Back to ELM2: Musculoskeletal
Upper Limb Anatomy & the Rotator Cuff
~1 min read
Lesson 1 of 20
Notes
Upper Limb Anatomy & the Rotator Cuff
Rotator Cuff Muscles (SITS)
| Muscle | Origin | Insertion | Action |
|--------|--------|-----------|--------|
| Supraspinatus | Supraspinous fossa | Greater tubercle | Abduction 0–15┬░ |
| Infraspinatus | Infraspinous fossa | Greater tubercle | External rotation |
| Teres Minor | Lateral border scapula | Greater tubercle | External rotation |
| Subscapularis | Subscapular fossa | Lesser tubercle | Internal rotation |
Clinical: Shoulder Impingement
- Supraspinatus tendon compressed under coracoacromial arch
- Painful arc 60–120┬░ abduction
- Empty can test (Jobe): patient abducts 90┬░, 30┬░ forward flex, thumbs down — resistance applied
Brachial Plexus Roots C5–T1
- C5/C6 → musculocutaneous n → biceps (elbow flex, supination)
- C7 → radial n → triceps, wrist extensors
- C8/T1 → ulnar n → intrinsic hand muscles
Dermatomes to Know
- C5: lateral arm (regimental badge)
- C6: thumb & index
- C7: middle finger
- C8: ring & little finger
- T1: medial forearm
Common Nerve Injuries
- Axillary n (C5/C6): surgical neck fracture → deltoid wasting, loss of shoulder abduction
- Radial n: mid-shaft humerus fracture → wrist drop
- Median n (carpal tunnel): thenar wasting, loss of thumb opposition
- Ulnar n: medial epicondyle → claw hand (ring & little), loss of finger abduction