Study Design: Prospective observational study.

Objective: To establish the sensitivity, specificity and cost-effectiveness of motor evoked potential (MEP) monitoring of lower lumbar nerve roots during instrumented spinal fusion.

Subjects: 161 patients undergoing elective lumbar spinal fusion monitored with the Neurosign 800 machine.

Outcome Measures: MEP evidence of pedicle breaches and nerve root over-distraction. Symptoms and signs of new neurological deficits postoperatively. EMG confirmation of neurological deficits in symptomatic post-operative patients.

Results: True positive results consisted of pedicle breaches detected in 15 patients (9.3%). Nerve root irritation on distraction was found in 9 patients (5.6%). These results allowed modification of the surgical technique to prevent subsequent neural injury. True negative results on active pedicle probing occurred in 134 patients (83.2%) and in 146 patients (90.7%) on passive monitoring. False positive results were detected in 7 patients (4.3%). Four patients had electrical connection problems and in three patients pedicle probing was positive but direct screw testing was negative. True negative results consisted of a failure of monitoring to detect clinically significant neurological events in five patients (3.1%). In four the symptoms and signs were transient, resolving within six weeks of surgery. In one, revision decompression of the L5 nerve roots was required.

Conclusions: MEP monitoring in our hands has a specificity of 95.4% and a sensitivity of 75%. The cost per case is around £75.

Study Design: Prospective randomised controlled trial.

Objective: To determine whether topical application of autologous growth factors (AGF) and thrombin as a spray to large spinal wounds can reduce blood loss after lumbar spinal fusion.

Subjects: Seventy patients undergoing single or multi-level lumbar spinal fusion were randomised to receive a spray of AGF and thrombin to the raw surfaces of the wound as a haemostat or to receive no spray, immediately prior to wound closure.

Outcome Measures: Intra-operative swab and suction blood loss and post-operative loss into suction drains.

Results: The median intra-operative blood loss in the two groups was similar (665 ml in the AGF/Thrombin spray group and 500 ml in the non-spray group), but the post-operative loss in the AGF/Thrombin spray group was 34% less than in the controls when expressed as the ratio of intra- to post-operative blood loss (median postoperative loss in AGF / Thrombin spray group 315 ml; median loss in the non-spray group 360 ml). There was an even greater difference (44%) when intra-operative blood loss was more than 500ml (median loss in AGF/Thrombin spray group 340 ml; median loss in the non-spray group 520 ml).

Conclusions: AGF/Thrombin spray applied to lumbar spine wounds reduces blood loss generally, but more particularly when the intra-operative loss has been considerable. This effect is probably due to local replacement of haemostatic agents when these have been systemically depleted by the surgical procedure. This study provides evidence to support the use of AGF/Thrombin spray as an effective haemostatic agent in major spinal surgery.