Establishing benchmarks for the volume-outcome relationship for common lumbar spine surgical procedures

The importance of surgeon volume as a quality measure has been defined for a number of surgical specialties. Meaningful procedural volume benchmarks have not been established, however, particularly with respect to lumbar spine surgery.

We aimed to establish surgeon volume benchmarks for the performance of four common lumbar spine surgical procedures (discectomy, decompression, lumbar interbody fusion, and lumbar posterolateral fusion).

A retrospective review of data in the Florida Statewide Inpatient Dataset (2011-2014) was carried out.

Patients who underwent one of the four lumbar spine surgical procedures under study comprised the study sample.

The development of a complication or hospital readmission within 90 days of the surgical procedure was the surgical outcome.

For each specific procedure, individual surgeon volume was separately plotted against the number of complications and readmissions in a spline analysis that adjusted for co-variates. Spline cut-points were used to create a categorical variable of procedure volume for each individual procedure. Log-binomial regression analysis was then separately performed using the categorical volume-outcome metric for each individual procedure and for the outcomes of 90-day complications and 90-day readmissions.

In all, 187,185 spine surgical procedures met inclusion criteria, performed by 5,514 different surgeons at 178 hospitals. Spline analysis determined that the procedure volume cut-point was 25 for decompressions, 40 for discectomy, 43 for interbody fusion, and 35 for posterolateral fusions. For surgeons who failed to meet the volume metric, there was a 63% increase in the risk of complications following decompressions, a 56% increase in the risk of complications following discectomy, a 15% increase in the risk of complications following lumbar interbody fusions, and a 47% increase in the risk of complications following posterolateral fusions. Findings were similar for readmission measures.

The results of this work allow us to identify meaningful volume-based benchmarks for the performance of common lumbar spine surgical procedures including decompression, discectomy, and fusion-based procedures. Based on our determinations, readily achievable goals for individual surgeons would approximate an average of four discectomy and lumbar interbody fusion procedures per month, three posterolateral lumbar fusions per month, and at least one decompression surgery every other week.