Shoulder

Introduction

The morphological area of the shoulder (female name) allows the junction of the trunk with the upper limb than the level of the arm. It comprises several Articulation S which contributes to make of it the most mobile articulation of the human body. It makes it possible to direct the upper limb in space, allowing in particular its effector end, the Main, to ensure its roles of Préhension and communication with the environment located at its range.

Anatomy

Osteology

The articular complex of the shoulder connects four bones:

the manubrium sternal (as well as the first coast),
the Clavicle,
the Scapula ( scapula ),
the head humérale.

Myologie

The articular complex of the shoulder connects twelve principal muscles:

the Sternocleidomastoid muscle
the Trapezius muscle
the Muscle deltoïde

Separation by the delto-pectoral furrow

the large Muscle pectoral
the large Muscle notched
muscles of the Cap of the rotators:

the muscle subscapular (or sub-scapularis)
the muscle know-thorn-bush (or supra-spinatus) N°7
the muscle infraspinator (or infra-spinatus) N°8
the small Muscle round (or teres minor) N°6

the large Muscle round (or teres major) N°5 note: the large round is not regarded as belonging to the muscles of the cap of the rotators.
the Muscle rhomboïde
the large Muscle dorsal N°3

Physiology

The shoulder comprises three articulations and two surfaces slip (also called false articulations ).

Girdle scapular

Articulation sterno-costo-claviculaire

It brings into play articular surfaces toroïdes, according to the mechanical model of the Cardan joint, which will allow two degrees of freedom, in the frontal plan and the horizontal plane. However, low articular congruence introduces a third degree of freedom: axial rotation (on the transverse axis) in liability. Its physiology is complex because it depends on the movements of the following articulation.

Articulation acromio-claviculaire

It is an articulation of the shoulder which links the acromion with the clavicle. Articulation of a synovial type planes which allows a slip and rotation of the scapula on the clavicle.

Omo-sérato-thoracic articulation

The scapula (scapula) is articulated on the costal grill via a double slip surface, between the sub-scapular and the large one notched on the one hand, and the large one notched and the thoracic wall on the other hand. It is an articulation of the syssarcose type or syncarthrose. The scapulo-thoracic junction considered as an articulation is a recent notion (1907) due to work of Doctor Miramond de Laroquette.

The great mobility of the scapula makes it possible to move and direct its cavity glénoïde to very strongly increase the operating range of the upper limb. The role of the clavicle is explained by the anatomy of the thorax: with the height of the scapula, this last with an elliptic section. So when the scapula sagitalise (movement of abduction of the scapula, corresponding to the ante-projection of the stub of the shoulder), it leaves the contact of the costal grill remotely, maintained sternum by the clavicle, which acts like a fulcrum. The scapula is animated movements of abduction-adduction, rise-lowering and rotation médiale and side known as movement of bell. This terminology is copied on the other articulations but proves to be inaccurate here because it there forever of displacement in only one plan for the scapula but, taking into account the form of the thorax and the presence of the clavicle, a combination of movement around the portion of ellipse of the trunk.

Anatomical shoulder

Slip surface under-deltoïdien

It allows mainly the muscle know-thorn-bush and the trochiter to slip under the deltoïde and the vault acromio-coracoïdienne during the abduction of the upper limb.

Articulation gléno-humérale

It is a énarthrose: it implies two conversely formed spherical surfaces, which present three axes of movement and three degrees of freedom. However, anatomical reality comes to complicate this too simple theory. The cavity glénoïde of the scapula is less concave than the head humérale is convex, and its surface is much smaller, this in spite of the presence of the pad fibro-cartilagineux glénoïdien. It results from it a complex physiology which combines vertical slips and antéropostérieurs with the movements of abduction-adduction, of inflection-extension (ante and rétropulsion) and axial rotation of the humérus.

General physiology and functional anatomy of the articular complex of the shoulder

If it is traditional to measure the articular amplitudes, this practice has very little direction when the shoulder is evaluated. Indeed, the exceptional number of articulations and degrees of freedom implied in the movements of the shoulder make this measurement vague, and do not allow in any event to draw some the useful conclusions. This is why the evaluation of the shoulder is before any functional calculus. One will refine exploration by a qualitative study of the specific mobility of the articulations (freedom of movement in all the indexed axes), like by the search for extra-articular limitations.

A good comprehension of the functional anatomy of the shoulder will be thus essential with the health professional during the evaluation and of the development of the plan of treatment with the affected patient by a problem of painful shoulder.

On the level of the scapulo-thoracic articulation, the muscles large notched, rhomboïde, sternocleidomastoid and trapezoid determine the positioning of the scapula compared to the rib cage. The stabilization and the adequate positioning of the scapulo-thoracic articulation contribute to the whole of the movements of the upper limb but become essential with the movements of more than 90 degrees of inflection or abduction (for example, of the movements bringing the arm above the horizontal plane in position upright).

On the level of the articulation gléno-humérale, the muscles of the major anatomical plan (the Cap of the rotators and the long portion of the biceps) have as main role to stabilize the head humérale in the cavity glénoïde while the powerful muscles of the surface anatomical plans generate the force and speed necessary to the movement concerned. These muscles are the deltoïde, the large Muscle pectoral, the large dorsal and the large round.

At the time them movements of launching, it is the coordination of the scapulo-thoracic movement of the articulations and gléno-humérale which, combined with those of the trunk, the elbow and the wrist which makes it possible to generate an optimal speed.

Pathology

The pain with the area of the shoulder is the most frequent complaint with character musculosquelettic in medicine after the evils of back. Other than the fractures, the most frequent causes of pains to the shoulder and their principal characteristics will be described briefly hereafter.

referred pains of cervical origin: a pain with the area of the shoulder can be the result of a conflict assigning one or the other of the nervous roots to the level of their origin on the various levels of the cervical rachis and innervant the upper limb. The presence of a concomitant pain to the cervical area, an irradiation of the pain on the level of the front armlever or hand, deficiencies sensitive or driving and a bilateral pain are elements which make it possible to evoke the possibility of a pain of cervical origin.

the distorsion acromio-claviculaire (commonly called “separation of the shoulder”): It is usually the result of a direct traumatism to the area of the shoulder which produces one or more tears, to variable degrees, ligaments acromio-claviculaires and coraco-claviculaires. A traditional mechanism of distorsion acromio-claviculaire is the force antéropostérieure resulting from the contact between the shoulder and an opponent circulating in direction opposed to the hockey. It is typically associated with an important post-traumatic pain with the area antérosupérieure with the shoulder which is increased by the direct palpation of the articulation and the horizontal adduction of the arm.

the instability of the shoulder (including luxation and the subluxation)
the syndrome of fixing of the shoulder
the retractile capsulite
the tear of the cap of the rotators

Surgery of the shoulder

Prostheses of shoulder

The indications of the prosthesis of shoulder include complex traumatic pathologies of the head humérale, osteoarthritis gléno-humérale, inflammatory arthritis, necroses it avasculaire head humérale. There are various types of prosthesis:

the hémiarthroplastie consists of a replacement of the humérale part without touching with the glénoïde.
the total prosthesis consists of the replacement of the 2 components, therefore articular surface of the head humérale and glénoïde (scapula).

The reversed prosthesis is a prosthesis with a spherical component fixed at the glénoïde and a component in the shape of horn cemented with the diaphyse of the humérus.

The patching huméral is a component with a skittle which is cemented with the head humérale without fixing with the diaphyse humérale.

External bonds

Luxation of the shoulder: catch of load in the winter sports resorts, the General practitioner n°2006, February 15th 2000
Frémont, P. Desmeules, F. Shouldering the bread: practical tools for evaluating and treating has painful shoulder. Canadian Newspaper off CME , May 2003; 15 (6): 110-20.

Simple: Shoulder

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