Kara Mc Conaghy, Geoffrey H. Westrich, Nicolas S. Piuzzi.

Response/Recommendation: Routine thromboprophylaxis is not indicated for patients with isolated patellar fracture but should be considered for patients with risk factors for venous thromboembolism (VTE).

Strength of Recommendation: Limited.

Rationale: Venous thromboembolism (VTE), which includes deep venous thrombosis (DVT) and pulmonary embolism (PE), is a serious complication that occurs in 1.6-21% of patients with lower extremity fractures^1–4.  However, there is limited data regarding the incidence of VTE in patients with isolated patellar fractures, and the use of routine VTE prophylaxis is controversial.  Tan et al.,⁵ conducted a retrospective review of 716 patients admitted to a single institution to investigate the incidence and location of postoperative DVT in patients who underwent operative repair of isolated patella fractures.  Duplex ultrasound (DUS) was used for diagnosis only in patients clinically suspected of DVT.  All patients received subcutaneous low-molecular-weight heparin (LMWH) and sequential compression devices (SCD) throughout admission as part of routine VTE prophylaxis.  Of the 716 patients, 29 cases were diagnosed with postoperative DVT, with an incidence of 4.1%.  The majority of the diagnosed DVT were located distally (n=22; 3.1%), while 0.98% (n=7) were located proximally (i.e., localized in the popliteal vein or proximally).  There were no cases of PE.  Tan et al.,⁶ conducted a similar study investigating preoperative DVT in patients with isolated patellar fractures using nearly identical methodology.  However, this study differed in that all participants underwent DUS of bilateral lower extremities at admission and then every three days until discharge.  Of the 790 included patients, 35 developed a preoperative DVT (4.4%), with 3.2% (n=25) located distally and 1.2% (n=10) located proximally.  No DVT were found on admission.  The authors recommend individualized risk stratification and early anticoagulation for patients with risk factors (age ≥65 years, D-dimer >0.5 mg/L and albumin <35g/L).  Similarly, Wang et al.,⁷ conducted a retrospective analysis of the perioperative incidence and location of DVT following isolated lower extremity fractures in patients that received routine thromboprophylaxis and DVT monitoring with DUS.  A small cohort of 59 patients with isolated patellar fractures were included in the study.  Overall, 15 (25.4%) patients in the patellar cohort developed a DVT.  One patient had a proximal DVT (1.7%), while the remaining DVT were distal (23.7%).  No patients with patellar fracture developed symptomatic PE.  The authors concluded that the perioperative incidence of DVT is high following isolated lower extremity fractures, although the majority were distal DVT, and the rate of symptomatic PE was low.

Only one study has assessed the rate of VTE in patellar fracture patients who did not receive any thromboprophylaxis.  Selby et al., conducted a multicenter prospective study in a population of patients with a variety of isolated lower extremity fractures including fractures of the tibia, fibula, ankle, patella and foot⁸.  Fractures treated both operatively and conservatively were included, and 82% of the patients were treated in a cast or splint for an average of 42 days.  All patients were followed with a telephone interview at two, six, and twelve weeks to determine the prevalence of symptomatic VTE.  Suspected DVT and PE were investigated in a standardized manner using DUS and computed tomography (CT) pulmonary angiography.  Overall, 1,200 patients were enrolled, of which 60 patients (5%) had patella fractures.  In total, there were seven confirmed VTE events (0.6%), including two proximal DVT (0.17%), three distal calf DVT (0.25%), and two PE (0.17%).  There were no fatal PE.  The overall event rates were too low to allow multivariate analyses for predictors of VTE.  Since a breakdown of VTE by fracture location was not reported, the true incidence of VTE in the patients with isolated patella fractures was unclear.

Additionally, several large database studies have investigated the incidence of VTE following operatively treated isolated patellar fracture in populations that included both patients who received routine prophylaxis and patients who did not.  Warren et al., used the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database to evaluate the annual incidence of 30-day thrombotic events for a variety of isolated lower extremity fractures from 2008 to 2016¹.  Overall, 2,825 patients with operatively managed patellar fracture were identified.  The VTE rate in this cohort was 0.9% (n=26), including 18 DVTs (0.6%) and 11 PEs (0.4%).  The authors concluded that the VTE rates from 2008 to 2016 have remained relatively unchanged and that thromboembolic guidelines should be reassessed.  Likewise, Kapilow et al.,⁹ also published a retrospective review using NSQIP that reported the early outcomes after surgical management of isolated patellar fractures in a population of 1,721 patients 65 years of age or older.  Overall, only 13 (0.8%) of these patients developed VTE, but the authors noted that this patient cohort was at higher risk for prolonged hospitalization, discharge to a facility, unplanned readmission or reoperation, and surgical site complications in the first 30 days.

Overall, the studies that utilized routine thromboprophylaxis in all patients found the incidence of DVT after isolated patellar fracture to range from 4.1% to 25.4%, with no recorded instances of PE in any of the studies^5–7.  The wide range in the reported incidence of DVT was influenced by the different methodologies used in these studies.  For example, the paper by Tan et al.⁵, which reported the lowest rate of VTE (4.1%), only scanned symptomatic patients and did not include intermuscular vein blood clots when calculating the incidence of DVT.  Conversely, Wang et al.,⁷ routinely screened all patients using DUS and included intramuscular vein blood clots, which resulted in the highest reported incidence of VTE (25.4%).  Notably, if the study by Wang et al.⁷ is excluded, the highest reported incidence of DVT drops from 25.4% to 4.4%.  This highlights the major discrepancy between studies using different clinical endpoints and VTE screening protocols.

The large cohort studies utilizing the NSQIP database did not control for the routine use of VTE prophylaxis; however, much lower rates of VTE between 0.8-0.9% were noted^1,9.  Unfortunately, the NSQIP database does not include VTE prophylaxis, so it is unclear if a prophylaxis was utilized, and if so, what specific type of VTE prophylaxis was used.  They also included the largest sample size of any of the included studies, and were the only studies not limited to a single institution, lending increased power and generalizability to their findings.

In all studies, distal DVT was more common than proximal DVT.  It is widely accepted that proximal DVT represents a greater risk for the development of PE and requires further treatment, while the clinical relevance of distal DVT remains uncertain and the risk of proximal propagation is not well defined^7,8.  The treatment of distal DVTs is not standardized and may be either monitored with serial scans or actively treated with anticoagulation.  The rate of proximal DVT reported in these studies was low, ranging from 0.17% to 1.2%^5–7.  The observed rate of PE was even lower, ranging from 0% to 0.4%.(1,5–8).  While the rate of VTE were very low, many studies on isolated patella fractures utilized routine VTE prophylaxis and there were no studies in the literature in which VTE prophylaxis was randomized.  As such, the recommendation to routinely use or omit VTE prophylaxis remains difficult to assess.  Despite the various methodologies utilized in the reviewed studies, the universally low rate of proximal DVT and PE should be considered in the decision to implement routine VTE prophylaxis in patients with isolated patellar fractures.  It may be safer and more cost-effective to initiate VTE prophylaxis only in patients with risk factors for VTE, such as elderly patients, those with longer length of stays, longer operative time, or arrhythmia^5,6.  However, given the limitations of the available data, future studies comparing the use of VTE prophylaxis versus no prophylaxis in patients with isolated patellar fracture are required.

References:

1.         Warren JA, Sundaram K, Hampton R, Billow D, Patterson B, Piuzzi NS. Venous thromboembolism rates remained unchanged in operative lower extremity orthopaedic trauma patients from 2008 to 2016. Injury. 2019;50(10):1620-1626. doi:10.1016/j.injury.2019.09.003

2.         Lapidus LJ, Ponzer S, Pettersson H, de Bri E. Symptomatic venous thromboembolism and mortality in orthopaedic surgery – an observational study of 45 968 consecutive procedures. BMC Musculoskelet Disord. 2013;14:177. doi:10.1186/1471-2474-14-177

3.         Park S-J, Kim C-K, Park Y-S, Moon Y-W, Lim S-J, Kim S-M. Incidence and Factors Predicting Venous Thromboembolism After Surgical Treatment of Fractures Below the Hip. J Orthop Trauma. 2015;29(10):e349-354. doi:10.1097/BOT.0000000000000336

4.         Tan L, Qi B, Yu T, Wang C. Incidence and risk factors for venous thromboembolism following surgical treatment of fractures below the hip: a meta-analysis. Int Wound J. 2016;13(6):1359-1371. doi:10.1111/iwj.12533

5.         Tan Z, Hu H, Deng X, et al. Incidence and risk factors for deep venous thrombosis of lower extremity after surgical treatment of isolated patella fractures. J Orthop Surg. 2021;16(1):90. doi:10.1186/s13018-021-02240-9

6.         Tan Z, Hu H, Wang Z, Wang Y, Zhang Y. Prevalence and risk factors of preoperative deep venous thrombosis in closed patella fracture: a prospective cohort study. J Orthop Surg. 2021;16(1):404. doi:10.1186/s13018-021-02558-4

7.         Wang H, Kandemir U, Liu P, et al. Perioperative incidence and locations of deep vein thrombosis following specific isolated lower extremity fractures. Injury. 2018;49(7):1353-1357. doi:10.1016/j.injury.2018.05.018

8.         Selby R, Geerts WH, Kreder HJ, Crowther MA, Kaus L, Sealey F. Symptomatic venous thromboembolism uncommon without thromboprophylaxis after isolated lower-limb fracture: the knee-to-ankle fracture (KAF) cohort study. J Bone Joint Surg Am. 2014;96(10):e83. doi:10.2106/JBJS.M.00236

9.         Kapilow J, Ahn J, Gallaway K, Sorich M. Early Outcomes After Surgical Management of Geriatric Patella Fractures. Geriatr Orthop Surg Rehabil. 2021;12:2151459320987699. doi:10.1177/2151459320987699