Axillary Nerve Injury After Shoulder Dislocation: Diagnosis and Management скачать в хорошем качестве

Axillary Nerve Injury After Shoulder Dislocation: Diagnosis and Management

Join this channel to support the channel    / @nabilebraheim   The axillary nerve is the most commonly injured nerve following a shoulder dislocation, occurring in approximately 5% of cases. This injury leads to inability to abduct the shoulder due to deltoid muscle paralysis, resulting in loss of muscle tone. However, the supraspinatus muscle remains functional and can still initiate the first 15 degrees of abduction. Patients with axillary nerve injury will also present with decreased or absent sensation over the lateral shoulder. Differentiating Axillary Nerve Injury from Rotator Cuff Tear In older patients, shoulder abduction weakness following a dislocation can also be attributed to a rotator cuff tear, a condition common in this age group. This can create a diagnostic challenge. To differentiate between the two conditions, assess sensation over the lateral shoulder. Regardless of whether the rotator cuff is intact or torn, the presence or absence of lateral shoulder sensation is the key to diagnosing axillary nerve palsy. Anatomy of the Axillary Nerve The axillary nerve originates from the posterior cord of the brachial plexus (C5-C6). It traverses over the subscapularis, curves posteriorly beneath the shoulder joint capsule, and enters the quadrangular space, where it is accompanied by the posterior circumflex humeral artery. This artery is considered the primary blood supply to the humeral head. Once it exits the quadrangular space, the axillary nerve divides into: Anterior division – Travels under the deltoid muscle, innervating its anterior portion. Posterior division – Innervates the teres minor, the posterior portion of the deltoid, and the skin over the lateral shoulder. During surgical procedures, the anterior branch of the axillary nerve is located 5–7 cm distal to the lateral edge of the acromion. To prevent axillary nerve injury, avoid extending the deltoid-splitting approach beyond 5 cm below the acromion. Additionally, adduction and external rotation of the arm during surgery can move the nerve away from the surgical field. Management of Axillary Nerve Injury Initial Treatment Immobilize the arm with a sling for comfort. Initiate physical therapy to maintain range of motion and prevent stiffness. Monitor clinical progress – Most cases of neuropraxia resolve spontaneously. Electrophysiological Studies (EMG/NCS) At 3–4 weeks, the presence of biphasic waveforms suggests nerve recovery. If no improvement is seen, fibrillation potentials and P-waves indicate denervation. Long-Term Considerations Failure to regain shoulder abduction after 4–6 months, despite physical therapy, suggests a poor prognosis for spontaneous recovery. If the rotator cuff fails to compensate for the loss of the deltoid function, the condition is considered permanent. Surgical Options for Permanent Axillary Nerve Injury Nerve Exploration and Reconstruction Surgical decompression, nerve repair, or nerve grafting (e.g., sural nerve graft). Tendon Transfer (if nerve repair is not viable) Trapezius transfer to the proximal humerus Outcomes of this procedure are typically poor, with limited improvement in shoulder function. QUIZZES 1. What is the most common nerve injured in shoulder dislocations? ✅ Axillary nerve A. Musculocutaneous nerve B. Axillary nerve C. Radial nerve D. Suprascapular nerve Explanation: The axillary nerve is the most commonly injured nerve in shoulder dislocations, affecting approximately 5% of cases. 2. Which muscle is paralyzed in axillary nerve injury? ✅ Deltoid A. Supraspinatus B. Infraspinatus C. Deltoid D. Subscapularis Explanation: The deltoid muscle is innervated by the axillary nerve and is responsible for shoulder abduction beyond 15 degrees. 3. What sensory deficit is seen in axillary nerve injury? ✅ Loss of sensation over the lateral shoulder A. Loss of sensation over the lateral forearm B. Loss of sensation over the lateral shoulder C. Loss of sensation over the medial arm D. Loss of sensation over the posterior forearm Explanation: The posterior branch of the axillary nerve supplies sensation to the lateral shoulder. 4. What is the primary blood supply to the humeral head? ✅ Posterior circumflex humeral artery A. Anterior circumflex humeral artery B. Posterior circumflex humeral artery C. Suprascapular artery D. Thoracoacromial artery Explanation: The posterior circumflex humeral artery is the dominant blood supply to the humeral head. 5. How far below the acromion should a deltoid-splitting approach be limited? ✅ 5 cm A. 3 cm B. 5 cm C. 7 cm D. 10 cm Explanation: The anterior branch of the axillary nerve is located 5–7 cm distal to the lateral acromion, so exceeding 5 cm risks nerve injury.