Outcomes of posterior lumbar interbody fusion with the 9-mm width lumbar I/F cage and the variable screw placement system.

Posterior lumbar interbody fusion (PLIF) using interbody cages and posterior pedicle screw fixation has increased the successful fusion rate to nearly 100% in the lumbar spine. In the design of the cage, only the surface area of the opening for bone graft contact with the endplates varied with the width of the cage. When space is limited, the 9-mm width cages may be the largest size that can be used. Fusion is potentially compromised by the smaller surface area of bone graft. It is important to study the clinical and fusion success of these narrow cages. The authors report 90 patients who had PLIF with 9-mm Lumbar I/F Cages and pedicle screws. Minimum follow-up was 24 months (range, 2-5 years). Seventy-five patients (83%) had clinical success, and 15 (17%) were clinically unsuccessful. Fusion was successful in 82 patients (91.1%). Fusion success with the 9-mm cage was statistically lower than previously reported for the implant system as a whole (p = .0015). Mechanical failure did not occur with 9-mm cage usage.