An In-House Computer-Aided Design and Computer-Aided Manufacturing Workflow for Maxillofacial Free Flap Reconstruction is Associated With a Low Cost and High Accuracy.

PURPOSE: In-house computer-aided surgical design and computer-aided manufacturing (CAD/CAM) can be used in oral and maxillofacial surgery for virtual surgical planning and 3-dimensional printing of patient-specific models. The purpose of this study was to measure the cost and accuracy of an in-house CAD/CAM workflow for maxillofacial free flap reconstruction. MATERIALS AND METHODS: A retrospective cohort study of patients undergoing mandibular resection and free flap reconstruction was performed between July 2017 and March 2018 in which in-house CAD/CAM was used. The predictor variable was the in-house CAD/CAM workflow. The outcome variables were in-house workflow cost, as measured by the material expenses, and accuracy, as measured by comparative distance, osteotomy angle, and surfaced overlay measurements and the root mean square (RMS) between the preoperative virtual reconstructive plan and the postoperative computed tomography scan. Additional variables evaluated were time required for in-house CAD/CAM workflow, and clinical and radiographic outcomes. RESULTS: In-house CAD/CAM was used for 26 patients undergoing mandibular resection for benign or malignant disease and free flap reconstruction with fibula (n = 24) or scapula free flap (n = 2). Overall flap success rate was 95%. The mean in-house workflow cost per case was $3.87 USD. There were no significant differences between the mean comparative distance and osteotomy angle measurements between the planned and actual mandibular reconstructions with an RMS ranging from 5.11 to 9.00 mm for distance measurements and 17.41° for the osteotomy angle measurements. The mean surface overlay difference was 1.90 mm with an RMS of 3.72 mm. CONCLUSIONS: The in-house CAD/CAM workflow is a low cost and accurate option for maxillofacial free flap reconstruction. The in-house workflow should be considered as an alternative to current practices using proprietary systems in select cases.

Influence of Power Delivery Timing on the Energetics and Biomechanics of Humans Wearing a Hip Exoskeleton.

A broad goal in the field of powered lower limb exoskeletons is to reduce the metabolic cost of walking. Ankle exoskeletons have successfully achieved this goal by correctly timing a plantarflexor torque during late stance phase. Hip exoskeletons have the potential to assist with both flexion and extension during walking gait, but the optimal timing for maximally reducing metabolic cost is unknown. The focus of our study was to determine the best assistance timing for applying hip assistance through a pneumatic exoskeleton on human subjects. Ten non-impaired subjects walked with a powered hip exoskeleton, and both hip flexion and extension assistance were separately provided at different actuation timings using a simple burst controller. The largest average across-subject reduction in metabolic cost for hip extension was at 90% of the gait cycle (just prior to heel contact) and for hip flexion was at 50% of the gait cycle; this resulted in an 8.4 and 6.1% metabolic reduction, respectively, compared to walking with the unpowered exoskeleton. However, the ideal timing for both flexion and extension assistance varied across subjects. When selecting the assistance timing that maximally reduced metabolic cost for each subject, average metabolic cost for hip extension was 10.3% lower and hip flexion was 9.7% lower than the unpowered condition. When taking into account user preference, we found that subject preference did not correlate with metabolic cost. This indicated that user feedback was a poor method of determining the most metabolically efficient assistance power timing. The findings of this study are relevant to developers of exoskeletons that have a powered hip component to assist during human walking gait.