Banne Nemeth, Clifford Colwell.

Response/Recommendation: 1. For patients with a non-displaced hip-fracture not requiring surgery, a standard prophylactic regimen of either low-molecular-weight- heparin (LMWH), fondaparinux, low dose unfractionated heparin (LDUFH), adjusted-dose vitamin K antagonist (VKA), or aspirin (ASA) should be considered.

2. For patients with a displaced hip fracture who are treated conservatively, venous thromboembolism (VTE) prophylaxis should be considered in a similar fashion to hip-fracture surgery patients.

Strength of Recommendation: Limited.

Rationale: Patients who undergo hip-fracture surgery (HFS) are at high-risk for developing post-operative VTE, including deep vein thrombosis (DVT) and/or pulmonary embolism (PE). Multiple randomized controlled trials (RCT) showed that either LMWH, fondaparinux, LDUFH, adjusted-dose VKA, or ASA reduced the occurrence of post-operative VTE.

While the majority of patients with hip fractures receive operative management, certain patients (4-8%) with either intracapsular fractures, significant medical morbidities precluding surgery, non-displaced patterns, or with delayed presentation are treated conservatively. For patients with a hip fracture who are treated conservatively, no RCT have been performed to investigate whether thromboprophylaxis is effective in preventing symptomatic VTE¹. However, numerous studies have investigated the preoperative prevalence of asymptomatic DVT in patients with a hip fracture.

In 1999, authors from Kings College Hospital United Kingdom (UK) performed a phlebography in hip-fracture patients awaiting surgery, and who were not operated on until after 48hours following their hospital admission. All patients were treated with 5,000 IU of unfractionated subcutaneous heparin at admission and every 12h thereafter. They found that 13/21 (62%) of patients had an asymptomatic DVT in the affected limb, and 1/21 (4.8%) patient had clinical signs and symptoms of VTE².

In another investigation,101 consecutive patients with a hip fracture who received preoperative prophylactic anticoagulation, underwent doppler ultrasound evaluation before surgery. DVT was found in 10/101 (9.9%) patients, and two patients (2%) developed a symptomatic PE. The authors suggested that a delay in surgery resulted in a higher risk of DVT³.

In another similar study among 208 individuals with a hip fracture, patients underwent indirect multidetector computed tomographic venography for preoperative VTE detection after admission. The prevalence of preoperative asymptomatic VTE was 11.1% (23/208 of patients). While no patients had a symptomatic event, they noted that VTE occurrence correlated with surgical delay⁴.

While multiple observational studies confirmed a 10-25% prevalence of asymptomatic VTE prior to surgery, no large studies substantiating the rates of symptomatic VTE in non-surgically treated hip fractures have been published yet. Nevertheless, one large study from a single institution in the UK showed that among 5,300 with a proximal femur fracture, 2.2% developed a post-operative symptomatic VTE despite the use of thromboprophylaxis⁵.

Considerations: For patients with a hip-fracture who are treated conservatively, the risk of asymptomatic VTE is certainly high and ranges between 10-25% in large observational studies. While the risk for symptomatic VTE in hip-fracture patients not receiving surgery remains unknown, smaller studies suggest a rate of 2% which is in line with studies among HFS patients.

Additionally, time until surgery is an important predictor for the occurrence of pre-operative VTE, hence it is expected that for patients with displaced hip fracture (thus those who are bed-confined), the risk for VTE is significant.

Finally, the data on the effectiveness of thromboprophylaxis in patients with a hip fracture not undergoing surgery remains lacking. However, extrapolating from HFS literature, we speculate that the effectiveness of thromboprophylaxis applies to non-surgical patients, as the risks of VTE in this patient population are at least similar, and perhaps greater in patients who are immobilized, or bed-confined.

References:

1.         Falck-Ytter Y, Francis CW, Johanson NA, et al. Prevention of VTE in orthopedic surgery patients: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):e278S-e325S. doi:10.1378/chest.11-2404

2.         Zahn HR, Skinner JA, Porteous MJ. The preoperative prevalence of deep vein thrombosis in patients with femoral neck fractures and delayed operation. Injury. 1999;30(9):605-607. doi:10.1016/s0020-1383(99)00163-1

3.         Smith EB, Parvizi J, Purtill JJ. Delayed surgery for patients with femur and hip fractures-risk of deep venous thrombosis. J Trauma. 2011;70(6):E113-116. doi:10.1097/TA.0b013e31821b8768

4.         Shin WC, Woo SH, Lee S-J, Lee JS, Kim C, Suh KT. Preoperative Prevalence of and Risk Factors for Venous Thromboembolism in Patients with a Hip Fracture: An Indirect Multidetector CT Venography Study. J Bone Joint Surg Am. 2016;98(24):2089-2095. doi:10.2106/JBJS.15.01329

5.         McNamara I, Sharma A, Prevost T, Parker M. Symptomatic venous thromboembolism following a hip fracture. Acta Orthop. 2009;80(6):687-692. doi:10.3109/17453670903448273