THE VALUE OF SPECT SCANS IN IDENTIFYING BACK PAIN LIKELY TO BENEFIT FROM FACET JOINT INJECTION

Lumbar facet disease is sometimes implicated in low back pain. Identif ication is difficult and this may account for a variable response. Sin gle photon emission computerized tomography (SPECT) is a scanning tech nique which enables localization of facet joint pathology. We determin ed whether recognition of facet disease by this method improved the re sponse to corticosteroid injection treatment. Fifty-eight patients wit h low back pain and displaying accepted clinical criteria for facet jo int disease were evaluated by SPECT. Twenty-two had facetal uptake of isotope. These and the tender facet joints of 36 scan-negative patient s were injected with 40 mg methylprednisolone and 1 mi 1% lignocaine u nder X-ray control. Pain was assessed by a blind observer using the Mc Gill questionnaire (MGQ), Present Pain Intensity score (PPI) and a Vis ual Analogue Scale (VAS). VAS, PPI and MGQ were reduced in the scan-po sitive patients at 1 month (P = 0.05: P = 0.0005, P = 0.005) and MGQ a t 3 months (P = 0.01), whilst scan-negative patients were unchanged. T he percentage of scan-positive patients who reported improvement was 9 5% at 1 month and 79% at 3 months, significantly greater than the cont rol group (P = 0.0005, P = 0.01). Within 6 months, pain improvement in the SPECT-positive group was no longer statistically significant. Ten derness did not correlate with increased uptake on SPECT scan. Osteoar thritis of the facets was more common in the SPECT-positive patients ( P < 0.001), but did not correspond with sites of increased uptake on S PECT scan. These results suggest that SPECT can enhance the identifica tion of back pain sufferers likely to obtain short-term benefit from f acet joint injection.