No abstract

Radiostereometic analysis (RSA) is an accurate method for rigid body pose (position and orientation) in three-dimensional space. Traditionally, RSA is based on insertion of periprosthetic tantalum markers and manual implant contour selection which limit clinically application. We propose an automated image registration technique utilizing digitally reconstructed radiographs (DRR) of computed tomography (CT) volumetric bone models (autorsa-bone) as a substitute for tantalum markers.Furthermore, an automated synthetic volumetric representation of total knee arthroplasty implant models (autorsa-volume) to improve previous silhouetteprojection methods (autorsa-surface). As reference, we investigated the accuracy of implanted tantalum markers (marker) or a conventional manually contour-based method (mbrsa) for the femur and tibia. The data are presented as mean (standard deviation). The autorsa-bone method displayed similar accuracy of −0.013 (0.075) mm compared to the gold standard method (marker) of −0.013 (0.085). The autorsavolume with 0.034 (0.106) mm did not markedly improve the autorsa-surface with 0.002 (0.129) mm, and none of these reached the mbrsa method of −0.009 (0.094) mm. In conclusion, marker-free RSA is feasible with similar accuracy as gold standard utilizing DRR and CT obtained volumetric bone models. Furthermore, utilizing synthetic generated volumetric implant models could not improve the silhouettebased method. However, with a slight loss of accuracy the autorsa methods provide a feasible automated alternative to the semi-automated method.

The Pivot-shift test is a clinical test for knee instability for patinets with Anterior cruciate ligament (ACL), however the test has low inter-observer reliability. Dynamic radiostereometry (dRSA) imaging is a highly precise method for objective evaluation of joint kinematics. The purpose of the study was to quantify precise knee kinematics during Pivot-shift test by use of the non-invasive dynamic RSA imaging.Eight human donor legs with hemipelvis were evaluated. Ligament lesion intervention of the ACL was performed during arthroscopy and anterolateral ligament (ALL) section was performed as a capsular incision. Pivot-shift test examination was recorded with dRSA on ligament intact knees, ACL-deficient knees and ACL+ALL-deficient knees.A Pivot-shift pattern was identifyable after ligament lesion as a change in tibial posterior drawer velocity from 7.8 mm/s in ligament intact knees, to 30.4 mm/s after ACL lesion, to 35.1 mm/s after combined ACL-ALL lesion. The anterior-posterior drawer excursion increased from 2.8 mm in ligament intact knees, to 7.2 mm after ACL lesion, to 7.6 mm after combined lesion. Furthermore a change in tibial rotation was found, with increasing external rotation at the end of the pivot-shift motion going from intact to ACL+ALL-deficient kneesThis experimental study demonstrates the feasibility of RSA to objectively quantify the kinematic instability patterns of the knee during the Pivot-shift test. The dynamic parameters found through RSA displayed the kinematic changes from ACL to combined ACL-ALL ligament lesion.