STUDY DESIGN

Retrospective multicenter cohort-study.

OBJECTIVE

We propose an evidence-based surgical algorithm for achieving normal pelvic balance while optimizing health-related quality of life (HRQoL) in high-grade spondylolisthesis.

SUMMARY OF BACKGROUND DATA

The principles of surgical treatment for young patients with high-grade L5-S1 spondylolisthesis remain unclear. There is a growing body of evidence supporting the central role of pelvic balance in the postural control and biomechanics of subjects with high-grade spondylolisthesis.

METHODS

This retrospective study assessed a multicenter cohort of 61 patients with high-grade L5-S1 spondylolisthesis. Classification and regression tree analysis was used to identify objective criteria associated with pelvic balance and HRQoL after surgery.

RESULTS

The most important predictor of a postoperative balanced pelvis was a postoperative L5 incidence ≤63.5 degrees. With postoperative L5 incidence ≤63.5 degrees,a residual slip percentage 9% and performing an L5-S1 posterior lumbar interbody fusion (PLIF)/transforaminal lumbar interbody fusion (TLIF) increased the likelihood of achieving a balanced pelvis postoperatively. When L5 incidence was 63.5 degrees,a balanced pelvis was most likely achieved with fusion limited to L5 proximally, residual slip percentage ≤40%, and residual lumbosacral angle 98 degrees. Predictors of postoperative HRQoL were the preoperative HRQoL score, L5 incidence and slip percentage.

CONCLUSIONS

A surgical algorithm is proposed to achieve normal pelvic balance, while optimizing HRQoL. The first step during surgery is to assess L5 incidence and if L5 incidence is <65 degrees, the next step depends on the pelvic balance. With a preoperative balanced pelvis, it is important not to reduce completely the slip percentage by leaving a slip percentage ≥10%. When the preoperative pelvis is unbalanced, a TLIF/PLIF at L5-S1 is recommended to facilitate correcting the angular deformity at L5-S1. If L5 incidence is ≥65 degrees,a TLIF/PLIF at L5-S1 should be performed to correct the angular deformity at L5-S1, and fusion should ideally end at L5 proximally, in addition to performing gradual reduction of the slip percentage. If fusion up to L4 is required, a lumbosacral angle ≥100 degrees is key.