Award-Winning Paper from Hackensack University Medical Center Researchers, Concludes Aspirin is Effective Treatment for Blood Clots Following Total Knee Replacement

September  4, 2021, Hackensack, NJ –  A new award-winning paper by orthopedic surgeons and researchers from Hackensack Meridian Hackensack University Medical Center, published in a recent supplement of The Bone & Joint Journal, concludes that aspirin, which is well established as a preventive agent for deep vein thrombosis (DVT), is also effective to treat infrapopliteal DVT (IDVT), blood clots found in the calf muscle, and is associated with a low rate of clot progression and stroke or thromboembolic events.1  The paper has been honored as the Knee Society 2021 John N. Insall Award Winner that  recognizes outstanding papers concerning clinical results and techniques.

“DVTs are serious because blood clots can loosen and lodge in the lungs. The optimal management of an infrapopliteal deep venous thrombosis, located in veins below the knee, following total knee arthroplasty has never been clear-cut for the clinicians managing postoperative care,” said Gregg R. Klein, M.D., the paper’s corresponding author and Physician Associate, Vice-Chairman, Department of Orthopedic Surgery, Hackensack University Medical Center, and Associate Professor, Department of Orthopedic Surgery, Hackensack Meridian School of Medicine.  “This study, to the best of the authors’ knowledge,  is the first to show that patients undergoing total knee replacement who developed blood clots below the knee can be effectively treated with aspirin.  While the optimal management of these types of clots following knee replacement surgery needs further prospective study, treatment with aspirin could be a new standard of care in orthopedics.” 

Additional co-authors of Dr. Klein’s research include: Hackensack University Medical Center physicians, Harlan Brett Levine, M.D., and Ari Seidenstein, M.D. and Bertrand Parcells, M.D. with Jersey Shore University Medical Center and Ocean Medical Center. 

The paper states that the risk of IDVT propagation and symptom progression must be balanced against potential hemorrhagic complications associated with administration of anticoagulation therapy. The researchers conducted a retrospective analysis of a group of patients diagnosed with IDVT following total knee replacement who were treated with aspirin, followed closely for development of symptoms, and scanned with ultrasound to determine resolution of IDVT.

After obtaining Institutional Review Board approval, the researchers examined medical records of patients who underwent primary or revision total knee arthroscopy between January 1, 2014 to January 1, 2019 at one institution. All patients who had the surgery during the study period received DVT prophylaxis that included early mobilization, mechanical prophylaxis, and prophylaxis with aspirin, heparin, or warfarin based on their risk profile.

Of the total group of 532 patients who had IDVT (out of 5,078 who underwent total knee replacement), 91 percent were treated with aspirin twice daily for three months. The other patients with IDVT were treated with anticoagulants other than aspirin. Follow up ultrasound was performed on 94 percent of the patients with IDVTs treated with aspirin,  and 2 percent showed propagation of the IDVT. 

Overall, the rate of pulmonary embolism in the patients with IDVTs who were treated with aspirin was 0.2 percent, representing one patient.

Dr. Klein and his colleagues concluded that the results of the study demonstrated a low rate of IDVT propagation in patients managed with aspirin.  Additionally, he said, no significant bleeding episodes, wound-related complications, or other adverse events were noted from aspirin therapy in the group of patients who were studied following their total knee replacement surgeries. 

Study Methods

Among a group of 5,078 patients undergoing TKA, 532 patients (695 TKAs, 12.6%) developed an IDVT between 1 January 2014 to 31 December 2019 at a single institution, as diagnosed using Doppler ultrasound at the first postoperative visit. Of the entire cohort of 532 patients with IDVT, 91.4% (486/532) were treated with aspirin (325 mg twice daily) and followed closely. Repeat lower limb ultrasound was performed four weeks later to evaluate the status of IDVT.


Follow-up Doppler ultrasound was performed on 459/486 (94.4%) patients and demonstrated resolution of IDVT in 445/459 cases (96.9%). Doppler diagnosed propagation of IDVT to the popliteal vein had occurred in 10/459 (2.2%) cases. One patient with an IDVT developed a pulmonary embolus six weeks postoperatively. 

“In conclusion, the findings of this study are encouraging and provide impetus to consider treating patients with acute IDVT with aspirin, which appears to be an effective treatment for this type of blood clot,” said Dr. Klein.  “It is inexpensive and well tolerated in patients, and lacks the major bleeding and wound-related complications that can occur with more potent anticoagulant therapy”

“Once thought to be inconsequential, the risk of IDVT propagation has shown to be a real risk in multiple studies. Therefore, until prospective studies can be performed regarding treatment for IVDT, we recommend the use of aspirin therapy when IDVT is diagnosed,” he added.

The Insall Award

The Insall Award was established to honor the pioneering English orthopedic surgeon Dr. John  Nevall Insall, who made extraordinary contributions to the field of orthopedics.  The award recognizes outstanding papers concerning clinical results and techniques. Dr. Insall contributed extensively to the advancement of total knee replacement surgery and designed four models of widely used systems. He was born in Bournemouth, England and attended Corpus Christi College, Cambridge, graduating in 1953. He died in New York City in the year 2000.The Insall Award was established to honor the pioneering English orthopedic surgeon Dr. John Nevall Insall, who made extraordinary contributions to the field of orthopedics. 

“We are immensely proud that the Knee Society chose to recognize this groundbreaking research by Dr. Klein and the other authors with the 2021 John N. Insall Award,” said Michael A. Kelly, M.D., Chairman, Orthopaedic Surgery, Hackensack University Medical Center. “The Award is a highly competitive honor named after my late surgical partner, Dr. John Insall, who was the father of total knee replacement in the United States and a past president of the Knee Society.  Dr. Kelly himself is a pioneer in total knee replacement who was a founding member of Insall Scott Kelly Institute in New York, and has served as past-president of the American Knee Society. Dr. Kelly has lectured nationally and internationally and has published extensively. Under Dr Kelly’s leadership, the total joint service at Hackensack University Medical Center has become one of the premier programs in NJ.

The Knee Society 

The Knee Society is an academic by-invitation-only membership organization currently consisting of 206 members who are internationally recognized thought-leaders, innovators, mentors, researchers, and educators. The Knee Society was founded in 1983 as an organization for education and research in the area of total knee arthroplasty as well as in the pathogenesis of osteoarthritis and other disease processes that lead to end-stage arthritis of the knee.

1Bone Joint J 2021;103-B(6 Supple A):18–22


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Hackensack University Medical Center, a 771-bed nonprofit teaching and research hospital located in Bergen County, is the largest provider of inpatient and outpatient services in New Jersey.  Founded in 1888, it was the county’s first hospital. It was the first hospital in New Jersey and second in the nation to become a Magnet®-recognized hospital for nursing excellence, receiving its sixth consecutive designation in 2019 from the American Nurses Credentialing Center. The academic flagship of the Hackensack Meridian Health network, Hackensack University Medical Center provides award-winning care on a campus that is home to facilities such as John Theurer Cancer Center, a consortium member of the NCI-designated Georgetown Lombardi Comprehensive Cancer Center and recognized as the #1 hospital for cancer care in New Jersey by U.S. News & World Report’s 2020-21 “Best Hospitals” Honor Roll; the Heart & Vascular Hospital; and the Sarkis and Siran Gabrellian Women’s and Children’s Pavilion, which houses the Joseph M. Sanzari Children’s Hospital and Donna A. Sanzari Women’s Hospital, designed in collaboration with The Deirdre Imus Environmental Health Center and listed on the Green Guide’s list of Top 10 Green Hospitals in the U.S. Recognized as being in the top 1% of hospitals in the nation and #2 in New Jersey by U.S. News & World Report’s 2020-21 “Best Hospitals” Honor Roll, Hackensack University Medical Center also ranked as high-performing in nine specialties: cancer care, cardiology and heart surgery, gastroenterology and GI surgery, geriatrics, nephrology, neurology and neurosurgery, orthopedics, pulmonology, and urology. Hackensack University Medical Center’s comprehensive clinical research portfolio includes studies focused on precision medicine, translational medicine, immunotherapy, cell therapy, and vaccine development. The hospital has embarked on the largest healthcare expansion project ever approved by the state: Construction of the Helena Theurer Pavilion, a 530,000-sq.-ft., nine-story building, which began in 2019. A $714.2 million endeavor, the pavilion is one the largest healthcare capital projects in New Jersey and will house 24 state-of-the-art operating rooms with intraoperative MRI capability, 50 ICU beds, and 150 private patient rooms, including a dedicated 50-bed Orthopedic Institute.



Hackensack Meridian Health is a leading not-for-profit health care organization that is the largest, most comprehensive and truly integrated health care network in New Jersey, offering a complete range of medical services, innovative research and life-enhancing care. 

Hackensack Meridian Health comprises 17 hospitals from Bergen to Ocean counties, which includes three academic medical centers – Hackensack University Medical Center in Hackensack, Jersey Shore University Medical Center in Neptune, JFK Medical Center in Edison; two children’s hospitals – Joseph M. Sanzari Children’s Hospital in Hackensack, K. Hovnanian Children’s Hospital in Neptune; nine community hospitals – Bayshore Medical Center in Holmdel, Mountainside Medical Center in Montclair, Ocean Medical Center in Brick, Palisades Medical Center in North Bergen, Pascack Valley Medical Center in Westwood, Raritan Bay Medical Center in Old Bridge, Raritan Bay Medical Center in Perth Amboy, Riverview Medical Center in Red Bank, and Southern Ocean Medical Center in Manahawkin; a behavioral health hospital – Carrier Clinic in Belle Mead; and two rehabilitation hospitals – JFK Johnson Rehabilitation Institute in Edison and Shore Rehabilitation Institute in Brick. 

Additionally, the network has more than 500 patient care locations throughout the state which include ambulatory care centers, surgery centers, home health services, long-term care and assisted living communities, ambulance services, lifesaving air medical transportation, fitness and wellness centers, rehabilitation centers, urgent care centers and physician practice locations. Hackensack Meridian Health has more than 36,000 team members, and over 7,000 physicians and is a distinguished leader in health care philanthropy, committed to the health and well-being of the communities it serves.

The network’s notable distinctions include having four hospitals among the top in New Jersey by U.S. News and World Report. Other honors include consistently achieving Magnet® recognition for nursing excellence from the American Nurses Credentialing Center and being named to Becker’s Healthcare’s “150 Top Places to Work in Healthcare/2019” list. 

The Hackensack Meridian School of Medicine opened in 2018, the first private medical school in New Jersey in more than 50 years, welcomed its third class of students in 2020 to its On3 campus in Nutley and Clifton. Additionally, the network partnered with Memorial Sloan Kettering Cancer Center to find more cures for cancer faster while ensuring that patients have access to the highest quality, most individualized cancer care when and where they need it. 

Hackensack Meridian Health is a member of AllSpire Health Partners, an interstate consortium of leading health systems, to focus on the sharing of best practices in clinical care and achieving efficiencies. 

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