Flatback syndrome.

Flatback syndrome is characterized by loss of normal lumbar lordosis, resulting in forward tilt of the trunk, inability to stand erect, back pain, and thigh pain from chronic hip flexion and knee bending. The usual etiology is iatrogenic, through previous fusions or with extension instrumentation. Surgical treatments described include extension osteotomy (Smith-Petersen), pedicle subtraction osteotomy, and polysegmental osteotomies.