TRANSFORAMINAL AND POSTERIOR DECOMPRESSIONS OF THE LUMBAR SPINE - A COMPARATIVE-STUDY OF STABILITY AND INTERVERTEBRAL FORAMEN AREA

Study Design. Ten fresh, cadaveric, two-vertebrae, functional spinal u nits were used to study the pathoanatomy, intervertebral foraminal are a, and flexibility changes after posterior and transforaminal decompre ssion. Objectives. To determine the feasibility of an endoscopic trans foraminal approach as an alternative to conventional approaches, to es tablish the adequacy of transforaminal decompression without destabili zing the spine, and to study the structural changes in the spine after decompressions. Summary of the Background Data. Posterior decompressi on entails major dissection and excision of bone and ligaments to acce ss the spinal canal. Posterior decompression may be complicated by acu te or chronic spinal instability, and the adequacy of lateral decompre ssion 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. P re- and postoperative flexibility and anatomic studies were performed to compare the results. Results. A 45.5% increase in the intervertebra l foraminal area was possible, there was no flexibility change, and mi nimal anatomic damage to the spine was noted after transforaminal deco mpression. 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 d ecompression produced a significantly larger increase in the intervert ebral foraminal area than posterior decompression, without increasing the range of motion or neutral zone in any direction. Because there wa s no violation of the anatomic integrity of the spine in the transfora minal approach, the risk of surgically induced instability was minimiz ed. Endoscopic transforaminal decompression is a feasible alternative to current approaches.