Analysis of Anterior-posterior Distance of Sacral Canal on MRI to See the Possibility of Sacral Laminar Hook Insertion

ABSTRACT

OBJECTIVE: Achieving successful posterolateral fusion across the lumbosacral junction is particularly problematic. In our hospital, bilateral S2 laminar hooks coupled with bilateral S1 screws have been appeared to provide successful posterolateral fusion of lumbosacral junction in high non-fusion risk patients. Therefore we study about the safety of sacral lamina hooks insertion. METHODS: We measured the anterior-posterior(A-P) diameter of sacral canal at a point where median sacral crest of S1 and S2 meet on lumbar magnetic resonance(MR) sagittal images. The number of analyzed subjects was one hundred and minimum A-P diameter of sacral canal to insert laminar hooks safely was thought to be 9mm. RESULTS: In 78% of study cases, the sacral canal diameter was 9mm or more. There were no statistically significant difference of sacral canal diameter with age, sex, weight and height. CONCLUSION: Preoperative analysis of the sagittal MR image may be helpful for the safe insertion of the sacral laminar hooks to enhance posterolateral fusion of lumbosacral junction in high non-fusion risk patients. And, safe sacral laminar hooks insertion may be possible in about 78% of study cases.