Short segmental kyphosis following fusion for Scheuermann's disease.

Six of 14 patients surgically treated for Scheuermann's disease developed a short segmental kyphosis adjacent to the fusion. In four patients, the original fusion had incorporated the end vertebrae of the curves. However, there was mild wedging of the end vertebra, which led to a loss of correction occurring at the junction between fused and unfused segments. These losses averaged 13 degrees (range, 6-29 degrees) at follow-up, ranging from 1 to 5.5 years (average, 2.8 years). The resultant short segmental kyphosis ranged in magnitude from 15 degrees to 34 degrees (average, 23 degrees). The kyphosis occurred distally in five patients and proximally in one patient. The risk of developing a short segmental kyphosis may be minimized if the fusion and instrumentation extend beyond all wedged vertebrae to the first "square" vertebra. This will necessitate fusing into the upper lumbar spine for many patients.