Marcelo Rodrigues Abreu MD, Presenter: Nothing to Disclose

Rafael Costa e Silva, Abstract Co-Author: Nothing to Disclose

Hyun Jin Kim, Abstract Co-Author: Nothing to Disclose

Debbra Trudell, Abstract Co-Author: Nothing to Disclose

Christine B. Chung MD, Abstract Co-Author: Nothing to Disclose

Donald L. Resnick MD, Abstract Co-Author: Nothing to Disclose

To explore the frequency and possible cause of Hoffa’s fat pad abnormalities in ACL-deficient knees and to study its normal anatomic relationships.

MR imaging studies of the knee performed during a one-year period in 54 patients with subsequent arthroscopy were retrospectively analyzed by two readers in consensus for abnormalities of Hoffa’s fat pad and ACL injuries. Readers determined the presence of alterations in Hoffa’s fat pad including tears, focal edema, diffuse edema, and synovial injuries. Arthroscopy reports were reviewed. Ten cadaveric knee specimens were studied with MR imaging, high resolution sectional radiographs, and inspection of sections to determine the normal morphology of Hoffa’s fat pad. In four specimens, histologic samples were obtained.

Of the 54 patients, 26% had ACL tears documented during arthroscopy: 8 complete tears and 6 partial tears. With MR imaging, ACL tears were found in 28% of patients: 10 complete tears and 5 partial tears. Twenty-one patients had alterations in Hoffa’s fat pad with MR imaging (tears-8, focal edema-12, diffuse edema-6, synovial alterations-7) and 7 with arthroscopy (tear-1, synovial alterations-5, scars-2). There was no association between the MR imaging and arthroscopic alterations (p>0.05). There was a statistical positive association between the presence of Hoffa’s fat pad alterations observed with MR imaging and the presence of an ACL tear observed with either MR imaging (p<0.01) or arthroscopy (p<0.05). In cadavers, the fat pad was the thickest structure that inserted into the intercondylar notch even in the presence of a ligamentum mucosum.

Abnormalities of Hoffa’s fat pad are commonly detected with MR imaging and, less frequently, at the time of arthroscopy. When seen with MR imaging, such abnormalities are commonly encountered in patients with a torn ACL, a finding that may relate to an intercondylar insertion site of Hoffa’s fat pad.

Abreu, M, Costa e Silva, R, Kim, H, Trudell, D, Chung, C, Resnick, D, Hoffa’s Fat Pad Injuries and Their Relationship to Anterior Cruciate Ligament Tears: New Observation Based on MR Imaging and Arthroscopy in Patients and MR Imaging--Anatomic Correlation in Cadavers.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4408295.html