Sagittal plane considerations and the pelvis in the adult patient.

Study Design: Research update, focused review.

Objective: Identify the role of the pelvis in the setting of adults with spinal deformity.

Summary Of Background Data: Sagittal plane alignment is increasingly recognized as a critical parameter in the setting of adult spinal deformity. Additionally, pelvic parameters reveal to be a key component in the regulation of sagittal alignment.

Methods: Analysis of the pelvis in the sagittal plane is commonly assessed by 3 angular measurements: the pelvic incidence (morphologic parameter directly linked to sagittal morphotypes), the pelvic tilt (or pelvis retroversion used to maintain an upright posture in the setting of spinal deformity), and the sacral slope. Recent work using force plate technology has revealed that in the setting of anterior trunk inclination ("spinal imbalance"), the pelvis shifted posteriorly (toward the heels) in order to maintain a balanced mass distribution. The complex relationship between pelvic and spinal parameter were investigated in order to construct predictive formulas of postoperative spinopelvic alignment. It has emerged that pelvic tilt is highly correlated with patient self reported function (ODI, SF-12, and SRS).

Conclusion: It has become evident that good clinical outcome in the treatment of spinal deformity requires proper alignment. Pelvis parameters play an essential role not only in terms of spine morphotypes but also in regulating standing balance and postoperative alignment. Thus, optimal treatment of a patient with spinal deformity requires integration of the pelvis in the preoperative evaluation and treatment plan.