Osteotomy of the spine for multifocal deformities

Introduction When a deformity involves more than one area of the spine, it becomes a multifocal deformity; such a deformity could either be extending on two adjacent segments, or be two separated deformities on two non-adjacent segments. Materials and methods The surgical management of multifocal spinal deformities is challenging and must be done through a thorough preoperative planning where spinal and pelvic parameters should accurately be determined. Different strategies should be applied depending on the type of the multifocal deformity, the area involved, the angulation and stiffness of the spine in that area, and the presence of either a pure sagittal malalignment or a combined coronal and sagittal malalignment. This paper discusses these strategies and gives guidelines regarding the use of the different osteotomy techniques depending on each different situation that the deformity spine surgeon may encounter. For instance, where is the ideal level to perform a pedicle subtraction osteotomy (PSO) in a multifocal deformity? How does one take advantage of the remaining high discs to increase the correction without the need for a second PSO? When and where does one perform an asymmetrical PSO? When and where does one perform two PSOs? How does navigation help the spine surgeon to push the surgical limits further in these complex cases? Conclusion All these questions about the management of multifocal deformities will be discussed and answered with technical details and concrete examples of the different situations that may be encountered.