The first of the three studies, “Aspirin Versus Potent VTE Chemoprophylaxis (VTEC) in Total Knee Arthroplasty: Reduced Postoperative Pain and Complications with Aspirin Use,” examined the experience of total knee arthroplasty (TKA) patients with postoperative pain who were also taking blood thinners. The study included 28,169 patients treated between 2016 and 2023; 18,413 received aspirin while 9,756 received a potent VTE.. Patients were monitored for 90 days following their procedure. The findings suggest that aspirin should be considered the preferred option for reducing postoperative pain in TKA patients.

Patients on more-potent blood thinners tend to experience more pain, swelling and inflammation after surgery, said Brian P. Chalmers, MD, a hip and knee surgeon at HSS and one of the study’s authors. “We have always known that non-steroidal anti-inflammatory medications can improve patients’ swelling and inflammation after surgery. However, the traditional thought and belief has been that we should avoid those in patients on anticoagulation. Our data show there is less risk and less postoperative pain when these patients are utilizing aspirin.”   

A second study, “The Effect of Concomitant Use of Potent Anticoagulation and Anti-Inflammatories on Early Outcomes of Total Hip Arthroplasty,” retrospectively evaluated 5,881 total hip arthroplasty patients who were on anticoagulation. The surgeries were performed between 2016 and 2023; of those patients, 4,867 were concomitantly prescribed NSAIDs and 1,040 received anticoagulation alone. Researchers concluded that the concomitant use of NSAIDs in patients on anticoagulants did not increase the risk of wound-related bleeding complications.

“The conventional thinking has often been that patients on an anticoagulant should not be on an NSAID, that there is going to be bleeding, more risk of wound problems and additional complications. But based on our retrospective data, we did not see increased risk in patients using both anticoagulation and NSAIDs. We did see some additional benefits, including less pain and a somewhat easier recovery,” Dr. Chalmers stated. “NSAIDs appear to be safe in this setting and may help decrease postoperative pain and reduce opioid use following surgery.”

The final study, “Cefazolin and the R-1 Side Chain: Why Your Joint Arthroplasty Patients With Cephalosporin Allergy Can Safely Be Given Cefazolin,” assessed the safety and effectiveness of the antibiotic Cefazolin in patients with documented cephalosporin allergies. This is the first study to evaluate these questions.

From 2016 to 2024, researchers compared patients with a reported cephalosporin allergy who received perioperative cefazolin with those who received alternative antibiotic prophylaxis. This study included 89,993 hip and knee arthroplasty patients. Of these, 1,267 had a documented allergy. The study resulted in zero incidence of IgE-mediated or “severe” type IV allergic reactions, concluding that cefazolin can be safely administered to most patients with an existing cephalosporin allergy.

“When patients have a mild allergic reaction, there is often a reflex to give them another antibiotic in a different family of drugs. However, alternative options aren’t always as effective,” said Matthew S. Austin, MD, hip and knee surgeon at HSS and a study author. “Clear protocols should be put in place to guide decision-making when managing these types of allergies.”

These findings underscore HSS’s ongoing commitment to challenging conventional assumptions and using data-driven research to refine perioperative care. The studies highlight how targeted medication strategies can improve safety, reduce complications and enhance outcomes for patients undergoing hip and knee arthroplasty.

Study Details 

“Aspirin Versus Potent VTE Chemoprophylaxis in Total Knee Arthroplasty: Reduced Postoperative Pain and Complications with Aspirin Use”

 Alex Anatone, Alexis Gabriel Gonzalez, Richard Hwang, David Andrew Kolin, Aaron Ira Weinblatt, Amar S Ranawat, Alejandro Gonzalez Della Valle, Brian Chalmers

“The Effect of Concomitant Use of Potent Anticoagulation and Anti-Inflammatories on Early Outcomes of Total Hip Arthroplasty”

Alexis Gabriel Gonzalez, Aaron Ira Weinblatt, Agnes Cororaton Jones, Stephen Lyman, Richard Hwang, Alex Anatone, Carlo Marega, Alejandro Gonzalez Della Valle, Brian Chalmers

“Cefazolin and the R-1 Side Chain: Why Your Joint Arthroplasty Patients With Cephalosporin Allergy Can Safely Be Given Cefazolin”

Josef Jolissaint, Katherine E Mallett, Andrew Thomson, Alberto V Carli, Matthew Austin

The Quiet Knee protocol, which some HSS surgeons began implementing several years ago, takes a more conservative approach to knee replacement recovery than traditional clinical protocols. This new technique focuses on controlling inflammation and swelling postoperatively through restricted mobility and passive range of motion (ROM) and aggressive cryotherapy (icing) for the first 10 days immediately following surgery. This contrasts with standard protocols, which often emphasize early and aggressive movement that can cause inflammation in surgical tissue that is healing.

All HSS total knee replacement patients from 2020 to 2024 were retrospectively reviewed as part of the study. A Quiet Knee group consisting of 271 patients received structured postoperative care and monitored telerehabilitation. One comparison group was given Quiet Knee guidance verbally, while a second cohort followed traditional early motion postoperative therapy.   

 “Patients are told they have to work really hard to get motion back after surgery—the no pain, no gain type of mentality,” said Brian P. Chalmers, MD, a hip and knee surgeon at HSS and one of the authors of the study. “The problem with that is that the more patients do in the early period of recovery—the more they bend, the more they are up and walking—the more the knee will swell.”

Every person undergoing TKA experiences pain and swelling after surgery, but the intensity differs, making the patient’s recovery process more challenging and often more painful than most other surgeries.

“It’s not uncommon to see a counterproductive early physical therapy program that is too aggressive,” Dr. Chalmers said. “In these cases, the knee becomes very swollen, which causes patients to have more pain. As the knee becomes more inflamed and patients are able to bend it less, it just becomes a cycle.”

Under the Quiet Knee protocol, patients avoid intensive physical therapy immediately after surgery, allowing the body time to heal before progressing to motion and other strength work. Early results suggest this approach helps set the stage for a smoother long-term recovery. The study also showed that the protocol significantly reduced 90-day opioid exposure by more than 25%.

“This isn't a surgeon-driven protocol or a research-driven protocol. It's a physiology-driven protocol,” said Michael P. Ast, MD, Chief of the Knee Service and Chief Medical Innovation Officer at HSS and co-author of the study. “It is a recognition of what the human body goes through in recovery from surgery. It is a very logical way of respecting the body's inflammatory response to trauma. Early on after surgery, less really is more. That is really the guiding principle of this protocol.”

Study Details

A Retrospective Cohort-Based Analysis of the “Quiet Knee” Protocol After Primary Total Knee Arthroplasty

Pravjit Bhatti, Lauren Moeller, Michael P Ast, Tony Sicheng Shen, Peter Keyes Sculco, David Jacob Mayman, Brian Chalmers

What follows are highlights from these studies:

Limiting Use of Tourniquets During Knee Replacement Surgery Improves Patient Outcomes

Tourniquets have traditionally been used during TKA to reduce blood loss and the need for transfusions. However, a new study of almost 18,000 patients from 2019 to 2023 found that prolonged tourniquet use was linked to increased pain, higher opioid use, and a longer recovery. 

“We found that limiting tourniquet use was associated with slightly lower rates of opioid use to control pain after surgery and a quicker ability to complete physical therapy and leave the hospital,” said Brian P. Chalmers, MD, hip and knee surgeon at HSS and co-senior author of the study.

Thanks to advances in medicine and technology, tourniquets may not be needed as often. For example, tranexamic acid (TXA) is now commonly used to effectively reduce bleeding and lower the likelihood of patients requiring a blood transfusion.

“If you have a drug that has this beneficial effect, then the need for a tourniquet may be reduced,” explained Alejandro Gonzalez Della Valle, MD, hip and knee surgeon at HSS and co-senior author of the research. “If you limit tourniquet use, patients will hurt less and will move sooner, and that will allow patients to go home sometimes the same day.” 

Dr. Della Valle notes that limiting tourniquet use can also reduce opioid consumption. The reason that tourniquet use during TKA has been associated with increased post-operative pain is because the device compresses the quadricep and hamstring muscles to restrict blood flow during the operation. The increased pain may impact the time it takes to complete rehabilitation.

Surgeons have also traditionally used tourniquets to keep the area between the knee implant and the bone as dry as possible, which helps bone cement create a stronger bond between the bone and the implant, potentially reducing the risk of loosening over time.

“Recent studies have shown that you can obtain a dry field without using a tourniquet, reducing its necessity during TKA,” explained Dr. Chalmers.  

Another development that has lessened the need for the use of tourniquets is cementless fixation, in which a specially-designed implant that allows the bone to grow into the implant and achieve long-term fixation without the use of cement.

There is currently no consensus in the literature or among surgeons throughout the country on the use of tourniquets during TKA. Surgeons use these devices differently based on individual patient needs. Some use a tourniquet from the time of incision until the implant is fixated to the bone, while others use it only during cementation or throughout the entire procedure until the wound is closed and the dressings are in place. Some surgeons may opt not to use a tourniquet at all. 

“What sets this study apart is that it captures what surgeons are doing in their daily practice,” said Dr. Chalmers. “To our knowledge, this is the only paper that addresses several different ways surgeons use tourniquets during TKA, including no usage, limited usage, and full usage.”

The study’s authors conclude that reduced tourniquet use should be considered within the realm of multiple advances that help patients recover faster after surgery and with less pain. These include newer drugs and tools used to reduce pain and blood loss during surgery, two major factors that often prolong hospital stays.

“Any measures we can take around the time of surgery to help those factors can significantly improve patient outcomes,” said Dr. Della Valle.

NSAIDs Reduce Risk of Fibrosis Needing Further Treatment after Knee Replacement Surgery

A new study led by surgeons at HSS shows that patients who were prescribed a non-steroidal anti-inflammatory drug (NSAID) after TKA had a reduced risk of developing painful scar tissue, a condition known as arthrofibrosis, which often requires additional procedures. The findings also shed light on the durations for NSAID use to prevent fibrosis following surgery.

In arthrofibrosis, excessive scar tissue forms in and around a joint after an operation. It can lead to stiffness, pain and reduced range of motion in the joint. Approximately 2% to 6% of patients require a minimally invasive procedure called manipulation under anesthesia (MUA) to treat this complication.

The researchers found that patients who were prescribed an NSAID had a significantly lower incidence of MUAs (5.3%) 90 days after surgery compared to those who did not have an NSAID prescription (12.6%). The study included more than 23,000 people who had TKA at HSS between 2017 and 2021.

“This study highlights the importance of NSAID use for early recovery after TKA,” says Peter K. Sculco, MD, hip and knee surgeon at HSS and senior author of the study. “These medications are associated with lower rates of fibrotic pain and stiffness requiring an intervention such as MUA.”

He added that decreased risk was not seen in patients who used NSAIDs for more than four weeks, suggesting patients stop within one month’s time to get the most benefit.

Some patients, however, cannot use NSAID medications due to risk of bleeding or gastrointestinal or kidney issues.

“We now use steroids for one week after TKA in patients who are unable to take NSAIDs,” explained Dr. Sculco. “However, further research is necessary to determine the effect of steroids on MUA rates and the appropriate dose and duration for this group of patients.”

Local Anesthetic Leads to Better Patient Outcomes after Revision Knee Replacement Surgery

A new study led by surgeons at HSS found that the use of a new local anesthetic at the time of revision TKA enabled patients to leave the hospital sooner and recover faster.

According to the findings, a recently introduced pain medication known as extended-release, dual-acting local anesthetic (ERDALA) used at the time of aseptic revision TKA was associated with better patient outcomes. These included completing physical therapy sooner, shorter hospital stays, and more patients being discharged within one day after surgery.

Approximately 5% to 10% of patients need aseptic revision TKA, a surgical procedure done to address loosening, stiffness, or instability of a non-infected knee joint that was previously replaced with TKA.

The study reviewed outcomes of 171 patients who had aseptic revision TKA at HSS between January 2021 and May 2023. Patients either received ERDALA (51.5%) or standard of care periarticular injections (PAI) (48.5%) during surgery. The researchers found that patients who received ERDALA went home nearly a day sooner and cleared physical therapy approximately 20 hours faster than those who received PAI.

“ERDALA did not reduce pain scores or the total amount of opioids prescribed in this study but was associated with helping patients reach early recovery milestones sooner,” noted Dr. Peter Sculco, who is also senior author of this study. “This medication can be a valuable tool in rapid recovery strategies used in aseptic revision TKA, which can lead to patients walking better and getting home faster.”

He added that further research is needed to explore these strategies in the revision population, especially as more revision surgeries are performed in the outpatient setting.

 Three studies focus on how to optimize total knee arthroplasty (TKA) surgery using biomechanics and computer modeling, while another study discusses how three-dimensional (3-D) modeling can improve total hip arthroplasty (THA).

 What follows are some highlights from the meeting:

Undersizing Tibial Baseplates in Cementless TKA Has Negative but Small Impact for Bone–Implant Interaction: A Computational Biomechanical Study

Computational biomechanical modeling is useful for taking a closer look at how making changes to orthopedic surgery techniques affects patient outcomes. A study led by Fernando J. Quevedo-González, PhD, assistant scientist in the Department of Biomechanics at HSS, and HSS hip and knee surgeon Jonathan M. Vigdorchik, MD, used these kinds of models to determine how best to minimize the risk of complications in cementless TKA. The model was developed using preoperative scans from 12 female patients about to undergo robotic TKA and was used to ask questions about how sizing the tibial baseplate (the metal part of the prosthesis that connects to the shin bone) affects outcomes. The investigators found that, in general, decreasing the size of the baseplate increased the amount of bone at risk of failure, but this risk was small compared with normal variability of bone quality among patients and how their individual knee joints were loaded as they used their knee in performing activities of daily living. Based on this result, they concluded that baseplate undersizing can be done to optimize the placement of the tibial component of the TKA without increasing the risk of bone failure.

Authors: Fernando J. Quevedo-González, PhD, Peter K. Sculco, MD, Cynthia Kahlenberg, MD, Joseph D. Lipman, MS, Timothy M. Wright, PhD, Jonathan M. Vigdorchik, MD.

Posterior Tibial Slope in Total Knee Arthroplasty: The Transmalleolar Sagittal Axis Underestimates Slope Compared to Traditional Intramedullary Axis

The tibial slope, one of multiple angles used to place a TKA, defines how the tibial component meets the knee and impacts the knee’s ability to bend and the strain that’s put on the ligaments throughout range of motion. A study led by HSS hip and knee surgeons Brian P. Chalmers, MD, and Steven B. Haas, MD, looked at how robotics and computer navigation influence the tibial slope in TKA. Historically, knee implants were designed using what is called the intramedullary axis to measure the tibial slope, but technology-assisted knee replacement operations determine the slope in a different way. The investigators retrospectively reviewed preoperative CT scans from 40 TKA procedures and reconstructed the 3-D geometry of the tibia and fibula to determine the slope based on the intramedullary axis. They determined that in many cases, the alternate calculation of the slope used in technology-assisted procedures resulted in a different slope in the newly implanted knee. This difference could have a negative effect on the knee’s movement and mechanics, suggesting that as more procedures are performed using robotic-assisted technology, the need to re-think implant designs to incorporate these changes is likely.

Authors: Brian P. Chalmers, MD, Fernando J. Quevedo-González, PhD, Michael P. Ast, MD, Steven B. Haas, MD.

The Initial Fixation of Cementless TKA Is Associated with the AP Translation During Gait: A Computational Study

The two main goals of TKA surgery are restoring the motion of the knee joint to as close to a native knee as possible, and ensuring that the implant is properly attached to the bone so that it lasts as long as possible and does not loosen. A novel study led by Jonathan Glenday, PhD, a postdoctoral fellow, and Fernando J. Quevedo-González, PhD, assistant scientist, both in the Department of Biomechanics at HSS, looked at the intricate relationship between attachment to the bone and joint motion, and how these two aspects of joint mechanics are related. The investigators used a computational model that included gait mechanics and anatomic information from CT scans to look at whether the anterior-posterior (AP) translation (front-to-back movement) of the femur with respect to the tibia while walking was correlated with bone-implant micromotion after surgery. Based on their models, they determined that the AP translation significantly related to the peak micromotion throughout gait, especially in the lateral portion of the knee; greater AP translation resulted in larger micromotions. This study highlights the connection between joint-level mechanics and fixation-level mechanics in TKA surgery and is the first time researchers at HSS have been able to look at both in tandem.

Authors: Jonathan Glenday, PhD, Peter K. Sculco, MD, Jonathan M. Vigdorchik, MD, Joseph D. Lipman, MS, Cynthia Kahlenberg, MD, David J. Mayman, MD, Timothy M. Wright, PhD,  Fernando J. Quevedo-González, PhD.

Three-Dimensional Functional Impingement in Total Hip Arthroplasty: A Biomechanical Analysis

Impingement after THA can lead to pain and, in the worst case, a dislocation of the prosthesis. Offset of components, which is related to the width of the hip, directly affects the impingement of the hip after surgery. Surgeons have multiple ways to alter offset during THA surgery; however, these alterations have only been studied in two dimensions. A team led by HSS hip and knee surgeon Jonathan M. Vigdorchik, MD, and former clinical fellow Eytan Debbi, MD, PhD, used 3-D models created from pre- and postoperative CT scans of 16 patients who underwent the procedure to retrospectively analyze the relationship between offset and impingement. They compared cup/liner (acetabular) offset to head/stem (femoral) offsets and looked at the effects that these configurations had on the patient’s range of motion and incidence of impingement after surgery. The investigators found that in all cases, increasing the offset reduced the amount of impingement, and increased the full range of motion of the hip. Acetabular offsets had greater impact than femoral offsets in the range of motion because they affect the offset of the center-of-rotation.

Authors: Eytan Debbi, MD, PhD (Cedars-Sinai), Fernando J. Quevedo-González, PhD, Seth A. Jerabek, MD, Timothy M. Wright, PhD, Jonathan M. Vigdorchik, MD.

HSS hip and knee surgeon Geoffrey H. Westrich, MD, and his colleagues found no difference in hospital length of stay, complications, hospital readmission within 90 days of surgery, or rates of revision surgery at two-year patient follow-up. The findings were presented today at the American Academy of Orthopaedic Surgeons 2022 Annual Meeting in Chicago.

With respect to time spent in the operating room (OR), researchers found that using the cementless implant reduced OR time by 25%, saving an average of 27 minutes. “In a cementless total knee replacement, you do not have to wait for the cement to harden and dry like you do in a cemented knee replacement,” explained Brian P. Chalmers, MD, hip and knee surgeon at HSS and study co-author.

“Reduced time in the OR under anesthesia is advantageous to patients, but that is not the only potential benefit of the cementless prosthesis,” added Dr. Westrich, who is also the research director emeritus of the Adult Reconstruction and Joint Replacement Service at HSS. “With the cementless knee replacement, the components are press fit into place for ‘biologic fixation,’ which basically means the bone will grow into the implant. If there is initial biologic fixation, implant loosening over time should be less likely and a total knee replacement could potentially last much longer.”

In a traditional knee replacement, implant components are secured in the joint using bone cement. It’s a tried-and-true technique that has worked well for decades. But eventually, over time, the cement starts to loosen from the bone and/or the implant. When it wears out or loosens, patients generally need a second knee replacement, known as a revision surgery.

Dr. Westrich believes that a well-designed cementless implant will make loosening over time less likely, enabling a total knee replacement to last much longer. Implant longevity is an important consideration, especially for younger patients with arthritis who opt for joint replacement to maintain their active lifestyle. They generally put more demands on their joint, causing more wear and tear and potential loosening. The cemented knee implant used in a traditional joint replacement usually lasts 15 to 20 years.

“Cementless implants have been used successfully in total hip replacement surgery for many years. It has been much more challenging to develop a cementless prosthesis that would work well in the knee because of the knee’s particular anatomy,” Dr. Westrich explained.

“In the past, a number of cementless knee implants were shown to have design flaws, with loosening from the tibia,” he added. “The newer cementless prosthesis used in our study did not demonstrate this type of loosening as in previous published studies. We set out to see how the implant fared in HSS patients.” 

Researchers reviewed 598 primary unilateral total knee replacements at HSS (170 cementless and 428 cemented) of the same design from 2016 to 2018. Demographic information, operative details and any complications were obtained from patients’ medical records. Patients undergoing the cementless procedure were younger overall, with a mean age of 63, versus 68 for those having a traditional cemented knee replacement. Good bone quality is important in the success of cementless knee fixation. Therefore, orthopedic surgeons preferentially select younger patients for the cementless procedure, Dr. Chalmers noted.

There was no statistically significant difference in hospital length of stay, complications, or hospital readmission for a problem in the first 90 days after surgery. Ninety-six percent of cementless knee replacement patients versus 95% of those with a cemented knee replacement maintained their implant without the need for revision surgery at two-year follow-up.

“The biggest question now is whether or not cementless total knee replacement will have better long-term durability and fixation than cemented knee replacement,” Dr. Chalmers said. “Following these patients to assess long-term outcomes is the next step.” 

Authors: Alioune Diane, Brian P. Chalmers, MD, Geoffrey H. Westrich, MD (HSS), Kyle Alpaugh, MD (Massachusetts General Hospital), Michael P. Ast, MD, Seth A. Jerabek, MD, Yu-Fen Chiu, MS (HSS).