Transforaminal and Posterior Decompressions of the Lumbar Spine

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Abstract
Study Design. Ten fresh, cadaveric, two-vertebrae, functional spinal units were used to study the pathoanatomy, intervertebral foraminal area, and flexibility changes after posterior and transforaminal decompression. Objectives. To determine the feasibility of an endoscopic transforaminal approach as an alternative to conventional approaches, to establish the adequacy of transforaminal decompression without destabilizing the spine, and to study the structural changes in the spine after decompressions. Summary of the Background Data. Posterior decompression entails major dissection and excision of bone and ligaments to access the spinal canal. Posterior decompression may be complicated by acute or chronic spinal instability, and the adequacy of lateral decompression is highly subjective. Methods. The functional spinal units were mounted in quick-setting epoxy blocks. Pre- and postoperative computed tomography scans were taken to study changes in the foraminal area. Pre- and postoperative flexibility and anatomic studies were performed to compare the results. Results. A 45.5% increase in the intervertebral foraminal area was possible, there was no flexibility change, and minimal anatomic damage to the spine was noted after transforaminal decompression. A 34.2% increase in the intervertebral foraminal area and a significant increase in extension and axial rotation flexibility were noted after the posterior decompression. Conclusion. Transforaminal decompression produced a significantly larger increase in the intervertebral foraminal area than posterior decompression, without increasing the range of motion or neutral zone in any direction. Because there was no violation of the anatomic integrity of the spine in the transforaminal approach, the risk of surgically induced instability was minimized. Endoscopic transforaminal decompression is a feasible alternative to current approaches.