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ACCURACY OF POST-CONTRAST CT AND MRI SCANS IN IDENTIFYING LUMBAR RECURRENT DISC PROLAPSE. A RETROSPECTIVE STUDY OF 192 LUMBAR IPSILATERAL REVISION DISCECTOMIES (LIRD) TO COMPARE THE PRE-OPERATIVE SCAN FINDINGS TO THE INTRA-OPERATIVE ONES.



Abstract

Aim: The aim is to assess the accuracy of post-contrast imaging in identifying recurrent disc prolapse (RDP).

Material and methods: 246 revision discectomies performed between January 1994 and June 2004 were considered. Of these, for 192 LIRDs, post-contrast scans (95 CTs and 97 MRIs) within 6 months of operation, and adequate operation records were available. Original scan reports and scan interpretation of an independent observer were taken into account.

Results: Of 95 post-contrast CTs, 88 showed RDP (29 large-contained, 12 large-sequestrated, 39 moderate-contained, and 8 small-contained), 2 hypertrophic epidural scar (HES), and 5 lateral recess stenosis but no RDP or HES. From operation records, 30 of these 88 were found to have HES, but no RDP. Also, operation records confirmed presence of RDP in 21 of 29 large-contained (72.4%), 10 of 12 large-sequestrated (83.3%), 16 of 39 moderate-contained (41%) and 2 of 8 small-contained (25%). Of the 5 which did not show RDP, 2 (40%) were found to have RDP (1 moderate-contained and 1 large-contained) during operation.

Of 97 post-contrast MRIs, 85 showed RDP (18 large-contained, 22 large-sequestrated, 26 moderate-contained,4 moderate-sequestrated,13 small-contained, and 2 small-sequestrated), 5 HES, and 7 lateral recess stenosis but no RDP or HES. From operation records, 31 of these 85 were found to have HES, but no RDP. Also, operation records confirmed presence of RDP in 10 of 18 large-contained (55.6%), 19 of 22 large-sequestrated (86.4%), 8 of 26 moderate-contained (30.8%), 4 of 4 moderate-sequestrated (100%), 6 of 13 small-contained (46.2%) and 1 of 2 small-sequestrated (50%). Of the 7 which did not show RDP, 1 (14.3%) was found to have moderate-contained RDP during operation.

Conclusion: Accuracy of post-contrast scans is proportional to the size of RDP. MRI has high accuracy for sequestrated RDP.

Correspondence should be addressed to SBPR c/o Royal college of Surgeons, 35 - 43 Lincoln’s Inn Fields, London WC2A 3PN