Study Design: In a prospective study, intervertebral disc material from 64 patients undergoing discectomy for sciatica and 23 control patients was analysed for the presence of bacteria.

Objective: There have been many theories postulated as to the pathogenesis of back pain and sciatica. Possible inflammatory or auto-immune aetiologies have been suggested. Stirling et al (2001) suggested a possible link between sciatica and bacterial infection by demonstrating the presence of bacteria in disc material from 19 of 36 patients with severe sciatica. Previously, we developed methods for improved detection of bacterial infection associated with failed hip implants (Tunney et al 1999).These techniques have now been applied to the detection of bacteria in intervertebral discs from patients with sciatica.

Outcome Measures: Bacterial culture and non-culture immunofluorescence microscopy, using specific monoclonal antibodies, were applied to intervertebral disc material for the detection of bacterial infection. The results were also compared with functional scores before and after surgery.

Results: This study found that 20% (n=13) of patients suffering from sciatica had culture-positive disc material compared to 9% (n=2) of controls. The anaerobe Propionibacterium acnes was the predominant bacterium isolated in both case and control groups. Bacteria were also identified in skin, wound tissue and wound washings in some patients.

Conclusions: We are unable to demonstrate an association between sciatica and infection (p=0.335). This study suggests that bacteria detected in retrieved disc material may result from skin contamination during surgery.

We studied the effect of total knee replacement on venous flow in 110 patients. Resting venous blood flow was measured using straingauge plethysmography before operation, after surgery and after discharge from hospital. There was a significant reduction in mean venous capacitance (p < 0.001) and mean venous outflow (p < 0.004) affecting only the operated leg. Both improved significantly after mobilisation in the early postoperative period, returning to preoperative levels by six days after surgery and before discharge from hospital.

Our findings showed that venous stasis may contribute to deep-vein thrombosis only in the first few days after total knee replacement. This would be the most important period for the use of flow-enhancing prophylactic devices.

Comparison with changes in blood flow after total hip replacement identified different patterns of altered haemodynamics suggesting that there are different mechanisms of venous stasis and thrombogenesis in hip and knee arthritis and during surgery for these conditions.