Spine behavior caudal to instrumentation in King II and IV curves.

This retrospective review of children surgically treated for King Type II or IV curvature of the spine required a minimum lumbar Cobb angle of 40 degrees and a minimum lumbar inclination (the angle formed between a line through the spinous processes of the three most caudal lumbar vertebrae and a line perpendicular to the floor) of 10 degrees. Twenty children had combined anterior thoracolumbar and posterior instrumentations whereas 20 had only posterior instrumentation. Children who had combined surgery had significantly better corrections of their lumbar Cobb angles. They had a mean correction of 43.3 degrees compared with 26.7 degrees in children with posterior instrumentation only. These superior corrections of the lumbar Cobb angles did not result in significantly better improvements in the lumbar inclinations. Patients who had the combined procedures had a mean improvement of 10.1 degrees, whereas patients who had posterior instrumentation only had a mean improvement of 8.0 degrees in lumbar inclination. Instead of having superior corrections of the lumbar inclinations, the combined surgeries resulted in a significant worsening of the angle between the end plates of the last instrumented vertebra and the next most caudal end plate. In patients who had combined surgery this angle averaged 8.4 degrees, whereas in patients who had posterior instrumentation only this angle averaged 4.1 degrees.