Short Fusion with Residual Deformity vs. Long Fusion with Better Correction – Which is Better?

o a- DePuy Spine

Introduction: In the treatment of Lenke 1C (King-Moe II) curves, choosing between a selective thoracic fusion (which may leave deformity in the lumbar spine) and a fusion into the lower lumbar spine (which may improve correction at the expense of lumbar motion) is debated.

Method: Twelve experienced scoliosis surgeons were asked to evaluate 40 pairs of postoperative PA radiographs and answer the following hypothetical question: "Which spine would you choose for yourself to live the rest of your life?" The x-ray comparisons varied with regard to the number of remaining motion segments and the residual lumbar deformity. The unanimity of votes for a given "winner" was considered high (11-12 votes), moderate (9-10 votes), or low (6-8 votes). A deformity/motion segment ratio was created for each radiograph by dividing the residual lumbar Cobb angle by the number of unfused motion segments. A low ratio implies a smaller deformity with greater motion--theoretically "better" for the long term.

Results: A lower deformity/motion segment ratio predicted the winner in greater than 70% of the pairings. The average ratio among the winners was 4° per preserved level of motion. When the vote had high unanimity, the difference in the ratio was significant (p <0 .001), with an average ratio difference of 2.5 between the x-ray comparisons. However, when unanimity was low, in vanished a 0.5 point

Discussion: The results confirm the existence of a perceived trade off between residual deformity and spared motion segments. These results are based only on expert opinion but do provide some guidelines in choosing a selective fusion when residual lumbar deformity is anticipated.