Comparison of 2 Surgical Approaches in the Treatment of Degenerative Spondylolysthesis: Posterolateral Fusion With Instrumentation (GPLI) Plus or Minus Transforaminal Lumbar Interbody Fusion (TLIF)

Patients are carefully positioned in the proned position and submitted to a posterior surgical approach under general anaesthesia. Surgical levels are viewed laterally by mean of intraoperative radiographs which can be performed at surgeon's demand during the whole surgery time. The preceding procedure is performed. In case of foraminal stenosis, decompression is performed at the same time as discal approach via the narrowest foramen. In addition to this, before preparation of bed for bone grafting, nerve roots are retracted and the disc nucleus is removed entirely, then endplate decortication is performed. The disc space is distracted. The most anterior part of the disc space is packed with cancellous bone. A cage packed with bone is inserted into the anterior portion of the interspace. According to cage location, bone graft could be inserted in the posterior portion of the interspace. Cage placement is radiologically checked. The end of the procedure is the same as for GPLI.

Patients are carefully positioned in pronation and submitted to a posterior surgical approach under general anaesthesia. Surgical levels are viewed laterally by mean of intraoperative radiographs performed at surgeon's demand during the whole surgery time. Pedicle screw instrumentation is performed, followed by posterior neural decompression depending on the type of stenosis: * Central stenosis: decompression is performed including medial facectomy, laminectomy; * Foraminal stenosis: foraminotomy is performed, while preserving a graft bed as large as possible; * Pure foraminal stenosis: spinal duct is not opened. Local bone is harvested from the lamina and the spinous process and carefully fragmented for autologous graft. Subperiosteal dissection is performed between the transverse processes and lateral aspects of the facet joints. Two rods are placed and locked on screws in maximum compression to optimize segmental lordosis. Bone autograft is placed into this bed.