Administrative Staff

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Dr. David A. Greuner MD, FACS, FICS

Minimally Invasive Surgery
Cardiovascular Surgery
Chief Medical Officer, Centers for Special Surgery

Dr. David Greuner is Chief Medical Officer at Centers for Special Surgery. He is a double board certified surgeon with over 10 years of surgical experience. Aside from a thriving clinical practice, Dr. Greuner has long been involved in the administrative workflow of medicine and is very passionate about improving clinical parameters in all aspects of surgical practice.

He is expert at creating and implementing clinical programs from inception to growth positions. In addition, Dr. Greuner supervises all procedural workflow, compliance, and clinical protocols to ensure the utmost safety, optimal outcomes, and cost effective care.



MG_4798-email-235x300-1Chief Executive Officer
Adam M Tonis, DC, CCRD

Dr Adam Tonis has 25 years of experience in both the treatment of patients as well as management of medical practices. Engaging in direct patient care helped Dr Tonis understand the individual care necessary to garner trust and render the most appropriate treatment for each person.

Dr Tonis found that he loved the managerial and business side of health care just as much if not more than actually treating patients.  He realized that being able to take his passion for individualized care to multiple physicians over multiple specialties would allow his vision to be multiplied greater than what he could do alone.

Over the years of leading teams and building multi specialty practices he now has found his years of experience and paying off for NY Surgical. Forging relationships with ancillary professionals to better assist treatment of each patient as well as designing implementing and managing new processes across the board allow the patient’s of our practice the greatest opportunity in getting the most advanced treatment possible.

Dr Tonis says “helping manage healthcare for patients requires a view from both 20,000 feet as well as up close and personal”. The healthcare landscape is consistently changing however patients needs remain constant. Being able to still deliver personalized attention while maintaining viability in the market place is essential. My hope is that every patient that walks into our facility leaves feeling as if they were heard, treated respectfully and given the most appropriate advice available.


Our Administrative Team leaders are always at work managing our daily operations and keeping their respective teams fluid to maintain the highest standard of care, not just in the clinical arena, but making approvals, billing, scheduling and follow up as easy as possible for our patient base. We care very much about patient satisfaction, and we strive to keep this as high as possible in every regard.

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Nicole Tonis MBA
Director, Business Process Management
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Karen Guerreri
Pre-authorizations Team Leader Karen Ann has been in medical administration management for 18 years. Her expertise in this area help our patients understand their insurance process and benefits. Her warm and friendly personality provide our patients a comforting level of care.

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Danielle Rizzo
Front Desk Administrative Team Leader Danielle Rizzo is our front desk team leader, and graduated from St. Johns University in New York City. Prior to joining our team at NYC Surgical, she spent several years both leading sales teams in the retail industry, as well as counseling school age students. These two skill sets in combination have made her adept at training, monitoring, and ensuring a high level of customer satisfaction with our front desk staff, who are our first interface with patients.

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Timothy Herbert
CNNT Radiologic Technologist; Materials ManagerMr. Timothy Herbert brings thirty years of radiology experience to the Centers for Special Surgery team. His training in many different clinical settings make him an asset to our team. He is proficient in various imaging techniques, fluoroscopic x-ray, nuclear medicine and various ultrasound procedures. Mr. Herbert has spent the last ten years working in the ambulatory surgery field. During this time, he has taken on various roles such as, materials management, life safety, and facilities management. His broad-based knowledge makes him a wonderful asset to our team.

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Megan Fabrizio
Office CoordinatorMegan Fabrizio, is, first and foremost, a coordinator; she ensures that all interactions between administration, employees, and patients and outside services run as smoothly as possible. She makes appointments, manages schedules, direct patients to proper locations and, if necessary, takes and process payments. She manages the physician and staff credentialing files.