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.

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.

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.

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.