An ASC in healthcare stands for Ambulatory Surgery Center, a facility designed exclusively for surgeries that don’t require an overnight hospital stay. These centers handle procedures where patients arrive, have surgery, and go home the same day, typically within 24 hours of admission. There are over 6,500 Medicare-certified ASCs operating across the United States, and they’ve become a major part of the surgical landscape for everything from cataract removal to knee replacements.
How ASCs Differ From Hospitals
The key distinction is scope. A hospital handles everything from emergency trauma to multi-week ICU stays. An ASC operates exclusively for planned surgical procedures on patients who don’t need to be hospitalized afterward. Federal regulations define an ASC as a “distinct entity that operates exclusively for the purpose of providing surgical services to patients not requiring hospitalization,” with services not expected to exceed 24 hours.
That narrow focus shapes the entire experience. ASCs are typically smaller, with streamlined check-in processes and shorter wait times. Because they only perform scheduled surgeries, there’s no competition for operating rooms with emergency cases. The staff specializes in a limited set of procedures, which creates a predictable, efficient workflow. Patient satisfaction data reflects this: one four-year study of a bariatric surgery center found ASC satisfaction scores averaged 9.74 to 9.95 out of 10, compared to 7.20 for hospital-based surgeries performed by the same surgeon.
What Procedures ASCs Perform
The range of surgeries performed at ASCs is broader than many people expect. The single most common procedure is cataract surgery, which accounts for about 8 percent of all major ambulatory surgeries and is the top procedure for adults over 65. Musculoskeletal procedures, including rotator cuff repairs, trigger finger release, knee meniscus removal, and knee replacements, collectively make up about 22 percent of ambulatory surgeries.
The full list of commonly performed procedures includes:
- Eye: Cataract and lens procedures
- Orthopedic: Rotator cuff repair, knee arthroscopy, knee replacement, spinal disc surgery
- General surgery: Gallbladder removal, hernia repair, appendectomy
- Gynecologic: Hysterectomy, breast lumpectomy
- ENT: Tonsillectomy, ear tube placement (the most common procedures for children)
- Cardiac: Pacemaker insertion or replacement
- Nerve: Carpal tunnel and other nerve decompression surgeries
The trend has been toward performing increasingly complex procedures in ASCs. Knee replacements and spinal surgeries that once required hospital stays are now routinely done on an outpatient basis in many centers, though patient selection matters. Not everyone is a candidate for having a complex procedure in a freestanding surgery center, and the decision depends on factors like overall health, body weight, and the specific surgery involved.
Why ASCs Cost Less
One of the most significant differences between ASCs and hospitals is price. Medicare pays ASCs roughly half of what it pays hospital outpatient departments for the same procedures. That gap has actually widened over time. ASCs were once reimbursed at about 85 percent of hospital outpatient rates, but that figure has dropped to around 50 percent on average.
This means every time a Medicare patient has surgery at an ASC instead of a hospital outpatient department, the Medicare program saves money. For patients, the savings can be substantial too, since out-of-pocket costs like copays and coinsurance are often calculated as a percentage of the facility’s total charge. A lower facility fee translates directly into lower patient costs.
Who Owns and Operates ASCs
Most ASCs have physician ownership. About 90 percent of ASCs in the U.S. have at least some physician ownership stake, and roughly 65 percent are solely owned by physicians. This physician-driven model is one reason ASCs tend to be highly specialized. A group of orthopedic surgeons might own a center focused on joint and spine procedures, while a group of ophthalmologists might run one dedicated to eye surgery.
Beyond physician-only ownership, joint ventures are common. These pair physicians with hospital systems or ASC management companies, blending clinical expertise with operational and business support. Hospital-owned ASCs, where a health system runs the center and brings in physicians through co-management agreements, are also growing. Each model balances physician control against the administrative complexity of running a surgical facility, handling insurance contracts, and meeting regulatory requirements.
Regulation and Quality Oversight
To participate in Medicare, an ASC must meet federal conditions for coverage set by the Centers for Medicare and Medicaid Services (CMS). Facilities can demonstrate compliance in two ways: through a state survey that inspects the center directly, or by earning accreditation from a national accrediting body that CMS recognizes as equivalent. In states that require licensure, accredited ASCs must also hold a state license.
ASCs are also required to participate in the Ambulatory Surgical Center Quality Reporting Program, a federal initiative that collects and publicly reports facility-level quality data. The program tracks outcomes, patient safety events, and care coordination measures using a combination of chart reviews, insurance claims data, and patient surveys. ASCs that fail to meet reporting requirements face a 2.0 percentage point reduction in their annual Medicare payment update, creating a direct financial incentive to participate fully.
Safety Compared to Hospitals
For appropriate candidates, ASC outcomes are generally comparable to hospital outcomes. Research on specific procedures tells a nuanced story. A meta-analysis of outpatient spinal fusion surgery (a relatively complex procedure for an ASC) found no statistically significant differences between inpatient and outpatient approaches for complications like stroke, blood clots, swallowing difficulty, or bleeding. The outpatient group actually showed lower reoperation rates and lower mortality.
The important caveat is patient selection. ASCs work best for patients whose health is stable enough to recover safely at home the same day. The shift toward performing more complex procedures in ASCs has raised questions about where the line should be drawn. For straightforward cases in otherwise healthy patients, the data supports ASCs as safe and effective. For patients with multiple chronic conditions or procedures that carry a higher risk of complications requiring overnight monitoring, a hospital setting may be more appropriate.