Revision Interbody Fusion

Posterior Lumbar Interbody Fusion and Transforaminal Lumbar Interbody Fusion

Posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF) are widely accepted procedures for achieving interbody arthrodesis. They use either a direct posterior (PLIF) or a posterolateral (TLIF) approach to enter the disk space. TLIF most commonly involves a unilateral approach via the foramen with insertion of a single oblique or banana-shaped cage. Some surgeons utilize a bilateral approach with placement of two cages obliquely. PLIF traditionally involves a wide laminectomy and at least partial facetectomies with orthogonal placement of a cage on each side of the vertebral disk spaces. Because of the posterolateral approach used in TLIF, less dural sac and exiting nerve root retraction is necessary than in PLIF. These procedures can be performed with a traditional open or minimally invasive approach.

Graft extrusion after PLIF or TLIF has been widely reported in the literature, with an incidence ranging from 0.35% to 6% ( Fig. 21.1 ). Bakhsheshian et al . reported their series of 513 patients undergoing minimally invasive TLIF and found 5 cases of graft extrusion. Of these 5 cases, 2 patients were asymptomatic and did not require surgery. Three patients had evidence of neurologic decline and underwent revision surgery. Similarly, Zhao et al. reported their series of 512 patients undergoing mini-open TLIF, with 6 patients having graft extrusion. They reported that small cages, rectangular cage shape, and multi-level procedures increased the risk of cage extrusion. Furthermore, the presence of linear endplates as opposed to concave presented a higher likelihood of extrusion. Other studies have reported similar risk factors.

Currently no direct comparative studies are investigating the rates of graft extrusion in open TLIF versus minimally invasive TLIF. Several studies have examined the relationship between unilateral versus bilateral pedicle screw fixation in TLIF. Although the data are not yet conclusive, it does appear that there may be a higher rate of cage migration in patients with unilateral pedicle screw fixation, suggesting that bilateral screws provide greater stability to the graft.

Lateral Lumbar Interbody Fusion

Lateral lumbar interbody fusion (LLIF) is a technique that was first described in 2006 by Ozgur et al., although variations of this technique have existed prior to that report. This procedure classically involves a retroperitoneal transpsoas approach to access the disk space orthogonally. It has been an increasingly popular technique that offers the advantages of a less-invasive approach with minimal blood loss, as well as providing an alternative means of achieving a more robust diskectomy with placement of a larger cage than with PLIF or TLIF. LLIF has been utilized both in a stand-alone fashion, as well as with posterior pedicle screw fixation or lateral plate fixation.

Overall reported rates of graft extrusion in LLIF have been low ( Fig. 21.2 ), although there are several case reports in the literature. However, larger case series describe graft subsidence to be a bigger complication of LLIF. Le et al. reported a 14.3% rate of radiographic subsidence and a 2.1% rate of clinical subsidence in a group of 140 LLIF patients, and noted that increasing construct length was associated with higher subsidence rates. Many cases of reported subsidence did require revision surgery, although the nature of the surgery has been inconsistently reported. In addition, the definition of subsidence has varied among authors. Several studies report associated vertebral body fractures. Owing to the heterogeneity of subsidence, some studies advocate conservative management, whereas other authors advocate for either placement of posterior instrumentation in cases with stand-alone cages, or supplementation with vertebroplasty/kyphoplasty in cases of vertebral body fracture.

Anterior Lumbar Interbody Fusion

Anterior lumbar interbody fusion (ALIF) is a technique that provides direct access to the anterior spine. It is typically performed by a vascular or general surgeon using either a transperitoneal or, more commonly, a retroperitoneal approach to expose the anterior disk space. With this approach, a robust diskectomy can be performed and a large interbody cage placed. ALIF can be performed as a stand-alone, with integral fixation, anterior plate fixation, or with posterior supplemental fixation. Although graft extrusion and implant migration have been described, they are relatively rare with the use of modern techniques. However, subsidence has been reported commonly, particularly in stand-alone ALIF ( Fig. 21.3 ).