Osteology of the Upper Limb (Clavicle) PDF

OSTEOLOGY OF THE UPPER LIMB (CLAVICLE) BY DR. A.O. OJEWALE 1  INTRO’  Each upper limb contains 32 bones namely:  Bones of the pectoral girdle:  Scapula, the shoulder blade (1). Clavicle, the collar bone (1). Humerus, the bone o...

OSTEOLOGY OF THE UPPER LIMB (CLAVICLE) BY DR. A.O. OJEWALE 1  INTRO’  Each upper limb contains 32 bones namely:  Bones of the pectoral girdle:  Scapula, the shoulder blade (1). Clavicle, the collar bone (1). Humerus, the bone of arm (1). Radius and ulna, the bones of forearm (2). Carpal bones, the bones of wrist (8). Metacarpals, the bones of hand (5). Phalanges, the bones of digits (fingers) (14). 2 Bones of the upper limb.  Clavicle The clavicle or collar bone is the long bone, with a slight S-shaped curve. It is located horizontally on the anterior aspect of the body at the junction of root of the neck and trunk. It articulates medially with the sternum and 1st rib cartilage and laterally with the acromion process of the scapula. It is subcutaneous. It is the only bony attachment between the trunk and upper limb. 3  Functions of the Clavicle It acts as a brace for holding the upper limb far from the trunk so that it can move freely. This allows free swing of the upper limb for various grasping acts such as holding, catching, etc. It transmits forces from the upper limb to the axial skeleton (sternum). It provides an area for the attachment of muscles. 4  The features of the clavicle It is the only long bone which lies horizontally. It has no medullary cavity. It is subcutaneous throughout its extent. It is the first bone to start ossifying (between the fifth and sixth week of intrauterine life) and last bone to complete its ossification (at 25 years). It is the only long bone which ossifies by two primary centers. It is the only long bone which ossifies in membrane except for its medial end (long bones ossify in cartilage). It may be pierced through and through by 5 cutaneous nerve (supraclavicular nerve).  Parts The clavicle consists of three parts: two ends (medial and lateral) and a shaft. Ends  The lateral (acromial) end is flattened above downwards and articulates with medial margin of the acromion process.  The medial (sternal) end is enlarged and quadrilateral. It articulates with the clavicular notch of the manubrium Right clavicle: Upper one, superior aspect; Lower one, inferior aspect. sterni. 6  Parts of the clavicle (Cont’d)  Shaft The shaft is curved. Its medial two-third is round and convex forwards, and its lateral one-third is flattened and concave forwards. The inferior surface of the shaft possesses a small longitudinal groove in its middle third. 7  Features and Attachments of the Parts of the Clavicle Lateral End/Acromial End: It is flattened above downwards. An oval facet on this end articulates with the facet on the medial margin of the acromion to form acromioclavicular joint. The lateral end provides attachment to fibrous capsule of acromioclavicular joint. 8 Right clavicle showing attachments of the muscles and ligaments:Superior surface.  Medial End/Sternal End The enlarged medial end has a saddle- shaped articular surface, which articulates with the clavicular notch of manubrium sterni to form sternoclavicular joint. It provides attachment to (a) fibrous capsule (b) articular disc, and (c) interclavicular ligament. 9 Right clavicle showing attachments of the muscles and ligaments: inferior surface  Shaft The shaft of the clavicle is divided into two parts: lateral one-third and medial two- third. The medial two-third of shaft is convex forward and lateral one-third is concave forward.  Lateral One-third It is flattened from above downwards. It has two surfaces, i.e., superior and inferior, and two borders, i.e., anterior and posterior. 10  Surfaces Superior surface: It is subcutaneous between the attachments of deltoid and trapezius. Inferior surface: It presents a conoid tubercle and trapezoid ridge, which provide attachments to conoid and trapezoid parts of coracoclavicular ligament, respectively. The conoid tubercle is located on the inferior surface near the posterior border at the junction of the lateral one-fourth and medial three-fourth of the clavicle. The trapezoid ridge extends forwards and laterally from conoid tubercle. 11  Borders Anterior border: It is concave forwards and gives origin to deltoid muscle. A small tubercle called deltoid tubercle may be present on this border. Posterior border: It is convex backwards and provides insertion to the trapezius muscle. 12 Medial Two-third of shaft of the clavicle It is cylindrical in shape and presents four surfaces: anterior, posterior, superior, and inferior. Anterior surface: It is convex forwards and gives origin to clavicular head of pectoralis major. Posterior surface: It is concave backwards and gives origin to sternohyoid muscle near its medial end.13  Cont’d Superior surface: The clavicular head of sternocleidomastoid muscle originates from medial half of this surface. Inferior surface: It presents the following features: Costoclavicular ligament is attached to an oval impression at its medial end. Subclavius muscle is inserted into the subclavian groove on this surface. Clavipectoral fascia is attached to the margins of subclavian groove. Nutrient foramen of clavicle is located on 14  Ossification of the clavicle The ossification of clavicle is membranocartilaginous. It ossifies in the membrane except its medial end which ossifies in the cartilage. The clavicle begins to ossify before any other bone in the body. It ossifies by four ossification centres-two primary centres for shaft and two secondary centres, one for each end. 15  Ossification centers of the clavicle Site of appearance Time of appearance Time of fusion Two primary centres 5-6 weeks of 45th day of IUL (medial and lateral) intrauterine life in the shaft (IUL) Secondary centre at 19-20 years (2years 25th year sternal end earlier in female) Secondary centre at 20th year Fuses immediately the acromial end (occasional) 16  Applied Anatomy Fracture of clavicle: IT is the most commonly fractured bone in the body. It commonly fractures at the junction of its lateral one-third and medial two-third due to blows to the shoulder or indirect forces, usually as a result of strong impact on the hand or shoulder, when person falls on the outstretched hand or the shoulder. When fracture occurs, the lateral fragment is displaced downward by the weight of the upper limb because trapezius alone is unable to support the weight of the upper 17  Cont’d  The fracture at the junction of lateral one-third and medial two-third occurs because: This is the weakest site. Two curvatures of clavicle meet at this site. The transmission of forces (due to impact) from the clavicle to scapula occur at this site through coracoclavicular ligament.Clavicle fracture: A, medial fragment; 18 B, lateral fragment  Cont’d Clavicular dysostosis: It is a clinical condition in which medial and lateral parts of clavicle remain separate due to non-union of two primary centers of ossification. Cleidocranial dysostosis: It is a clinical condition characterized by partial or complete absence of clavicle associated with defective