Strength of Evidence.
| Baseline strength: HIGH = majority of articles Level I/II LOW = majority of articles Level III/IV | |||||
| Upgrade: Large magnitude of effect and/or dose response gradient | |||||
| Downgrade: Inconsistency of results, indirectness of evidence, imprecision of effect estimates | |||||
| Strength of evidence | Conclusion/Comments | Baseline | Upgrade | Downgrade | |
| Question 1: What is the effectiveness of the various surgical approaches for HGS? | |||||
| Clinical outcome (Pain, function, etc.) | Low | Three LOE III and one LOE IV retrospective cohort studies reported good outcomes for function, pain, and satisfaction in patients with solid fusion regardless of the surgical procedure, but circumferential fusion provided the best clinical outcome results. | LOW | NO | NO |
| Radiographic outcome | Low | One LOE III and two LOE IV retrospective cohort studies reported no difference in fusion rate, but two Level III Evidence and one Level IV Evidence studies reported significantly higher pseudarthrosis rate in posterior-only procedures. | LOW | NO | NO |
| Question 2: What is the effectiveness of additional surgical maneuvers for HGS? | |||||
| Reduction | Low | Overall, the evidence on the incorporation of reduction is inconsistent. Three LOE III and two LOE IV clinical studies reported negative clinical outcome in partial reduction group with worse ODI and SRS scores but positive radiographic outcome with less pseudarthrosis and deformity progression on reduction of slip angle and slip grade. One LOE IV study reported full reduction in 95% of patients undergoing complete reduction but had high complication rate. For children and adolescents, in situ fusion with long-term follow-up is recommended. | LOW | NO | NO |
| Instrumentation | Low | No studies used instrumentation as the sole primary variable. Most studies included instrumentation with varying surgical approaches or other additional surgical maneuvers such as reduction. Use of instrumentation is dependent on surgical approach and surgeon preference. Luque box, Jackson intrasacral rod and double-plate technique are not recommended. | LOW | NO | NO |
| Decompression | Insufficient | There is no study directly examining decompression as an independent variable. Three Level III Evidence studies performing in situ fusion without decompression reported good clinical and radiographic outcome. Higher-level studies reporting on decompression are necessary for a definitive conclusion. | LOW | NO | NO |
| Question 3: What is the comparative safety of the various surgical approaches for HGS? | |||||
| Circumferential vs. Posterior-only vs. Anterior-only | Low | Three Level III Evidence and one Level IV Evidence retrospective cohort studies report no long-term difference in complications. Operation time and hospital stay was slightly higher in circumferential procedures. One Level IV Evidence retrospective study reported higher operative blood loss in PLIF compared to ALIF, but outcomes were similar. | LOW | NO | NO |
| Question 4: Who is at risk for progression to higher grade spondylolisthesis? | |||||
| Pelvic Incidence | HIGH | Two Level II Evidence studies indicated no correlation between higher PI and progression. | HIGH | NO | NO |
| Sacral slope | HIGH | Two Level II Evidence studies indicated no correlation between higher SS and progression. They reported that higher PI controls have high PT and SS and that SS may be predictive of reducibility. | HIGH | NO | NO |
| Age and grade of spondylolisthesis | HIGH | One Level II Evidence study indicated positive correlation between higher PI, age and grade of spondylolisthesis but not of progression. | HIGH | NO | NO |