The effect of TLIF cage position on segmental and regional lordosis

2011

SUMMARY

This clinical study correlates rectangular cage position and level treated with segmental and regional lordosis and clinical outcomes in 72 consecutive patients undergoing TLIF using a single obliquely placed rectangular cage at 1-2 levels(107 discs). At 3 years follow-up, cage position within the disc did not affect segmental or regional lordosis or clinical outcome. Regional lordosis was unaffected by TLIF level and 1 vs. 2-level TLIF.

INTRODUCTION

Common TLIF techniques include a single rectangular cage placed obliquely within the interspace, or a semilunar cage placed along the anterior disc margin. This clinical study correlates rectangular cage position and level treated with segmental and regional lordosis and clinical outcomes.

METHODS

A review of 72 consecutive patients who underwent posterior instrumented fusion and TLIF using a single obliquely placed rectangular cage at 1-2 levels (107 discs). Radiograph analysis pre-op, 6 weeks, 1 year, and 2 years: TLIF level, disc height, disc angle, regional lordosis (T12-S1), and cage position. Oswestry (ODI), pain scores (VAS), complications, fusion rates were compared by anatomic level, cage position, and 1 vs. 2 level fusions. Data was analyzed using ANOVA, paired t-tests, Anderson-Darling, Mann-Whitney, Sign Test, and chi-square as appropriate.

RESULTS

At 35 months follow-up (24 – 47mo), complications: adjacent degenerative changes-19, adjacent fracture-3, infection-2, temporary foot-drop-2, nonunion-0, revision surgery-4. Pre-op disc height and angle were similar pre-op but taller at L5-S1, L4-5 than L3-4(16.5mm vs. 13.1mm). For single level fusions, change in disc angle was dependent upon cage position (p=0.02), but not level (p=0.5), other factors showing no preference. Regional lordosis was unaffected by cage position, level, or 1 vs. 2 level TLIF (P=0.9). Patients with 2 levels fused improved VAS 5.7pre to 3.4 at 2 years (p=0.017); ODI improved 51pre to 28 at 2 years (p<0.001). Single level TLIF similarly improved VAS from 6.5pre to 3.8at 2 years (p=0.026), ODI improved from 48 to 27 at 2 years (p<0.001). A significant difference (p<0.001) was observed in the rate of degenerative disk disease for 2 level TLIFs (26/35) vs. single level TLIF (8/32).

Conclusions Rectangular cage position affects segmental but not regional lordosis or clinical outcome. Regional lordosis is unaffected by TLIF level and 1 vs. 2-level. Adjacent level degeneration was more common after 2-level TLIF.

SIGNFICANCE

The obliquely placed TLIF cage effectively supports disc height and angle however deeply placed within the disc.