The TANGENT™ Posterior Impacted Instrument Set allows a surgeon to perform the Posterior Lumbar Interbody Fusion operation with minimal amount of neural retraction required. It also maximizes the amount of disc space distraction that is possible, and facilitates precise endplate preparation.

The TANGENT™ Posterior Impacted Instrument Set can also be used with the METRx™ System. The objective of the METRx™ System is the same as conventional open surgery - to decompress the nerve root. This is accomplished by applying open surgical techniques through a tubular retractor under microsurgery visualization. For the first time, a laminotomy, medial facetectomy, foraminotomy, nerve root retraction and discectomy can be performed microscopically. In so doing, the METRx™ System combines the benefit of conventional open surgery with the advantages of a minimally invasive technique.

Minimal Access Spinal Technologies
The microsurgery revolution has had a positive effect on the operative experiences of many patients in virtually every surgical field. Smaller incisions, limited tissue disruption, enhanced visualization and illumination of the tissues, shorter hospital stays, and faster recovery times have all been realized in many surgeries that previously required more extensive surgical dissections in order to accomplish the goals of the operation. In the case of lumbar discectomy, the primary objective of surgical treatment is to decompress the affected nerve root. The affected nerve root must be left fully decompressed and freely mobile at the end of the operation. Minimally invasive techniques for lumbar discectomy have been able to achieve this goal, but until now, the surgeon has not been able to simultaneously accomplish an interbody fusion through the same small incision required for the discectomy. The TANGENT™ Impacted Posterior Instrument Set, from Medtronic Sofamor Danek, now allows the surgeon to insert precision machined bone grafts into the intervertebral space via a minimally invasive posterior lumbar interbody fusion technique. This technique preserves much of the normal anatomy of the posterior aspect of the spine and limits the amount of bone removed in order to visualize the intervertebral space. The procedure can be accomplished via bilateral hemi-laminectomies and medial facetectomies, with the goal of inserting a 10mm wide graft with minimal or no retraction on the neural structures.

While many of the surgical techniques for minimally invasive spine surgery are still in their infancy, they hold great promise for improving patient outcomes after surgery by decreasing the amount of tissue retraction, dissection, and exposure of the spine that is necessary. Medtronic Sofamor Danek, the world leader in spinal instrumentation, has a strong commitment to further developing and refining these techniques. In addition to the METRx™ System and the SEXTANT™ Percutaneous Instrument Set, the lumbar interbody fusion instrumentation of the TANGENT™ Impacted Posterior Instrumentation Set adds to the armamentarium of the modern spine surgeon who is interested in minimally invasive alternatives to more traditional surgical techniques.

Posterior Lumbar Interbody Fusion
The majority of surgery for disc herniation occurs in the lumbar spine. Some common problems that may accompany a herniated lumbar disc include neurological dysfunction as the nerve is "pinched" by the herniation, structural instability, and deformity and pain due to abnormal alignment. If instability occurs in association with a herniated disc, excision of the disc alone may not completely relieve the symptoms of back pain. Many patients who have spinal instability, in addition to disc pathology, may benefit from a fusion of the involved vertebral bodies in order to obtain more complete relief from their symptoms. This fusion can be accomplished at the same time as their discectomy, but until now, the surgical approach for fusing the involved vertebral levels from a posterior approach has required a significantly larger surgical dissection than that required for the discectomy alone.

With the development of minimally invasive and microsurgical techniques for treating spinal disorders, surgeons and implant manufacturers have continued to research and design new ways to perform spinal fusion surgery with minimal dissection of the surrounding soft tissues. There are two common approaches to fuse two adjacent vertebral bodies: from the front of the spine, called an Anterior Lumbar Interbody Fusion (ALIF) and from the back of the spine, called a Posterior Lumbar Interbody Fusion (Posterior Lumbar Interbody Fusion).

The Posterior Lumbar Interbody Fusion technique allows surgeons to fuse two adjacent vertebrae together with an intervening bone graft from a posterior approach to the spine. The Posterior Lumbar Interbody Fusion requires that the surgeon perform a laminectomy and carefully expose the dural sac and the spinal roots at the level of the fusion, protect these structures during the removal of the disc material, and as a fusion cage or bone graft is inserted into the intervertebral disc space. Bone grafts that are placed into the intervertebral space are designed to maintain the height of the previously excised disc and produce a solid fusion between the two vertebrae as the bones grow together. This procedure is usually accomplished through a standard midline incision centered over the affected levels along the posterior aspect of the spine and requires a complete laminectomy and wide facetectomy for sufficient visualization of the intervertebral space and placement of the graft.

Minimally invasive techniques for performing the Posterior Lumbar Interbody Fusion procedure after discectomy are improving with the development of new instrumentation for graft insertion. In addition, new techniques for processing and machining allograft bone into precision wedges for insertion into the intervertebral space after discectomy has further simplified the Posterior Lumbar Interbody Fusion procedure while reducing the negative impacts of harvesting bone graft from the iliac crest of the patient. Medtronic Sofamor Danek developed the TANGENT™ Impacted Posterior Instrument Set for performing the Posterior Lumbar Interbody Fusion procedure through a minimally invasive approach via bilateral hemi-laminectomies at the affected level. The advantages of the TANGENT™ Instrument Set are realized by inserting a allograft cortical wedge into the intervertebral disc spaces using the Posterior Lumbar Interbody Fusion technique. This new instrumentation allows for the maximum amount of disc space retraction for insertion of the graft with the minimum amount of neural retraction. This makes the combination of the minimally invasive exposure, disc removal and the Posterior Lumbar Interbody Fusion procedure technically feasible and safe.

The placement of machined wedges of cortical bone in the intervertebral disc space is often also accompanied by supplemental internal fixation with pedicle screw instrumentation. The combination of these two techniques completes a 360° fusion - wherein both the anterior, middle, and posterior columns of the spine are rigidly held in place by bone grafts between the vertebral bodies and the screw and rod combination along the posterior aspect of the spine. This construct creates a rigid segment that is a favorable environment for fusion to occur in.