2 research outputs found

    Pelvic kinematics as confounding factor for cam hip impingement

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    The purpose of this thesis was to explore a range of biomechanical factors linked to the development of symptoms and potentially early onset hip OA in people with cam hip impingement. This was achieved through shape analysis on 3D bone models (segmented from medical images), and motion analysis performed during walking and squatting. Following ethical approval, kinematic and morphological variables were obtained from 19 pre-operative hip impingement patients and 18 healthy controls, and these were compared between groups. Patients demonstrated reduced neck-shaft-angles (-6.0°, p<.01) and increased anterior pelvic tilt during gait (+3.2°, p=.04) which are thought to predispose to impingement by decreasing the proximity between the cam and acetabular rim and making abutment more likely. The transverse pelvic plane is used to measure pelvic tilt during motion analysis, it is therefore interesting that the angle between the transverse and anterior pelvic plane is increased (+4.6°, p=.03) in patients, emphasising that the interplay between shape and function is a priority for further research. Avoidance of hip extension (-5.9°, p<.01) was also observed, which could be a compensatory mechanism to prevent further damages to the hip. Furthermore, large cams are thought to act as a mechanical constraint and limit rotation movement allowed within the acetabulum, as demonstrated by reduced peak hip internal rotation (during squat, -8.5°, p=.03). Controls were regrouped based on morphology to allow comparison between asymptomatic (CAM-; n=11) and symptomatic (CAM+, n=16) cams. Symptomatic cams have an increased width (+41.4°, p<.01), and start more superiorly (-29.4°, p<.01). Increased sagittal pelvic mobility (e.g. during a squat; -11.2° for CAM+, p<.01) is thought to be protective against hip impingement symptoms, as during high flexion angles the pelvic tilts backwards reducing the risk of abutment. These findings highlight the need to establish thresholds taking confounding factors into account.Open Acces

    Inertial measurement unit for radiation-free navigated screw placement in slipped capital femoral epiphysis surgery

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    © Springer International Publishing Switzerland 2015. Slipped Capital Femoral Epiphysis (SCFE) is a common pathologic hip condition in adolescents. In the standard treatment, a surgeon relies on multiple intra-operative fluoroscopic X-ray images to plan the screw placement and to guide a drill along the intended trajectory. More complex cases could require more images, and thereby, higher radiation dose to both patient and surgeon. We introduce a novel technique using an Inertial Measurement Unit (IMU) for recovering and visualizing the orthopedic tool trajectory in two orthogonal Xray images in real-time. The proposed technique improves screw placement accuracy and reduces the number of required fluoroscopic X-ray images without changing the current workflow. We present results from a phantom study using 20 bones to perform drilling and screw placement tasks. While dramatically reducing the number of required fluoroscopic images from 20 to 4, the results also show improvement in accuracy compared to the manual SCFE approach
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