics were ineffective at preventing endplate destruction once an intradiscal inoculum was established.

Prophylactic cephazolin to prevent discitis in an ovine model.

STUDY DESIGN: An ovine model of discitis was used to determine the efficacy of the antibiotic cephazolin for prophylactic use in spinal surgery. OBJECTIVES: To determine in juvenile and adult sheep spines if 2-g cephazolin given at intervals over a 4-hour period would prevent iatrogenic discitis, and determine the concentration of cephazolin in nucleus and anulus tissue after administration of a bolus dose. SUMMARY OF BACKGROUND DATA: It is standard practice at our institutions to give patients undergoing spinal surgery a single prophylactic (1-2 g) dose of cephazolin with a second dose for prolonged (>4 hours) procedures. Although this regimen provides therapeutic serum levels, the levels of antibiotic in the intervertebral disc are significantly lower. Because cephazolin is a negatively charged molecule, it is thought to diffuse poorly into the disc, raising questions about its efficacy as a prophylactic antibiotic for spinal procedures. METHODS: There were 18 animals, including 9 lambs and 9 sheep, that received a single 2-g dose of cephazolin intravenously at 30-minute intervals over a 4-hour period. Two control animals (1 sheep and 1 lamb) did not receive antibiotic. All animals had diskograms at 2 previously incised lumbar levels and 2 nonincised levels using contrast that was deliberately contaminated with bacteria. Lateral spine radiographs were taken at postoperative intervals. After 12 weeks, all animals received another 2-g dose of cephazolin intravenously at intervals before the spines were removed for pathologic and biochemical analysis. RESULTS: Discitis was detected in all control animals. Of those animals given cephazolin, discitis developed in 1 sheep and 4 lambs. Discitis did not develop in any of the sheep that received cephazolin 30 minutes before inoculation. Cephazolin was detected throughout the disc but was more concentrated in the anulus fibrosus. Disc levels of cephazolin peaked at 15 minutes, at which time serum levels were up to 50 times higher. Cephazolin levels in nonoperated and incised discs were not significantly different. CONCLUSIONS: A single prophylactic 2-g dose of cephazolin administered anytime over a 4-hour period prevented discitis in almost all animals but was not as effective in lambs. Although lambs have a higher vascular supply to deliver antibiotics to the disc, it is likely that some other physiologic factor may be responsible for the increased infection rate. This study supports that timing of antibiotic prophylaxis is critical to prevent iatrogenic disc infection.

Aortic flap valve presenting as neurogenic claudication: a case report.

STUDY DESIGN: A case report of a patient who presented with pain in both lower limbs related with walking and standing as a result of an unusual vascular etiology. OBJECTIVES: To describe the pathology and treatment of an unusual case of vascular claudication. SUMMARY OF BACKGROUND DATA: Symptoms of neurogenic claudication may be mimicked by intermittent vascular claudication. Not infrequently, arterial disease coexists with spinal canal stenosis. Determination of correct diagnosis is the prerequisite for effective treatment. METHODS: The patient was a 64-year-old woman who presented with bilateral buttock pain spreading to the calves. The symptom was related to walking and climbing stairs and relieved by sitting down. MRI of the lumbosacral spine corroborated severe spinal stenosis at L3-L4 and L4-L5. Based on findings on physical examination of the peripheral pulses, an aortogram revealed a flap in the lumen functioning like a valve as the cause of her lower limb ischemic pain. RESULTS: The patient was managed by insertion of a self-expandable metallic stent with complete resolution of her symptoms. CONCLUSIONS: We report a case that was diagnosed as neurogenic claudication on clinical features and MRI evidence. However, subsequent to an aortogram the diagnosis was revised. Intermittent claudication is often difficult to distinguish from neurogenic claudication. There are no sensitive discriminators based on history alone. In the presence of poor or absent peripheral pulses, an arteriogram is necessary to ascertain the relative importance of the peripheral arterial circulation.