Treadmill-to-Overground Mapping of Marker Trajectory for Treadmill-Based Continuous Gait Analysis.

A treadmill was used to perform continuous walking tests in a limited space that can be covered by marker-based optical motion capture systems. Most treadmill-based gait data are analyzed based on gait cycle percentage. However, achieving continuous walking motion trajectories over time without time normalization is often required, even if tests are performed under treadmill walking conditions. This study presents a treadmill-to-overground mapping method of optical marker trajectories for treadmill-based continuous gait analysis, by adopting a simple concept of virtual origin. The position vector from the backward moving virtual origin to a targeted marker within a limited walking volume is the same as the position vector from the fixed origin to the forward moving marker over the ground. With the proposed method, it is possible (i) to observe the change in physical quantity visually during the treadmill walking, and (ii) to obtain overground-mapped gait data for evaluating the accuracy of the inertial-measurement-unit-based trajectory estimation. The accuracy of the proposed method was verified from various treadmill walking tests, which showed that the total travel displacement error rate was 0.32% on average.

Quaternion-Based Local Frame Alignment between an Inertial Measurement Unit and a Motion Capture System.

Local frame alignment between an inertial measurement unit (IMU) system and an optical motion capture system (MCS) is necessary to combine the two systems for motion analysis and to validate the accuracy of IMU-based motion data by using references obtained through the MCS. In this study, we propose a new quaternion-based local frame alignment method where equations of angular velocity transformation are used to determine the frame alignment orientation in the form of quaternion. The performance of the proposed method was compared with those of three other methods by using data with different angular velocities, noises, and alignment orientations. Furthermore, the effects of the following three factors on the estimation performance were investigated for the first time: (i) transformation concept, i.e., angular velocity transformation vs. angle transformation; (ii) orientation representations, i.e., quaternion vs. direction cosine matrix (DCM); and (iii) applied solvers, i.e., nonlinear least squares method vs. least squares method through pseudoinverse. Within our limited test data, we obtained the following results: (i) the methods using angular velocity transformation were better than the method using angle transformation; (ii) the quaternion is more suitable than the DCM; and (iii) the applied solvers were not critical in general. The proposed method performed the best among the four methods. We surmise that the fewer number of components and constraints of the quaternion in the proposed method compared to the number of components and constraints of the DCM-based methods may result in better accuracy. Owing to the high accuracy and easy setup, the proposed method can be effectively used for local frame alignment between an IMU and a motion capture system.

Wire or Hook Traction for Reducing Zygomatic Fracture

BACKGROUND: Variable methods have been introduced for reduction of the zygomatic fractures. The Dingman elevator is used widely to reduce these fractures but is inappropriate in certain types of fractures which require atypical traction vectors. We introduce and examine an alternate method of reducing zygomatic fractures using wire and hook traction. METHODS: A retrospective study was performed for all zygomatic fracture patients admitted between 2008 and 2014. Medially rotated fractures were reduced by using a wire looped through an intermaxillary screw secured on the medial side of the zygoma. Laterally rotated fractures were reduced using a hook introduced through an infrazygomatic skin incision. RESULTS: No accidental bleeding or incomplete reduction was observed in any of the cases. Postoperative imaging demonstrated proper reduction immediately after the operation. Follow-up computed tomography study at 1 month after operation also demonstrated proper reduction and healthy union across the previous site of fracture. CONCLUSION: The hook and wire method allowed precise application of traction forces across zygomatic fractures. The fractured bone fragment could be pulled in the direction precisely opposite to the vector of impact at the time of trauma. Soft tissue damage due to dissection was minimized. In particular, this method was effective in reducing rotated bone fragments and can be an alternative option to using the zygoma elevator.

Removal of Microfat Graft in Lower Eyelid with Transconjunctival Approach

PURPOSE: Microfat graft is a common procedure for correcting tear trough deformity and dark circle. Because the tissue in this area is very thin, the grafted fat, sometimes, induces palpable lumps and uneven skin contour. When it happens, the surgical removal of the grafted fat is often needed. The authors made attempt of transconjunctival approach for removal, and this made infraorbital fat repositioning possible at the same time. METHODS: 15 female patients with history of microfat graft on lower eyelid, got operation for the grafted fat removal with transconjunctival approach from April of 2009 to July of 2010. The dissection was performed in accordance with infraorbital fat repositioning surgery. Through the transconjunctival incision, knotted fat on orbital septum and orbicularis oculi muscle was removed without damage on skin. After grafted fat removal, subperiosteal space was made 1~2mm below the inferior orbital rim by elevating periosteum. With preserving orbital septum, infraorbital fat was repositioned and anchored to subperiosteal space. Finally, transconjunctival incision was closed with absorbable suture material. RESULTS: 14 patients in the study showed satisfactory results. The problems like uneven skin contour and knotted fat mass, were all solved. In only one patient, incomplete correction was observed, as bulging on her right lower eyelid still remained. One patient complained of transient numbness on lower eyelid, but there was no specific complication other than this. CONCLUSION: The authors attempted the method of transconjunctival approach to remove former grafted fat in lower eyelid and reposition infraorbital fat simultaneously. Since the study brought great results, the method would be helpful to patients and surgeons.

Donor Site Morbidity after Sural Nerve Harvesting for Peripheral Nerve Reconstruction

PURPOSE: Although the sural nerve is the most commonly used donor for autologous nerve graft, its morbidity after harvesting is sparsely investigated. The sural nerve being a sensory nerve, complications such as sensory changes in its area and neuroma can be expected. This study was designed to evaluate the donor site morbidity after sural nerve harvesting. METHODS: Among the 13 cases, who underwent sural nerve harvesting between January 2004 and August 2009, 11 patients with proper follow up were included in the study. The collected data included harvested graft length, actual length of the grafted nerve, anesthetic and paresthetic area, presence of Tinel sign and symptomatic neuroma, and scar quality. RESULTS: In 7 patients, no anesthetic area could be detected. Of the patients with a follow up period of more than 2 years, all the patients showed no anesthetic area except two cases who had a very small area of sensory deficit (225 mm2) on the lateral heel area, and large deficit (4,500 mm2) on the lateral foot aspect. The patients with a short follow up period (1~2 m) demonstrated a large anesthetic skin area (6.760 mm2, 12,500 mm2). Only one patient had a Tinel sign. This patient also showed a subcutaneous neuroma, which was visible, but did not complain of discomfort during daily activities. One patient had a hypertrophic scar in the retromalleolar area, whereas the two other scars on the calf were invisible. CONCLUSION: After a period of 2 years the size of anesthetic skin in the lateral retromalleolar area is nearly zero. It is hypothesized that the size of sensory skin deficit may be large immediately after the operation. This area decreases over time so that after 2 years the patient does not feel any discomfort from nerve harvesting.