Success and failure of minimally invasive decompression for focal lumbar spinal stenosis in patients with and without deformity.

STUDY DESIGN: Observational cohort study. Retrospective review of prospectively collected outcomes data.

OBJECTIVE: The purpose of this study was to evaluate the clinical efficacy of minimally invasive (MIS) decompression for focal lumbar spinal stenosis (FLSS) in patients with and without deformity.

SUMMARY OF BACKGROUND DATA: MIS, facet-preserving decompression has the potential of offering a significantly less morbid alternative to decompression and fusion in patients with leg dominant symptoms from degenerative spondylolisthesis and/or scoliosis.

METHODS: Single surgeon, consecutive series (n=75), evaluated over 5 years. All patients had MIS lumbar laminoplasty (bilateral decompression from a unilateral approach) for FLSS (1-2 level). Patients had leg dominant, claudicant/radicular pain. Patients were divided into 4 groups: (A) stenosis with no deformity, n=22; (B) stenosis with spondylolisthesis only, n=25; (C) stenosis with scoliosis, n=16; and (D) stenosis combined with spondylolisthesis and scoliosis, n=12. The primary clinical outcome measures were the Oswestry Disability Index (ODI) and surgical revision rate. Preoperative and postoperative standing radiographs were assessed.

RESULTS: The average age was 68 years (40-89) with a mean time from surgery of 36.5 months (18-68). Average clinical improvement in ODI was 49.5% to 23.9% [mean postoperative follow-up of 31.8 months (24-72): group A=mean of 34.6; B=28.9; C=32.7; D=30 months]. Incidence of preoperative grade I spondylolisthesis was 46%. Spondylolisthesis progression (mean=8.4%) occurred in 9 patients and 2 patients developed spondylolisthesis. Overall revision rate was 10% [repeat decompression alone (n=2) and decompression and fusion (n=6)]. Subgroup analysis of preoperative and postoperative ODI and revision rate revealed (A) 48% to 18.7%, 0%; (B) 48% to 24.6%, 4%; (C) 50.7% to 31.5%; 25%; and (D) 53% to 22%, 25%, respectively. The revision rate for patient with scoliosis (C+D) was significant (P=0.0035) compared with those without. Six of the 8 revised patients had a preoperative lateral (rotatory) listhesis (3 in C and 3 in D).

CONCLUSION: MIS decompression alone for leg dominant symptoms is a clinically effective procedure in the majority of patients including those with degenerative spondylolisthesis or scoliosis. However, patients with scoliosis, particularly those with lateral listhesis, have a significantly higher revision rate that needs to be considered in operative decision-making.