Interlaboratory comparison of femur surface reconstruction from CT data compared to reference optical 3D scan.

BACKGROUND: The present study contrasts the accuracy of different reconstructed models with distinctive segmentation methods performed by various experts. Seven research groups reconstructed nine 3D models of one human femur based on an acquired CT image using their own computational methods. As a reference model for accuracy assessment, a 3D surface scan of the human femur was created using an optical measuring system. Prior to comparison, the femur was divided into four areas; "neck and greater trochanter", "proximal metaphysis", "diaphysis", and "distal metaphysis". The deviation analysis was carried out in GEOMAGIC studio v.2013 software. RESULTS: The results revealed that the highest deviation errors occurred in "neck and greater trochanter" area and "proximal metaphysis" area with RMSE of 0.84 and 0.83 mm respectively. CONCLUSION: In conclusion, this study shows that the average deviation of reconstructed models prepared by experts with various methods, skills and software from the surface 3D scan is lower than 0.79 mm, which is not a significant discrepancy.

Biomechanical comparison of anatomical plating systems for comminuted distal humeral fractures.

PURPOSE: Six different mono-axial and poly-axial distal humeral plating systems with an anatomical plate design were compared. The aim of the biomechanical tests was to examine differences regarding system stiffness, median fatigue limit, and failure mechanisms. METHODS: Different configurations of two double plate fixation systems by two manufacturers for the treatment of complex distal humeral fractures (AO/OTA type C2.3) were biomechanically tested in a physiologically relevant setup. RESULTS: The 180° Stryker configuration presented itself as the system with the highest stiffness, being significantly stiffer (p < 0.001) than every system other than the poly-axial 180° aap system (p = 0.378). For the median fatigue limit the 180° Stryker and poly-axial aap systems were ranked first and second. The failure mechanism for all 90° systems was a fatigue breakage of the posterolateral plate. The 180° aap systems demonstrated breakage of the most distal screws of the lateral plate. The 180° Stryker system demonstrated screw breakage on both the medial and lateral plates. DISCUSSION: Breakage of the posterolateral plate as a failure mechanism for the 90° systems was expected. The 180° systems demonstrated a higher stiffness compared to the 90° constructs for the axial loading. In conclusion, both poly-axial anatomical plating systems provide sufficient stability in this scenario, and the 180° configurations demonstrated superior stiffness.

Daily subcutaneous Teriparatide injection increased bone mineral density of newly formed bone after tibia distraction osteogenesis, a randomized study.

Long bone defects are often treated by bone segment transport with the Ilizarov method requiring months spent with fixator mounted until bony consolidation of the newly formed bone. Shortening of consolidation would allow earlier fixator removal and earlier return to work. In pre-clinical studies parathyroid hormone, increased bone mineral density and mechanical properties of regenerate bone formed during distraction osteogenesis. Clinical studies showed that Teriparatide accelerated fracture healing in patients with osteoporotic fracture of the pelvis, hip, wrist and shoulder. We hypothesized that rhPTH(1-34) (Teriparatide) administered to patients who had undergone distraction osteogenesis, would increase mineralization of the regenerate formed during the consolidation phase. Sixteen patients with tibial defects after infection, underwent bone segment transport and at the time of docking the transport segment, were randomized to 8 weeks treatment with daily subcutaneous 0.20-µg Teriparatide injection followed by 8 weeks with no treatment, or to 8 weeks with no treatment followed by 8 weeks with daily subcutaneous 0.20 µg Teriparatide injection. Bone mineral density (BMD) of the regenerate was measured at the time of docking, 8 weeks after docking and 16 weeks after docking with DEXA. Functional evaluation was performed after one year. The design was a cross-over study. Overall BMD increased 0.14 g/cm2 in 8 weeks without treatment and 0.33 g/cm2 under Teriparatide treatment. After adjustment for a potential phase difference, 8 weeks of Teriparatide treatment led to an additional 0.19 g/cm2 BMD increase (95%-CI:[0.11,0.28], p < 0.001). The ratio of the BMD increase between the two treatments was 0.33/0.14 = 2.43 (CI: [1.21,3.65]). Teriparatide treatment during the consolidation phase of distraction osteogenesis doubled the mineralization rate of the regenerate when compared to no treatment.

Relation between the amount of daily activity and gait quality in transfemoral amputees.

Gait variability is often associated with reduced coordination and increased instability during walking. Especially for patients with musculoskeletal conditions, variability in gait might be associated with the level of daily activity. Therefore, this study examines kinematic variability during walking and the association with daily activity in patients with transfemoral amputation. Therefore, 15 transfemoral amputees, using the C-leg prosthesis of Otto Bock, between 18 and 65 years were recruited during their hospital stay. All patients were able to walk without crutches in everyday life and were familiar with walking using the C-leg system. Gait parameters and data of variability were captured during walking in a gait laboratory by eight infrared cameras (Vicon). Daily activity was assessed using a three-dimensional acceleration sensor of VitaMove. Patients showed variability from 0.84° up to 1.96° in frontal pelvis motion and from 0.9° up to 4.02° in trunk obliquity. The results show a significant correlation between activity and variability in trunk (r = -0.58; P ≤ 0.05) and pelvis (r = -0.63; P ≤ 0.01) as well as gait velocity (r = 0.6; P ≤ 0.05). However, kinematic variability and gait velocity are not related to each other. In conclusion, the results show that kinematic gait variability is associated with the extent of activity and therefore presents an important parameter for assessing amputees' gait quality and daily activity.

A round-robin finite element analysis of human femur mechanics between seven participating laboratories with experimental validation.

Finite element analysis is a common tool that has been used for the past few decades to predict the mechanical behavior of bone. However, to our knowledge, there are no round-robin finite element analyses of long human bones with more than two participating biomechanics laboratories published yet, where the results of the experimental tests were not known in advance. We prepared a fresh-frozen human femur for a compression test in a universal testing machine measuring the strains at 10 bone locations as well as the deformation of the bone in terms of the displacement of the loading point at a load of 2 kN. The computed tomography data of the bone with a calibration phantom as well as the orientation of the bone in the testing machine with the according boundary conditions were delivered to seven participating laboratories. These were asked to perform a finite element analysis simulating the experimental setup and deliver their results to the coordinator without knowing the experimental results. Resultantly, four laboratories had deviations from the experimentally measured strains of less than 40%, and three laboratories had deviations of their numerically determined values compared to the experimental data of more than 120%. These deviations are thought to be based on different material laws and material data, as well as different material mapping methods. Investigations will be conducted to clarify and assess the reasons for the large deviations in the numerical data. It was shown that the precision of finite element models of the human femur is not yet as developed as desired by the biomechanics community.

Variability in trunk and pelvic movement of transfemoral amputees using a C-leg system compared to healthy controls.

OBJECTIVE: Gait variability is a measure of gait disturbance, and therefore constitutes a useful parameter for gait assessment as well as planning of therapeutic and medical interventions. To date, variability during walking has not been adequately analyzed in amputees. The aim of this examination was to evaluate trunk and pelvic movement variability in transfemoral amputees. The effect of different types of walking surfaces on variability in trunk and pelvic movement was also studied. METHOD: This prospective clinical examination compares 20 transfemoral amputees (17 ♂, 42 ±â€¯16 years; 3 ♀, 48 ±â€¯3 years) with a group of 20 age and mass matched healthy controls regarding the extent of variability in trunk and pelvic movement. Kinematic data of trunk and pelvic movement during walking on level, uneven ground and slope was captured by eight infrared cameras (Vicon Nexus ™, Oxford, UK). Variability in trunk and pelvic movement was analyzed. Univariate ANCOVA and ANOVA with repeated measures and post hoc tests were used for statistical comparison. Fall history was retrospectively collected from medical history to assess the association between falls and variability in trunk and pelvic movement. RESULTS: Trunk and pelvic movement variability in amputees was significantly higher during walking on uneven ground and slope compared to healthy controls (p ≤ 0.05). Variability in trunk and pelvic movement was increased during walking on uneven ground and slope compared to even ground for both groups (p ≤ 0.05). CONCLUSION: Amputees showed increased trunk and pelvic movement variability during walking on uneven ground and slope, indicating an affected gait pattern in comparison to healthy controls. Therefore, trunk and pelvic movement variability could be a potential marker for gait quality with diagnostic implications.

Biomechanical comparison of a novel monocortical and two common bicortical external fixation systems regarding rigidity and dynamic stability.

AIM: To biomechanically compare a monocortical single frame external fixator (Orthofix UNYCO) with two bicortical fixator systems (dual frame: Stryker Hoffmann and single frame: Synthes LEF) with respect to system rigidity and stability under cyclic loading. METHODS: The fixator systems were assessed for axial rigidity under loads which would occur clinically during fixator application and dynamic stability (cyclic fatigue) under loads which would occur in the first week postoperatively. Tests were performed on porcine tibiae (n>5 per group) with characteristic frame configurations. Loads were applied with an electrodynamic material testing machine and pin and frame deformations were continuously monitored with a marker based motion capturing system. RESULTS: The bicortical single frame fixator revealed the largest rigidity (276±55) N/mm and was 20% (p=0.116) stiffer compared to the bicortical dual frame configuration and 39% (p=0.003) stiffer compared to the monocortical system. All systems survived 4000 cycles of loading, with the smallest vertical displacement (2.44±0.54 mm) observed for the bicortical dual frame system, followed by the monocortical single frame (3±0.55 mm, p=0.85) and bicortical single frame (3.25±0.96 mm, p=0.215). CONCLUSION: The monocortical fixation system performed comparably to the bicortical systems for its intended use as a temporary treatment before a definitive fracture osteosynthesis by plating or nailing.

Unicortical self-drilling external fixator pins reduce thermal effects during pin insertion.

INTRODUCTION: External fixation is associated with the risk of pin loosening and pin infection potentially associated to thermal bone necrosis during pin insertion. OBJECTIVE: This study aims to investigate if the use of external fixator systems with unicortical pins reduces the heat production during pin insertion compared to fixators with bicortical pins. METHODS: Porcine bone specimens were employed to determine bone temperatures during insertion of fixator pins. Two thermographic cameras were used for a simultaneous temperature measurement on the bone surface (top view) and a bone cross-section (front view). Self-drilling unicortical and bicortical pins were inserted at different rotational speeds: (30-600) rpm. Maximum and mean temperatures of the emerging bone debris, bone surface and bone cross-section were analyzed. RESULTS: Maximum temperatures of up to 77 ± 26 °C were measured during pin insertion in the emerging debris and up to 42 ± 2 °C on the bone surface. Temperatures of the emerging debris increased with increasing rotational speeds. Bicortical pin insertion generated significantly higher temperatures at low insertion speed (30 rpm) CONCLUSION: The insertion of external fixator pins can generate a considerable amount of heat around the pins, primarily emerging from bone debris and at higher insertion speeds. Our findings suggest that unicortical, self-drilling fixator pins have a decreased risk for thermal damage, both to the surrounding tissue and to the bone itself.

A systematic review of trials investigating strength training in schizophrenia spectrum disorders.

This systematic review analyzed strength training (ST) in patients with schizophrenia. Two independent reviewers searched PubMed and CENTRAL. Only two studies reported on the effects of isolated ST. ST with a single exercise did not improve psychopathology but walking performance. ST for several large muscle groups significantly improved muscle strength and psychopathology. To date, no treatment recommendations can be made for ST. Consistent with recommendations for healthy people combined strength and endurance training can be recommended for schizophrenia. For higher transparency regarding trainings aspects, we recommend for future studies to use the sport science checklist proposed in this paper.