Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Introduction: Indirect decompression by distracting interbody space is gaining popularity as it avoids unnecessary meddling of spinal canal.  Selecting ideal candidates for indirect decompression has been a problem as there is no objective way to confidently demonstrate the possible amount of spinal canal decompression before surgery. The information obtained in the supine MRI and dynamic load bearing radiographs are of value while performing direct neural decompression but may not provide the necessary information required for decision making for indirect decompression which works entirely on the principle of distraction. The present study aims to evaluate the utility of pre-operative traction radiographs and MRI in predicting the success of indirect decompression and correlates with clinical symptoms.

Methods: This prospective clinico-radiological study and included 20 patients with degenerative lumbar spondylolisthesis planning to undergo single level indirect decompression procedure. All patients underwent through clinical examination and radiological evaluation by pre-operative radiographs and MRI in traction as well as in supine and standing positions. Radiological parameters and cross sectional area of the thecal sac measured in all three positions.

Results: By applying traction, the cross sectional area of the thecal sac, mid sagittal thecal sac area and foraminal height was found to increase by 50% compared to those in standing position. By applying traction, there was also nearly 50% reduction in intervertebral listhesis index and translation compared to standing in both plain radiographs and load bearing MRI.

Discussion: Our study presents a novel attempt at identifying predictors of success of indirect decompression in degenerative disc disease of lumbosacral spine. Present study evaluates the utility of pre-operative traction imaging which in principle mimics the surgical indirect decompression in selecting ideal candidates for indirect decompression. For the first time, present study documented that a 50% reduction in spondylolisthesis index or translation (measured on both radiographs and MRI) could result in 50% increases in the cross sectional area and foraminal area of the lumbar spine on MRI. This data has huge clinical implications as traction and standing radiographs can be readily obtained pre-operatively.