Shoulder and Humerus Injuries

1. The 2-Minute Kinematics

• Anterior Shoulder Dislocations: Accounting for more than 90% of all shoulder dislocations, these are frequently caused by a fall onto an outstretched arm that is externally rotated and abducted. The patient typically presents with the affected extremity held in adduction and internal rotation due to extreme pain.
• Posterior Sternoclavicular (SC) Dislocations: Caused by significant force (e.g., motor vehicle collisions or high-impact sports), this injury displaces the clavicle posteriorly into the superior mediastinum. This biomechanical failure is a true orthopedic emergency due to the high risk of life-threatening compression or laceration of the great vessels, trachea, and brachial plexus.
• Proximal Humerus Fractures: Often resulting from a fall, these fractures carry a catastrophic biomechanical risk: any fracture involving the anatomic neck or the articular surface may severely compromise the blood supply to the articular segment of the humeral head, risking subsequent ischemic/avascular necrosis.

2. The Bedside Action Plan

• Immediate Stabilization & Pain Control: Provide rapid analgesia and support the injured extremity in a temporary sling. Examine for any "tenting" of the skin (especially over clavicle fractures), which warns of an impending open fracture and is an absolute indication for operative reduction and fixation.
• Reduction Techniques: For anterior shoulder dislocations, the Milch technique is highly recommended as it is simple, effective, allows for reduction by a single practitioner, and can often be attempted without procedural sedation. The traction/countertraction method is also effective but requires two people. Do not use the older Hippocratic method or the Kocher maneuver, as they carry a high incidence of axillary nerve injury, humeral fractures, and capsular damage.
• Splinting Applications: Minimally displaced proximal humerus fractures should be managed with sling immobilization, ice, analgesics, and early mobilization to prevent adhesive capsulitis. Significantly angulated surgical neck fractures must be strictly immobilized in the position of presentation to avoid neurovascular tearing.

3. The Diagnostic Grid

• Targeted Physical Exam: Inspect the shoulder for a "squared off" appearance; anterior dislocations present with a prominent acromion, loss of the rounded deltoid contour, and a humeral head palpable anteroinferiorly to the glenoid.
• Mandatory Neurovascular Checks: Perform before and after any manipulation.
• Axillary Nerve: Check sensation over the lateral aspect of the shoulder (the "regimental badge" area).
• Musculocutaneous Nerve: Check sensation over the anterolateral forearm.
• Radial Nerve: Test motor function via extension of the thumb and first finger.
• Indications for CT/Angiography: If there is high concern for a vascular injury—particularly with significantly angulated surgical neck fractures or posterior SC dislocations—a CT scan with intravenous contrast is the most appropriate imaging modality.

4. The Visual Board

• Explicit X-Ray Interpretation: A complete three-view trauma series is mandatory, consisting of a true anteroposterior (AP) view (45-degree lateral), a trans-scapular lateral ("Y" view), and an axillary lateral view. The true AP is preferred because it visualizes the glenohumeral joint without bony overlap.
• Signs of Occult Injuries (The Posterior Dislocation): Posterior shoulder dislocations are frequently missed on standard imaging; you must obtain orthogonal views like the modified axillary lateral, apical oblique, or trans-scapular Y view. Missing this can result in a "locked" posterior dislocation requiring orthopedic intervention under general anesthesia.

5. The Classification Matrix

• Proximal Humeral Epiphysis (Salter-Harris): In pediatric patients, fractures of the proximal humeral epiphysis demand urgent orthopedic consultation, as this physis accounts for 80% of the longitudinal growth of the bone; mismanagement leads to significant permanent disability.
• Clavicle Fracture Stratification: Displaced middle-third clavicle fractures carry up to a 25% rate of symptomatic malunion and a 15% to 20% rate of nonunion. Type III lateral clavicle fractures carry a high risk of subsequent acromioclavicular (AC) joint osteoarthritis.

6. The Danger Zone

• Cognitive Trap (Post-Reduction Neuropathy): If a patient with a midshaft humerus fracture is placed in a sling or splint and subsequently develops new difficulty extending their thumb and first finger (radial nerve palsy), the splint must be adjusted or removed immediately to undo the offending manipulation, and the patient must be admitted for operative repair. Discharging this patient is a fatal cognitive error.
• Avascular Necrosis: Do not underestimate minimally displaced fractures of the anatomic neck; the disruption of blood flow here makes avascular necrosis of the humeral head a prime complication.
• Premature Diagnostic Closure: Do not diagnose an acute rotator cuff tear in a patient with shoulder pain and limited range of motion until a posterior glenohumeral dislocation has been definitively ruled out with adequate orthogonal X-rays.

7. Mcq Masterclass

• High-Yield "Buzzwords": "Squared off appearance" or "prominent acromion" equals anterior shoulder dislocation. "Tenting of the skin" equals surgical indication to prevent an open fracture.
• Associated Nerve Injuries: Anterior shoulder dislocations classically injure the axillary nerve (deltoid sensation) and the musculocutaneous nerve. Midshaft humerus fractures classically injure the radial nerve.
• Common Exam Distractors: Offering the Hippocratic or Kocher maneuvers as the "best" reduction technique (they are contraindicated due to iatrogenic fracture/nerve risk). Offering discharge for a new radial nerve palsy after humerus splinting (requires admission/surgery). Suggesting posterior sternoclavicular dislocations can be reduced outpatient (they are immediate life-threats).

8. The Boardroom Script

"I am consulting you for a [Patient Age]-year-old [Right/Left]-hand dominant patient who sustained a high-energy injury resulting in a [Diagnosis, e.g., displaced surgical neck humerus fracture / posterior sternoclavicular dislocation]. On examination, there is gross deformity with precise [displacement/angulation], and no evidence of skin tenting or open fracture. My mandatory neurovascular check reveals [intact/compromised] function; specifically, the axillary and radial nerve motor and sensory distributions are [intact/absent], and radial pulses are 2+ and symmetric. I have avoided contraindicated reduction maneuvers, provided targeted analgesia, and placed the arm in temporary immobilization in the position of presentation. Orthogonal radiographs confirm the diagnosis. The patient is currently stable but requires your urgent evaluation for definitive operative management."