Impact of recent guideline changes on aspirin prescribing after knee arthroplasty

Prior to 2012, the American Academy of Orthopaedic Surgeons (AAOS) and American College of Chest Physicians (ACCP) differed in their recommendations for postoperative pharmacologic venous thromboembolism prophylaxis (VTEP) after total joint arthroplasty. More specifically, aspirin (ASA) monotherapy was not endorsed by the ACCP as an acceptable prophylaxis. In 2012, the ACCP supported ASA monotherapy compared with no prophylaxis. Our aim was to investigate the impact of the convergence of ACCP and AAOS recommendations on surgeon prescribing patterns after knee arthroplasty (KA).

This is a retrospective chart review. We collected data to assess preoperative VTE risk and examined VTEP prescriptions on postoperative day 1 (POD1) and at discharge (D/C) from 7/2008 to 12/2011 (pre-period) and 1/2012 to 7/2014 (post-period). Adult patients undergoing primary and revision KA were identified by ICD-9 procedure codes. Patients on preoperative full-dose anticoagulation and with hypercoagulability disorders were excluded.

Of 368 records reviewed, 329 were included in the analysis. There were no differences between the two period groups for age, sex, BMI, estrogen therapy, malignancy, smoking status, prior VTE, bilateral procedures, or surgery within 3 months. On POD1, in the pre-period, 4.6 % were prescribed ASA monotherapy versus 44.4 % in the post-period (p < 0.001). On D/C, in the pre-period, 13.9 % were prescribed ASA versus 55.6 % in the post-period (p < 0.001).

Our results indicate a statistically significant change in orthopedist prescribing patterns after guideline convergence. Furthermore, there was no apparent change in VTE risk between the two study groups when excluding patients necessitating full anticoagulation. Prior literature has shown that the divergence in guidelines influenced physicians away from ASA and toward more potent anticoagulants in order to avoid potential litigation. Once its role in VTEP was supported by the ACCP, it appears that ASA monotherapy was readily and rapidly incorporated into clinical practice. ASA may be favored over other VTEP agents for its lower bleeding risk profile and cost. This study highlights the profound impact clinical practice guidelines have on clinician prescribing patterns. Although prospective randomized trials are needed to compare the efficacy of ASA with other VTEP agents, ASA is now a predominant part of the VTEP armamentarium after KA.