Do Structural Interbody Grafts Preserve Saggital Alignment Better Than Morselized Rib Autograft in Anterior Instrumentation of Thoracolumbar and Lumbar Adolescent Idiopathic Scoliosis?

Summary: To determine if structural interbody grafts preserve sagital alignment in the treatment of thoracolumbar and lumbar adolescent idiopathic scoliosis, 34 patients treated by anterior instrumentation with single solid rod, single screw constructs were assessed. The structural grafts placed in disc spaces below T12 were able to maintain sagital alignment over this region, while the spines that received only morselized rib graft collapsed into kyphosis. We advocate the use of structural grafts below T12.

Purpose: To determine if structural interbody grafts preserve sagital alignment in the treatment of thoracolumbar and lumbar adolescent idiopathic scoliosis.

Methods: Pre-operative, post-operative and two-year follow-up radiographs of 34 patients treated by anterior instrumentation with single solid rod, single screw constructs were assessed. Sixteen of the patients received structural grafts as interbody spacers in disc levels below T12, while the other 18 patients received only morselized rib allograft. Radiographs were measured for: primary, secondary, and fractional Cobb curves, coronal and sagital C7-sacrum plumb lines, T5-HIV (Highest Instrumented Vertebrae), instrumented levels, LIV (Lowest Instrumented Vertebrae) - S1, T12-LIV, and T12-S1 angles, and LID-A (Lowest Instrumented Disc - Angle).

Results: The increase in kyphosis from preoperative to follow-up radiographs of the angle between T12-HIV was significantly more for the patients with morselized rib graft compared to those with structural grafts, +8.6° and +0.8°, respectively (p <0 .05). The rib patients tended to compensate for this increased kyphosis with hyperlordosis below the instrumentation more than graft patients, -3.8° and 0.7°, respectively. Of note, did not occur at disc immediately caudal instrumentation; LID-A change from preop follow-up was +0.3 +2.4 patients. Despite tendency offset T12-LIV instrumentation, still their lateral plumb line C7-S1 by 14.9mm preoperative follow-up, as compared decrease of 1.9mm in All three these later findings were statistically significant, perhaps due low sample size.

Conclusions: The structural grafts placed in disc spaces below T12 were able to maintain sagital alignment over this region, while the spines that received only morselized rib graft collapsed into kyphosis. We advocate the use of structural grafts below T12.