In a move to expand its outpatient surgery services, Santa Rosa Memorial Hospital has acquired a controlling stake in Advanced Surgery Institute, a state-of-the-art ambulatory center founded by a group of local surgeons.

The Santa Rosa surgery center's 19 physicians will retain a 39 percent interest in the venture while Memorial Hospital, which is part of St. Joseph Health Sonoma County, will own 51 percent. Regent Surgical Health, an Illinois company that develops and manages surgery centers, will hold the remaining 10 percent interest.

The center opened in 2010 as a venture between the Santa Rosa physicians and Regent, which manages 24 surgical centers in the United States and Europe. Eighteen of its centers have entered into joint ventures with hospitals.

Health care reform is driving hospitals to provide more services on an outpatient basis, which is designed to reduce hospital admissions and lower costs while providing efficient care to patients who do not require hospitalization.

St. Joseph said the deal will "enable greater collaboration" between the hospital and the 19 surgeons at the facility. Specialties at the center include general surgery, orthopedics, gastric banding, pain management, plastic surgery, podiatry and ear, nose and throat surgery.

"We're proud to establish this partnership with the outstanding physicians of ASI, with whom we have worked closely in patient care throughout their careers," Kevin Klockenga, CEO of St. Joseph Health's Northern California region, said in a statement.

Dr. Stefan Zechowy, an ear, nose and throat surgeon who serves as president of the center's board of directors, said the deal will benefit the center's doctors and their patients.

"Aligning with Santa Rosa Memorial further strengthens our relationship in the community with the region's major health care provider, who shares our commitment to quality and service," he said in a statement.

Regent will continue to manage and provide administrative services for the surgical center, which employs 30 people. The center is exploring opportunities to add additional specialties including gastrointestinal surgery, endoscopy and urology.