OBJECTIVE::
A retrospective review of the clinical and radiographic outcomes from a multi-center study of surgical treatment for high-grade spondylolisthesis (HGS) in adults. The objective was to assess the safety of surgical reduction, its ability to correct regional deformity, and its clinical effectiveness.

METHODS::
Retrospective, multi-center review of adults (age >18 y) with lumbo-sacral HGS (Meyerding grade 3-5) treated surgically with open decompression, attempted reduction, posterior instrumentation and interbody fusion. Pre- and post-operative assessment of the Meyerding grade, slip angle and sacral inclination were performed based on standing radiographs. Pre-operative VAS scores were compared with those at the mean follow-up period. Prolo and Oswestry Disability Index (ODI) scores at most recent follow-up were assessed.

RESULTS::
A total of 25 patients, aged 19-72 years, met inclusion criteria. 17 interbody cages were placed, including 15 transforaminal lumbar interbody fusions (TLIF), 1 posterior lumbar interbody fusion (PLIF) and 1 anterior lumbar interbody fusion (ALIF). Five patients required sacral dome osteotomies. The average follow up was 21.3 months.At most recent follow-up there was a statistically significant improvement in both the Meyerding grade and the slip angle (P< 0.05). There was one intra-operative complication resulting in a neurological deficit (4%) and one intra-operative vertebral body fracture (4%). No additional surgery was required for any of these patients. There were no cases of nonunion or device failure except for one patient who suffered an unrelated traumatic injury one-year after surgery. The mean ODI and Prolo scores at mean follow up of 21.3 months were 20% (minimum disability) and 8.2 (grade 1) respectively.

CONCLUSION::
The present study suggests that reduction, when accomplished in conjunction with wide neural element decompression and instrumented arthrodesis, is safe, effective, and durable with low rates of neurologic injury, favorable clinical results, and high fusion rates.