Evidence-based thresholds for the volume-value relationship in shoulder arthroplasty: outcomes and economies of scale

Whereas several studies suggest that high-volume surgeons and hospitals deliver superior patient outcomes with greater cost efficiency, no evidence-based thresholds separating high-volume surgeons and hospitals from those that are low or medium volume exist in shoulder arthroplasty. The objective of this study was to establish meaningful thresholds that take outcomes and cost into consideration for surgeons and hospitals performing shoulder arthroplasty.

Using 9546 patients undergoing primary shoulder arthroplasty for osteoarthritis from an administrative database, we created and applied 4 models using stratum-specific likelihood ratio (SSLR) analysis of a receiver operating characteristic (ROC) curve. We generated 4 sets of thresholds predictive of adverse outcomes, namely, increased length of stay (LOS) and increased cost for both surgeon and hospital volume.

SSLR analysis of the 4 ROC curves by surgeon volume produced 3 volume categories. LOS and cost by annual shoulder arthroplasty surgeon volume produced the same strata: 0-4 (low), 5-14 (medium), and 15 or more (high). LOS and cost by annual shoulder arthroplasty hospital volume produced the same strata: 0-3 (low), 4-14 (medium), and 15 or more (high). LOS and cost decreased significantly (P < .05) in progressively higher volume categories.

Our study validates economies of scale in shoulder arthroplasty by demonstrating a direct relationship between volume and value through SSLR analysis of ROC curves for risk-based volume stratification using meaningful volume definitions for low-, medium-, and high-volume surgeons and hospitals. The described volume-value relationship offers patients, surgeons, hospitals, and other stakeholders meaningful thresholds for the optimal delivery of shoulder arthroplasty.