Scapular Mechanics & Dysfunction
A patient presents with difficulty lifting their arm above 90° and a prominent medial scapular border. Which muscle is likely weak, which nerve may be injured, and why does this impair overhead motion?
Serratus anterior; long thoracic nerve; without serratus anterior, upward rotation of the scapula is impaired, limiting arm elevation.
A patient has weakness in initiating abduction of the arm (first 15°) but full strength afterward. Which muscle is torn, what nerve is affected, and why is deltoid able to compensate after 15°?
Supraspinatus; suprascapular nerve; deltoid takes over after supraspinatus initiates abduction.
A patient experiences recurrent anterior shoulder dislocations after a seizure. Which ligamentous structures are likely damaged, and how does arm position during seizure contribute?
Inferior glenohumeral ligament and anterior capsule; abduction and external rotation during seizure stress the anterior capsule.
A patient presents with weak shoulder abduction and decreased lateral arm sensation after a humeral surgical neck fracture. Which nerve is involved, and which artery runs in close proximity?
Axillary nerve; posterior circumflex humeral artery.
A patient post-stroke exhibits shoulder subluxation when sitting. Which muscles are paralyzed, what causes the subluxation, and what positioning can reduce risk?
Rotator cuff and deltoid; gravity pulls humeral head inferiorly; support with sling and proper scapular alignment reduces risk.
Following a cervical spine injury, a patient cannot retract the scapula effectively. Which muscles are likely compromised, and what is the underlying nerve root involvement?
Rhomboid major and minor; dorsal scapular nerve (C5); dorsal scapular nerve paralysis prevents scapular retraction.
An elderly patient presents with difficulty externally rotating the arm. MRI shows a tear at the greater tubercle posteriorly. Which rotator cuff muscle is likely torn, and what movement is impaired?
Infraspinatus; external rotation.
Chronic overhead activity leads to posterior shoulder pain and limited internal rotation. Which glenohumeral adaptation occurs, and how does it predispose to impingement?
Glenohumeral internal rotation deficit (GIRD) due to posterior capsule tightness; anterior-superior impingement risk increases.
During radical mastectomy, a patient develops winged scapula and difficulty elevating the arm. Which nerve was likely damaged, and which surgical landmark is critical to avoid injury?
Long thoracic nerve; lateral thoracic wall near pectoralis minor.
A swimmer develops pain during late shoulder flexion and internal rotation. Which structures are likely impinged, and what corrective exercises would you prescribe?
Supraspinatus tendon and subacromial bursa; strengthen lower trapezius and serratus anterior, stretch pectoralis minor.
During overhead throwing, excessive anterior tilting of the scapula occurs. Which muscle imbalance contributes, and what is the typical result on shoulder impingement risk?
Weak lower trapezius and serratus anterior with overactive pectoralis minor; increases subacromial impingement risk.
A baseball pitcher complains of anterior shoulder pain and instability during late cocking of throwing. Which rotator cuff and joint structures are stressed, and how does this relate to common labral injuries?
Subscapularis and supraspinatus; anterior glenohumeral capsule and superior labrum; excessive external rotation stresses the labrum, predisposing to SLAP or anterior labral tears.
A patient has a Bankart lesion. Explain the mechanism of injury, the structures involved, and the expected functional deficit.
Anterior-inferior glenoid labrum tear from anterior shoulder dislocation; results in anterior instability, especially in abduction/external rotation.
After clavicle fracture, a patient has numbness in the medial arm and forearm, with weak grip. Which trunk of the brachial plexus is injured, and why is shoulder function often spared?
A: Lower trunk (C8-T1); upper plexus (C5-C6) often intact, preserving deltoid and supraspinatus.
A patient presents with isolated weakness in scapular retraction, but arm abduction is normal. Which nerve is implicated, and what muscle is the primary mover?
Dorsal scapular nerve; rhomboid major and minor.
A patient demonstrates scapular winging when pushing against a wall, but no weakness with arm abduction. Which muscle and nerve are affected, and why does abduction remain intact?
Serratus anterior; long thoracic nerve; deltoid and rotator cuff compensate for abduction, so the deficit is subtle except during scapular stabilization tasks.
During a physical exam, a patient cannot internally rotate the humerus against resistance but can externally rotate normally. Which muscle and nerve are implicated?
Subscapularis; upper and lower subscapular nerves; internal rotation weakness isolated to subscapularis.
MRI reveals a Hill-Sachs lesion. Describe its location, mechanism, and relationship to shoulder dislocation.
Posterolateral humeral head compression fracture; occurs when humeral head impacts glenoid during anterior dislocation; can exacerbate recurrent instability.
Compression between the first rib and clavicle causes arm swelling, tingling, and cyanosis. Which structures are compressed, and what anatomical variation can predispose to this?
Subclavian vein and brachial plexus; cervical rib or scalene hypertrophy.
After shoulder dislocation, a patient reports anterior shoulder pain and catching sensation during external rotation. What imaging would you order, and what lesion is suspected?
MRI with arthrogram; Bankart lesion or SLAP tear.
fter a fracture of the medial scapular border, a patient has difficulty with downward rotation and scapular depression. Which muscles are involved, and what compensatory movement might you observe?
Rhomboids and levator scapulae; patient may elevate shoulder or use trunk rotation to assist arm movement.
Following a fall on an outstretched hand, a patient cannot abduct or externally rotate the shoulder. Which rotator cuff muscles are likely affected, and what imaging would best confirm the injury?
Supraspinatus and infraspinatus; MRI with contrast (arthrogram) to visualize tendon tears.
A patient with a torn rotator cuff and labral injury has difficulty elevating the arm above 90°. Explain the interplay of scapulohumeral rhythm and dynamic stabilization deficits.
Rotator cuff tear reduces humeral head depression, labral injury reduces stability; scapulothoracic compensation is insufficient, leading to impaired overhead motion.
After penetrating trauma to the posterior shoulder, a patient cannot extend or externally rotate the arm. Which nerve is likely injured, and what muscle is most affected?
Axillary nerve; deltoid.
In rehabilitation of rotator cuff repair, why is early passive motion emphasized over active motion, and which tendon is most vulnerable?
Minimizes stress on healing tendon; supraspinatus tendon is most commonly repaired and vulnerable to re-tear.