Venous thromboembolism (VTE) following hip fractures and hip/knee arthroplasty—both deep vein thrombosis (DVT) and pulmonary embolism (PE)—has been relatively well studied. We therefore have a fairly clear understanding what the risks for DVT and PE are with no treatment as well as with modern preventive chemotherapeutic agents. However, such clarity on the need for and effectiveness of VTE prophylaxis is lacking for below-the-knee (BTK) orthopaedic procedures. This is largely due to the fact that such procedures have been deemed “low risk”—despite a dearth of supporting evidence for that assumption. In the March 20, 2019 issue of The Journal, Heijboer et al. used a sophisticated propensity score matching methodology to evaluate the rate of VTE in >10,000 BTK surgery patients at their tertiary care referral center.
The authors evaluated patients who underwent orthopaedic surgery distal to the proximal tibial articular surface, including foot/ankle procedures, open reduction of lower-leg fractures, and BTK amputations. They performed propensity score matching to compare 5,286 patients who received any type of chemotherapeutic prophylaxis with the same number who did not, across several key risk categories. The good news is that VTE prophylaxis effectively lowered the risk of symptomatic DVT or PE from 1.9% to 0.7% (odds ratio of 0.38, p <0.001).
Unfortunately (but not surprisingly), this effectiveness came at the price of increased systemic or local bleeding among patients using chemical VTE prophylaxis, with an incidence of 1.0% in the no-prophylaxis group and 2.2% in the prophylaxis group (odds ratio of 2.18, p <0.001). The authors did not assess the incidence of deep infection or hematoma formation, which often accompany increased local bleeding. The low overall incidence of VTE and bleeding did not allow for subgroup analysis according to location of surgery, and aspirin use was not controlled for in their study. In addition, Heijboer et al. used hospital coding data, and the accuracy of the database was not assessed.
The authors recommend that “anticoagulant prophylaxis be reserved only for patient groups who are deemed to be at high risk for VTE,” but we still don’t know precisely who is at high risk among BTK surgery patients. It is my hope that these findings will prompt large, prospective multicenter trials in the foot and ankle community to better determine which types of patients should be exposed to an increased risk of postoperative bleeding complications in order to achieve a clinically important decreased risk of VTE with chemical prophylaxis.
Marc Swiontkowski, MD
OrthoBuzz occasionally receives posts from guest bloggers. This guest post comes from Matthew Herring, MD in response to a recent study in the Journal of Orthopaedic Trauma.
Pulmonary embolism (PE) is a potentially life-threatening complication among many orthopaedic trauma patients. PE can be a silent killer, with only about 30% of fatal PEs being detected before death. Chemical prophylaxis with “blood thinners” such as injectable enoxaparin is effective in mitigating the risk of PE, but in the poly-traumatized patient, its application is often contraindicated. In an effort to develop a more effective approach to PE prevention in the trauma population, Starr et al. built a tool to estimate the risk of PE early and effectively, and then developed a multidisciplinary protocol for deep vein thrombosis (DVT) prophylaxis. They present their preliminary experience with the risk-assessment tool and the new protocol in the February 2019 issue of the Journal of Orthopaedic Trauma.
The smart-phone app (ParkLandOrtho) to risk-stratify trauma patients in the ED is based on 7 easily captured variables that the authors’ prior work identified as statistically significant predictors for developing a PE. Patients who are identified as “high risk” are aggressively started on enoxaparin, with the first dose ideally given prior to ED discharge. If contraindications for chemical prophylaxis are present, enoxaparin is withheld for up to 24 hours after admission. After 24 hours, if the patient is still unable to receive enoxaparin, a removable inferior vena cava (IVC) filter is placed.
The authors performed a retrospective review of PE incidence among 368 consecutive orthopaedic trauma patients admitted to their hospital after this new protocol was implemented and compared it to PE incidence among a historic cohort of 420 similar consecutive patients admitted during the year prior to the protocol. The two groups were similar in age and injury severity. In the control group, 51 patients were retrospectively classified as high risk, and 9 patients (2.1%) developed symptomatic PEs, one of which was fatal. In the group managed under the new protocol, 40 patients were identified as high risk, and only 1 patient (0.27%) developed a nonfatal PE. The difference in incidence of PE between the two groups was statistically significant (P = 0.02).
This paper highlights two significant achievements in my opinion. First, I was excited to see the success of a smart-phone app to facilitate rapid risk assessment. This was a significant key to the success of the multidisciplinary PE protocol, which depends on buy-in and compliance. Second, this thoughtful, decisive, and team-based protocol for DVT/PE prophylaxis in an orthopaedic trauma setting seems to be making a meaningful impact on patient outcomes.
The authors report that they are currently designing a multicenter trial to prospectively validate their protocol. I eagerly await this and hope that their next step includes a ParklandOrtho app release for Android devices, as it is only available now for iPhone and Samsung users.
Matthew Herring, MD is a fellow in orthopaedic trauma at the University of California, San Francisco and a member of the JBJS Social Media Advisory Board.