ePoster #726 - ISHA Annual Scientific Meeting 2016

Validation Of A Novel Digitally Reconstructed Radiograph Based Radiostereometric Analysis Method For Evaluation Of Femoroacetabular Impingement Pathomechanics

Lars Hansen, BA, Aarhus DENMARK
Sepp De Raedt, MSc, PhD , Aarhus DENMARK
Peter Bo Jørgensen, MSc, Aarhus DENMARK
Bjarne Mygind-Klavsen, MD, Aarhus DENMARK
Maiken Stilling, MD, PhD, Associate Prof., Holstebro DENMARK

Department of Orthopaedic Research, Aarhus University Hospital, Aarhus , DENMARK

FDA Status Not Applicable

Summary: A fully automated digitally reconstructed radiograph based radiostereometric analysis method for evaluation of hip biomechanics in relation to femoroacetabular impingement is validated, is shown to be precise, and could be used to analyze in-vivo hip kinematics.

Background: The pathomechanics of femoroacetabular impingement (FAI) are not fully understood. Moreover, the effects of arthroscopic cheilectomy and -rim trimming have not been investigated. Dynamic radiostereometric analysis (dRSA) using inserted markers is an accurate method for tracking three-dimensional movement of objects. With dRSA hip joint kinematics can be evaluated. Current marker-based RSA (MM) is invasive and requires bone markers to be inserted and therefore cannot be used for preoperative and diagnostic evaluations. Traditional model-based RSA (MBM) is noninvasive and uses CT-reconstructed bone models which are matched to stereoradiographs by manual edge selection. However, analysis with model-based RSA is time consuming and subject to inter- and intra-observer variation. In this study we introduce a fully automated volume based analysis method based on a digitally reconstructed radiograph (DRR) for tracking of bone volume in dynamic stereoradiographic recordings.

Objective: To validate the precision of DRR and MBM with respect to MM as gold standard.

Methods: Seven human cadaveric hemipelves were CT-scanned and bone models were segmented. Eight to 10 tantalum beads were placed in the ilium and ischium (combined pelvis) and proximal femoral bone. RSA-recordings of the hips were performed during flexion, adduction and internal rotation (FADIR), with the pelvis fixed. Two recordings were performed for each specimen, between which the legs were remounted. Stereoradiographic recordings were all analyzed with DRR, MBM and MM. The initial calibration of the stereoradiographs was identical for all methods. Migratory results for MBM and DRR with respect to MM were compared. Precision was assessed as systematic bias (mean difference) and random variation (Pitman’s test for equal variance).

Results: In total 288 dRSA images were analyzed. Systematic bias for DRR and MBM with respect to MM in translations (mean diff <.018mm) and rotations (mean diff<0.009°) were approximately zero and no difference between DRR and MBM was found (p>0.36). Pitman’s test showed lower random variation in all degrees of freedom for DRR compared to MBM (P<0.001).

Conclusions: Systematic error was approximately zero for both DRR or MBM. However, precision of DRR was statistically significantly better than MBM. Since DRR does not require marker insertion it can be used for comparison of in vivo pre- and post-operative FAI kinematics.