Objectives: Bone resulting from a complete resection of the posterior arch can be cut into an autograft bone that contains the facet joint structure and morselised bone for interbody fusion. However, whether a strut autograft that contains this trimmed facet joint can produce the same clinical and radiographic outcomes as a cage for interbody fusion remains unclear. The aim of this study was to compare the outcomes of a local facet joint autograft alone to those of polyetheretherketone (PEEK)+autograft for posterior lumbar interbody fusion (PLIF) in the treatment of adult isthmic spondylolisthesis. Patients and methods: A retrospective analysis was performed on 84 patients with single lumbar isthmic spondylolisthesis who were treated with a local facet joint autograft alone (group A; n=44) or PEEK+autograft (group B; n=40) in PLIF with a minimum follow-up period of 24 months. Pain and disability were assessed using the visual analogue scale, Oswestry disability index and Kirkaldy-Willis criteria. In the radiological evaluation, disc height, slippage reduction, and fusion status were examined. Postoperative complications were also monitored. Results: At the last follow-up examination, 84.1% (37/44) of the patients in group A and 82.5% (33/40) of the patients in group B had a good outcome, and there were no significant differences between the two groups. Bob Methods led to significant improvements in disc height, and while PEEK+autograft produced a smaller loss in disc height, the difference was insignificant. The improvements in slippage and the fusion and complication rates between the two groups were similar. Conclusion: There were no significant differences in the clinical outcomes or radiographic improvements of both fusion methods in the treatment of adult isthmic spondylolisthesis. An autograft excised from a complete posterior arch containing a facet joint for interbody fusion is effective and affordable for treating isthmic spondylolisthesis. (C) 2017 Elsevier B.V. All rights reserved.