PECTORAL GIRDLE AND ASSOCIATED JOINTS

PECTORAL GIRDLE AND ASSOCIATED JOINTS
JOINTS
Joint is the coming together of bones or the union of bones. Joints are classified based on the uniting medium
FIBROUS JOINTS; Joints formed or union by fibrous tissue. Here there is little or no movement
CARTILAGENOUS JOINTS; Joints formed or union by cartilage. Here there is slight movement
SYNOVIAL JOINTS; Here the two uniting bones remain separate, but are held together by fibrous (ligamentous) capsule and containing synovial fluid thereby allowing free movement
Four main features of the synovial joints are;
The uniting bones are separate
They are held together by a cuff of fibrous tissue ( capsule or capsular ligament)
The capsule is lined by a synovial membrane
The opposing surfaces are covered by cartilage ( usually hyaline but sometimes fibrous)
CLASSIFICATION OF SYNOVIAL JOINT
Ball and socket; found in the hip and shoulder joints and allow movement in all plane
Ellipsoid ; found in the wrist and allows movement in all plane except the longitudinal axis
Condyloid; found in the knee joint and movement is in one plane
Saddl- shaped; found in the carpometacarpal joint of the thumb and movement is in all plane
Hinge; found in the ankle and movement is in one plane
Pivot; joint between the dens of the axis and the ring formed by the anterior arch and movement is about a longitudinal axis
Plane; found at the joint between the articular processes of the thoracic vertebrae in which joint surfaces are flat and movement is limited to slight gliding, tilting and rotation.
JOINTS ASSOCIATED WITH THE PECTORAL GIRDLE
They include; sternoclavicular joint, glenohumeral joint and the acromioclavicular joint
STERNOCLAVICULAR JOINT
TYPE OF JOINT; This is a saddle type of synovial joint although it functions like a ball and socket joint
INTODUCTION; it is the only joint between the axial skeleton and the upper limbs. This joint is divided into two parts by an articular disc which is firmly held by the anterior, posterior and the interclavicular ligaments. This joint serves as a shock absorber for all forces transmitted along the clavicle from the upper limb
ARTICULATION; This  joint’s articulation is formed by the attachment of the medial end of the clavicle to the sternum of the manubrium and the attachment below of the clavicle to the cartilage of the first costal rib
LIGAMENTS; Anterior and posterior sternoclavicular ligament which strengthens the joint anteriorly and posteriorly. Interclavicular ligament which strengthens the joint superiorly. Costoclavicular ligament which strengthens the joint inferiorly ( the first 3 are intrinsic ligaments while the last is extrinsic)
MOVEMENT; Flexion, Rotation and circumduction (adduction and abduction)
BLOOD SUPPLY; Internal thoracic artery and suprascapular artery
NERVE SUPPLY; nerve to subclavius and suprascapular nerve
CLINICAL CORRELATES; Dislocation of the joint (rare). Ankylosis of this joint – stiffening and fixation
ACROMIOCLAVICULAR JOINT
TYPE; This is a plane type of synovial joint
INTRODUCTION; In general, while sternoclavicular joint deals with the association of the clavicle and the manubrium, acromioclavicular joint deals with the association of the clavicle with the scapula. Its articular surfaces are covered by fibrocartilage and are separated by articular disc. Being a synovial joint, it is also covered by a capsule
ARTICULATION; This joint is formed by the articulation of the acromial end of the clavicle (its lateral end ) and the acromion of the scapula
LIGAMENTS; The major ligament here is the acromioclavicular ligament which strengthens the joint superiorly and the coracoclavicular ligaments (conoid ligament behind and trapezoid ligament in front) helps it to maintain its integrity. (The first ligament is intrinsic, while the second is intrinsic).
BLOOD SUPPLY; Thoracoacromial and suprascapular artery
NERVE SUPPLY; Lateral pectoral nerve and axillary nerve
CLINICAL CORRELATES; Dislocation (the joint is weak and so can be easily dislocated especially in contact sport).
GLENOHUMERAL JOINT
TYPE; This is a ball and socket type of joint
INTRODUCTION; this joint deals with the association between the humerus and the scapula (glenoid cavity of the scapula)
ARTICULATION; Its articulating surfaces are the head of the humerus and the glenoid cavity of the scapula. This articulation is further enhanced by glenoid labrum which helps to deepen the insertion
LIGAMENTS; Glenohumeral ligament which helps to thicken the capsule of this joint anteriorly. Transverse humeral ligament which forms a thickening at the margin (or strengthens the margin) as it bridges over the intertubercular groove and  converts it into a canal (it holds the synovial sheath and the tendon of biceps brachii). Coracohumeral ligament is an extracapsular structure which runs laterally from the coracoids process and blends with the upper part of the capsule and supraspinatus tendon ( this ligament strengthens the joint superiorly). Coracoacromial ligament which formed by the inferior aspect of the acromion and the coracoids process of the scapula ( it prevents upward displacement of the humerus from the glenoid cavity. Note that the first 3 ligaments are intrinsic, while the last is extrinsic
BURSAE; Subacromial / subdeltoid bursae which lies between the coracoacromial ligament and the deltoid muscle (above) and between the tendons of the supraspinatus and infraspinatus (below). Subscapular bursae which is found in the joint capsule medial to the lesser tuberosity and separates the subscapularis from the capsule. Intertubercular synovial sheath.
MUSCLES/ TENDONS; Tendons of the supraspinatus strengthens the capsule above, that of the infraspinatus and the teres minor strengthen it behind and subscapularis strengthens it in front ( these are the rotator cuff muscles).Axioappendicular and scapohumeral muscles are also associated with this joint.
BLOOD SUPPLY;  Anterior and posterior humeral circumflex artery and branches of the suprascapular artery
NERVE SUPPLY; Suprascapular nerve,axillary nerve and lateral pectoral nerve
CLINICAL CORRELATE; Dislocation ( this joint is the commonest dislocated joint of the body)