Posterior lumbar interbody fusion versus posterolateral fusion in adult isthmic spondylolisthesis

Study Design. A prospective study with historical controls. Objective. To compare the outcome of posterior lumbar interbody fusion (PLIF) and posterolateral fusion (PLF) in adult isthmic spondylolisthesis. Summary of Background Data. On theoretical grounds, PLIF has been suggested to result in an improved outcome compared with PLF. Data to support this view, however, are lacking. Methods. A total of 86 patients ( age range, 18 - 55 years) with adult isthmic spondylolisthesis were operated on with PLIF. The comparison group consisted of 77 patients operated on with PLF with iliac bone autograft, 40 with and 37 without pedicle fixation. The 2 groups had similar socioeconomic, age and sex distribution, level of pain, and disability. Inclusion criteria and outcome measurements were identical in both groups. The PLIF group was operated on with autograft and carbon fiber ramps with pedicle fixation. Before surgery and at the 2-year follow-up, pain ( VAS) and functional disability were quantified by the Disability Rating Index (DRI, 0 - 100) and the Oswestry Disability Index (ODI). The global outcome was assessed by the patient as much better, better, unchanged, or worse. Results. The follow-up rate was 98% in the PLIF group and 97% in the PLF group. In PLIF patients, pain index improved from 66 to 35 ( P < 0.0001) and the DRI from 47 to 30 ( P < 0.01). The levels of pain and DRI were similar to that of the PLF group ( pain 37, DRI 29, not significant), and the ODI was identical in both groups ( 25); 74% of the patients in both groups classified the results as much better or better. Conclusion. Type of fusion, PLIF or PLF, does not affect the 2-year outcome of surgical treatment of adult isthmic spondylolisthesis. Despite the theoretical advantages of PLIF, no improvement on patient outcome compared with posterolateral fusion could be demonstrated, questioning the need of anterior support in short lumbar fusions.