Surgical treatment of high-grade spondylolisthesis.

High-grade spondylolisthesis is defined as Meyerding grade 3, 4, or 5 with an increased L5-SI kyphosis/slip angle. Modern-day treatment of high-grade spondylolisthesis usually involves some reduction of the spondylolisthesis along with pedicle screw instrumentation and circumferential fusion at L5-S1, achieved entirely through a posterior approach or through separate anterior and posterior approaches. Complications include implant failure distally, nonunion, and footdrop.