Doctors

David Prybyla, MD

Dr David Prybyla | Orthopaedic Surgeon Chelmsford MADr. Prybyla is a graduate of Yale University and Albany Medical College. He completed his residency training at the University of Massachusetts Medical School in Worcester, followed by subspecialty training in adult joint reconstruction surgery at the New England Baptist Hospital in Boston. Dr. Prybyla is interested in adult joint replacement surgery and trauma.


Christopher Baker, MD

Dr Christopher Baker | Orthopaedic Surgeon Chelmsford MADr. Baker is a graduate of the University of Michigan and Boston University School of Medicine. He completed his residency training at the University of Massachusetts Medical School in Worcester. He also completed subspecialty training in adult Foot and Ankle surgery at the New England Baptist Hospital in Boston.  Dr. Baker holds privileges at Lowell General Hospital.

Dr. Baker is board certified by the American Board of Orthopedic surgeons and is a member of the American Orthopedic Foot and Ankle Society. Dr. Baker is interested in adult foot and ankle surgery and trauma.


Physician Assistants

ALLISON MOEN, PA-C

DJ TIBBETTS, PA-C

 

Nurse Practitioners

Roula Johnstone, NP-C

Roula Johnstone is a Board Certified Acute Care Nurse Practitioner who has worked directly with Dr. Alter since 2011. Roula assists Dr. Alter in providing orthopedic care to patients with upper extremity disorders.

Roula is a graduate of Northeastern University with a Master's of Science degree in Nursing, where she also obtained her Acute Care Nurse Practitioner certification in 2011. She obtained her Bachelors Degree of science in Nursing from UMASS Lowell in 1999. Roula also obtained her Registered Nurse First Assistant certificate from Delaware County Community College in 2006, and has since been assisting in surgery.

Prior to her masters degree, she worked as a critical care nurse and registered nurse first assistant at Saints Medical Center in Lowell.

She is a member of the American Academy of Nurse Practitioners, the Massachusetts Coalition of Nurse Practitioners, and the Association of Operating Room Nurses.


Kristen Proverb, NP-C

Kristen Proverb is a certified nurse practitioner who has provided specialized orthopaedic care to patients of Dr. Scott Sigman since 2006. At Orthopaedic Surgical Associates, Kristen assists in the diagnosis and treatment of a wide range of orthopaedic conditions, focusing primarily on sports medicine. She has experience with x-ray, MRI, CT and other imaging exams, as well as pre- and post-operative care.

Kristen graduated with her Bachelor’s degree in Political Science at the University of Massachusetts before completing a Master of Science degree in Nursing at Northeastern University as part of the Direct Entry ANP Program. Upon graduation, Kristen was certified as an Adult Nurse Practitioner. Kristen served as a clinical Nurse at Massachusetts General Hospital specializing in vascular surgery and critical care at North Shore Medical Center.

Before joining Dr. Sigman’s team, Kristen served as a Clinical Nurse at Massachusetts General Hospital and North Shore Medical Center. She is a member of the American Academy of Nurse Practitioners and the Massachusetts Coalition of Nurse Practitioners.


June Stott, APRN, BC, MS, CRNFA


Jessica Carey, NP-C