Complicated postoperative flat back deformity correction

The number of patients with iatrogenic spinal deformities is increasing with the global increase in the number of instrumented spinal operations. Correcting such a deformity could prove to be challenging due to the complex anatomical structure of the spine caused by previous surgeries. For these cases, extensive preoperative planning and proper implementation of the surgical plan are vital for surgical success.

The aim of this study was to generate a virtual and 3D printed patient-specific model to understand the complex anatomical-geometrical problem presented in a patient with severe sagittal and coronal malalignment due to repetitive surgical interventions over a 39-year period; and to develop the optimal plan for the deformity correction.

A patient-specific virtual geometry was defined using segmentation based on the preoperative CT scan. A 3D virtual plan was created with a cut out wedge shape of the L4 vertebrae to simulate a three-column pedicle subtraction osteotomy (PSO) surgery with 20° of correction in the sagittal plane.

In parallel, the developed virtual geometry was printed using a fused deposition modelling device to help the surgeon visualise the deformed spine and provide guidance in the preoperative planning phase, but also aid the surgeon in understanding the complex anatomy of the surgery.

The surgery was performed successfully, and no complications were registered. Using the preoperative and six month follow-up x-ray scans, the spinopelvic parameters were measured to calculate the amount of correction the surgery provided. The sagittal vertical axis decreased by 7cm, while the distance between the C7 plumb line and the sacral vertical line in the coronal plane was reduced by 4cm. A 30° correction was achieved for the lumbar lordosis following the PSO at the L4 vertebrae.