A Prospective Clinical Study Comparing MISS TLIF with Unilateral Vs Bilateral Transpedicular Fixation In Low Grade Lumbar Spondylolistesis

Presented at SMISS Annual Forum 2014
By Jose-Antonio Soriano MD
With

Disclosures: Jose-Antonio Soriano MD None

Introduction:
Minimally Invasive Lumbar Interbody Fusion (MISS-TLIF) has become a standard technique. This procedure is usually accompanied by the placement of bilateral transpedicular screws in the corresponding segment. Some authors have demonstrated that instrumentation with unilateral transpedicular screws after fusion produces clinical and radiological results comparable with bilateral screw instrumentation.

Aims/Objectives:
To evaluate the efficacy of unilateral compared with bilateral transpedicular fixation as complement of MISS-TLIF in patients with low-grade symptomatic lumbar spondylolisthesis. The main outcome measure was the Oswestry disability index at 12 months.

Methods:
A prospective comparative study was performed in 67 patients with low-grade symptomatic lumbar spondylolisthesis. Patients were allocated to unilateral (n=33) or bilateral (34) screw fixation. Clinical measured outcomes were: Oswestry disability index, radicular pain-VAS, lumbar pain-VAS, and Short Form-36 Health Survey (SF-36) before the operation and at 1, 3, 6 and 12 months postoperatively. Differences between groups and change over time were analyzed. Statistical analyses included: Friedman test, Student’s t-test and Mann-Whitney’s U. A two-tailed p-value of <0.05 was considered significant.

Results:
Along the evaluated period, unilateral fixation group had a diminution in the measured outcomes: Oswestry (p<0.001), radicular pain VAS (p<0.001), lumbar pain VAS (p<0.001), and SF-36 (p=0.004). The same was observed in the bilateral fixation group: radicular pain VAS (p<0.001), Lumbar pain VAS (p<0.001), Oswestry (p<0.001) and SF-36 (p=0.004). Oswestry was similar preoperatively (p=0.842) and so kept at 1 (p=0.210), 6 (p=0.466), and 12 months (p=0.189); at month 3, unilateral group scored 5.75 points higher than the bilateral (p=0.023). Patients in the unilateral group had an initial radicular pain 1.5 VAS-points higher than the bilateral group (p=0.003). At 3, 6 and 12 months, the unilateral group remained with 2 (p=0.013), 1 (p<0.001) and 1 (p<0.001) VAS-points higher than the bilateral group. Baseline lumbar pain VAS score was similar between groups (p=0.933), and thus maintained in the following evaluations at 1 (p=0.131), 3 (p=0.944), 6 (p=0.493) and 12 months (p=0.314). SF36 values were alike between groups before surgery (p=0.251) and so continued to be at 1 (p=0.369), 6 (p=0.626) and 12 months (p=0.121); at month 3, patients in the unilateral group had 10.67 less points (p=0.006) than the patients in the bilateral group.

Conclusions:
Patients with low-grade symptomatic lumbar spondylolisthesis treated with MISS-TLIF with unilateral transpedicular fixation had similar clinical results than those treated with bilateral fixation at 12 months postoperatively.