Introduction: The reduction of severe spondylolisthesis remains controversial and is not without risk. The reduction should aim, primarily, to restore the lumbosacral angle.

Aim: To review the principle author’s experience with reduction of severe lumbosacral spondylolisthesis with emphasis on the restoration of the lumbosacral alignment.

Methods: Thirty patients have undergone reductions of severe lumbosacral spondylolistheses. All were treated by two-staged operations with variation. The anterior operations involved subtotal disc clearances with leverage to distract the discs and restore the lumbosacral angulation. Posteriorly, ala-transverse fusions and L5 laminectomies were performed. More recently pedicle screws were used. Initially hyperextension traction was employed between operations, but this was subsequently abandoned.

Results: Significant reductions (p< 0.01) of displacements were achieved at each stage but significant improvements in slip-angles only occurred with the initial operations. Loss of sagittal and angular corrections were noted at the one-year follow-up. Loss of angular corrections were significantly less with internal fixation (p=0.03). The final alignments were significantly improved when compared with the initial positions.

Conclusions: Satisfactory restoration of the lumbosacral alignment was achieved in severe spondylolisthesis by staged anterior and posterior procedures. Leverage to restore lumbosacral angulation during the anterior procedure facilitated reduction. Post-operative loss of correction was limited by pedicle screw fixation.

Introduction: Progression of lumbosacral spondylolisthesis during adolescence is not uncommon, but it is rare in adults. Structural changes in adolescent spondylolisthesis have been reported as possibly predictive and contributory to progression.

Aim: To review the structural changes that occur with and possibly contribute to slip progression in lumbosacral spondylolisthesis.

Methods: The radiographs of 42 patients with lumbosacral spondylolisthesis who had been followed for a mean period of six years were reviewed. The following radiological parameters were determined from the initial and latest radiographs:

Percentage slip

Slip angle

Rounding of the sacrum

Trapezoid index of L5 vertebral body

Progression of a lumbar lordosis was defined as an increase in slip of 5% or more.

Results: Strong correlations (p< 0.01) existed between all radiological parameters at the time of the initial examination and at follow-up. Changes in percentage slip over time correlated with changes in all radiological parameters (p< 0.01). Slip progression correlated with increased slip angle (p< 0.01), increased trapezoid index (p< 0.05), and increased lordosis (p< 0.01) but not with age (p=0.16), adolescence (p=0.10), gender or with spondylolysis. The risk of slip progression was greatest for adolescents with an initial slip of 30% or more (p=0.13, Odds Ratio=5.7).

Conclusions: Slip progression in lumbosacral spondylolisthesis was associated with corresponding proportional structural changes in the sacrum and the L5 vertebral body, possibly related to growth and remodelling. The tendency to progress was greatest in adolescents with slips of greater than 30%. This relationship was sufficiently strong to consider prophylactic fusion.