Luis Saura Beltran MD, Presenter: Nothing to Disclose

Holly Delaney MBBCH, MRCPI, Abstract Co-Author: Nothing to Disclose

James S. Babb PhD, Abstract Co-Author: Nothing to Disclose

Michael Paul Recht MD, Abstract Co-Author: Nothing to Disclose

To determine if trochlear dysplasia and lateralization of the tibial tubercle, as defined by objective MR measurements, are associated with acute transient patellar dislocation and concomitant osteochondral injuries.

50 MR knee examinations of patients with acute patellar dislocation were retrospectively evaluated for the presence of 1) Patellofemoral morphologic abnormalities: trochlear dysplasia (trochlear sulcus depth (TSD) < 5mm and/or trochlear sulcus angle (TSA) > 144 degrees), lateralization of the tibial tubercle (tibial tubercle-trochlear groove distance (TTTG) > 15 mm) and 2) Osteochondral injuries (cartilage defects or bone contusions) of the medial patella and lateral femoral condyle. The TSD, TSA, and TTTG values were classified as normal or abnormal. The ostechondral injuries were classified as 0 (none), 1 (bone contusion or cartilage defect), and 2 (both) in the medial patella and lateral femoral condyle. An exact 95% confidence interval was derived for the frequency of morphological abnormalities (TSD, TSA and TTTG).  The Cochran-Armitage trend test was used to assess any correlation between the percentage of subjects with a specific morphological abnormality and the number of medial patellar and lateral femoral condyle osteochondral injuries.

The frequencies of patellofemoral morphologic abnormalities were: TSD=70% (CI 56.6 – 81.8%), TSA=76% (CI 62.6 – 86.9%), TTTG=44% (CI 30.3 to 58.8%). The percentage of subjects with abnormal TSD exhibited a significant monotonic increase as the number of osteochondral injuries in the medial patella increased; 37.5% (3/8) for 0, 66.7% (16/24) for 1, 88.9%(16/18) for 2, p = 0.0075. There was no significant correlation between abnormal TSA or TTTG and medial patellar osteochondral injury. There was no significant correlation between frequency of abnormal TSA, TSD or TTTG and lateral femoral condyle osteochondral injuries.

In patients with acute transient patellar dislocation, there is a higher frequency of MR findings of trochlear dysplasia than lateralization of the tibial tubercle. The incidence of trochlear dysplasia as indicated by an abnormal trochlear sulcus depth on MR imaging correlates with increasing incidence of medial patellar osteochondral injuries.

The presence of trochlear dysplasia on MRI is a significant predictor of osteochondral injury in the medial patella following acute transient patellar dislocation.

Beltran, L, Delaney, H, Babb, J, Recht, M, Trochlear Dysplasia and Lateralization of the Tibial Tubercle on MR Imaging: Is It Associated with Acute Transient Patellar Dislocation and Osteochondral Injuries?.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12027592.html