Humerus

Summary

The humerus (ˈhjuːmərəs; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a rounded head, a narrow neck, and two short processes (tubercles, sometimes called tuberosities). The body is cylindrical in its upper portion, and more prismatic below. The lower extremity consists of 2 epicondyles, 2 processes (trochlea & capitulum), and 3 fossae (radial fossa, coronoid fossa, and olecranon fossa). As well as its true anatomical neck, the constriction below the greater and lesser tubercles of the humerus is referred to as its surgical neck due to its tendency to fracture, thus often becoming the focus of surgeons. Etymology The word "humerus" is derived from humerus, umerus meaning upper arm, shoulder, and is linguistically related to Gothic ams shoulder and Greek ōmos. Structure Upper ext

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https://en.wikipedia.org/wiki/Humerus

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Fiber distribution in a 3D FEM Model of the Supraspinatus Tendon

Romy Alexandra Hasler

The supraspinatus tendon is often involved in rotator cu↵ tears. The pathogenesis of such tears is not well known and can be multicausal (mechanical, inflammatory, ...). The idea of this project was to analyse the mechanical contribution to rotator cuff tears with a numerical deformation analysis of the supraspinatus tendon. The tendon was simulated under tension in two conditions: an isotropic case and an anisotropic case. In the isotropic case, the tendon was simulated with the same material properties in every direction. In the anisotropic case, the tendon’s fiber were computed and the material was defined in the fiber direction and in the transverse direction. In the isotropic case, the strain was found to be higher in the two studied position (90 ̊abduction and rest position) than in the anisotropic case. In both cases (isotropic and anisotropic) the maximal strain is situated at the distal side of the tendon insertion on the humeral head. The di↵erence in the strain value is due to the fact that the isotropic material definition is averaged in all direction and therefore is softer in the fiber direction and stronger in the transverse direction. The isotropic model is herefore not very consistant with a real tendon structure. Both models are consistent with clinical observations as supraspinatus tears occur usually at the distal side of the insertion. However, for qualitative deformation analysis an anisotropic material choice is recommended.

2014

Introduction: The olecranon Chevron osteotomy (OCO) is commonly used to approach complex intraarticular fractures of the distal humerus. Predrilled tension band wiring (TBW) has historically been used to fix OCO. However, clinical outcomes are burdened by secondary loss of reduction and up to 21.3% non-union rates. The biomechanical stability of anatomic locking compression plate (LCP) was reported to be superior to TBW in olecranon fracture fixation. We hypothesised that this implant may also be superior to TBW in the anatomic reconstruction of the articular surfaces of the ulnar greater sigmoid notch after OCO by predrilling the holes of the angular stable plate with the threaded drill guide prior to osteotomy. Materials and methods: Lateral standardised and calibrated radiographs of twenty synthetic ulnar bones were obtained using a custom-made holder prior to preparation by a senior orthopaedic trauma surgeon. Ten specimens were then predrilled using the threaded drill bit guide of an olecranon LCP, while the other ten samples were predrilled with two 1.6 mm Kirschner wires. A distal "V" OCO was performed using a 0.6 mm oscillating saw. After repositioning and fixation with the corresponding device, lateral radiographs were repeated. Two independent observers used the TraumaCad planning software to document the articular geometry of the ulnar greater sigmoid notch pre- and postoperatively. The diameter of the best-fitting circle (diameter), the distance between the tip of the coronoid and the olecranon processes (distance) and the maximum articular depth were measured. Results: With the TBW technique, after OCO and fixation, all three postoperative measurements were significantly (p = 0.13). Inter and intra-observer measurement reliability was strong to very strong (intraclass correlation coefficients >= 0.793) for all three variables. Conclusion: Our study reveals that the predrilled LCP technique is more accurate than the predrilled TBW in restoring the anatomic articular geometry of the ulnar greater sigmoid notch after OCO. (C) 2020 Elsevier Ltd. All rights reserved.

ELSEVIER SCI LTD2020

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The goal of the present work was assess the feasibility of using a pseudo-inverse and null-space optimization approach in the modeling of the shoulder biomechanics. The method was applied to a simplified musculoskeletal shoulder model. The mechanical system consisted in the arm, and the external forces were the arm weight, 6 scapulohumeral muscles and the reaction at the glenohumeral joint, which was considered as a spherical joint. The muscle wrapping was considered around the humeral head assumed spherical. The dynamical equations were solved in a Lagrangian approach. The mathematical redundancy of the mechanical system was solved in two steps: a pseudo-inverse optimization to minimize the square of the muscle stress and a null-space optimization to restrict the muscle force to physiological limits. Several movements were simulated. The mathematical and numerical aspects of the constrained redundancy problem were efficiently solved by the proposed method. The prediction of muscle moment arms was consistent with cadaveric measurements and the joint reaction force was consistent with in vivo measurements. This preliminary work demonstrated that the developed algorithm has a great potential for more complex musculoskeletal modeling of the shoulder joint. In particular it could be further applied to a non-spherical joint model, allowing for the natural translation of the humeral head in the glenoid fossa.

Elsevier2010

ELSEVIER SCI LTD2020