Object: The purpose of this study was to investigate and compare clinical and radiographic outcomes of 2 kinds of lumbar interbody fusion (LIF) for the treatment of adult low-grade isthmic spondylolisthesis at L4-5 and L5-S1 levels.
Methods: The medical records and radiographs of 86 patients who underwent anterior LIF (ALIF) (L4-5, 42 patients; L5-S1, 44 patients) and 42 patients who underwent transforaminal LIF (TLIF) (L4-5, 22 patients; L5-S1, 20 patients) between 2001 and 2004 were retrospectively reviewed. Clinical results were investigated using the visual analog scale (VAS) and Oswestry Disability Index (ODI) scores, and using radiographic measurements, including disc height (DH), degree of spondylolisthesis, segmental lordosis, whole lumbar lordosis (WL), sacral slope (SS), and pelvic tilt; the L-1 axis S-1 distance (LASD) and pelvic incidence were also obtained.
Results: In both groups, VAS and ODI scores had significantly improved at both treatment levels. Statistical analysis showed no significant difference in postoperative VAS scores between groups at the L4-5 level and in postoperative VAS/ODI scores at the L5-S1 level. However, ODI scores were better in the TLIF than in the ALIF group at the L4-5 level. In terms of radiological changes, there were no significant differences between the 2 groups at the L4-5 level; however, at the L5-S1 level, radiographic results indicated that ALIF was superior to TLIF in its capacity to restore DH, WL, SS, and LASD. The radiological evidence of fusion shows no intergroup difference and no interlevel difference.
Conclusions: Considering the clinical and radiological outcomes in both groups, the authors recommend that instrumented mini-TLIF is preferable at the L4-5 level, whereas instrumented mini-ALIF might be preferable at the L5-S1 level for the treatment of unstable isthmic spondylolisthesis.