Rotator cuff

(View in the front)(like you put your hand on someone’s shoulder from the back)

• Supraspinatus (suprascapular nerve)
  • Abducts arm initially (before the action of the deltoid)
  • Most common rotator cuff injury (trauma or degeneration and impingement leading to tendinopathy or tear)
  • Assessed by the “empty/full can” test
• Infraspinatus (suprascapular nerve)
  • Externally rotates arm
  • The only one of these four muscles that does not participate in abduction.
  • Common pitching injury
• Teres minor (axillary nerve)
  • Adducts and externally rotates arm
• Subscapularis (upper and lower subscapular nerves)
  • Internally rotates and adducts arm (only one responsible for internal rotation t)
  • Subscapularis tendinopathy

Abduction of the upper limb

• (0°-15°) Abduction of the upper extremity is initiated by the supraspinatus muscle (suprascapular nerve).
• (15°-110°) Further abduction to the horizontal position is a function of the deltoid muscle (axillary nerve).
• (110°-180°) Raising the extremity above the horizontal position requires scapular rotation by action of the trapezius (accessory nerve CN XI) and serratus anterior (long thoracic nerve).

Mnemonic

“Start Dancing, Then Spin!”

• Start (Supraspinatus: 0°–15°)
• Dancing (Deltoid: 15°–110°)
• Then (Trapezius: 110°–180°)
• Spin! (Serratus anterior: 110°–180°)

Rotator cuff tear

• Etiology & Risk Factors:
  • Supraspinatus tendon most commonly affected (watershed area). c
  • Degenerative tears: Age > 40, repetitive overhead activities (painters, pitchers).
  • Acute traumatic tears: Fall on outstretched hand (FOOSH), anterior shoulder dislocation.
• Clinical Presentation:
  • Anterolateral/lateral shoulder pain exacerbated by overhead motion and lying on affected side at night.
  • True motor weakness and catch/crepitus during active elevation.
• Physical Examination:
  • Decreased active ROM with preserved passive ROM (hallmark).
  • Supraspinatus: Positive Drop arm test and Empty-can (Jobe) test. c
  • Infraspinatus / Teres minor: Weakness on resisted external rotation, external rotation lag sign.
  • Subscapularis: Weakness on resisted internal rotation, positive Lift-off test.
• Diagnosis:
  • Initial test: X-ray shoulder (AP, axillary, scapular Y) to rule out fracture/OA; chronic tears show superior humeral head migration.
  • Confirmatory / Gold standard: MRI shoulder without contrast (determines partial vs. full-thickness, size, retraction, and muscle atrophy).
  • Diagnostic maneuver: Subacromial lidocaine injection (relieves pain; persistent true weakness confirms tear vs. tendinopathy).
• Differential Diagnosis:
  • Rotator cuff impingement/tendinopathy: Painful arc (60°–120°), normal strength once pain is relieved with lidocaine.
  • Adhesive capsulitis (Frozen shoulder): Loss of both active AND passive ROM in all planes.
  • Cervical radiculopathy (C5–C6): Pain radiates below elbow, positive Spurling sign, dermatomal sensory loss.
• Management:
  • First-line (Conservative): NSAIDs, activity modification, physical therapy (PT) ± subacromial corticosteroid injection (indicated for partial tears, degenerative tears in low-demand/elderly pts).
  • Surgical repair: Indicated for acute traumatic full-thickness tears in young/active pts (ideally within 6 weeks) or failure of conservative therapy after 3–6 months.
  • Refractory / Chronic end-stage: Reverse total shoulder arthroplasty (rTSA) for rotator cuff tear arthropathy.
• Complications:
  • Irreversible muscle atrophy and fatty infiltration (worsens surgical prognosis).
  • Rotator cuff tear arthropathy (secondary glenohumeral osteoarthritis).

Adhesive capsulitis

• Definition & Pathophysiology:
  • Chronic inflammation, capsular thickening, and fibrosis causing contracture of the glenohumeral joint.
• Risk Factors:
  • DM (strongest association; up to 20%, often bilateral) and hypothyroidism.
  • Shoulder immobilization (post-CVA, post-op, trauma), female sex (age 40–65).
• Clinical Presentation:
  • Insidious dull shoulder pain (worse at night) with progressive stiffness.
  • Phases: Freezing (pain > stiffness) $\to$ Frozen (stiffness > pain) $\to$ Thawing (gradual ROM resolution).
• Physical Exam (Exam Hallmark):
  • ↓ Active AND passive ROM in multiple planes.
  • External rotation and abduction are most severely restricted.
• Diagnosis:
  • Clinical: Based on loss of active + passive ROM.
  • X-ray: Typically normal; initial step to rule out glenohumeral OA and fractures.
  • MRI: Indicated only if refractory or atypical; shows thickened capsule and contracted axillary pouch.
  • Key Labs: Screen for secondary causes with HbA1c and TSH.
• High-Yield Differentials:
  • Rotator cuff pathology: Passive ROM is preserved; only active ROM/strength is decreased.
  • Glenohumeral OA: Active and passive ROM decreased, but X-ray demonstrates joint space narrowing/osteophytes.
  • Subacromial impingement: Passive ROM is preserved; painful arc present (60°–120°).
  • Cervical radiculopathy: Preserved shoulder ROM; dermatomal numbness/weakness, (+) Spurling test.

c

Condition	Active ROM	Passive ROM
Adhesive capsulitis	↓	↓
Rotator cuff tear	↓	Preserved
Axillary nerve injury	↓ abduction	Preserved
Cervical radiculopathy	Variable	Preserved

• Management:
  • First-line: Gentle daily stretching/PT + NSAIDs or acetaminophen.
  • Second-line: Intra-articular glucocorticoid injection (best for persistent/severe pain; accelerates ROM recovery when combined with PT).
  • Refractory (> 6–12 months): Closed manipulation under anesthesia (MUA) or arthroscopic capsular release.