Michael Kogler MD, Abstract Co-Author: Nothing to Disclose

Markus Reichkendler, Abstract Co-Author: Nothing to Disclose

Petr Vavron, Abstract Co-Author: Nothing to Disclose

Ehrenfried Schmaranzer, Presenter: Nothing to Disclose

Delamination of acetabular cartilage is a frequent lesion in cam impingement. The purpose of the present study was to demonstrate the need of leg traction in MR arthrography to identify this pathological changing.

Institutional review board approval and informed consent were waived for this retrospective study. 70 consecutive patients (mean age, 34.4 years; range, 18 – 51 years) with cam and mixed cam-pincer impingement were included. Each of them underwent MR arthrography without and with traction documented in three planes on a 1.5 Tesla unit. For leg traction a dedicated device was used. MR arthrographic findings were compared to diagnosis at surgery, setting the reference standard.

MR diagnostic criterion for acetabular cartilage delamination was a high signal intensity under the cartilage flap on T1 weighted images. In hip arthroscopy cartilage delamination was seen in 38 patients (54%). At MR arthrography with leg traction the lesion was described in 34 patients resulting in a sensitivity of 89%. However, without leg traction only in 6 cases cartilage delamination was detectable, yielding a sensitivity of 16%. The reason for infrequent finding of cartilage delamination without using traction is the insufficient interface between femoral and acetabular cartilage. 4 patients showed a typical wave sign at surgery but the cartilage detachment, even retrospectively, was not detectable at MR arthrography with traction due to lack of contrast medium under the cartilage flap. In these cases the interface was insufficient although traction was applied. An explanation for this might be mixed cam-pincer types. According to our observations it is not always possible to achieve sufficient joint distension in mixed impingement forms.

With the use of axial traction to the hip joint delamination of the acetabular cartilage can be identified accurately at MR arthrography. And also other pathological changes of the femoral and acetabular cartilage can be excellently visualized. The presence and exact extent of a cartilage lesion are necessary for the orthopedic surgeon in preoperative planning of appropriate cartilage treatment strategies such as refixation, microfracturing or cartilage transplantation.

MR arthrography with leg traction is a simple examination that permits excellent assessment of cartilage lesions and is essential for preoperative planning in orthopedic surgery.

Kogler, M, Reichkendler, M, Vavron, P, Schmaranzer, E, Acetabular Cartilage Delamination in Femoroacetabular Cam Impingement: Diagnostic Accuracy of MR Arthrography with and without Leg Traction in Comparison to Arthroscopy.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12030889.html