Bipolar hybrid posterior instrumentation tecnique for the correction of Scheuermann's kyphosis.

ABSTRACT

Scheuermann´s kyphosis (SK) is the most common cause of painful and progressive structural hyperkyphosis in adolescents. Surgical treatment should be considered in cases of refractory pain or progressive deformities. We present the clinical and radiological results obtained using a bipolar, hybrid posterior instrumentation tecnique. We analysed 12 males and 6 females, with mean age of 15.8 years. Minimum follow-up was 2 years. We used transverse process hooks at the cranial level and polyaxial screws for the remaining levels. We did not instrument the periapical segment. We used the sagittal stable vertebra (SSV) as the lower instrumented vertebra (LIV) in most cases, the "barely touched SSV" if the above disc space is lordotic. The mean preoperative kyphosis was 73.6º, mean postoperative kyphosis 44.7º, and mean correction of 28.9º (p = 0.0002). The mean reduction in lumbar lordosis (LL) was 8.9º (p = 0.0018). There were no significant differences in the spinopelvic parameters or sagittal balance. The mean number of instrumented levels was 8.9. Type II osteotomies were necessary in only three patients. Three patients had a cranial sagittal angle greater than 10°, all of them asymptomatic. Postoperatively, all patients had VAS scores less than 2 and SRS-22 scores greater than 4. Hybrid bipolar posterior instrumentation offers adequate curve correction, less operative time, implant density, bleeding, material protrusion and risk of spinal cord injury, leaving a large periapical bed for graft supply. We propose to measure the flexibility of the curve in MRI. In flexible curves (those that correct at least 20% in the supine decubitus position), wide facetectomies offer adequate correction of the deformity.