“The HSS Digital Twin Platform is poised to impact all aspects of orthopedic care, fundamentally transforming how clinicians diagnose, treat and rehabilitate musculoskeletal injuries,” said Andrew D. Pearle, MD, Chief Emeritus of Sports Medicine and Program Director of the Digital Twin project. “Thanks to this transformational gift, HSS stands at the threshold of a new paradigm in personalized orthopedic care.”

“Longtime supporters of HSS, the Steers have been impressed by the continual efforts and commitment of HSS physicians and scientists to advance the standard of care in orthopedics,” said HSS President and CEO Bryan T. Kelly, MD, MBA. “Their incredible gift represents a landmark moment for HSS, transforming a bold idea into a reality and improving patient care through innovation.”

The development and clinical expansion of the HSS Digital Twin Platform in Orthopedics is a four-year project that brings together a multidisciplinary team of HSS surgeons, radiologists, biomechanical engineers and artificial intelligence and data specialists. The initial focus is on the knee, where surgeons will use the tool to create virtual 3D replicas from magnetic resonance imaging (MRI) scans and simulate how the joint moves and responds to different surgical options. The tool’s web-based interface will make it easy for surgeons to implement clinically and for patients to understand various scenarios and outcomes.

The HSS Digital Twin Platform is based on more than a decade of work by HSS orthopedic surgeons and biomechanical engineers who recently evolved their computational model of the knee to incorporate artificial intelligence and advanced image processing. In one of its first clinical applications, HSS knee surgeons have been using the tool to determine whether patients who require anterior cruciate ligament (ACL) revision surgery may benefit from an additional procedure to reshape the top of the shin bone, called a slope reduction osteotomy. The HSS Digital Twin Platform allows them to model this complex procedure virtually, one degree at a time, to predict how forces and knee motion will change. Dr. Pearle, along with HSS surgeons Drs. Danyal H. Nawabi, Mark J. Amirtharaj, and Thomas L. Wickiewicz, recently published a milestone paper in the American Journal of Sports Medicine, that demonstrated how the digital twin technology can help surgeons determine whether a slope reduction osteotomy is necessary and, if so, the precise surgical angle for reducing the risk of ACL re-injury.¹ These early applications showcase the platform’s potential to guide precise surgical decisions while laying the foundation for broader use across other joints and procedures.

The potential for the HSS Digital Twin Platform to transform surgical planning and personalized care and provide long-term support for continual innovation inspired the Steers’ decision to make this extraordinary gift to HSS. An endowed chair—the Lauren and Robert Steers Chair in Orthopedic Research and Innovation—also funded by the gift, will be held by Dr. Pearle and will provide long-term support to advance future discoveries in the field.

“We look forward to scaling up the HSS Digital Twin Platform to optimize orthopedic care with unprecedented precision across HSS,” Dr. Pearle said. “After scaling up knee applications, we plan to create digital twins for hip and shoulder. Ultimately, we envision a future where all HSS patients will have online access to a digital twin care companion that aggregates comprehensive musculoskeletal data with the potential to replace the traditional medical record.”

Reference

¹ Sagittal Slope-Reducing High Tibial Osteotomy Decreases Anterior Cruciate Ligament Force and Coupled Internal Tibial Rotation Under Pivoting Loads: A Computational Modeling Study. 

Authors: Mark J. Amirtharaj, MD, Reza Pourmodheji, PhD, Mitchell G.A. Wheatley, PhD,

Julien Leluc, MD, Andrew E. Pechstein, PhD, Jacob M. Hirth, BS, Michael K. Parides, PhD,

Thomas L. Wickiewicz, MD, Andrew D. Pearle, MD, Matthieu Ollivier, MD, PhD,

Carl W. Imhauser, PhD, Danyal H. Nawabi, MD.

About HSS

HSS is the world’s leading academic medical center focused on musculoskeletal health. At its core is Hospital for Special Surgery, nationally ranked No. 1 in orthopedics (for the 16th consecutive year), No. 3 in rheumatology by U.S. News & World Report (2025-2026), and the best pediatric orthopedic hospital in NY, NJ and CT by U.S. News & World Report “Best Children’s Hospitals” list (2024-2025). In a survey of medical professionals in more than 20 countries by Newsweek, HSS is ranked world #1 in orthopedics for a fifth consecutive year (2025). Founded in 1863, the Hospital has the lowest readmission rates in the nation for orthopedics, and among the lowest infection and complication rates. HSS was the first in New York State to receive Magnet Recognition for Excellence in Nursing Service from the American Nurses Credentialing Center five consecutive times. An affiliate of Weill Cornell Medical College, HSS has a main campus in New York City and facilities in New Jersey, Connecticut and in the Long Island and Westchester County regions of New York State, as well as in Florida. In addition to patient care, HSS leads the field in research, innovation and education. The HSS Research Institute comprises 20 laboratories and 300 staff members focused on leading the advancement of musculoskeletal health through prevention of degeneration, tissue repair and tissue regeneration. In addition, more than 200 HSS clinical investigators are working to improve patient outcomes through better ways to prevent, diagnose, and treat orthopedic, rheumatic and musculoskeletal diseases. The HSS Innovation Institute works to realize the potential of new drugs, therapeutics and devices. The HSS Education Institute is a trusted leader in advancing musculoskeletal knowledge and research for physicians, nurses, allied health professionals, academic trainees, and consumers in more than 165 countries. The institution is collaborating with medical centers and other organizations to advance the quality and value of musculoskeletal care and to make world-class HSS care more widely accessible nationally and internationally. www.hss.edu.

“I’m very proud of our team for publishing this work, which validates hip arthroscopy as a longer-term joint-preserving procedure in carefully selected patients,” says Bryan T. Kelly, MD, MBA, President and CEO of HSS and a world-renowned pioneer in the field of hip arthroscopy who also served as senior author on the study. “At HSS, we focus on providing excellence in clinical care through innovation and evidence-based research. This paper is a prime example of the benefits of advancing innovations in surgical techniques and analyzing patient data collected over many years so we can understand and share the factors associated with optimal results.”

Hip impingement, also called femoroacetabular impingement (FAI), is a condition that typically arises between the teenage years and middle age, and is the underlying cause of hip pain in about 40% of patients in this age range. Hip impingement occurs when the bones of the hip joint are not shaped properly, causing them to rub against one another. Over time, the persistent friction can lead to pain and stiffness, eventually progressing to advanced arthritis. 

Prior studies have shown that 85-90% of patients with hip impingement who undergo modern arthroscopy return to their usual activity level. However, until now, little has been known about whether modern arthroscopy can slow the progression of arthritis in these patients. To explore this connection, investigators examined X-ray images of 200 hips from 100 patients who exhibited signs of impingement in both hips but only underwent arthroscopy for their symptomatic hip between 2010 and 2012. The severity of arthritis in each hip was assessed retrospectively using X-ray images taken before surgery and at least 10 years later. Notably, the researchers were unaware of which hips had undergone surgical correction during the assessment.

The resulting analysis revealed only 28% of operative hips showed an increase in arthritis progression at a minimum of 10 years after surgery in comparison to 48% of nonoperative hips. This difference translated to a relative risk reduction of 42% across all patients. 

While there was no difference in the natural development of arthritis between the operative and nonoperative hips for 70% of patients, one in four, or 25%, had less arthritis in their operative hip compared to their nonoperative hip 10 years later.

“Previous studies by other centers have reported underwhelming 10-year arthroplasty outcomes for patients with hip impingement. However, those studies reported on older surgical indications and older surgical techniques,” explains lead author and former HSS fellow Prem N. Ramkumar, MD, MBA, now an orthopedic surgeon at Long Beach Lakewood Orthopedic Institute, in Long Beach, California. “By contrast, we studied the effect of modern arthroscopic methods by comparing the degree of arthritis in each patient’s operative hip versus their nonoperative hip. Our research design controlled for variables such as age, medical history, lifestyle, and individual mechanics like rotational profile, spinal alignment and gait—leaving history of arthroscopy as the single factor driving any resulting differences in arthritis progression.”

In addition, the investigators identified a small subset of patients whose arthritis progressed more rapidly in the operative hip as compared to the nonoperative hip. Specifically, older age, a higher arthritis grade, an alpha angle greater than 65 degrees and evidence of borderline hip dysplasia before surgery were the primary risk factors associated with the 5% of hip impingement patients whose arthritis in the operative hip worsened more quickly after surgery.

“We can now identify patients most likely to benefit from arthroscopy for hip impingement and inform patients about their anticipated odds of successful outcomes based on their personal risk factors. For ideal candidates, the evidence shows that hip arthroscopy may delay or prevent arthritis for one in four patients. That’s very powerful information,” says Danyal H. Nawabi, MD, FRCS, an HSS orthopedic surgeon and an author on the study.

Dr. Nawabi also points to the importance of the modern techniques used to care for patients in the study, all of whom were patients of Dr. Kelly. These methods include labrum repair, removal of bony abnormalities on the ball and socket, and proper closure of the joint capsule enveloping the hip joint. “This study is a testament to the fact that where you go for orthopedic care truly matters,” he adds.

Thus far, the paper has garnered two awards: the 2024 American Orthopedic Society for Sports Medicine Fellow Research Award for Clinical Science, which will be presented at the AOSSM Annual Meeting in July, as well as the Philip D. Wilson, MD, Award, presented by HSS in honor of the hospital’s fifth Surgeon-in-Chief to a fellow who has demonstrated excellence in orthopedic surgery research.

Recognized as the world’s leading academic medical center focused on musculoskeletal health, HSS will be an important ally of USYS and its 54 member State Associations. Ranked No. 1 for orthopedics 11 years in a row by U.S. News & World Report (2020-2021), HSS will help USYS deliver invaluable health information, resources and services to their members to aid in injury prevention, recovery and access to the latest in medical guidance.

The partnership will be led by an HSS Sports Medicine Council comprised of sports medicine surgeons Riley J. Williams III, MD, medical director for the New York Red Bulls (MLS) professional soccer team; Drs. Benedict Nwachukwu, MD, MBA, and Danyal H. Nawabi, MD, FRCS, team physicians for the New York Red Bulls, and Patrick Vignona, PT, sports rehabilitation and performance specialist.

Founded in 1863, Hospital for Special Surgery (HSS) is the oldest orthopedic hospital in the United States. More than 32,000 surgical procedures are performed annually. HSS performs more hip surgeries and more knee replacements than any other hospital in the US.

This partnership will provide USYS with a singular musculoskeletal health partner so that its members can access the very best information and resources to improve, maintain and support their physical health. “USYS is on a mission to provide world-class support, resources and leadership, helping every member fulfill their goals on and off the field of play. HSS gives USYS an opportunity to deliver unparalleled physical health resources and benefits to our entire USYS Family,” said Skip Gilbert, CEO US Youth Soccer. “Doctors and physical therapists from HSS are team physicians and athletic trainers for some of the premiere professional and college sports teams in America. HSS experts, experience and medical information are unmatched and will allow our players and families to tap into the same state-of-the-art resources and technology that the pros get so they too can pursue their pathway to achievement.”

“HSS has a long-standing history of caring for elite and professional athletes. What we have learned from treating this population we have been able to apply to the development of young athletes, everything from the principles of injury prevention to proper movement patterns,” said Dr. Williams. “The USYS partnership will allow us to work in collaboration with its athletic directors, coaches, and trainers to effectively reduce sports-related injuries in adolescents.”

About the United States Youth Soccer Association (US Youth Soccer)

US Youth Soccer, the largest youth sport organization in the country, is on a mission to provide world-class support, resources and leadership, helping every member fulfill their goals, on and off the field of play. US Youth Soccer registers nearly 3 million players annually. Through its programming, resources and leadership, US Youth Soccer is advancing the game for its 54 Member State Associations, 10,000 clubs and leagues and nearly 1 million administrators, coaches and volunteers. US Youth Soccer connects families and communities to the power of sports and its shared love of soccer. US Youth Soccer provides a path for every player, offering programs that provide a fun, safe and healthy environment for players at every level of the game. We Are Youth Soccer. For more information, visit www.usyouthsoccer.org.

“We are dedicated to providing outstanding medical care to elite athletes, and our designation as a FIFA Medical Centre of Excellence by the Feder the Fédération Internationale de Football Association recognizes our expertise and enthusiasm in treating professional soccer players,” said Dr. Williams. “With the new members of the medical team, we will continue to provide the high level of care Red Bull players depend on to be their best on the field and to get back in the game if they sustain an injury.”

A nationally recognized leader in cartilage repair and restoration, Dr. Williams specializes in knee, shoulder, and elbow surgery at the HSS Sports Medicine Institute. Along with the Red Bulls, Dr. Williams serves as medical director and head team physician for the Brooklyn Nets (NBA), Long Island Nets (G-League), and New York Liberty (WNBA), and as a team physician for USA Basketball.

The new members of the medical team are highly specialized in treating a wide range of orthopedic injuries.

Danyal H. Nawabi, MD, an orthopedic surgeon in the HSS Sports Medicine Institute, specializes in knee, shoulder, and hip surgery, including arthroscopic procedures and joint replacement.

Orthopedic surgeon Andrew J. Elliot, MD, treats conditions of the foot and ankle, including athletic injuries, bunions, tendon tears and ruptures, hammertoes, osteochondritis dissecans, fractures and arthritis.

Benedict Nwachukwu, MD, is an orthopedic surgeon and specialist in hip, knee and shoulder surgery at HSS. Along with the Red Bulls, Dr. Nwachukwu serves as a team physician for the New York Liberty and medical consultant for the National Basketball Players Association.

About the New York Red Bulls

The New York Red Bulls are one of 27 teams in Major League Soccer (MLS). RBNY, one of the ten charter clubs of MLS, have competed in the league since its founding in 1996. The Red Bulls play home matches at Red Bull Arena (RBA) in Harrison, New Jersey.The three-time MLS Supporters' Shield Winners are owned by the Austrian beverage company Red Bull for which the team is named. The New York Red Bulls offer one of the nation's premier youth soccer development programs, from local soccer partnerships across New York and New Jersey to Regional Development Schools and the Red Bulls Academy teams.

Reconstruction is the current standard of care surgical treatment for tears of the anterior cruciate ligament (ACL). This procedure typically uses a graft, or a piece of tissue, placed in the knee minimally invasively, using small incisions. About 300,000 ACL reconstructions are performed annually in the United States with well documented rates of success.

ACL repair is an older technique that involved suturing (sewing) torn ACL tissue, not rebuilding it with a graft. ACL repair was performed in the 1970s at select institutions, including Hospital for Special Surgery, but was abandoned due to unacceptably high failure rates of up to 50%.

Today, ACL repair has been modernized and can be performed through a minimally invasive approach. Proponents suggest that modern ACL repair techniques may be performed safely and may lead to a quicker recovery than ACL reconstruction. However, the limited studies to date raise questions that must be discussed in detail with your surgeon.

1. It is critically important to get ACL surgery right the first time.

When ACL surgery fails, surgeons must do a revision procedure to correct or revise the problems that were not fully addressed the first time. Revision requires reconstructive ACL surgery with a graft. (ACL repairs cannot be done as revisions.) Redoing ACL surgery may result in higher rates of failure, lower rates of return to sports, and increased risk of osteoarthritis.

The importance of successful initial ACL surgery holds true for people of all ages, but it is particularly critical for young athletes, for whom a failed surgery can have devastating consequences, including years lost from sport in the short term as well as chronic pain and loss of function in the long term.

2. Failure rates for ACL repair appear to be significantly higher than those for ACL reconstruction in people of all ages.

Current studies suggest that modern ACL repair techniques have a failure rate that may be five to ten times higher than that of ACL reconstruction^1,2,3. One major recent study in a prominent sports medicine journal found that arthroscopic ACL repair has unacceptable outcomes in young athletes, with short-term failure rates of close to 50%².

It has been suggested that ACL repair may be appropriate for older adults who have a type of ACL tear called a proximal avulsion and who do not participate in “cutting and pivoting” sports such as basketball, volleyball, and soccer. For these patients, failure rates in the short term appear to be much higher than ACL reconstruction in this age group^1,2,3.

3. There is still much we don’t know about ACL repair.

There has been no scientific evidence that shows a difference in postoperative pain between ACL repair and reconstruction. Rehabilitation and return-to-play protocols for ACL repair have not yet been established. Proper guidelines for rehabilitation and return to sports are essential to keep people safe from re-injury.
 

Andrew D. Pearle, MD

Chief, HSS Sports Medicine Institute

Bryan T. Kelly, MD

HSS Surgeon-in-Chief and Medical Director

Answorth A. Allen, MD

David W. Altchek, MD

Struan H. Coleman, MD, PhD

Frank A. Cordasco, MD, MS

David M. Dines, MD

Joshua S. Dines, MD

Stephen Fealy, MD

Andreas H. Gomoll, MD

Lawrence V. Gulotta, MD

Jo A. Hannafin, MD, PhD

Anne M. Kelly, MD

John D. MacGillivray, MD

Robert G. Marx, MD, MSc, FRCSC

Michael J. Maynard, MD

Moira M. McCarthy, MD

Danyal H. Nawabi, MD, FRCS

Stephen J. O’Brien, MD, MBA

Anil S. Ranawat, MD

Scott A. Rodeo, MD

Howard Anthony Rose, MD

Beth E. Shubin Stein, MD

Sabrina M. Strickland, MD

Karen M. Sutton, MD

Samuel A. Taylor, MD

Russell F. Warren, MD

Thomas L. Wickiewicz, MD

Riley J. Williams III, MD

References

1. Jonkergouw A, van der List J, DiFelice G. Arthroscopic primary repair of proximal ACL tears: outcomes of the first 56 consecutive patients and the role of additional internal bracing. Knee Surg Sports Traumatol Arthrosc. 2019 Jan;27(1):21-28.

2. Gagliardi AG, Carry PM, Parikh HB, Traver JL, Howell DR, Albright JC. ACL repair with suture ligament augmentation is associated with a high failure rate among adolescent patients. Am J Sports Med. 2019 Mar;47(3):560-566.

3. Wright RW et al. Risk of tearing the intact ACL in the contralateral knee and rupturing the ACL graft during the first 2 years after ACLR: A prospective MOON cohort study. Am J Sports Med. 2007 Jul;35(7):1131-4.

For more information visit https://www.hss.edu/condition-list_torn-acl.asp.

Danyal H. Nawabi, MD, FRCS, sports medicine surgeon at HSS, who did not treat Flacco, explains there are two main reasons not to play before fully recovering.

First, a player should not have lingering discomfort. "If you get them back to 80, 90 percent, they're playing at 80, 90 percent the whole season with a little bit of a nick, which then predisposes you to further injury because you're not activating all your muscles and using your joint as it should be used," says Dr. Nawabi.

Secondly, it's important to prevent longer-term damage by allowing a player to play prematurely. "And the key thing with the hip joint is degenerative joint disease, subjecting that hip to becoming arthritic, which unfortunately we see more and more now in younger patients," states Dr. Nawabi.

Read the full article at BaltimoreSun.com. This also appeared in the December 1, 2018 print edition.