Rajiv Gandhi, Abstract Co-Author: Nothing to Disclose

David Charles Salonen MD, Abstract Co-Author: Research Consultant, Targeted Genetics Corporation Research Consultant, Abbott Laboratories Research Consultant, Johnson & Johnson Research Consultant, Wyeth

Monica Khanna MBBS, FRCR, Presenter: Nothing to Disclose

Sean McSweeney MBBS, FRCR, Abstract Co-Author: Nothing to Disclose

J Roderick Davey, Abstract Co-Author: Nothing to Disclose

Khalid Syed, Abstract Co-Author: Nothing to Disclose

Nizar Mohamed, Abstract Co-Author: Nothing to Disclose

William Geerts, Abstract Co-Author: Nothing to Disclose

To report the prevalence of an acute pulmonary embolism in the first post operative day following total hip (THA) and total knee arthroplasty (TKA) in asymptomatic patients using CTPA.

CTPA examinations were prospectively performed on 48 consecutive THA/TKA patients between 24-36 hours after surgery. Examinations were performed on a 64 row multidetector computed tomographic unit (MDCT). Volumetric acquisition was obtained during arrested inspiration, from the lung apices to the costophrenic angles. All studies were reconstructed with a 1mm slice thickness with coronal reformats. Nonionic iodinated contrast agent (270mg/L) was injected at a rate of 5 ml/sec using 60 to 100 ml depending on patient size. All patients were asymptomatic for a PE. Patients underwent routine post operative care and data was collected for the development of symptoms such as tachycardia, fever, chest pain, or shortness of breath. All CTPA scans were blinded until completion of study recruitment and then read by 2 independent radiologists for findings of acute PE.  

48 patients underwent a CTPA, 27 (56%) were TKA patients and 21 (44%) THA patients. In the knee cohort, 11/27 (41%) CTPA scans were positive for an acute PE as compared to 1/21 (5%) hip patients (p=0.004). Of the 11 asymptomatic PEs in the knee cohort, the largest clot was in the main pulmonary artery in 1 patient, the lobar artery in 5 patients, and the segemental arteries in 5 patients. The asymptomatic PE in the hip patient demonstrated a clot in the lobar, segmental, and sub-segmental arteries. All patients diagnosed with an asymptomatic PE were discharged from hospital without developing clinical symptoms suggestive of thrombosis. One knee patient was treated for a clinically significant PE diagnosed on post-operative day 2, however their asymptomatic scan was read as negative.

The rate of asymptomatic PE was substantial; greatest in the knee patients compared to the hip patients ( 41% vs 5% respectively). The reliability of CTPA for detection of clinically meaningful PE in this population is questioned emphasising the need for a diagnostic algorithm to assist the treating clinician determine the need for ordering an imaging scan.

The rate of asymptomatic PE is substantial in post arthroplasty patients immediately postoperatively questioning the reliability of CTPA in the detection of clinically meaningful PEs.

Gandhi, R, Salonen, D, Khanna, M, McSweeney, S, Davey, J, Syed, K, Mohamed, N, Geerts, W, Computed Tomography Pulmonary Angiography (CTPA) Findings in the Detection of Pulmonary Embolism within 36 Hours Following Total Hip and Knee Arthroplasty in Asymptomatic Patients.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9003746.html