Evaluating computational performances of hyperelastic models on supraspinatus tendon uniaxial tensile test data

It is understood that accurate modelling of the mechanical behaviour of tendon tissues is vital due to the tendon’s essential role in the facilitation of joint mobility in biological mechanisms. The supraspinatus tendon helps to maintain dynamic stability at the glenohumeral joint in conjunction with other rotator-cuff tendons, namely infraspinatus, subscapularis and teres minor. These tendons are thought to support the action of the more powerful forces that are innovated at that joint by the deltoid, pectoralis major, biceps and triceps muscles. The supraspinatus tendon is often prone to injury especially in careers or sporting activities that involve frequent arm abduction. It is therefore important to understand the mechanical behaviour of this tendon in order to devise better rehabilitation therapies in case of injury. This paper evaluates the relative modelling capabilities of three hyperelastic models, namely the Yeoh, Humphrey and Veronda-Westmann material models on the tensile behaviour of three tendon specimens. We compare their fitting accuracies, convergence rates during optimisation, and the different forms of sensitivities to data-related features and initial parameter estimates. The results show that the Yeoh model outperforms the other two hyperelastic models and therefore makes it relatively better choice for further investigation of the mechanical behaviour of tendons.

Locating the rotator cable during subacromial arthroscopy: bursal- and articular-sided anatomy.

The shoulder.

Ultrasound elastography–based assessment of the elasticity of the supraspinatus muscle and tendon during muscle contraction

BackgroundThe supraspinatus muscle and tendon are an integral part of shoulder joint function and stability. The supraspinatus tendon is one of the four tendons forming the rotator cuff in the shoulder. Supraspinatus tendon tear is a frequent lesion that occurs due to various causes like lifting heavy objects, falls onto the shoulder, a dislocation of the shoulder, swimming, trauma, sports injury, occupational activity and degenerative change. Smoking, hypercholesterolemia, and hereditary predisposition are all established risk factors for developing RC tears, which affect the age dependent tendon degeneration process. Only a few articles were found discussing the histological characteristics of degenerative change of the supraspinatus tendon in rotator cuff tears.ObjectiveTo evaluate the histological characteristics of degenerative changes in the supraspinatus tendon associated with rotator cuff tears.MethodsRotator cuff disease is a major cause of shoulder pain and shoulder dysfunction in adults; not every patient is symptomatic, though. We examined morphological features of human surgical specimens of the supraspinatus tendon in patients with full thickness tears of the rotator cuff.ResultsHistological analysis of the surgical specimen revealed significant degenerative changes, including disorganization and tearing of the collagen fiber bundles, sparingly distributed, rounded tenocytes, and increased vascularity (neovascularization) within the tendon matrix.ConclusionThese findings provide direct evidence of intrinsic tendon degeneration as a key pathological factor in full thickness rotator cuff tears, which may be helpful for future research on the pathophysiology of the condition.

A 13-year-old 128-kg miniature donkey gelding was evaluated for right forelimb lameness of 7 weeks' duration. Muscular atrophy of the infraspinatus and supraspinatus muscles over the right scapula with a palpable bony prominence over the point of the shoulder was evident. At the walk, the cranial phase of the stride was reduced with adduction of the distal aspect of the limb, dragging of the toe, and lameness (grade, 4/5). Lateral and craniocaudal radiographs of the right shoulder joint revealed lateral luxation of the humerus in relation to the scapula with bony proliferation and remodeling of the humeral head. Glenoid ostectomy was performed. Immediately after surgery, the donkey was able to intermittently stand squarely on the limb but maintained a reduced cranial phase of the stride at the walk. The donkey had no short-term complications and was discharged from the hospital 11 days after surgery. Following discharge, the donkey was confined to a box stall for 60 days, followed by a gradual increase in movement to full pasture turnout. The lameness continued to improve, and at 15 months after surgery the donkey was turned out in pasture and had mild lameness (grade, 3/5) at the trot. Mild muscular atrophy of the supraspinatus and infraspinatus muscles was present with no signs of pain on palpation or manipulation of the limb. Shoulder joint radiography at 15 months after surgery revealed remodeling of the glenoid cavity of the scapula and humeral head with formation of a pseudoarthrosis. Glenoid ostectomy should be considered as an alternative to shoulder joint arthrodesis in small equids with shoulder joint luxation. Other indications for this procedure could include chronic osteoarthritis or fractures affecting the shoulder joint.

A hyperelastic model to capture the mechanical behaviour and histological aspects of the soft tissues

Measurement of the hyperelastic properties of ex vivo brain tissue slices

Objective To assess the diagnostic value of MRI for the long head of the biceps brachii tendon tear,and to compare the diagnostic efficiency between routing MRI and MR arthrography. Methods A retrospective study was conducted in 215 cases with shoulder MR examination (107 with MR arthrography, and 108 with routing MRI) and subsequent shoulder arthrescopy and surgery. Two radiologists analyzed all MR examinations independently, and the results were compared with those of arthroscopy and surgery. Sensitivity, specificity, and accuracy were calculated. Kappa values were used to quantify the interobserver agreement. Results Based on the results of arthroacopy and surgery, 215 patients comprised 7 cases of complete tear of the long head of the biceps brachii tendon, 29 cases of partial tear, and 179 cases without tear. The overall sensitivity, specificity, and accuracy for the diagnosis of tears (complete and partial tear) of the long head of the biceps brachii tendon were 72.2% (26/36), 91.6% (164/179), and 88.4% (190/215) respectively for observer 1, 80.6% (29/36), 93.8% (168/179), and 91.6% (197/215) respectively for observer 2. The interobserver agreement was good (Kappa value=0.681). For the complete tear of the biceps brachii tendon, the sensitivity, specificity, and accuracy were all 100% (7/7), 100% (208/208), and 100% (215/215) for both observers. For the tear of the long head of the biceps brachii tendon, the accuracy of MR arthrography were 93.4% (100/107) for observer 1 and 96.3% (103/107) for observer 2. They were higher than the Accuracy of routing MRI, which were 83.3% (90/108)and 87.0% (94/108) respectively for two observers (P<0.05). Conclusion Shoulder MRI is a moderate reliable method for evaluating the tear of the long head of the biceps brachii tendon, and the accuracy of MR arthrography is found to be superior to that of routine MRI. Key words: Shoulder joint; Injuries; Magnetic resonance imaging

Safety design of robot arm is important for human-robot interaction. In this article, an anthropomorphic seven-DOF cable-driven manipulator, including a three-DOF shoulder joint module, a one-DOF elbow joint module, and a three-DOF wrist joint module, is proposed for human-robot interaction. These three joint modules are connected serially and the motion transmission is realized by rope. The joint stiffness and workspace of joint module are numerically analyzed and compared to that of the human arm joint. A protype of manipulator is machined and used to evaluate the joint stiffness and workspace of the joint module through experiments. The mass of the designed manipulator is approximately 4.8 kg, which is similar to that of a human arm. The stiffness of elbow joint is 185.25 N·m/rad in positive direction and 133.75 N·m/rad in negative direction, which is smaller than that of the human elbow joint. The stiffness of wrist joint is 48.25 N·m/rad. The stiffness of shoulder joint under two configurations is 138 and 124 N·m/rad. The workspace matching index (WMI) is used to evaluate the workspace of joint module by comparing to that of the human arm joint. The WMI of the developed shoulder joint is approximately 40% of the human shoulder joint due to the structure constraint. While the workspaces of the developed elbow joint and wrist joint are the same with that of human joint.

Several authors have proposed different parameters to include the softening effect in hyperelastic models; however, for a number of materials, softening parameters could be further improved. This article proposes a new softening parameter to include Mullins effect in hyperelastic material models. The methodology employed can be also used in cases with hysteresis or damage in a hyperelastic material, however this methodology modifies the behavior of the material differently from damage theories. Common hyperelastic constitutive models do not include dissipation effects and so the present work intends to fill this gap. Experimental data for silicone in uniaxial tensile test, equibiaxial, and pure shear tests were modeled in order to calibrate the models. The softening parameters essentially changes the constitutive law from the loading to the unloading path. Therefore, it is still necessary to use a hyperelastic model, and here Ogden and Hoss-Marczak material models were used. The obtained results show good agreement with experimental data even when simulating with a compressible finite element code and it can model isotropic Mullins effect.

Objective To discuss the effect of arthroscopic latissimus dorsi transfer with rotator cuff repair for posterosu-perior irreparable massive rotator cuff tear (iMRCT). Methods From September 2014 to December 2015, data of 13 iMRCT including 4 male and 9 female who underwent arthroscopic latissimus dorsi transfer with rotator cuff repair were retrospectively analyzed. The age was ranged from 54 to 65, with a mean age of 58.5±4.3. The mean duration of symptom was 2.1±0.6 years. During operation, complete or partial rotator cuff repair was performed, followed by complete repair of injured subscapularis tendon and tenotomy or tenodesis of the long head of biceps tendon. An arc incision was then made in the axillary fossa to harvest latissimus dorsi tendon from its humeral insertion. The tendon was then introduced into subacromial space and fixed at the footprint of greater tuberosity arthroscopically. X-ray and MRI were conducted prior to and one day after the surgery and at the last follow-up. Pain visual analog scale (VAS) and active range of motion in all planes as well as Constant-Murley score and Fudan University shoulder score (FUSS) were documented before the surgery and at the last follow-up. Results All 13 patients accomplished the follow-up, with a duration from 17 to 22 months and a mean period of 19.6±0.9 months. No complications occurred. No re-tear was identified. The mean acromiohumeral distance increased from 5.4±1.1 mm to 7.0±0.6 mm. The mean VAS decreased from 4.8±1.3 to 0.5±0.7. The mean 0° abduction external rotation, 90° abduction external rotation, flexion, as well as abduction increased from 17.3°±10.5°, 12.4°±7.8°, 89.2°±41.2°, 87.3°±40.7° to 41.2°±12.5°, 56.5°±16.6°, 120.5°±25.1°, and 113.5°±25.4° respectively. Constant-Murley score and FUSS increased from 33.5±9.9 and 50.9±7.6 to 62.8±8.1, and 81.7±7.0, respectively. The improvement in all measurements was significant. Conclusion For posterosuperior iMRCT, arthroscopic latissimus dorsi transfer with rotator cuff repair can decrease shoulder pain and improve shoulder function. Key words: Shoulder joint; Arthroscopy; Soft tissue injuries

The following conclusions can be drawn from our investigations: We could not find out isolated ruptures of the supraspinatus tendon, which were caused exclusively by injury. Mostly ruptures of the rotatory cuff develop spontaneously, the basic degenerative changes involve also the shoulder joint and the acromioclavicular joint. The term rupture of rotatory cuff is misleading, because it signals to the patient the existence of aftermath of injuries and for the most part the rupture is not found in the tendons of the rotatory muscles but in the supraspinatus tendon. The degenerative cuff defects with spontaneous ruptures must be differentiated in medical certificate from the rare rotatory cuff ruptures, which are caused by injury alone. Seldom exogenous mechanical stress may lead to an enlargement of a preexistent rupture with symptoms and clinical signs, which occur for the first time. On the promises, that an adequate injury has occurred, that roentgenographic changes deteriorated within 3 months after the injury and a degenerative defect of rotatory cuff with clinical relevance can be excluded for the time before the injury, the damage of the shoulder has to be accepted by the insurance as an injury after accident. In the most times occasional causes with inadequate injuries to the shoulder are brought up, to assert an old degenerative defect of the shoulder as an aftermath of injury. There are no interrelations between intraoperative findings and mechanism of injury. The anamnestic statement of the patient concerning earlier diseases and injuries are often unreliable.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of rotator cuff tears on reaction forces at the glenohumeral joint

Finite element modeling approaches of human cervical spine facet joint capsule