Improving local and regional lordosis in degenerative scoliosis: Preliminary findings on the effect of an expandable TLIF cage

2013

Summary

Ninety-eight crescent shaped hydraulic expandable TLIF cages (FDA approved for TLIF) were used to improve segmental and regional lumbar lordosis in 45 patients with degenerative lumbar scoliosis.  Cages were expanded up to 6mm beyond insertion height of the cage.  Radiographic analysis showed improvement of 8.5mm in disc height, 8.3 degrees in segmental lordosis, and 22 degrees in regional lordosis.  There were no cage-related complications, and early clinical results showed significant improvements in VAS and ODI compared to preop scores. 

Background

Previous studies have shown expanding TLIF expanding cages have the potential to improve both segmental and regional lordosis when compared to static height cages in patients undergoing fusion for degenerative disease.  This is the first report of the expanding cage effect on sagittal parameters in patients with degenerative lumbar scoliosis (DLS) undergoing arthrodesis, with early clinical and radiographic outcomes and complications.

Methods

45 consecutive adults undergoing primary or revision spinal arthrodesis for DLS augmented with TLIF at average 1.8 levels using a new hydraulic expanding cage at 4 centers. Age averaged 64 years (40-80 years); Number of TLIF levels: one- 7 patients, two- 23 patients, three- 15 patients. Posterior instrumented fusions averaged 6.6 levels (2-16 levels). Technique: Expanding cages were placed front and center in the disc space, expanded up to 6mm above insertion height to improve cage fit and fill within the disc.  Cage expansion assisted in distracting the anterior interspace and acting as a fulcrum to increase segmental lordosis when combined with posterior compression instrumentation, with or without Smith-Petersen osteotomies. Backfill bone graft was used in the disc space at all TLIF levels. 

Results

All sagittal parameters improved (P<0.01). TLIF anterior disc height: Preop- 6.7mm (range 0-14), 1 year- 15.2mm (range 10-20). Segmental Lordosis (degrees): Pre-op- 4.9°, 1year- 13.2°(range 4-30°). Regional lordosis (L1-S1): Preop- 27.8° (range 8-50°), 1year- 49.8° (range 36-62°).  Two patients remained in global imbalance>5mm. Early complications: neurologic deficit -0, loss of cage expansion height – 0.  Revision surgery was required in 2 for unrelated adjacent level fractures in the thoracolumbar spine in deformity patients.  For 15 patients with more than 1 year follow-up, improvement was noted in VAS: pre- 6.1, 1 year– 2.9; ODI scores improved: preop– 47.5 (P<0.05), 1 year – 25.0(P<0.05). 

Conclusions

This study demonstrates the ability to improve lumbar lordosis with a new, crescent shaped hydraulic cage in patients undergoing surgery for degenerative scoliosis.  Early clinical outcomes are favorable in these patients and there have been no adverse cage related events in this study population.