Citations

A common complication associated with aging is the stiffening of skeletal muscles. The purpose of this study was to determine the ability of magnetic resonance elastography (MRE) to study this phenomenon in vivo. Twenty female subjects were included in the study with an age range of 50 to 70 years. Shear modulus was calculated for the tibialis anterior of each subject. There was not a significant relationship between age and shear modulus. However, three subjects had abnormally high values and were among the oldest subjects tested. There was a significant relationship between age and tissue stiffness homogeneity. More research is needed to determine whether the changes seen here are reflective of increased tissue cross-linking or related to reduced muscle quality. However, MRE shows promise as a tool to study aging-related muscle stiffness changes or to evaluate treatments to counteract these changes.

ABSTRACTThe purpose of the current study was to develop a novel technology to enhance tendon‐to‐bone interface healing by trypsinizing and mineralizing (TM) an intrasynovial tendon allograft in a rabbit bone tunnel model. Eight rabbit flexor digitorum profundus (FDP) tendons were used to optimize the trypsinization process. An additional 24 FDP tendons were stratified into control and TM groups; in each group, 4 tendons were used for in vitro evaluation of TM and 8 were transplanted into proximal tibial bone tunnels in rabbits. The samples were evaluated histologically and with mechanical testing at postoperative week 8. Maximum failure strength and linear stiffness were not significantly different between the control and TM tendons. A thin fibrous band of scar tissue formed at the graft‐to‐bone interface in the control group. However, only the TM group showed obvious new bone formation inside the tendon graft and a visible fibrocartilage layer at the bone tunnel entrance. This study is the first to explore effects of TM on the intrasynovial allograft healing to a bone tunnel. TM showed beneficial effects on chondrogenesis, osteogenesis, and integration of the intrasynovial tendon graft, but mechanical strength was the same as the control tendons in this short‐term in vivo study. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:468–474, 2015.

Pre‐surgical measurement of supraspinatus muscle extensibility is important for rotator cuff repair. The purpose of the present study was to explore the potential feasibility of a shear wave ultrasound elastography (SWE)‐based method, combined with B‐mode ultrasound, to measure the in vivo stiffness of the supraspinatus muscle non‐invasively and thus obtain key information about supraspinatus muscle extensibility. Our investigation comprised two steps. First, we determined the orientation of the supraspinatus muscle fibers in cadaveric shoulders without rotator cuff tear in order to optimize the ultrasound probe positions for SWE imaging. Second, we investigated the feasibility of quantifying the stiffness of the normal supraspinatus muscle by SWE in vivo. The supraspinatus muscle was divided into four anatomical regions: anterior superficial (AS), posterior superficial (PS), anterior deep (AD), and posterior deep (PD). Each region was examined by SWE. The SWE stiffnesses of AD, AS, PD, and PS were 40.0 ± 12.4, 34.0 ± 9.9, 32.7 ± 12.7, 39.1 ± 15.7 kPa, respectively. SWE combined with B‐Mode ultrasound imaging could be a feasible method for quantifying the local stiffness of the rotator cuff muscles. Clin. Anat. 28:213–218, 2015. © 2014 Wiley Periodicals, Inc.

AbstractTendon‐to‐bone integration is a great challenge for tendon or ligament reconstruction regardless of use of autograft or allograft tendons. We mineralized the tendon, thus transforming the tendon‐to‐bone into a “bone‐to‐bone” interface for healing. Sixty dog flexor digitorum profundus (FDP) tendons were divided randomly into five groups: (1) normal FDP tendon, (2) CaP (non‐extraction and mineralization without fetuin), (3) CaPEXT (Extraction by Na2HPO4 and mineralization without fetuin), (4) CaPFetuin (non‐extraction and mineralization with fetuin), and (5) CaPEXTFetuin (extraction and mineralization with fetuin). The calcium and phosphate content significantly increased in tendons treated with combination of extraction and fetuin compared to the other treatments. Histology also revealed a dense mineral deposition throughout the tendon outer layers and penetrated into the tendon to a depth of 200 µm in a graded manner. Compressive moduli were significantly lower in the four mineralized groups compared with normal control group. No significant differences in maximum failure strength or stiffness were found in the suture pull‐out test among all groups. Mineralization of tendon alters the interface from tendon to bone into mineralized tendon to bone, which may facilitate tendon‐to‐bone junction healing following tendon or ligament reconstruction. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1713–1719, 2013

Hip simulators are regularly used by researchers to assess total hip arthroplasty (THA) implants, range of motion, stability, and alignment of acetabular cup and stem. Previous papers have described three types of simulators: three-dimensional protractors, biaxial rocking motion (BRM) protractors, and single-axis prosthetic range-of-motion (PROM) devices. We have developed a new hip simulator in which the ROM device is completely automated in three independent axes (elevation, internal/external rotation, and plane of elevation). Coupled with the simulator, we used a FaroArm Gold Series coordinate measuring machine (CMM) to accurately align the implant components. The results show that the methodology and alignment setup are accurate and repeatable. With this simulator and digitizer, we are able to study the characteristics of numerous THA implants at various orientations of the pelvis, acetabular cup, stem, and femur.

The complex modulus E* and elastic modulus E′ of agarose gels (2% to 4%) are measured with a dynamic mechanical analyzer in frequency sweep shear sandwich mode between 0.1 and 20 Hz. The data showed that E* and E′ increase with frequency according to a power law which can be described by a fractional derivative model to characterize the dynamic viscoelasticity of the gel. The functions between the model parameters including storage modulus coefficient H and the power law exponent (β) and the agarose concentration are established. A molecular basis for the application of the fractional derivative model to gel polymers is also discussed. Such an approach can be useful in tissue culture studies employing dynamic pressurization or for validation of magnetic resonance elastography.

The specific aim of this study was to develop a quantitative method and a kinematic method to evaluate the maximal workspace of the trapeziometacarpal (TM) joint. Six fresh-frozen human cadaver hands were disarticulated 4 cm proximal to the wrist joint and used in this experiment. The three-dimensional motion data of the TM joint was collected by an electromagnetic tracking device at 30 Hz. The workspace was reconstructed according to a complete set of motion data included circumduction, flexion-extension and abduction-adduction. A spherical fitting technique was used to obtain a sphere encompassing all the motion trajectories and estimating the centre of the sphere. The surface area of the maximal TM workspace, located on the one part of the sphere surface, was calculated by surface integration. The interclass correlation coefficient values for the reliability estimation of the repeated measurements of the radius and surface area of all specimens were 0.91 and 0.98 respectively. The mean coefficients of variance of the measured radius and the surface area were 2.04 per cent and 3.65 per cent respectively. The results also showed that using a spherical model to calculate the maximal workspace as an index for assessing TM joint impairment is practical.