Sagittal deformities of the spine: factors influencing the outcomes and complications.

Degenerative changes have the potential to greatly disrupt the normal curvature of the spine, leading to sagittal malalignment. This phenomenon is often treated with operative modalities, such as osteotomies, though even with surgery, only one-third of patients may reach neutral alignment. Improvement in surgical outcomes may be achieved through better understanding of radiographic spino-pelvic parameters and their association with deformity. Methodical surgical planning, including selection of levels of instrumentation and site of the osteotomy, is crucial in determining the optimal plan for a patient's specific pathology and may minimize risk of developing postoperative proximal junctional kyphosis/failure. While sagittal alignment is essential in operative strategy, the coronal plane should not be overlooked, as it may affect the osteotomy technique. The concepts of sagittal balance and alignment are further complicated in patients with neuromuscular diseases such as Parkinson's disease, and appreciation of the interplay between anatomic and postural deformities is necessary to properly treat these patients. Finally, given the importance of sagittal alignment and the role of osteotomies in treatment for deformity, the need for future research becomes apparent. Novel intraoperative measurement techniques and three-dimensional analysis of the spine may allow for vastly improved operative correction. Furthermore, awareness of the relationship between alignment and balance, the soft tissue envelope, and compensatory mechanisms will provide a more comprehensive conception of the nature of spinal deformity and the modalities with which it is treated.