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Supracondylar Fracture of the Humerus with Cubitus Varus Deformity

MS Orthopaedics Long Question Answer

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1. Introduction

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2. Anatomy & Relevant Points

• The distal humerus is composed of two columns (medial and lateral) supporting the articular surface (trochlea + capitellum)
• Carrying angle: Normal outward deviation of the extended, supinated forearm from the arm axis — normally 10–15° (greater in females). Disappears on pronation or full flexion
• The Baumann angle (humeral–capitellar angle on AP X-ray) = normally 70–75°; reflects the carrying angle indirectly
• CRITOE — ossification centres appear in sequence: Capitellum (1–2 yr), Radial head (4–5 yr), Internal epicondyle (4–5 yr), Trochlea (8–10 yr), Olecranon (8–9 yr), External epicondyle (10–11 yr)

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3. Mechanism of Injury

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4. Classification — Modified Gartland (Extension Type)

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5. Clinical Features

• Swollen, flexed elbow
• S-shaped deformity in extension type (posterior swelling + anterior fullness)
• Loss of normal bony triangular relationship (medial epicondyle, lateral epicondyle, olecranon) — this triangle is preserved in supracondylar fracture (distinguishing it from elbow dislocation)

• Posterior prominence of distal humerus (not of olecranon)
• Marked tenderness in supracondylar region
• Bony triangle intact (Hueter's triangle preserved)

• Anterior interosseous nerve (AIN) — most commonly injured (tests: "OK" sign — tip-to-tip pinch; or FPL/FDP to index)
• Radial nerve — wrist/finger extension
• Median nerve — LOAF muscles
• Ulnar nerve — intrinsics

• Radial pulse — present/absent/diminished?
• Capillary refill, hand warmth, oximetry

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6. Radiological Evaluation

Key Radiological Lines:

Gartland III X-ray appearance:

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7. Differential Diagnosis

1. Posterior dislocation of the elbow — Hueter's triangle disrupted; bony relationship between radius and capitellum lost
2. Lateral condyle fracture — fracture line more distal; radius does not point to capitellum
3. Medial epicondyle fracture
4. Trans-physeal separation (infant/toddler)

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8. Management

General Principles

• Undisplaced (Type I): Collar and cuff or posterior backslab for 3 weeks; progressive mobilisation
• Displaced (Type II–IV): Closed reduction + percutaneous K-wire fixation (CRPP) ± above-elbow cast

Closed Reduction Technique (Dunlop / modified Blount):

1. Adequate anaesthesia
2. Traction along the long axis, correct rotation
3. Restore medial–lateral alignment on AP
4. Flex elbow while pushing distal fragment forward (Blount manoeuvre)
5. Confirm Baumann angle and anterior humeral line restoration
6. Insert 2–3 lateral K-wires divergently (or crossed pins — more stable but 3–8% risk of iatrogenic ulnar nerve injury with medial pin)

Immobilisation:

• Above-elbow cast, elbow ~90° flexion, forearm in neutral
• Caution: Do not hyperflex if vascular compromise is present — this increases compartment pressure

Indications for ORIF:

• Failed closed reduction
• Open fracture
• Vascular injury requiring exploration

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9. Neurovascular Complications

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10. Cubitus Varus — The Key Complication

Definition

Incidence

Pathogenesis

• Results from malunion — specifically varus tilt + internal rotation of the distal fragment — NOT from growth arrest (this is a common examination point)
• The medial column collapses preferentially; the distal fragment tilts into varus
• Varus–valgus remodelling at the distal humerus is poor (unlike AP plane remodelling which is reasonable), hence cubitus varus persists

Clinical Features

• Cosmetic deformity — prime complaint; parents notice asymmetrical elbow
• Carrying angle reduced or reversed on the affected side
• Function generally preserved (flexion/extension and forearm rotation maintained)
• Gunstock appearance on extension
• Later complications:
  • Posterolateral rotatory instability (PLRI) of the elbow
  • Tardy ulnar nerve palsy — less common than in cubitus valgus, but reported
  • Lateral condyle stress fracture (rare)

Investigations

• AP X-ray both elbows standing (compare Baumann angles)
• Measure Humeroulnar angle (carrying angle) bilaterally — the difference defines severity
• CT if needed for rotational deformity assessment

Indications for Surgery

• Significant cosmetic deformity causing psychological distress
• Progressive neurological symptoms
• PLRI with functional impairment

Surgical Correction — Lateral Closing Wedge Supracondylar Osteotomy

1. Measure the varus angle = difference between carrying angles (affected vs normal side)
2. Calculate the wedge angle to be removed from the lateral column

1. Lateral approach to distal humerus (between brachioradialis and brachialis)
2. Mark the osteotomy level just proximal to the olecranon fossa
3. Remove a laterally based bone wedge whose apex equals the varus angle
4. Close the osteotomy — medial periosteum acts as hinge
5. Fix with 2–3 crossed K-wires (lateral-entry configuration) or plate fixation
6. Above-elbow cast for 4–6 weeks

• Lateral scar prominence (cosmetic)
• Under/overcorrection — careful preoperative planning essential
• Ulnar nerve injury
• Lateral condyle fracture
• Loss of elbow motion

• Dome (French) osteotomy — allows correction in multiple planes; reduced prominence
• Medial opening wedge osteotomy — avoids lateral scar but requires bone graft
• Step-cut osteotomy — more stable; allows correction of rotational deformity simultaneously

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11. Other Complications of Supracondylar Fracture

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12. Summary Box — Examination Points

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