posterior tilt and, to a lesser extent, external rotation of the scapula which may increase or maintain the volume of the subacromial space reducing the likelihood of subacromial impingement. Weakness of the serratus anterior leads to altered line of pull of the rotator cuff muscle which could increase the risk of subacromial impingement syndrome.Īlso, serratus anterior is needed for scapula upward rotation. Muscular avulsion of the serratus anterior muscle is from the less recognized causes of scapular winging. Neuropraxia of the long thoracic nerve could result from compression or stretch injuries. Other causes of isolated serratus anteiro palsy are traumas, strenrous work, athletics, anesthesia, infection and idiopathic causes. The long thoracic nerve descends across the lateral thoracic wall, making it susceptible to injury during anterolateral thorax surgeries. The most common cause of scapular winging is injury to the long thoracic nerve, leading to serratus anterior palsy. Explaining the scapular “winging” posture associated with weak serratus anterior. If this position is maintained it’d lead to adaptive shortening of the pectoralis minor muscle resulting in more scapular anterior tilt and inwards rotation. Weakness of the serrratus anterior muscle, leads to the unopposed action of the glenohumeral abductors which result in scapula downwards rotation, inwards rotation and anterior tilt during shoulder abduction and flexion. Clinical Relevance Scapular Winging ĭysfunction of the serratus anterior muscle is from the causes of scapular winging. When the shoulder blade is in fixed position, e.g : breathing after a sprint, the serratus anterior lifts the ribcage and thus supports breathing. The serratus anterior and trapezius muscles form another forcre-couple that guides scaplular posterior tilt and outwards rotation, which maintains the volume of the subacromial space. The force-couple of the serratus anterior and trapezius muscles results in scapula upwards rotation which is essential during shoulder abduction and flexion. Also in push-up plus exercise, the reverse protraction action of both serratus anterior results in lifting the trunk and ribs upwards. Scapular protraction function of serratus anterior occurs simultaneously when reaching forward or pushing objects away from the body, increasing the functional length of the arm. It also keeps the medial boarder and inferior angle of the scapula close to the thoracic wall. The main actions are protraction and upward rotation of the scapulothoracic joint, moving the scapula forward across the thoracic wall. Lateral thoracic artery, the superior thoracic artery and the thoracodorsal artery. The long thoracic nerve, which arises from C5 to C7 nerve roots of the brachial plexus. It is the most powerful and prominent part. Lower / Inferior : 4th to 9th rib → medial border and inferior angle of scapula.
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