Non-invasive Dynamic Identification of Femoroacetabular Impingement: A Cadaveric Validation Study
Femoroacetabular impingement (FAI) is caused by anatomic deviation of the acetabular rim or proximal femur. These deformities cause chronic groin pain and can lead to osteoarthritis of the hip joint. Radiological identification of FAI can be challenging, especially if the deformities are small. Advances in 3D imaging with the use of CT scans enable simulation of FAI but require validation to be of clinical value. In this prospective cadaveric study we evaluated the efficacy of Articulis, a CT-based software system for the radiological detection and quantification of FAI.
The range of motion (ROM) of five cadaveric hips was measured using an electromagnetic tracking system (EMTS) (Flock of Birds, Ascension Technology, United States). K-wires were fixed into specific marked sports in the femur and pelvis to create reproducible EMTS registration points. For each hip we registered maximum flexion, abduction, internal rotation and internal rotation at 30°, 60° and 90° of flexion. We then introduced cam deformities using nylon screws with a diameter of 1 cm and a thickness of 3.5 mm, after which the motion measurements were repeated. The hips were subsequently imaged using high resolution CT. We used a proprietary software tool, Articulis (Clinical Graphics, Delft, The Netherlands), to simulate the ROM during the presence and absence of the induced cam deformities. We then compared the simulated reduction in ROM in Articulis to ROM measured with the EMTS.
According to the EMTS, 13 of the 30 measured ROM end points were restricted by more than 5° due to the induced cam deformities. Using Articulis and with the same 5° threshold, we correctly detected 12 of these 13 end point limitations and detected no false positives. The median error of the simulated ROM limitations compared to the EMTS measured limitations was 1.9° (interquartile range, 1.1° till 4.4°). The maximum absolute error was 5.4°.
This cadaveric study evaluated the use of software to determine the presence of motion limiting deformities of the femoroacetabular joint using radiological imaging. To our knowledge this study is the first to validate 3D ROM simulation on pre- and post-operative scenarios representing cam type deformities. The simulation software we use can non-invasively detect a reduction in achievable ROM, caused by a cam-type deformity. This technique is promising as a clinically diagnostic tool for FAI diagnostics and for preoperative planning.
Reference: Röling, M., Visser, M., Bloem, R., Oei, E., Kleinrensink, G.J., & Pilot, P. (2013). Non-invasive Dynamic Identification of Femoroacetabular Impingement: A Cadaveric Validation Study. Arthroscopy: The Journal of Arthroscopic and Related Surgery, 29(12), e193-e194