Is Cubitus Varus a Rotational issue?

Courtesy: William Mackenzie, duPont Hospital, Jefferson Medical College, USA

Definition

• Post-traumatic deformity of distal humerus
• Characterized by:
o Varus angulation
o Extension
o Internal rotation
Also called “Gunstock deformity”
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Etiology (Most Important )

• Malunion after supracondylar fracture
o Especially extension type
o Most commonly with posteromedial displacement
Why it happens:
• Inadequate reduction
• Loss of reduction
• Poor fixation (casting > pinning risk)
Incidence:
• ~8% with casting
• ~2% with pin fixation
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Pathoanatomy

• Primary deformity = Varus tilt (coronal plane)
• NOT mainly due to:
o Translation
o Rotation  (minor role only)
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Clinical Features

• Cosmetic deformity (main complaint)
• Decreased carrying angle
• Elbow:
o Hyperextension
o Reduced flexion arc (shifted into extension)
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Functional & Late Complications

• Posterolateral rotatory instability (PLRI)
• Tardy ulnar nerve palsy
• Predisposition to:
o Lateral condyle fractures
• Cosmetic concern (major indication for surgery)
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Evaluation

1. X-ray
• Compare both sides
2. Important Measurements
• Baumann’s angle
o Compare with opposite side (more reliable)
• Anterior humeral line
o Should pass through middle 1/3 of capitellum
3. Long arm view
• Better for carrying angle assessment
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Causes (Less Common)

• Medial growth arrest
• Lateral overgrowth (hyperemia)
• Trochlear osteonecrosis
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Treatment

1. Observation
• Most cases (especially mild deformity)
• No functional limitation  no surgery
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2. Hemiepiphysiodesis

• If progressive deformity in growing child
• Example:
o Lateral growth modulation (8-plate)
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3. Corrective Osteotomy (Main Surgical Option)

Gold standard:
Lateral closing wedge osteotomy
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Principles of Osteotomy

• Correct:
o Varus
o Extension
o Internal rotation (if needed)
• Avoid lateral prominence
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Types of Osteotomy

• Lateral closing wedge (most common )
• Dome osteotomy
• Step-cut osteotomy
• Ilizarov correction (gradual)
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Complications of Surgery

• Stiffness
• Nerve injury
• Recurrence
• Lateral condyle prominence
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Surgical Tip (High Yield)

• Make wedge distally directed
Prevents lateral bump deformity
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Key Exam Pearls

• Most common cause = malunion, NOT growth arrest
• Posteromedial displacement ? varus deformity
• Varus tilt = main deformity
• Cosmetic problem > functional problem
• Compare Baumann angle with opposite side
• Treatment of choice (if needed) –  lateral closing wedge osteotomy