Unilateral Minimally Invasive Posterior Lumbar Interbody Fusion (Unilateral Micro-PLIF) for Degenerative Spondylolisthesis: Surgical Technique

Degenerative spondylolisthesis has long been recognized as a cause of chronic low back pain and sciatica. Extensive anatonmical and embryological studies have not fully explained the cause of this painful condition. The mechanism of pain in degenerative spondylolisthesis has been confirmed by demonstrating the disc lesion pre-operatively by X-rays and MR imaging followed by surgical treatment in which the abnormal disc is totally removed and replaced with bone grafts to effect an interbody fusion. Ralph Cloward first performed the posterior lumbar interbody fusion (PLIF) in 1940 in Hawaii.(1952, 1953, 1981, 1985) . Over the last decade, PLIF has become a popular technique for achieving interbody fusion. The development of pedicle screw fixation system is significant in the history of PLIF. PLIF with pedicle screw systems have apperently improved the rate of arthrodesis (Bridwel et al., 1993, Zdeblick et al., 1993, Yvon et al., 1994, Fischgrund et al., 1997). However, the result of exposure technique can be ischemic necrosis induced by forceful retraction of the paraspinal muscles and postoperative low back pain. The first percutaneous screw placement technique was reported by Magerl (1982) and involved the use of external fixators. The development of technology for minimum invasive placement of rods and pedicle screws was driven by concerns over the amount of paraspinal muscle retraction required in the open approaches. Forley (2001) made a significant contribution to resolving this dilemma with his invention of instruments and a technique to pass rods in a minimally traumatic fashion using an arcbased system called Sextant (Medtronic). The percutaneous pedicle screw system have served as adjuvants in the development of minimally invasive PLIF. And also, interbody spacers have far more better results in term of disc height maintenance and in direct neural decompression than bone grafts alone. Various radiolucent interbody spacers, such as carbon cages (Brantigan & Steffee, 1993), and polyetheretherketone (PEEK) interbody spacers (Park & Foley, 2008), are wide and long and provide a large surface area for fusion and generous reconstruction of collapsed disc spacers on the use of interbody spacers for