Posterior Lumbar Interbody Fusion (PLIF): Spinal Stabilization
Posterior Lumbar Interbody Fusion (PLIF) involves the surgical stabilization and bone grafting of one or more lumbar intervertebral disc spaces using a posterior (from behind) approach. It may be carried out for a variety of indications and there are now many different techniques. PLIF is particularly useful in the correction of degenerative lumbar deformity such as spondylolisthesis, scoliosis or disc space collapse and in the management of associated of neurological compression.
(Left) Pre-operative (Right) Post-operative x-ray of a spondylolisthesis
First described in the 1940's, PLIF has a number of theoretical advantages over other fusion techniques such as posterior or posterolateral (rear/side) fusion. Nevertheless, the technical demands, variable results and complications associated with the early techniques did not lead to its widespread uptake by surgeons. The newer techniques however, in conjunction with technological advances in interbody implants have made PLIF surgery much more attractive. They have improved the surgical ease and safety while retaining the biomechanical and other advantages of PLIF surgery.
Posterior Lumbar Interbody Fusion (PLIF) was first described by Briggs and Milligan in 19445 using laminectomy bone chips. In 1946, Jaslow7 described posterior interbody fusion, using an excised portion of spinous process, rotated into position within the intervertebral space. It was Cloward however, in the 1950's using impacted blocks of iliac crest (pelvis), who initially popularized PLIF surgery. While some surgeons reported favorably on their early experience with PLIF, difficulties with inconsistent fusion rates and complications related to blood loss, dural/neural injury, graft extrusion, and arachnoiditis (inflammation of a specific spinal cord membrane) limited its appeal.
Its popularity rose in the 1990's with the advent of supplementary interbody implants (cages) to support and stabilize the disc space while bone graft, placed within the cages, united the bone of the vertebral end-plates (1,4,11). The first of these was the threaded cylindrical fusion cage, initially used by Bagby in horses (13). As with previous PLIF techniques, these implants used the principle of compression-distraction to achieve spinal stabilization.
Fusion rates improved with many authors reporting successful fusion in up to 90-95%. Ray (11) reported a 96% fusion rate at 2 year follow-up with 86% satisfactory relief of back or radicular leg pain.
More recently, newer and more streamlined impacted implants made of titanium, plastic PEEK polymers (Polyetheretheketone) or allograft bone (donor bone) has gained popularity. In a recent article by Barnes et al (2) they found significantly lower nerve root injury rates with the use of impacted allograft wedges when they compared their earlier experience with allograft cylindrical threaded fusion cages (0% vs. 13.6% respectively). The Insert and Rotate technique of implant placement (see below) is also gaining popularity.
Some surgeons are now starting to perform PLIF procedures through minimal access (keyhole) approaches using either impacted or insert and rotate techniques, aided by advances in image-guided / computer assisted technology. Khoo et al (8) have recently written an excellent article on this approach. These minimal access techniques utilize the principles developed for minimal access laminectomy surgery and for image guided pedicle screw stabilization.