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Become a member and receive career-enhancing benefits

Our top priority is providing value to members. Your Member Services team is here to ensure you maximize your ACS member benefits, participate in College activities, and engage with your ACS colleagues. It's all here.

Become a Member
Become a member and receive career-enhancing benefits

Our top priority is providing value to members. Your Member Services team is here to ensure you maximize your ACS member benefits, participate in College activities, and engage with your ACS colleagues. It's all here.

Membership Benefits

Executive Officers

The following surgeons are the elected officers of the new Excelsior Surgical Society:



Colonel Jeremy W. Cannon, MD, FACS, MC, USAF

Colonel Cannon is the trauma program medical director and an associate professor of surgery at the University of Pennsylvania, PA. He is an active reservist currently assigned to Health Affairs in Falls Church, VA. He is a graduate of the U.S. Air Force Academy and Harvard Medical School and holds a Master of Science in Mechanical Engineering from MIT. He has been a Fellow of the American College of Surgeons since 2008 and an active member of the Excelsior Surgical Society since 2016.


Vice-President (President-Elect)

Colonel Jennifer Gurney, MD, FACS, MC, USA

Colonel Jennifer Gurney is the Chief of the Joint Trauma System and has worked with JTS since 2012. Since joining active-duty Army, COL Gurney has served at William Beaumont Army Medical Center, as the Chief of General Surgery at Landstuhl Regional Medical Center, and has deployed seven times, serving as the Theater Trauma Director in her last deployment to Iraq. Gurney has led efforts to better surgical practices and procedures across the globe and has supported a number of projects such as the development of a military-civilian partnership guide, Combat Readiness metrics for deploying surgeons, and detailed expectations for expeditionary surgery.



Captain Matthew Tadlock, MD, FACS, USN

Captain Tadlock is a Trauma/Critical Care Surgeon currently assigned to 1st Medical Battalion-Detachment San Diego,1st Marine Logistics Group, where he is an attending surgeon at NMRTC-San Diego. He is an associate professor of surgery through the Uniformed Services University and associate clinical professor of surgery (non-salaried) at University of California San Diego. He has 5 deployments providing Health Service Support to USN, USMC, and NATO units in the Indo-Pacific, Central and Western Asia, on both land and sea; including two CVN's, one DDG, and as the Chief of Trauma at the Kandahar NATO Role 3. He has also deployed in support of military Humanitarian Assistance and Disaster Relief missions. He has held numerous leadership roles, most recently as the Navy Trauma Specialty Leader. He currently serves as the chair of the BUMED Trauma Advisory Board. Captain Tadlock has been a Fellow of the American College of Surgeons since 2015 and a member of the Excelsior Society since 2016.

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Lieutenant Colonel John Horton, MD, FACS, USA

Lieutenant Colonel Horton is a pediatric surgeon and one of the deputy consultants to the Surgeon General of the Army. He grew up in Houston, Texas and completed his undergraduate education at Southern Methodist University where he participated in ROTC. Subsequently, LTC Horton attended the Uniformed Services University for medical school and William Beaumont Army Medical Center for general surgery training. He developed a passion for the surgical care of children and completed his pediatric surgery fellowship at OHSU in Portland, OR in 2012. Since graduating from fellowship, LTC Horton has been stationed at Madigan Army Medical Center where he has served as an assistant program director, medical student coordinator and general surgery consultant to the RHC-P. He has deployed four times to Afghanistan where he led small surgical resuscitative teams often positioned at the edge of the battlefield. LTC Horton enjoys cooking, skiing and spending time with his family.


Councilperson at Large, U.S. Army

Major Maggie Gallagher, MD, FACS, USA

Dr. Gallagher is originally from Waukesha, Wisconsin. After completing her undergraduate degree at the United States Military Academy at West Point, she received her medical degree from the Uniformed Services University of the Health Sciences (USUHS) in Bethesda, MD. She completed her general surgery residency at Tripler Army Medical Center in Honolulu, HI. She then completed her pediatric surgery fellowship at the Children’s Hospital at Vanderbilt in Nashville, TN. She is board certified in general and pediatric surgery and is currently at Blanchfield Army Community Hospital in Fort Campbell, Kentucky.


USN Councilperson at Large

Commander Tamara Worlton, MD, FACS, USN

Commander Worlton received her Doctor of Medicine from the Uniformed Services University of the Health Sciences. She completed her general surgery residency at National Naval Medical Center (NNMC) and a bariatric surgery fellowship at Cleveland Clinic in Cleveland, Ohio. She was the Ship's Surgeon for the USS Abraham Lincoln (CVN 72) and deployed to Tarin Kowt a Role 2 in Afghanistan. She served as the Director of Surgical Services at the Expeditionary Medical Facility in Camp Lemonnier, Djibouti. Commander Worlton served aboard the USNS MERCY (T-AH 19) and USNS COMFORT (T-AH 20) with the most recent mission being the deployment to New York City for COVID-19. She serves as the director for global surgery at USU, director of surgical operations at the Center for Global Health Engagement, and is the metabolic and bariatric surgery director at Walter Reed National Military Medical Center (WRNMMC).


Councilperson at Large, Reserve/National Guard

Colonel Jamison Nielsen, DO, MBA, MCR, FACS, FAWM, USAR

Colonel Nielsen is a trauma and acute care surgeon with the Tacoma Trauma Trust. He serves as the associate trauma medical director for St. Joseph Medical Center. He is currently assigned to the 367th Forward Resuscitative Surgical Detachment, Vancouver, Washington. He was recently designated as the 61J reserve deputy consultant to the Surgeon General. In his Army Reserve capacity he enjoys teaching and has had the opportunity to mobilize twice to Soto Cano AB, Honduras. Previously he was on active duty for 13 years. During that time he deployed to Afghanistan twice – first with the 67th FST (Airborne) for 1 year and later with the 2nd FST. He had the opportunity to participate in a White House mission to Tanzania and a humanitarian mission to New Guinea. His duty locations included Tripler Army Medical Center, Landstuhl Regional Medical Center, OHSU, and the US Army Institute of Surgical Research/Brooke Army Medical Center.


Councilperson at Large, U.S. Air Force

Lieutenant Colonel Brian Gavitt, MD, MPH, FACS, USAF

Lieutenant Colonel Brian Gavitt serves as the Trauma Director for the US + UAE Trauma, Burn, and Rehabilitation Medicine (TBRM) Mission and the Trauma and Surgical Critical Care Consultant to the US Air Force Surgeon General. Gavitt has served as an active duty surgeon since 2004 and has operated under a number of roles such as an instructor for the Critical Care Air Transport Team (CCATT) advanced course, trauma faculty at the University of Cincinnati Medical Center, and deployed as the Trauma Czar for Craig Joint Theater Hospital at Bagram Air Base in Afghanistan.


Councilperson at Large, Civilian

John S. Oh, MD, FACS

Dr. John S. Oh served for 20 years in the U.S. Army upon graduation from the United States Military Academy at West Point, NY in 1993. After completing medical school at N.Y. Medical College on the Army Health Professions Scholarship in 1998, he completed a residency in General Surgery at the William Beaumont Army Medical Center. He then served as an Army general surgeon, completing tours in Korea, Kosovo, Afghanistan and Iraq. Dr. Oh completed a fellowship in surgical critical care at the San Antonio Uniformed Services Health Education Consortium in 2010.

Dr. Oh was then assigned as the trauma medical director at Landstuhl Regional Medical Center. Dr. Oh oversaw the delivery of urgent surgical and critical care for all U.S., NATO, and allied combat and non-combat casualties from Afghanistan, Iraq, Europe, and Africa. He also served as a critical care physician on the U.S. Air Force Acute Lung Injury Team with the capability of rapidly deploying extra-corporeal lung support to trauma and medical casualties in combat zones within Afghanistan and Iraq.

Dr. Oh was then assigned to Walter Reed National Military Medical Center in Bethesda, Maryland where he led the General Surgery Service which included trauma, colorectal, minimally invasive, pediatric, and oncologic surgery. During this time, he also served as the Director of the Division for Global Surgery at the Uniformed Services University of the Health Sciences.

Dr. Oh has conducted clinical research in combat casualty care, resuscitation in trauma, global surgery, and humanitarian medicine. He currently has active protocols in surgical disease epidemiology in low resource countries, use of whole blood, and radiologic indicators of frailty in trauma patients. After retiring from active military service, Dr. Oh joined the trauma division at Penn State Health, Milton S. Hershey Medical Center as a trauma and acute care surgeon in July, 2017 where he maintains an active clinical practice. He currently serves as the director for the surgical intensive care unit, Program Director of the Surgical Critical Care fellowship, and Director of the Global Surgery Program.


Councilperson at Large, Resident/Fellow

RMKD “Kal” Gunasingha, MD

R. M. Kalpanee D. Gunasingha is a general surgery resident at Walter Reed National Military Medical Center. She is a Captain in the U.S. Army. She graduated from Duke University School of Medicine in 2017 and received a Bachelor of Science in chemical engineering from LSU (Geaux Tigers!) in 2013. She plans to pursue a fellowship in vascular surgery and hopes to apply her engineering background in her future career and research. She is interested in clinical research as well as quality improvement. In her free time, she likes to spend time with her wonderful fiancé and her family, go hiking, paint, and try new recipes.