Press Release


Bob Young

For Release:

January 31, 2024

CWCI Analyzes California Workers' Comp Inpatient Care

[Note:  this Bulletin was revised in March 2024 with updated data on major joint replacement inpatient and outpatient procedures.]

Oakland, CA - The number of inpatient hospitalizations in the California workers’ compensation system declined 51.1% between 2012 and 2022, spurred by declining claim volume, technological advances and changes in Medicare rules that allow more outpatient procedures, the elimination of redundant payments for spinal surgery hardware, and the expansion of evidence-based guidelines for spinal fusions and other surgeries.  

A new analysis by the California Workers’ Compensation Institute (CWCI) uses data on 28.7 million inpatient hospital stays with 2012 through 2022 discharge dates compiled by the California Department of Health Care Access and Information (HCAI) to measure and compare the use of inpatient services and procedures covered by workers’ compensation, Medicare, Medi-Cal and private coverage.  Workers’ comp is by far the smallest of those payer systems, and excluding hospital stays related to pregnancy, childbirth, and newborns, which are not part of the system, the study found that the number of workers’ comp inpatient stays has declined from 21,505 (0.9% of the total for all four payer groups) in 2012 to 10,516 (0.4%) in 2022.  Between 2021 and 2022, the number of workers’ comp hospitalizations declined by 5.6%, bringing the total decline over the past 11 years to 51.1%.  In comparison, the number of hospital stays paid under private coverage fell 23.5% over that same period, while Medicare hospital stays were only down 1.4%, and those paid by Medi-Cal increased by 45.7% due to surging Medi-Cal enrollments following passage of the Affordable Care Act in 2014. 

The CWCI analysis notes that the decline in the number of workers’ comp inpatient stays dates back more than a decade, fueled by fluctuations in the number and types of work injury claims, the adoption of utilization review and independent medical review programs requiring that treatment meet evidence-based medicine standards, and a sharp reduction in the number of spinal fusions.  The most recent data suggest that many of those factors continue to help contain the volume of workers’ comp inpatient stays, as unlike the other systems where inpatient hospitalizations have rebounded after falling sharply in 2020 (the first year of the pandemic), workers’ comp inpatient stays have continued to drop.  The one exception is inpatient spinal fusions, which were up 5.0% between 2020 to 2022, driving spinal fusion hospital stays back up to 18.7% of all workers’ comp inpatient discharges in 2022, the highest proportion since 2016.  

The historical data also show that in the 8 years prior to the pandemic, diseases and disorders of the respiratory system (MDC 04) accounted for 2.5% to 3.0% of all workers’ comp inpatient stays, but with the introduction of COVID claims into the system, that percentage jumped to 7.4% in 2020 and 7.0% in 2021 before falling back to 3.7% in 2022.  With the recent decline in COVID-related hospitalizations, the distribution of workers’ comp inpatient stays by diagnosis shifted back toward pre-pandemic levels.  In 2022, diseases and disorders of the musculoskeletal system and connective tissue were the predominant diagnostic category, representing 60.3% of injured worker inpatient stays, followed by diseases and disorders of the nervous system, accounting for 6.2%.

The breakdown of Surgical vs. Medical (non-surgical) stays across the different payer systems shows that Surgical stays remain far more prevalent in workers’ comp, accounting for 68.4% of inpatient discharges in 2022, compared to 24.1% for Medicare, 20.9% for Medi-Cal, and 31.6% for private coverage.  Among the workers’ comp Surgical hospitalizations, those associated with various types of spinal fusions declined 58.8% between 2012 and 2022, but they still ranked first among Surgical stays and continued to account for a much higher proportion of the Surgical procedures in workers’ comp than in other systems, representing 18.7% of the workers’ comp inpatient surgeries in 2022 compared to 1.3% of the Medicare surgeries, 0.6% of the Medi-Cal surgeries, and 1.8% of the surgeries paid by private coverage.  Joint replacements (major hip and knee joint replacements or reattachment of a lower extremity) represented 8.8% of injured worker inpatient surgeries in 2022, compared to 0.5% in Medi-Cal, 1.0% in private coverage, and 1.5% in Medicare. 

Notably, the study found that the decline in workers’ comp inpatient surgeries has been moderated somewhat by the growing number of injured worker spinal fusions and total joint replacements performed on an outpatient basis.  Data from HCAI and CWCI’s Industry Research Information System database showed that the percentage of spinal fusions provided on an outpatient basis jumped from 0.8% in 2014 to 13.3% in 2022, while the percentage of major joint replacement or revision surgeries performed on an outpatient basis increased from 3.2% in 2014 to 62.4% in 2022, with the biggest increases occurring after Medicare removed these procedures from its “Inpatient Only” list, which is used to determine the appropriate setting for workers’ comp procedures.   

CWCI has issued a Research Update Report on its study, “Utilization of Inpatient Care in California Workers’ Compensation, 2012-2022.”  CWCI members and subscribers can access the report and a summary Bulletin at  Others can purchase a copy for $18 at

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