• Photo of nurse touching senior man's hand on railing, illustrating physical therapy

Physician Assistants

Our invaluable group of physician assistants help prevent and treat illness and injury at the direction of the TOCA physicians.

A Physician Assistant (PA-C), is a healthcare professional who is trained to practice medicine as part of a team with physicians. Physician assistants conduct physical exams, diagnose and treat illnesses, order and interpret tests, prescribe medications, counsel on preventive health care and may assist in surgery.

Michelle Armijo, PA-C

TOCA is pleased to have Michelle as a PA to our top-tier Orthopedic group. Michelle works in the Phoenix clinic on  Mondays and at our Glendale Arrowhead office Tuesday-Thursday helping to ensure patient access and timely appointments. She is part of TOCA’s team of PAs and NPs who complement the Physicians here, working in partnership to deliver amazing healthcare as effectively as possible. Michelle is a graduate of Midwestern University and brings a high level of knowledge and partnership to our teams. Some of you might recognize Michelle, as she was a part of the TOCA group for 7 years prior.

Matthew Cocking, PA-C

PA-C to Dr. Yacobucci (Sports Medicine, Arthroscopic & Reconstructive Surgery of the Knee & Shoulder)

Matt has been working as a PA with Dr. Yacobucci since 2001. He did his PA training locally at Midwestern University. He has a great understanding of orthopedic and sports medicine related conditions, particularly of the knees and shoulders. He is a skilled surgical assistant and performs many of the procedures carried out in the clinic, such as joint injections. He is also trained in using Ultrasound to guide in some of these procedures. He has co-authored articles and participated in clinical research on orthopedic topics.
Matt has spent time as a preceptor for medical students in the clinic and surgery settings, and has also served as a guest speaker and instructor to medical students and professionals teaching proper technique for intra-articular joint injections. In addition, he has helped provide medical coverage for the Arizona Rattlers arena football team as well as several local high schools. Matt was a recipient of the Cystic Fibrosis Foundation’s Arizona’s Finest Award in 2003.


  • B.S. Medical Science
    Midwestern University Physician Assistant Program
    Glendale, AZ. 2001


  • NCCPA Physician Assistant Certification 10/2001
  • Arizona State License for Physician Assistants 11/2001

Clinical Experience

  • Orthopedic Surgery Physician Assistant
    The Orthopedic Clinic Association

Physician Assistant Student

  • Midwestern University Physician Assistant Program

Shane Ewalt PAS-III

PA to Dr. Duhon

Shane has been working as a PA with Dr. Duhon since 2017. He did his PA training locally at Midwestern University. He has great understanding of orthopedic and sports medicine-related conditions, particularly reconstructive surgeries and sports injuries. He is a skilled surgical assistant and performs many of the procedures carried out in the clinic.


  • Master’s of Medical Science in Physician Assistant Studies Midwestern University, Glendale, AZ

Jamie Lloyd ACNP-BC

Nurse Practitioner working with Dr. Christopher Huston

Jamie has been working with Dr. Huston since 2014 in the evaluation and treatment of various spine disorders. She performs various office procedures independently and also assists Dr. Huston in ambulatory surgery center procedures. She graduated from GCU: MSN-acute care nurse practitioner program 2014. She is ACNP board certified with ACCN. She Graduated from ASU with her BSN. She is also ACLS/BLS certified. Prior to coming to TOCA she was a critical care RN for 14 years. Jamie is an independent licensed practitioner.

Mark Moyer, PA-C

PA-C to Dr. Padley (Arthroscopic Surgery, Sports Medicine, Knee, Hip, Shoulder & Elbow)

  • 18 yrs. experience as a Sports medicine Physician Assistant (specializing in ultrasound guided injections)
  • 2001 graduate Daemen College Buffalo NY 1995-2000 Surgical Technologist
  • 1991-1995 Advanced EMT
  • 1985 – 1990 served in USMC

Mark’s interest in orthopedics was sparked as an EMT on an ambulance squad taking care of trauma patients, but working as a surgical technologist in orthopedics quickly became his favorite specialty. Upon graduation from PA school he worked as a Physician Assistant for the the head team doctor of the Buffalo Sabers. While there, he trained in ultrasound-guided injections, eventually performing them on professional and collegiate athletes.

Mark relocated to Phoenix in 2011 to escape the long Buffalo winters (we can’t blame him). He enjoys camping, hiking and traveling with his wife and two children.

Brad Nigbur, PA-C

PA-C to Dr. Haber (Orthopedic Surgery of the Hand & Wrist)

Brad Nigbur, PA-C, brings his expertise and experience as a certified physician assistant to the patients of The Orthopedic Clinic Association working alongside Dr. Joseph Haber.

Brad received his Bachelor of Science in Dietetics from the University of Wisconsin in Madison, Wisconsin. He then went on to complete a Master of Science degree in Physician Assistant Studies at the University of St. Francis in Albuquerque, New Mexico. Brad received his clinical training in several specialties including family medicine, internal medicine, general surgery, pediatrics, and emergency medicine. He also had extensive clinical training in orthopedics. Wanting to focus on his main interest of the hand and wrist he joined The Orthopedic Clinic Association in 2011.

Brad resides in Scottsdale. He enjoys golfing, swimming, hiking, and paddle boarding. Brad is active in the community volunteering his time performing sports and geriatric physicals.

Brad is involved in an international study for the collagen case injection for Dupuytren’s Disease. He is a member of the American Academy of Physician Assistants (AAPA) and is certified in Advanced Cardiovascular Life Support (ACLS) as well as Basic Life Support (BLS).

Ashlyn Sala, PA-C

Physician Assistant to Dr. Cummings (The Bone Health Clinic)

Ashlyn Sala is a board-certified Physician Assistant working in The Bone Health Clinic at The Orthopedic Clinic Association. Ashlyn received her Bachelor of Science in Molecular & Cellular Biology from the University of Arizona in Tucson, AZ. She then continued her education at Midwestern University in Glendale, AZ, where she received her Master of Medical Science in Physician Assistant Studies. She received clinical training in a variety of medical specialties, including family medicine, internal medicine, emergency medicine, pediatrics, general surgery and psychiatry. She also received training in orthopedics, including a clinical rotation in orthopedic surgery with Dr. Cummings at The Orthopedic Clinic Association. This sparked her passion for bone health and orthopedics, prompting her to join The Orthopedic Clinic Association in September 2018.

Cassandra Smith, PA-C

Board Certified Physician Assistant to Dr. Cummings

As a Board-Certified Physician Assistant to Dr. Dean Cummings since 2016,  I specialize in Sports Medicine and Orthopedics/Orthopedic surgery of the Shoulder, Elbow, Knee and currently a serve as a team member of the Bone Health Clinic as a Specialist. I received a Bachelors of Science in Biology and pre-Physician Assistant studies from Grand Canyon University in Arizona and continued on to obtain a Masters degree in Physician Assistant Studies at MCPHS University in Boston, Massachusetts. My clinical training covered all specialties of health sciences including internal medicine, pediatrics, emergency medicine, family practice, psychiatry, women’s health, general surgery, and Orthopedics/orthopedic surgery where I worked alongside Dr. Duhon within TOCA.

As a native to Arizona I returned after school to work permanently alongside Dr. Cummings specializing in sports medicine and orthopedic/reconstructive surgery of the shoulder, elbow and knee; as well as a Bone health specialist for treatment and prevention of Osteopenia, Osteoporosis, and osteoporotic related fractures.

I enjoy spending time with my TOCA team daily where they challenge me and as I do them. My past times are spent with physical and outdoor activities such as hiking, fishing, hunting, as well as a new obsession with my puppy.


Alyssa Tyler, PA-C

PA to Dr. Johnsen

Alyssa is a board-certified Physician Assistant working alongside Dr. Steen Johnsen. She received her Philosophy degree at College of Saint Benedict and Saint John’s University in Minnesota. After college, she took a job as a CNA, which sparked her passion for medicine. She completed her Masters in Physician Assistant studies locally at Midwestern University. Alyssa worked as a Cardiology PA for over two years before pursuing her desire to work in Orthopedics.

Alyssa resides in Cave Creek with her husband and two dogs. Their family loves spending time outdoors exploring the desert landscape and enjoying their separation from Midwestern winters.

Top Doctors for 20 years and counting!

Phoenix Magazine has consistently awarded TOCA doctors with the coveted Top Doctor award since 1996 – the very first year the award was introduced!

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