Makindo Medical Notes

ℹ️ About

• 🔗 The Acromioclavicular (AC) Joint sits at the top of the shoulder, where the acromion (part of the scapula) meets the clavicle.
• 🦴 It stabilises the shoulder girdle and allows coordinated motion of the scapula and clavicle → essential for arm elevation and rotation.
• 💥 Common site of injury in contact sports and falls.

📍 Injury Types (Rockwood Classification)

• 🔹 Type I/II: Sprain or subluxation (partial injury, ligaments stretched or partially torn)
• 🔹 Type III: Superior dislocation with complete ligament rupture → step deformity
• 🔹 Type IV–VI: Posterior or inferior displacement of clavicle (rare, but severe, with mediastinal risk)

⚡ Typical Mechanism

• 🤕 Direct fall onto the lateral shoulder (e.g. fall from bike, sports tackle)
• ⚡ Sometimes fall onto an outstretched hand can transmit force upwards

⚠️ Pitfalls & Complications

• 😣 Persistent pain, cosmetic deformity (“piano key” sign with step-off deformity)
• ⚡ Posterior/inferior dislocations → risk of mediastinal neurovascular compression (subclavian vessels, brachial plexus, trachea, oesophagus) → always consider CT
• 🛑 Chronic instability if not treated properly

🔎 Investigations

• 🩻 Shoulder X-rays (AP, Zanca view) → compare with opposite side
• 🖥️ CT if posterior/inferior dislocation suspected or mediastinal concerns

💊 Management

• 🩹 Type I/II (mild sprain/subluxation): Broad-arm sling, analgesia, early mobilisation with physiotherapy.
• 🩹 Type III: Often conservative, but fixation considered if highly active/manual worker or persistent symptoms.
• 🛑 Posterior/inferior dislocation: Orthopaedic emergency → urgent CT + referral for possible surgical reduction.
• 🏥 Follow-up in fracture clinic for assessment of recovery and stability.

📌 Exam Pearl: – Step deformity at shoulder tip = classic for AC dislocation. – Posterior/inferior types are rare but dangerous → always think mediastinal compromise. – Most AC injuries (Rockwood I–III) are treated conservatively with sling + physio.

📚 References

• TeachMeSurgery – AC Joint Injury
• Orthobullets – AC Joint Injury