Sagittal imbalance.

Sagittal imbalance may be either segmental (type 1) or global (type 2). Careful preoperative evaluation is essential to determine the presence and extent of any inherent flexibility in the deformity. Flexible deformities may be corrected with careful intraoperative positioning and instrumented fusion. More rigid or fixed sagittal plane deformities may be corrected with one or more osteotomies. Thorough planning and meticulous execution of osteotomies are essential to obtaining optimal surgical results.