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Thus far, there is a lack of scientific investigation regarding the hypothesis that biomechanical factors contribute to the cross-species pathogenesis of osteochondrosis (OC). Therefore, the aim of this pilot study was to investigate whether high (peak) pressures occur in the porcine femorotibial (FT) joint. In this experimental, ex vivo study, the right hind limbs of seven weaned piglets were subjected to maximal joint excursions, as a priori radiologically estimated. Subsequently, the intra-articular pressures were measured using sensors placed in both the medial and the lateral compartments of the FT joint. The overall highest individual peak pressure was found in the lateral FT joint during maximal extension (2611 kPa; group mean ± standard deviation (SD) 982.3 ± 988.2 kPa). In the medial FT joint, the highest individual peak pressure was found during maximal adduction (1481 kPa; group mean ± SD 664.9 ± 393.2 kPa). Moreover, nearly 30% of the ex vivo peak pressures were above published thresholds for cartilage catabolism (>500 kPa/0.5 MPa), but not for interfering with cell viability (>5 MPa). In conclusion, this ex vivo study on FT joint pressures in weaned piglets showed that FT joint movements at maximal excursions are related to concomitant internal peak joint pressures. More studies should be performed to evaluate the possible biomechanical relation of these observations with osteochondrosis, which would allow the design of preventive measures in the pig industry, to avoid extreme limb movements and concomitant joint peak pressures in vivo.

Background: The forces acting on the human clavicle in vivo are difficult if not impossible to measure. The goal of this study is to quantify the forces acting on the human clavicle during shoulder abduction, forward humeral elevation and three activities of daily living using the Delft Shoulder and Elbow Model. Methods: The Delft Shoulder and Elbow Model and a computed tomography scan of a clavicle were used to calculate the forces and moments acting on the entire clavicle and on three planes within the middle third of the clavicle during the simulated movements. Findings: The largest resultant force simulated across the clavicle was 126 N during abduction. Maximum resultant moments of 2.4 Nm were identified during both abduction and forward humeral elevation. The highest forces in the middle third of the clavicle were of a compressive nature along the longitudinal axis of the clavicle, increasing to 97 N during forward humeral elevation and 91 N during abduction. Forces in opposite direction along the y-axis were identified on either side of the conoid ligament. The three simulated activities of daily living had similar ranges of forces and moments irrespective of the sagittal plane in which these activities were performed. Interpretation: Peak forces occurred at different locations on the middle third of the clavicle during different movements. The results create an understanding of the forces and their distribution across the clavicle during activities of daily living. These data may be helpful in the development of clavicular fixation devices. Level of evidence: Biomechanical study.

Contains fulltext : 171692.pdf (Publisher’s version ) (Open Access), PURPOSE: To review the ability of various types of external immobilizers to restrict cervical spine movement. METHODS: With a systematical review of original scientific articles, data on range of motion, type of used external immobilization device and risk of bias were extracted. The described external immobilization devices were grouped and the mean restriction percentage and standard deviation were calculated. Finally, each device was classified based on its ability to restrict movement of the cervical spine, according to five levels of immobilization: poor (MIL <20 %), fair (MIL 20-40 %), moderate (MIL 40-60 %), substantial (MIL 60-80 %), and nearly complete (MIL >/=80 %). RESULTS: The ability to reduce the range of motion by soft collars was poor in all directions. The ability of cervico-high thoracic devices was moderate for flexion/extension but poor for lateral bending and rotation. The ability of cervico-low thoracic devices to restrict flexion/extension and rotation was moderate, while their ability to restrict lateral bending was poor. All cranio-thoracic devices for non-ambulatory patients restricted cervical spine movement substantial in all directions. The ability of vests with non-invasive skull fixation was substantial in all directions. No studies with healthy adults were identified with respect to cranial traction and halo vests with skull pins and their ability to restrict cervical movement. CONCLUSIONS: Soft collars have a poor ability to reduce mobility of the cervical spine. Cervico-high thoracic devices primarily reduce flexion and extension, but they reduce lateral bending and rotation to a lesser degree. Cervico-low thoracic devices restrict lateral bending to the same extent as cervico-high thoracic devices, but are considerably more effective at restricting flexion, extension, and rotation. Finally, cranio-thoracic devices nearly fully restrict movement of the cervical spine.

Musculoskeletal (dys-)function relies for a large part on muscle architecture which can be obtained using Diffusion-Tensor MRI (DT-MRI) and fiber tractography. However, reconstructed tracts often continue along the tendon or aponeurosis when using conventional methods, thus overestimating fascicle lengths. In this study, we propose a new method for semiautomatic segmentation of tendinous tissue using tract density (TD). We investigated the feasibility and repeatability of this method to quantify the mean fascicle length per muscle. Additionally, we examined whether the method facilitates measuring changes in fascicle length of lower leg muscles with different foot positions. Five healthy subjects underwent two DT-MRI scans of the right lower leg, with the foot in 15° dorsiflexion, neutral, and 30° plantarflexion positions. Repeatability of fascicle length measurements was assessed using Bland–Altman analysis. Changes in fascicle lengths between the foot positions were tested using a repeated multivariate analysis of variance (MANOVA). Bland–Altman analysis showed good agreement between repeated measurements. The coefficients of variation in neutral position were 8.3, 16.7, 11.2, and 10.4% for soleus (SOL), fibularis longus (FL), extensor digitorum longus (EDL), and tibialis anterior (TA), respectively. The plantarflexors (SOL and FL) showed significant increase in fascicle length from plantarflexion to dorsiflexion, whereas the dorsiflexors (EDL and TA) exhibited a significant decrease. The use of a tract density for semiautomatic segmentation of tendinous structures provides more accurate estimates of the mean fascicle length than traditional fiber tractography methods. The method shows moderate to good repeatability and allows for quantification of changes in fascicle lengths due to passive stretch.

Contains fulltext : 171692.pdf (Publisher’s version ) (Open Access), PURPOSE: To review the ability of various types of external immobilizers to restrict cervical spine movement. METHODS: With a systematical review of original scientific articles, data on range of motion, type of used external immobilization device and risk of bias were extracted. The described external immobilization devices were grouped and the mean restriction percentage and standard deviation were calculated. Finally, each device was classified based on its ability to restrict movement of the cervical spine, according to five levels of immobilization: poor (MIL <20 %), fair (MIL 20-40 %), moderate (MIL 40-60 %), substantial (MIL 60-80 %), and nearly complete (MIL >/=80 %). RESULTS: The ability to reduce the range of motion by soft collars was poor in all directions. The ability of cervico-high thoracic devices was moderate for flexion/extension but poor for lateral bending and rotation. The ability of cervico-low thoracic devices to restrict flexion/extension and rotation was moderate, while their ability to restrict lateral bending was poor. All cranio-thoracic devices for non-ambulatory patients restricted cervical spine movement substantial in all directions. The ability of vests with non-invasive skull fixation was substantial in all directions. No studies with healthy adults were identified with respect to cranial traction and halo vests with skull pins and their ability to restrict cervical movement. CONCLUSIONS: Soft collars have a poor ability to reduce mobility of the cervical spine. Cervico-high thoracic devices primarily reduce flexion and extension, but they reduce lateral bending and rotation to a lesser degree. Cervico-low thoracic devices restrict lateral bending to the same extent as cervico-high thoracic devices, but are considerably more effective at restricting flexion, extension, and rotation. Finally, cranio-thoracic devices nearly fully restrict movement of the cervical spine.

Contains fulltext : 171692.pdf (Publisher’s version ) (Open Access), PURPOSE: To review the ability of various types of external immobilizers to restrict cervical spine movement. METHODS: With a systematical review of original scientific articles, data on range of motion, type of used external immobilization device and risk of bias were extracted. The described external immobilization devices were grouped and the mean restriction percentage and standard deviation were calculated. Finally, each device was classified based on its ability to restrict movement of the cervical spine, according to five levels of immobilization: poor (MIL <20 %), fair (MIL 20-40 %), moderate (MIL 40-60 %), substantial (MIL 60-80 %), and nearly complete (MIL >/=80 %). RESULTS: The ability to reduce the range of motion by soft collars was poor in all directions. The ability of cervico-high thoracic devices was moderate for flexion/extension but poor for lateral bending and rotation. The ability of cervico-low thoracic devices to restrict flexion/extension and rotation was moderate, while their ability to restrict lateral bending was poor. All cranio-thoracic devices for non-ambulatory patients restricted cervical spine movement substantial in all directions. The ability of vests with non-invasive skull fixation was substantial in all directions. No studies with healthy adults were identified with respect to cranial traction and halo vests with skull pins and their ability to restrict cervical movement. CONCLUSIONS: Soft collars have a poor ability to reduce mobility of the cervical spine. Cervico-high thoracic devices primarily reduce flexion and extension, but they reduce lateral bending and rotation to a lesser degree. Cervico-low thoracic devices restrict lateral bending to the same extent as cervico-high thoracic devices, but are considerably more effective at restricting flexion, extension, and rotation. Finally, cranio-thoracic devices nearly fully restrict movement of the cervical spine.

Musculoskeletal (dys-)function relies for a large part on muscle architecture which can be obtained using Diffusion-Tensor MRI (DT-MRI) and fiber tractography. However, reconstructed tracts often continue along the tendon or aponeurosis when using conventional methods, thus overestimating fascicle lengths. In this study, we propose a new method for semiautomatic segmentation of tendinous tissue using tract density (TD). We investigated the feasibility and repeatability of this method to quantify the mean fascicle length per muscle. Additionally, we examined whether the method facilitates measuring changes in fascicle length of lower leg muscles with different foot positions. Five healthy subjects underwent two DT-MRI scans of the right lower leg, with the foot in 15° dorsiflexion, neutral, and 30° plantarflexion positions. Repeatability of fascicle length measurements was assessed using Bland–Altman analysis. Changes in fascicle lengths between the foot positions were tested using a repeated multivariate analysis of variance (MANOVA). Bland–Altman analysis showed good agreement between repeated measurements. The coefficients of variation in neutral position were 8.3, 16.7, 11.2, and 10.4% for soleus (SOL), fibularis longus (FL), extensor digitorum longus (EDL), and tibialis anterior (TA), respectively. The plantarflexors (SOL and FL) showed significant increase in fascicle length from plantarflexion to dorsiflexion, whereas the dorsiflexors (EDL and TA) exhibited a significant decrease. The use of a tract density for semiautomatic segmentation of tendinous structures provides more accurate estimates of the mean fascicle length than traditional fiber tractography methods. The method shows moderate to good repeatability and allows for quantification of changes in fascicle lengths due to passive stretch.

PURPOSE: To evaluate the functional biomechanical performance of a novel anatomically shaped, polycarbonate urethane total meniscus implant.METHODS: Five human cadaveric knees were flexed between 0° and 90° under compressive loads mimicking a squat movement. Anteroposterior (AP) laxity tests were performed in 30° and 90° flexion. Meniscal kinematics and knee laxity were quantified using roentgen stereophotogrammetric analysis. Tibial cartilage contact mechanics were determined in 90° flexion. Measurements were repeated for the native medial meniscus, the implant, after total medial meniscectomy and allograft transplantation.RESULTS: The implant and allograft displayed increased posterior and medial displacements compared to the native meniscus, yet no differences were found between the implant and allograft. Meniscal condition did not affect rotational laxity. Compared to the native joint, AP laxity for the implant was increased in 30° flexion, but not in 90°. The implant reduced the mean contact pressure compared to meniscectomy but could not restore contact pressures to native meniscus levels. Compared to the native meniscus, the implant significantly increased the peak pressure, while the contact area was reduced. Contact mechanics of the implant and allograft were never statistically different.CONCLUSIONS: Biomechanical performance was similar for the implant and allograft. However, both meniscal replacements could not restore outcomes to native meniscus levels or sufficiently improve outcomes after meniscectomy. This was presumably caused by the mobility allowed by the suture-only horn fixation. The similarity of implant and allograft performance suggests that the novel implant has the biomechanical potential to serve as an alternative to meniscal allograft transplantation.

PURPOSE: To evaluate the functional biomechanical performance of a novel anatomically shaped, polycarbonate urethane total meniscus implant.METHODS: Five human cadaveric knees were flexed between 0° and 90° under compressive loads mimicking a squat movement. Anteroposterior (AP) laxity tests were performed in 30° and 90° flexion. Meniscal kinematics and knee laxity were quantified using roentgen stereophotogrammetric analysis. Tibial cartilage contact mechanics were determined in 90° flexion. Measurements were repeated for the native medial meniscus, the implant, after total medial meniscectomy and allograft transplantation.RESULTS: The implant and allograft displayed increased posterior and medial displacements compared to the native meniscus, yet no differences were found between the implant and allograft. Meniscal condition did not affect rotational laxity. Compared to the native joint, AP laxity for the implant was increased in 30° flexion, but not in 90°. The implant reduced the mean contact pressure compared to meniscectomy but could not restore contact pressures to native meniscus levels. Compared to the native meniscus, the implant significantly increased the peak pressure, while the contact area was reduced. Contact mechanics of the implant and allograft were never statistically different.CONCLUSIONS: Biomechanical performance was similar for the implant and allograft. However, both meniscal replacements could not restore outcomes to native meniscus levels or sufficiently improve outcomes after meniscectomy. This was presumably caused by the mobility allowed by the suture-only horn fixation. The similarity of implant and allograft performance suggests that the novel implant has the biomechanical potential to serve as an alternative to meniscal allograft transplantation.

In the field of tissue engineering, mechano-regulation theories have been applied to help predict tissue development in tissue engineering scaffolds in the past. For this, finite element models (FEMs) were used to predict the distribution of strains within a scaffold. However, the strains reported in these studies are volumetric strains of the material or strains developed in the extracellular matrix occupying the pore space. The initial phase of cell attachment and growth on the biomaterial surface has thus far been neglected. In this study, we present a model that determines the magnitude of biomechanical signals on the biomaterial surface, enabling us to predict cell differentiation stimulus values at this initial stage. Results showed that magnitudes of the 2D strain--termed surface strain--were lower when compared to the 3D volumetric strain or the conventional octahedral shear strain as used in current mechano-regulation theories. Results of both ?CT and CAD derived FEMs from the same scaffold were compared. Strain and fluid shear stress distributions, and subsequently the cell differentiation stimulus, were highly dependent on the pore shape. CAD models were not able to capture the distributions seen in the ?CT FEM. The calculated mechanical stimuli could be combined with current mechanobiological models resulting in a tool to predict cell differentiation in the initial phase of tissue engineering. Although experimental data is still necessary to properly link mechanical signals to cell behavior in this specific setting, this model is an important step towards optimizing scaffold architecture and/or stimulation regimes.? 2014

In the field of tissue engineering, mechano-regulation theories have been applied to help predict tissue development in tissue engineering scaffolds in the past. For this, finite element models (FEMs) were used to predict the distribution of strains within a scaffold. However, the strains reported in these studies are volumetric strains of the material or strains developed in the extracellular matrix occupying the pore space. The initial phase of cell attachment and growth on the biomaterial surface has thus far been neglected. In this study, we present a model that determines the magnitude of biomechanical signals on the biomaterial surface, enabling us to predict cell differentiation stimulus values at this initial stage. Results showed that magnitudes of the 2D strain--termed surface strain--were lower when compared to the 3D volumetric strain or the conventional octahedral shear strain as used in current mechano-regulation theories. Results of both ?CT and CAD derived FEMs from the same scaffold were compared. Strain and fluid shear stress distributions, and subsequently the cell differentiation stimulus, were highly dependent on the pore shape. CAD models were not able to capture the distributions seen in the ?CT FEM. The calculated mechanical stimuli could be combined with current mechanobiological models resulting in a tool to predict cell differentiation in the initial phase of tissue engineering. Although experimental data is still necessary to properly link mechanical signals to cell behavior in this specific setting, this model is an important step towards optimizing scaffold architecture and/or stimulation regimes.? 2014

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