Human Shoulder Research Articles

Biomechanical comparison of single versus double plate osteosynthesis in acromion type III fractures.

One of complications of the reverse shoulder arthroplasty is acromion fractures, and its therapy is controversial. The aim of the study was to investigate the double-plate osteosynthesis for these fractures. An acromion type III fracture according to classification of Levy was simulated in 16 human shoulder cadavers, and the specimens were randomly divided into two groups. Single-plate osteosynthesis was performed in the first group (locking compression plate) and double-plate osteosynthesis (locking compression plate and one-third tubular locking plate) in the second group. Biomechanical testing included cycling load and load at failure on a material testing machine. During the test, the translation was measured using an optical tracking system. The load at failure for the single-plate osteosynthesis was 167 N and for the double-osteosynthesis 233.7 N (P = 0.328). The average translation was 11.1 mm for the single-plate osteosynthesis and 16.4 mm for the double-plate osteosynthesis (P = 0.753). The resulting stiffness resulted in 74.7 N/mm for the single-plate osteosynthesis and 327.9 N/mm for the double-plate osteosynthesis (P = 0.141). Results of the biomechanical study showed that double-plate osteosynthesis had biomechanical properties similar to those of single-plate osteosynthesis for an acromion type III fracture at time point zero. The missing advantages of double-plate osteosynthesis can be explained by the choice of plate configuration.

A Novel Passive Shoulder Exoskeleton Using Link Chains and Magnetic Spring Joints.

Work-related musculoskeletal disorders represent a major occupational disability issue, and 53.4% of these disorders occur in the back or shoulders. Various types of passive shoulder exoskeletons have been introduced to support the weight of the upper arm and work tools during overhead work, thereby preventing injuries and improving the work environment. The general passive shoulder exoskeleton is constructed with rigid links and joints to implement shoulder rotation, but there exists a challenge to align with the flexible joint movements of the human shoulder. Also, a force-generating part using mechanical springs require additional mechanical components to generate torque similar to the shoulder joint, resulting in increased overall volume and inertia to the upper arm. In this study, we propose a new type of passive shoulder exoskeleton that uses magnetic spring joint and link chain. The redundant degrees of freedom in the link chains enables to follow the shoulder joint movement in the horizontal direction, and the magnetic spring joint generates torque without additional parts in a compact form. Conventional exoskeletons experience a loss in the assisting torque when the center of shoulder rotation changed during arm elevation. Our exoskeleton minimizes the torque loss by customizing the installation height and initial angle of the magnetic spring joint. The performances of the proposed exoskeleton were verified by an electromyographic evaluation of shoulder-related muscles in overhead work and box lifting task.

Sensory innervation of the human shoulder joints in healthy and in chronic pain shoulder syndromes

BackgroundAfferent innervation of shoulder joints plays a fundamental role in nociception and mechanoception and its alteration result in shoulder´s disease that course with pain and functional disability. MethodsJoints shoulder from healthy subjects (n = 20) and with chronic pain shoulder syndromes (n = 17) were analyzed using immunohistochemistry for S100 protein to identify nerve structures (nerve fibers and sensory corpuscles), coupled with a quantification of the sensory formations. Sensory nerve formations were quantified in 13 distinct areas in healthy joint shoulder and in the available equivalent areas in the pathological joints. Statistical analyses were conducted to assess differences between healthy shoulder and pathological shoulder joint (p< 0.05). ResultsAll analyzed structures, i.e., glenohumeral capsule, acromioclavicular capsule, the extraarticular structures (subcoracoid region and subacromio-subdeltoid bursa) and intraarticular structures (biceps brachii tendon and labrum articulare) are variably innervated except the extrinsic coracoacromial ligament, which was aneural. The afferent innervation of healthy human shoulder joints consists of free nerve endings, simple lamellar corpuscles and Ruffini’s corpuscles. Occasionally, Golgi-Mazzoni’s and Pacinian corpuscles were found. However, the relative density of each one varied among joints and/or the different zones within the same joint. As a rule, the upper half and anterior half of healthy glenohumeral capsules have a higher innervation compared to the lower and posterior respectably. On the other hand, in joints from subjects suffering chronic shoulder pain, a reduced innervation was found, involving more the corpuscles than free nerve endings. ConclusionsOur findings report a global innervation map of the human shoulder joints, especially the glenohumeral one, and this knowledge might be of interest for arthroscopic surgeons allowing to develop more selective and unhurt treatments, controlling the pain, and avoiding the loss of afferent innervation after surgical procedures. To the light of our results the postero-inferior glenohumeral capsular region seems to be the more adequate to be a surgical portal (surgical access area) to prevent nerve lesions.

The Construction of Teaching Effect Indicator Management System for Wushu Courses in Colleges and Universities Oriented by “Internet+Education”

Abstract In this paper, the simpler wavelet transform method is used to remove the Gaussian noise contained in the image, reconstruct the approximation signal and the final processed detail signal, and obtain the estimated value of the noise signal to complete the image preprocessing. In the process of human static feature extraction, due to the structural limitations of the human body shoulder joint activity angle is low. Therefore, the local spherical coordinates are used to represent the joint angle characteristics of the human body in the static posture and, through the completion of the calculation of the distribution function of the action features of the target, to be tested to realize the recognition of the martial arts action. After completing the judgment matrix and consistency test, we finally establish the teaching effect index system for college wushu courses and analyze the teaching of ‘Internet Education’ wushu courses. The results show that the accuracy of the results of the four algorithms test dataset is stably maintained between 0.8 and 0.9, DNN algorithm, CNN algorithm, RNN algorithm, this paper’s algorithm loss average value of 1.34, 1.58, 1.75, 1.23, respectively, the combined accuracy and loss value, this paper’s algorithm compared to DNN algorithm, CNN algorithm, RNN algorithm performs better. Namely, the algorithm in this paper can accomplish action recognition with high accuracy. In the analysis of the teaching effect index evaluation of wushu course, the experts think that the matter dimension wushu course design index weight (0.800) &gt; wushu teaching system (0.200), and wushu lecturers should design the course key points before the class. In this study, through the digital construction of teaching wushu courses in colleges and universities, we can achieve long-term development.

Effect of isokinetic eccentric training on the human shoulder strength, flexibility, and muscle architecture in physically active men: A preliminary study.

Strengthening the rotator cuff muscles is important for injury prevention and rehabilitation. Since muscle fascicle length improves motor performance and is suggested to reduce the risk of injury for the hamstring, it may be an important variable to promote multidirectional changes in the function and macroscopic structure for the shoulder. Recent literature reviews overwhelmingly suggest that eccentric exercises improve fascicle length and functional measures for the lower limb. However, there is a research gap for the shoulder. Since ultrasound imaging is the most commonly used imaging technique to quantify muscle structure, but has yielded heterogeneous results in different studies, there is another issue and a research gap for the imaging method. Based on the research gaps, the purpose of this study was to evaluate the effects of standardized eccentric strength training on the function and structure of the external rotator cuff muscles using an isokinetic dynamometer and MRI. Therefore, a preliminary pre-post intervention study was conducted and 16 physically active men were recruited in October 2021. For the right shoulder, an eccentric isokinetic training was performed twice a week for almost six weeks. The primary outcome measures (external rotators) were active and passive range of motion, eccentric and concentric torque at 30, 60, and 180°/s isokinetic speed, and fascicle length and fascicle volume for the supraspinatus and infraspinatus muscles. The findings show a training effect for the absolute mean values of eccentric strength (+24%, p = .008). The torque-angle relationship increased, especially in the final phase of range of motion, although a 4% (p = .002) decrease in passive range of motion was found in the stretch test. Positive changes in muscle structure were shown for the supraspinatus muscle fascicle length (+16%, p = .003) and fascicle volume (+19%, p = .002). Based on the study results, we can conclude that eccentric isokinetic training has a significant positive effect on the shoulder. To our knowledge, this is the first eccentric training study using both isokinetic dynamometer and muscle diffusion tensor imaging to access functional and structural changes in the human shoulder rotator cuff muscles. The methods were shown to be applicable for interventional studies. Based on these results, populations such as high-performance handball players with highly trained shoulders should be included in future studies.

Does enforcing glenohumeral joint stability matter? A new rapid muscle redundancy solver highlights the importance of non-superficial shoulder muscles.

The complexity of the human shoulder girdle enables the large mobility of the upper extremity, but also introduces instability of the glenohumeral (GH) joint. Shoulder movements are generated by coordinating large superficial and deeper stabilizing muscles spanning numerous degrees-of-freedom. How shoulder muscles are coordinated to stabilize the movement of the GH joint remains widely unknown. Musculoskeletal simulations are powerful tools to gain insights into the actions of individual muscles and particularly of those that are difficult to measure. In this study, we analyze how enforcement of GH joint stability in a musculoskeletal model affects the estimates of individual muscle activity during shoulder movements. To estimate both muscle activity and GH stability from recorded shoulder movements, we developed a Rapid Muscle Redundancy (RMR) solver to include constraints on joint reaction forces (JRFs) from a musculoskeletal model. The RMR solver yields muscle activations and joint forces by minimizing the weighted sum of squared-activations, while matching experimental motion. We implemented three new features: first, computed muscle forces include active and passive fiber contributions; second, muscle activation rates are enforced to be physiological, and third, JRFs are efficiently formulated as linear functions of activations. Muscle activity from the RMR solver without GH stability was not different from the computed muscle control (CMC) algorithm and electromyography of superficial muscles. The efficiency of the solver enabled us to test over 3600 trials sampled within the uncertainty of the experimental movements to test the differences in muscle activity with and without GH joint stability enforced. We found that enforcing GH stability significantly increases the estimated activity of the rotator cuff muscles but not of most superficial muscles. Therefore, a comparison of shoulder model muscle activity to EMG measurements of superficial muscles alone is insufficient to validate the activity of rotator cuff muscles estimated from musculoskeletal models.

Analysis of the concurrent validity and reliability of five common clinical goniometric devices

Measurement errors play an important role in the development of goniometric equipment, devices used to measure range of motion. Reasonable validity and reliability are critical for both the device and examiner before and after to testing in human subjects. The objective is to evaluate the concurrent validity and reliability of five different clinical goniometric devices for the purpose of establishing an acceptable measurement error margin for a novel device. We explored the validity and inter- and intrarater reliability scores of five goniometric devices namely (i) the universal goniometer (UG), a two-armed hand-held goniometer, (ii) the inclinometer (IC), featuring a single base, fluid level, and gravity-weighted inclinometer, (iii) the digital inclinometer (DI), functioning as both a DI and dynamometer, (iv) the smartphone application (SA), employing gyroscope-based technology within a smartphone platform application and (v) the modified inclinometer (MI), a gravity pendulum-based inclinometer equipped with a specialized fixing apparatus. Measurements were obtained at 12 standard angles and 8 human shoulder flexion angles ranging from 0° to 180°. Over two testing sessions, 120 standardized angle measurements and 160 shoulder angle measurements from 20 shoulders were repetitively taken by three examiners for each device. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable change (MDC) were calculated to assess reliability and validity. Concurrent validity was also evaluated through the execution of the 95% limit of agreement (95% LOA) and Bland–Altman plots, with comparisons made to the UG. The concurrent validity for all device pairs was excellent in both study phases (ICC > 0.99, 95% LOA − 4.11° to 4.04° for standard angles, and − 10.98° to 11.36° for human joint angles). Inter- and intrarater reliability scores for standard angles were excellent across all devices (ICC > 0.98, SEM 0.59°–1.75°, MDC 1°–4°), with DI showing superior reliability. For human joint angles, device reliability ranged from moderate to excellent (ICC 0.697–0.975, SEM 1.93°–4.64°, MDC 5°–11° for inter-rater reliability; ICC 0.660–0.996, SEM 0.77°–4.06°, MDC 2°–9° for intra-rater reliability), with SA demonstrating superior reliability. Wider angle measurement however resulted in reduced device reliability. In conclusion, our study demonstrates that it is essential to assess measurement errors independently for standard and human joint angles. The DI is the preferred reference for standard angle testing, while the SA is recommended for human joint angle testing. Separate evaluations across the complete 0°–180° range offer valuable insights.

Design and Characterization of a Self-Aligning End-Effector Robot for Single-Joint Arm Movement Rehabilitation

Traditional end-effector robots for arm rehabilitation are usually attached at the hand, primarily focusing on coordinated multi-joint training. Therapy at an individual joint level of the arm for severely impaired stroke survivors is not always possible with existing end-effector robots. The Arm Rehabilitation Robot (AREBO)—an end-effector robot—was designed to provide both single and multi-joint assisted training while retaining the advantages of traditional end-effector robots, such as ease of use, compactness and portability, and potential cost-effectiveness (compared to exoskeletons). This work presents the design, optimization, and characterization of AREBO for training single-joint movements of the arm. AREBO has three actuated and three unactuated degrees of freedom, allowing it to apply forces in any arbitrary direction at its endpoint and self-align to arbitrary orientations within its workspace. AREBO’s link lengths were optimized to maximize its workspace and manipulability. AREBO provides single-joint training in both unassisted and adaptive weight support modes using a human arm model to estimate the human arm’s kinematics and dynamics without using additional sensors. The characterization of the robot’s controller and the algorithm for estimating the human arm parameters were performed using a two degrees of freedom mechatronic model of the human shoulder joint. The results demonstrate that (a) the movements of the human arm can be estimated using a model of the human arm and robot’s kinematics, (b) AREBO has similar transparency to that of existing arm therapy robots in the literature, and (c) the adaptive weight support mode control can adapt to different levels of impairment in the arm. This work demonstrates how an appropriately designed end-effector robot can be used for single-joint training, which can be easily extended to multi-joint training. Future work will focus on the evaluation of the system on patients with any neurological condition requiring arm training.

New Paradigms for Thoracic Outlet Compression and Thoracic Outlet Syndrome, with or without Complications or Sequelae: A Trans-Continental and Trans-Disciplinary Opinion Paper

The anatomy of the human shoulder predisposes the neurovascular bundle to compression at different levels of the thoracic outlet during abduction of the arm. There are four possible levels of compression at the thoracic outlet pathway: at the costo-clavicular angle, the inter-scalenic angle, under the pectoralis minor muscle or at the level of the humeral head. The positional thoracic outlet compression (TOC) often remains completely asymptomatic. When symptomatic, compressions are collectively referred to as thoracic outlet syndrome (TOS) and may require surgery if physical therapy fails to improve symptoms. The “thoracic outlet compression with complications or sequelae” (the acronym of which is “TOC-CS”, which can be simplified as “TOX”) will almost invariably lead to surgery to release the compression, and other possible treatment targeting the complications as required. There is a continuum between TOC, TOS and TOX, which are simply different clinical stages of the same mechanical issue, just like the Rutherford grades represent different stages of lower extremity arterial disease. We believe that discriminating between TOC, TOS and TOX clarifies clinical definitions and their respective treatment options. TOC is to be considered as a physiological positional phenomenon, TOS requires medical or surgical treatment and surgery should be considered as a primary option in TOX.

Three-dimensional architecture of the human subscapularis muscle in vivo

Detailed analysis of skeletal muscle architecture provides insights into skeletal muscle function. To date, measurements of the human subscapularis architecture have been limited to cadaveric measurements. In this study we demonstrate the feasibility of using anatomically constrained fibre tractography to reconstruct and quantify the 3D architecture of the human subscapularis muscle, and provide the first quantitative measurements of the architecture of the human subscapularis muscle in vivo. mDixon and diffusion tensor magnetic resonance images were obtained from the right shoulders of 20 healthy young adults. Anatomically constrained fibre tractography, in which fascicle reconstructions were forced to terminate on the internal aponeurosis of the subscapularis, was used to reconstruct muscle fibre architecture of the subscapularis muscles. Qualitatively, architectural reconstructions resembled the known subscapularis anatomy well, demonstrating face validity of the reconstructions. Muscle architectural parameters (means ± SDs) were: muscle volume 138 ± 42 cm3, fascicle length 63.6 ± 5.9 mm, physiological cross-sectional area (PCSA) 22 ± 6 cm2, and pennation angle 16 ± 2°. Architectural measurements of the subscapularis fell within the range reported in cadaver studies and were relatively insensitive to variations in fibre tractography parameters. The anatomically detailed whole-muscle reconstructions can be used to quantify the effects of joint surgery on muscle architecture and to advance computational models of the human shoulder.

Variation in human limb joint articular morphology.

Synovial joints in human limbs strike a balance between mobility, stability, and articular fit, yet little is known about how these conflicting demands pattern intraspecific variation in articular shape. In this study, we use geometric morphometrics to establish the apportionment and magnitude of morphological variance of the articular surfaces of the human shoulder, elbow, hip, and knee. We hypothesize that variances will be comparable between articulating surfaces within a joint and will be larger in joints with smaller ranges of motion, given their plurality of functional demands. Three-dimensional landmarks were taken on the articular surfaces of the glenohumeral, humeroulnar, acetabulofemoral, and tibiofemoral joints from CT scans of 200 skeletons from the University of Tennessee Donated Skeletal Collection (84 females, 116 males). Root mean-squared distances between articulations calculated from Procrustes shape coordinates were used to determine variance distributions. We found no difference in variances for each articular surface between the sexes or between left and right articular surfaces. A high range of motion is associated with greater morphological variance; however, this pattern is largely driven by the concave articular surfaces of each joint, which consistently exhibit statistically greater variance than their convex counterparts. The striking pattern of differential variance between articulating morphologies points to potential disparities in development between them. Consistently higher variance in concave surfaces may relate to chondral modeling theory for the formation of joints. Establishing intraspecific morphological variance patterns is a first step in understanding coordinated evolution among articular features.

Covariance in human limb joint articular morphology.

Limb synovial joints exhibit complex shapes that must accommodate often-antagonistic demands of function, mobility, and stability. These demands presumably dictate coordination among joint articular shapes, but the structure of morphological covariance within and among joints is unknown. This study analyzes the human shoulder, elbow, hip, and knee to determine how articular covariance is structured in relation to joint structure, accessory cartilage, and function. Surface models were created from the CT scans of 200 modern skeletons from the University of Tennessee Donated Skeletal Collection. Three-dimensional landmarks were collected on the shoulder, elbow, hip, and knee joints. Two-block partial least squares were conducted to determine associations between surfaces of conarticular shapes, functionally analogous articulations, and articulations belonging to the same bone. Except for the components of the shoulder, all conarticular pairs exhibit covariance, though the strength of these relationships appears unrelated to the amount of accessory cartilage in the joint. Only the analogous articulations of the humerus and femur exhibit significant covariance, but it is unlikely that this pattern is due to function alone. Stronger covariance within the lower limb than the upper limb is consistent broader primate patterns of within-limb integration. With the exception of the elbow, complementary joint function does not appear to promote strong covariance between articulations. Analogous humeral and femoral surfaces are also serially homologous, which may result in the articular associations observed between these bones. Broadly, these patterns highlight the indirect relationship between joint congruence and covariance.

Seamless Weft Knit Vest with Integrated Needle Sensing Zone for Monitoring Shoulder Movement: A First Methodological Study.

The integration of textile-based flexible sensors and electronic devices has accelerated the development of wearable textiles for posture monitoring. The complexity of the processes required to create a complete monitoring product is currently reflected in three main areas. The first is the sensor production process, which is complex. Second, the integration of the sensor into the garment requires gluing or stitching. Finally, the production of the base garment requires cutting and sewing. These processes deteriorate the user experience and hinder the commercial mass production of wearable textiles. In this paper, we knitted a one-piece seamless knitted vest (OSKV) utilizing the one-piece seamless knitting technique and positioned an embedded needle sensing zone (EHSZ) with good textile properties and electrical performance for monitoring human shoulder activity. The EHSZ was knitted together with the OSKV, eliminating the need for an integration process. The EHSZ exhibited good sensitivity (GF = 2.23), low hysteresis (0.29 s), a large stretch range (200%), and excellent stability (over 300 cycles), satisfying the requirement to capture a wide range of deformation signals caused by human shoulder movements. The OSKV described the common vest process structure without the stitching process. Furthermore, OSKV fulfilled the demand for seamless and trace-free monitoring while effortlessly and aesthetically satisfying the knitting efficiency of commercial garments.

Variation of temperature stratification during and after the human movement in displacement ventilation

Indoor temperature stratification can be weakened or even eliminated by human movement in displacement ventilation (DV). Thus far, the investigations of temperature destratification and stratification recovery during and after indoor human body movement are still very limited. This study investigated the influence of movement velocity (v), movement distance (A), human shoulder breadth (B), indoor heating load (P), and air change rate (ACH) on indoor temperature stratification. The concepts of the dimensionless degree of temperature destratification (φ), time required for temperature destratification (td), and time required for the recovery of temperature stratification (tr) were proposed to evaluate the robustness of such thermal stratification. The Richardson number (Ri) was a suitable dimensionless parameter for assessing the overall effects of influencing factors comprehensively. The results are as follows：(1) For the temperature destratification process during human movement, φ was linearly correlated with Ri number: φ = a × Ri. The symbol a was a dimensionless coefficient determined by boundary conditions. Likewise, there was a positive linear correlation between Ri and td. (2) For the recovery process of temperature stratification after the cessation of human movement, tr was only related to φ and indoor air change rate. tr had a negative relationship with φ when the ACH kept constant. Similarly, tr tended to a constant value when the ACH exceeded 6 h−1 with the constant φ value. This study can guide designers to strengthen the temperature stratified anti-disturbance performance by increasing the supply air volume and supply air temperature in the design stage of DV.

Design of 9-DOF humanoid arms inspired by the human’s inner shoulder to enhance versatility and workspace

Many humanoid arms have six degrees-of-freedom (DOFs), similar to the human joint configuration. Moreover, humanoid arms with 7-DOF or 8-DOF have been designed to enhance the range of motion or structural versatility. Notably, these arms exhibit structural limitations and thus cannot effectively implement versatile and complex motions such as valve closing motion. To address this problem, this paper proposes a novel 9-DOF humanoid arm, named RoK-Arm9, inspired by the human inner shoulder. Two additional joints are introduced inside the shoulder to increase the versatility and workspace. To demonstrate the superiority of RoK-Arm9 over the existing robots for complex dual-arm manipulation, we analyzed the corresponding manipulability measure, bimanual task areas, and dual-arm manipulability measure. Finally, we confirmed that the actual RoK-Arm9 can conduct the same motion as the simulation.

Biomechanical analysis of plating techniques for unstable lateral clavicle fractures with coracoclavicular ligament disruption (Neer typeIIB).

Neer type IIB lateral clavicle fractures are inherently unstable fractures with associated disruption of the coracoclavicular (CC) ligaments. Because of the high rate of nonunion and malunion, surgical fixation is recommended; however, no consensus has been reached regarding the optimal fixation method. A newplating technique using a superior lateral locking plate with anteroposterior (AP) locking screws, resulting in orthogonal fixation in the lateral fragment, has been designed to enhance stability and reduce implant failure. The purpose of this study was to biomechanically compare 3 different clavicle plating constructs within a fresh frozen human cadaveric shoulder model. Twenty-four fresh frozen cadaveric shoulders were randomized into 3 groups (n=8 specimens): group 1, lateral locking plate only (Medartis Aptus Superior Lateral Plate); group 2, lateral locking plate with CC stabilization (No. 2 FiberWire); and group 3, lateral locking plate with 2 AP locking screws stabilizing the lateral fragment. All specimens were subject to cyclic loading of 70 N for 500 cycles. Data were analyzed for gap formation after cyclic loading, construct stiffness, and ultimate load to failure, defined by a marked decrease in the load displacement curve. After 500 cycles, there was no statistically significant difference between the 3 groups in gap formation (P=.179). No specimen (0/24) failed during cyclic loading. Ultimate load to failure was significantly higher in group 3 compared to group 1 (286 N vs. 167 N; P=.022), but not to group 2 (286 N vs. 246 N; P=.604). There were no statistically significant differences in stiffness (group 1: 504 N/mm; group 2: 564 N/mm; group 3: 512 N/mm; P=.712). Peri-implant fracture was the primary mode of failure for all 3 groups, with group 3 demonstrating the lowest rate of peri-implant fractures (group 1: 6/8; group 2: 7/8; group 3: 4/8; P=.243). Biomechanical evaluation of the clavicle plating techniques showed effective fixation across all specimens at 500 cycles. The lateral locking plate with orthogonal AP locking screw fixation in the lateral fragment demonstrated the greatest ultimate failure load, followed by the lateral locking plate with CC stabilization. This new plating technique showed compatible stiffness and gap formation when compared to conventional lateral locking plates as well as plates with CC fixation. The use of orthogonal screw fixation in the distal fragment may negate against the need for CC stabilization in these types of fractures, thus minimizing surgical dissection around the coracoid and potential complications.

Biomechanical Evaluation of the Efficacy of Suture Tape Augmentation for Subscapularis Peel Repair.

Failure of a subscapularis repair construct after anatomic total shoulder arthroplasty can result in difficulty with internal rotation and an increased likelihood of dislocation. Although suture tape has been demonstrated to be an efficacious augment for tendonous repairs elsewhere in the body, it has not been investigated as a method for augmenting subscapularis peel repairs. To determine the biomechanical efficacy of suture tape augmentation for the repair of a subscapularis peel. Controlled laboratory study. Twelve human cadaveric shoulders underwent a subscapularis peel. Specimens were randomly split into 2 groups: 6 specimens underwent repair using a transosseous bone tunnel technique with 3 high-strength sutures placed with a Mason-Allen configuration (control group), and 6 specimens underwent the control repair using augmentation with 2 suture tapes placed in an inverted mattress fashion and secured to the proximal humerus using a suture anchor (augmentation group). Shoulders underwent biomechanical testing to compare repair displacement with cyclic loading, load at ultimate failure, and construct stiffness. There were no significant between-group differences in displacement after cyclic loading at the superior (P = .87), middle (P = .47), or inferior (P = .77) portions of the subscapularis tendon. Load to failure was significantly greater in the augmentation group (585.1 ± 97.4 N) than in the control group (358.5 ± 81.8 N) (P = .001). Stiffness was also greater in the augmentation group (71.8 ± 13.7 N/mm) when compared with the control group (48.7 ± 5.7 N/mm) (P = .003). Subscapularis peel repair with augmentation via 2 inverted mattress suture tapes secured with an anchor in the proximal humerus conferred significantly greater load at ultimate failure and construct stiffness when compared with a traditional repair using 3 Mason-Allen sutures. There was no difference in repair displacement with cyclic loading between the repair groups. Suture tape augmentation of subscapularis peel repairs after shoulder arthroplasty provides an effective segment to the strength of the repair.

Subject-specific computational modeling of acromioclavicular and coracoclavicular ligaments.

Disruption of the acromioclavicular joint is a common injury. Despite the different surgical procedures described for treating this injury, complications such as loss of reduction and failure of fixation remain unacceptably high. We developed a computer model of the acromioclavicular joint to better understand the biomechanical contributions of the ligaments that are typically injured. Six fresh frozen human cadaveric shoulders were tested on an AMTI VIVO 6-degree of freedom test platform to measure force-displacement in inferior translation, anteroposterior translation, and internal rotation before and after sequentially transecting the coracoclavicular and acromioclavicular ligaments. These data were used to construct computer models of each specimen. Three-dimensional computed tomographic scans were used to generate a rigid-body dynamics model using the AnyBody Modeling System. The scapula and clavicle were connected by the acromioclavicular joint capsule, the conoid ligament, and the trapezoid ligament. Subject-specific ligament properties were calculated by matching computer predictions to experimental force-displacement data. The calculated free lengths of the conoid, trapezoid, and acromioclavicular ligaments were 13.5 (±3.2), 11.8 (±2.4), and 11.0 (±2.7) mm, respectively. The calculated stiffnesses of the conoid, trapezoid, and acromioclavicular ligaments were 34.3 (±6.3), 28.4(±3.2), and 33.8 (±8.2) N/mm, respectively. Root mean square deviation (RMSD) of predicted force-displacement curves relative to experimental force-displacement curves (during inferior and anteroposterior translation) was less than 1 mm. For validation of subject-specific models, after ligament properties were calculated, the RMSD of the predicted torque over 15° of internal rotation was 12% of maximum rotational torque (average for 6 specimens). Acromioclavicular disruption results in multidirectional instability, which requires careful consideration of the individual contributions of the injured ligaments. In addition, variations in patient anatomy can significantly affect the biomechanical stability of the reconstruction. Subject-specific models can enhance our understanding of the individual and collective biomechanical contributions of the injured soft tissues to the multiaxial stability of the acromioclavicular joint. These models may also be useful for analyzing and assessing biomechanical stability after various types of surgical reconstruction.

Biomechanical and histological changes secondary to aging in the human rotator cuff: A preliminary analysis.

The high failure rate of rotator cuff repair surgeries is positively correlated with age, yet the biomechanical changes to the tendons of the rotator cuff with age have not been described. As such, we sought to benchmark and characterize the biomechanical and histopathological properties with the accompanying gene expression of human rotator cuff tendons as a function of age and histopathological degeneration. All four rotator cuff tendons from fresh human cadaver shoulders underwent biomechanical, histopathological, and gene expression analyses. Following cadaver availability, samples were grouped into Younger (i.e., less than 36 years of age, n = 2 donors) and Aged (i.e., greater than 55 years of age, n = 3 donors) as a means of characterizing and quantifying the age-related changes exhibited by the tendons. Biomechanical testing and subsequent computational modeling techniques revealed both differences in properties between tendons and greater Young's moduli in the Younger tendons (supraspinatus 3.06x, infraspinatus 1.76x, subscapularis 1.25x, and teres minor 1.32x). Histopathological scoring using the semi-quantitative Bonar scoring scheme revealed a positive correlation with age across all tendons (r = 0.508, p < 0.001). These data contextualize the biomechanical and histopathological changes to tendons that occurs naturally with aging, highlighting the innate differences in biomechanical properties of all four rotator cuff tendons, as well as the difference in their degenerative trajectories. Additionally, the histopathological scoring revealed moderate signs of degeneration within the Younger supraspinatus tendons, suggesting tissue quality may decrease in this specific tendon in patients less than 40 years old, before clinical symptoms or tears.

Biomechanical evaluation of subscapularis peel repairs augmented with the long head of the biceps tendon for anatomic total shoulder arthroplasty.

Subscapularis failure is a troublesome complication following anatomic total shoulder arthroplasty (aTSA). Commonly discarded during aTSA, the long head of the biceps tendon (LHBT) may offer an efficient and cheap autograft for the augmentation of the subscapularis repair during aTSA. The purpose of this study was to biomechanically compare a standard subscapularis peel repair to 2 methods of subscapularis peel repair augmented with LHBT. 18 human cadaveric shoulders (61±9 years of age) were used in this study. Shoulders were randomly assigned to biomechanically compare subscapularis peel repair with (1) traditional single-row repair, (2) single row with horizontal LHBT augmentation, or (3) single row with V-shaped LHBT augmentation. Shoulders underwent biomechanical testing on a servohydraulic testing system to compare cyclic displacement, load to failure, and stiffness. There were no significant differences in the cyclic displacement between the 3 techniques in the superior, middle, or inferior portion of the subscapularis repair (P>.05). The horizontal (436.7±113.3 N; P=.011) and V-shape (563.3±101.0 N; P<.001) repair demonstrated significantly greater load to failure compared with traditional repair (344.4±82.4 N). The V-shape repair had significantly greater load to failure compared to the horizontal repair (P<.001). The horizontal (61.6±8.4 N/mm; P<.001) and the V-shape (62.8±6.1; P<.001) repairs demonstrated significantly greater stiffness compared to the traditional repair (47.6±6.2 N). There was no significant difference in the stiffness of the horizontal and V-shape repairs (P=.770). Subscapularis peel repair augmentation with LHBT autograft following aTSA confers greater time zero load to failure and stiffness when compared to a standard subscapularis peel repair.