Finite element models are used for qualitative comparison of the risk of fracture associated with clavicle tunnels in reconstruction of the coracoclavicular ligaments for treatment of high-grade acromioclavicular joint (ACJ) injury. The two-tunnel reconstruction technique is found likely to have higher fracture risk than the less anatomic single tunnel reconstruction. The models suggest that four point bending is more likely than three point bending, cantilever bending, or axial loading to differentiate the reconstruction techniques in a laboratory experiment. The results must be narrowly interpreted only in a laboratory context due to the limitations of the study.

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<div>Safe navigation of an autonomous vehicle (AV) requires a fast and correct perception of its driving environment. Meaning, the AV needs to persistently detect and track moving objects around it with high accuracy for safe navigation. These tasks of detection and tracking are performed by the AV perception system that utilizes data from sensors such as LIDARs, radars, and cameras. The majority of AVs are typically fitted with multiple sensors to create redundancy and avoid dependence on a single sensor. This strategy has been shown to yield accurate perception results when the sensors work well and are calibrated correctly. However, over time, the cumulative use of the AV or poor placement of sensors may lead to faults that need correcting. This article proposes an online algorithm that corrects the faulty perception of an AV by determining a set of transformations that would align a cluster of measurements, from a moving vehicle in the scene to a corresponding detection in an image taken by the synchronized, forward-facing camera of the AV. The correction algorithm is first tested, assuming the availability of ground truth information to correct the LIDAR, and then tested with camera images which are used to determine ground truth. The comparison metric between expected and optimal parameters is the mean absolute error (MAE). The translation, scale, and orientation errors between the expected and optimal parameters when using ground truth data in the correction algorithm are 9.41 × 10^–4 m, 3.84 × 10^–7, and 3.82 × 10^–2 degrees, respectively; and the errors for camera images are 0.414 m, 0.017, and 0.007 degrees, respectively.</div>

Objectives: Biomechanical testing supports anatomic reconstruction for high-grade acromioclavicular injuries to achieve improved stability, however, clavicle fractures have been reported following reconstruction. Thus, this study used laboratory experiments and finite element models to investigate the influence of tunnel parameters on the clavicle biomechanical performance. Methods: Composite synthetic clavicles were subjected to four-point bending on a servohydraulic load frame. Two established surgical techniques were compared; a single 3 mm tunnel technique and a double 6 mm tunnel technique. Finite element (FE) models were validated against experimental findings. Subsequent FE models explored a broad range of tunnel parameters to determine their biomechanical consequences. Results: The single tunnel (3 mm) specimens exhibited a stiffness of 19.9 ± 1.55 Nm 2 and failed at 686 ± 45.2 N through the tunnel. The double tunnel technique exhibited a stiffness of 15.8 ± 1.18 Nm 2 and failed at 390 ± 31.7 N through the medial tunnel. In FE models of the experiments (Fig. 1), the double tunnel technique has 69% of the strength of the single tunnel (vs 57% in the experiments) and failure was predicted at the medial tunnel. In 200 variations of tunnel configuration, the double tunnel technique exhibited increased stress concentration relative to a single tunnel. Larger tunnels exhibited higher stresses than smaller tunnels. Fig. 1: FE models exhibit greater stress concentration of the double 6 mm tunnel (right) technique compared to the single 3 mm tunnel (left) and technique. Conclusion:Experimental and FE results demonstrate that the double 6 mm tunnel reconstruction has a higher stress concentration than the single 3 mm tunnel technique when subjected to four-point bending. The validated FE model supports the use of small tunnels and suggests that a double tunnel configuration may have biomechanical disadvantages that must be weighed against the perceived advantages of "anatomic" reconstruction.