Expandable TLIF cages may produce better sagittal alignment than static height cages for degenerative scoliosis

2016

Summary

In the first study of expandable cages, prospective data from 43 consecutive adults who underwent posterior fusion with TLIF for deformity was divided into similar groups by type of TLIF cage used: expandable vs static height. Though numbers were small, expandable cage group consistently trended toward better disc height, segmental lordosis, lumbar lordosis, and sagittal balance compared to the static height cage group. There was no difference in clinical outcomes at 4 years followup. These preliminary observations warrant further study.

Hypothesis

Expandable cages (EC) create better sagittal alignment (disc height, segmental lordosis, lumbar lordosis) than static height cages (SC) after posterior correction of degenerative lumbar scoliosis (DLS).

Design

Prospective data from 43 consecutive DLS patients (pts) who underwent posterior fusion (PSF) with TLIF at 1-3 levels with SC (25 pts, 57 levels) or EC (18 pts, 37 levels).

Introduction

TLIF with cage enhances fusion and stability in deformity surgery. The difference between EC and SC has not been studied.

Methods

Radiographs measured at pre-op, 1 year, and 2 years. To compare SC vs EC, TLIF disc categorized by pre-op height: (Short:0-8mm, Medium:9-12mm, Tall: >12mm) and angle (Low: 0-4°, Medium: 5-11°, High: >12°). Lumbar Lordosis (T12-S1) and Sagittal Balance (C7-S1) were also recorded. Visual Analog pain scores (VAS), Oswestry Disability Index (ODI), and pain medication use recorded pre-op, 1 year, 2 years, and latest follow-up.

Results

At 47months followup (26-68 months) there was no significant difference SC vs EC for age (68yrs), smoking, prior surgery, levels of TLIF, preop disc height (7mm), pre-op sagittal imbalance (8cm) and lumbar lordosis (35°). SC had average 3° more pre-op segmental lordosis at TLIF levels than EC. Both groups had similar PSF (6.3 levels), and all had Ponte osteotomies. SC group had more 3 level TLIFs (14 vs 4) and 1-level TLIFs (7 vs 3). After surgery, EC produced better 2-year anterior disc height (14.5mm vs 11.1mm), segmental lordosis (13.7° vs 9.7°), lumbar lordosis (52° vs 47°) and sagittal balance (4.0cm vs 6.0cm) than the SC group. Complications were similar SC vs EC: Adjacent fracture-9, symptomatic sagittal imbalance-6 (SC-3, EC-3), revision surgery-3. Clinical improvement for both groups was p<0.01: VAS (preop-6.5, 2 year-3.4), ODI (preop-49.3, 2 year- 27.2), without significant difference SC vs EC. Pain med use showed similar trend.

Conclusions

EC consistently trended toward better disc height, segmental lordosis, lumbar lordosis, and sagittal balance compared to SC in similar DLS pts at 2 years. The preliminary observation that EC may perform better in TLIF than SC in DLS patients warrants further study.