Predicting the outcome of selective thoracic fusion in false double major lumbar "C" cases with 5 to 15 year followup

2009

SUMMARY

The adequacy of selective thoracic fusion (STF) for "C" lumbar modifier false double major curves is uncertain. 32 patients underwent STF with 5 to 15 year follow up at a single institution and we compared those with excellent outcomes vs. those who required revision or had suboptimal results. Standing lumbar lordosis taken at the 2 month post-operative visit best correlated with outcome at final follow up. AVR, AVT, overall balance, cobb angles, and their respective ratios were not significant.

INTRODUCTION

The efficacy of selective thoracic fusion (STF) in lumbar "C" false double major curves is controversial. We examined the 5 to 15 year outcomes of patients with "C" lumbar curves who underwent STF at a single institution to determine which factors help predict successful outcome.

METHODS

32 patients (age 14.8±2.0 yrs) with a lumbar "C" modifier underwent primary selective thoracic fusion and had minimum 5 year follow up (mean 6.8 yrs). All patients were fused distally to either T12 or L1. At latest follow up, 18 were considered successful (group S), 2 required re-operation to accommodate worsening deformity (group R) and 12 were considered marginal outcomes (group M), as defined by >3cm coronal imbalance (n=5), >5mm worsening of lumbar apical vertebra translation compared with preop (n=4), >1 Nash-Moe grade worsening of lumbar apical vertebra rotation (n=1), >10 degrees of thoracolumbar junction kyphosis which was at least 5 degrees worse than pre-op (n= 5), and lumbar cobb angle >5 degrees worse than pre-op (n=2).

RESULTS

Of the multiple factors considered, 2 month post-op standing lumbar sagittal alignment was most predictive for long term outcome (p < 0.019 by Kruskal-Wallis ANOVA). Satisfactory outcomes had statistically significantly greater T12-S1 lordosis than those that were marginal (64.8° (S) vs. 52.0° (M), p = 0.014) or required reoperation (64.8° (S) vs. 38.0° (R), p < 0.001). Traditionally considered variables such as AVR, AVT, cobb angle magnitudes, coronal and sagittal balance, and their respective thoracic to lumbar ratios were not independently significant.

CONCLUSION

Long term follow-up of selective thoracic fusion demonstrates efficacy in lumbar "C" modifier type curves, when careful consideration is given to ensure that lumbar lordosis is preserved.

SIGNIFICANCE

Postoperative standing lumbar lordosis is the most predictive factor to success in selective thoracic fusions of false double major curves with a "C" lumbar modifier.