In a synthetic humerus model of supracondylar humerus fractures, medial comminution was shown to reduce torsional stability significantly in all pin configurations. There was no statistical difference in torsional stability between 3 lateral pins and standard crossed pins in specimens with medial comminution.

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To determine the effectiveness of stereolithography modeling technologies in the surgical treatment of complex acetabular fractures, five patients with a complex fracture of the acetabulum and three patients with posterior wall fractures were considered in this study. The patients were surgically treated using an interposition template for accurate positioning of the fixation plate and screw trajectories. Intraoperative fluoroscopy confirmed precise plate placement and that all screw trajectories missed the hip joint. Fluoroscopy was only needed for confirmation of fracture reduction and for confirmation of screw location. Application of a life-size stereolithographic model of the pelvis and an interpositioning template along with the computer model of the reversed nonfractured contralateral hemipelvis provides an effective means for preoperative planning and accurate fixation of acetabular fractures. Further studies with this type of preplanning equipment may show a decrease in operative time and morbidity, decrease in radiation exposure, and improvement in accuracy of plate and screw placement.

Background Impaired postural control in Parkinson’s disease (PD) seriously compromises life quality. Although balance training improves mobility and postural stability, lack of quantitative studies on the neurophysiological mechanisms of balance training in PD impedes the development of patient-specific therapies. We evaluated the effects of a balance-training program using functional balance and mobility tests, posturography, and a postural control model. Methods Center-of-pressure (COP) data of 40 PD patients before and after a 12-session balance-training program, and 20 healthy control subjects were recorded in four conditions with two tasks on a rigid surface (R-tasks) and two on foam. A postural control model was fitted to describe the posturography data. The model comprises a neuromuscular controller, a time delay, and a gain scaling the internal disturbance torque. Results Patients’ axial rigidity before training resulted in slower COP velocity in R-tasks; which was reflected as lower internal torque gain. Furthermore, patients exhibited poor stability on foam, remarked by abnormal higher sway amplitude. Lower control parameters as well as higher time delay were responsible for patients’ abnormal high sway amplitude. Balance training improved all clinical scores on functional balance and mobility. Consistently, improved ‘flexibility’ appeared as enhanced sway velocity (increased internal torque gain). Balance training also helped patients to develop the ‘stability degree’ (increase control parameters), and to respond more quickly in unstable condition of stance on foam. Conclusions Projection of the common posturography measures on a postural control model provided a quantitative framework for unraveling the neurophysiological factors and different recovery mechanisms in impaired postural control in PD. Electronic supplementary material The online version of this article (10.1186/s12984-019-0574-0) contains supplementary material, which is available to authorized users.

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