Malunion of the Elbow: Cubitus Varus and Cubitus Valgus

INTRODUCTION AND NORMAL CARRYING ANGLE

• Abnormally decreased or reversed - called Cubitus Varus
• Abnormally increased - called Cubitus Valgus

Fig. Normal carrying angle (right) vs cubitus varus deformity (left) - S Das, Manual of Clinical Surgery

PART I: CUBITUS VARUS

Definition

Aetiology / Cause

• Most common cause: Malunion of a supracondylar fracture of the humerus in children - it is the most common angular deformity resulting from supracondylar fractures
• Varus tilting of the distal fragment is the most important cause of the change in carrying angle
• Mechanisms of varus tilting (Fig. 38.19 - Campbell's):
  • A. Medial impaction of the fracture
  • B. Medial tilting of the distal fragment
  • C. Horizontal rotation of the distal fragment
• Less common: medial column instability leading to collapse when treated with cast alone (without pinning) - even with apparently benign Type II fractures
• Rare cause: Osteonecrosis and delayed growth of the trochlea with relative overgrowth of the lateral side of the distal humeral epiphysis (progressive - cannot be prevented by stabilization)

FIGURE 38.18 - Cubitus varus deformity of left elbow (Campbell's Operative Orthopaedics 15e)

Clinical Features

• Typically presents in a child with a history of a previous supracondylar fracture
• Obvious cosmetic deformity - the elbow has a gun-stock appearance
• Carrying angle is reduced or negative compared to the normal side
• Baumann's angle on X-ray is reduced (normal: 9-26°; reduced in cubitus varus)
• Function is generally preserved - historically considered a cosmetic problem

Complications (Why it is NOT just cosmetic)

1. Ulnar nerve dislocation and ulnar neuropathy
2. Snapping of the medial head of the triceps over the medial epicondyle
3. Secondary fractures - distal humeral or lateral condylar fractures (due to altered mechanics)
4. Osteonecrosis of the distal humeral epiphysis
5. Joint ganglia
6. Osteoarthritis
7. Posterolateral rotatory instability (PLRI) - occurring up to 51 years later
   • The mechanical axis, olecranon, and triceps line of pull are all displaced medially
   • This causes repetitive external rotation torque on the ulna, stretching the lateral collateral ligament complex
   • Physical findings: positive posterolateral rotatory apprehension test, positive lateral pivot shift, posterolateral rotatory drawer signs
8. Tardy ulnar nerve palsy can occur (though more classically associated with cubitus valgus)

Remodeling

• 100% remodeling has been shown in children younger than 5 years
• Only minimal remodeling occurs after age 8 years
• Malrotation of the distal humerus will not remodel but is compensated by shoulder motion

Treatment of Cubitus Varus

Conservative

• Observation is acceptable in mild deformity, especially in young children (<5 yrs) where remodeling may occur

Surgical (Corrective Osteotomy)

Lateral Closing Wedge Osteotomy - Key Steps (Campbell's Technique 38.5):

1. Lateral approach to the elbow with tourniquet
2. Under fluoroscopy, insert 2 K-wires into the lateral condyle before osteotomy
3. Make a closing wedge osteotomy laterally, leaving the medial cortex intact; cuts can be angled in sagittal plane to correct flexion/extension deformity
4. Weaken medial cortex with drill holes if needed; apply valgus stress in pronation to complete osteotomy
5. Close osteotomy; advance K-wires or cannulated screws from lateral condyle into medial cortex of proximal fragment
6. Stabilize with K-wires (younger patients) or plate-and-screw fixation (adolescents)
7. Immobilize in long-arm cast at 60° flexion and full pronation

FIGURE 38.21 - A: Clinical photo of cubitus varus deformity. B: Pre-op X-ray. C: Post-osteotomy screw fixation (Campbell's Operative Orthopaedics 15e)

PART II: CUBITUS VALGUS

Definition

Aetiology / Cause

1. Most common cause: Nonunion of lateral condylar fractures - this is the most frequent cause of true cubitus valgus
2. Malunion of a distal humeral fracture (including lateral condylar fractures in children)
3. Lateral growth arrest following lateral condyle fractures (Milch classification)
4. Note: Cubitus valgus after supracondylar fracture is mentioned in literature but rarely occurs (since the normal carrying angle increases from childhood to adulthood, an increase in valgus is less cosmetically noticeable)

Why Cubitus Valgus is Important

Tardy Ulnar Nerve Palsy (TUNP)

• This is the most important complication of cubitus valgus
• "Tardy" = delayed (develops years to decades after the original injury)
• Mechanism: In cubitus valgus, the ulnar nerve is gradually stretched around the medial epicondyle as the valgus deformity increases the traction on the nerve over time
• This causes incomplete, progressive ulnar nerve paralysis - hence "tardy"
• The nerve is also susceptible to compression by callus or osteophytes at the malunited site

Features of Tardy Ulnar Nerve Palsy:

• Onset: Insidious, years after original fracture (average 10-20 years later, though can be much longer)
• Sensory: Numbness and tingling in the little finger and ring finger (ulnar 1.5 fingers)
• Motor:
  • Wasting of hypothenar eminence and intrinsic muscles of the hand
  • Claw hand (more pronounced in ring and little fingers - "ulnar claw")
  • Weakness of grip
  • Positive Froment's sign (weakness of adductor pollicis)
• Investigation: Nerve conduction studies confirm slowing at the elbow

Other Complications of Cubitus Valgus:

• Degenerative joint disease (osteoarthritis) of the elbow
• Restricted elbow movements

Treatment of Cubitus Valgus

For the Deformity:

• Corrective osteotomy (medial closing wedge or lateral opening wedge at the supracondylar level) - if the deformity is significant and causing functional problems
• This is less commonly needed than in cubitus varus, as valgus may be tolerated better

For Tardy Ulnar Nerve Palsy:

COMPARISON TABLE: CUBITUS VARUS vs CUBITUS VALGUS

IMPORTANT EXAM POINTS (High-yield)

1. Cubitus varus = most common complication of supracondylar fracture in children
2. Gun-stock deformity = synonym for cubitus varus
3. Cubitus valgus = tardy ulnar nerve palsy - this association is the most tested fact
4. Tardy UNP mechanism: Progressive stretching of ulnar nerve over the medial epicondyle due to valgus angulation
5. Most common cause of cubitus valgus: Nonunion (not malunion) of lateral condylar fracture
6. Surgery for cubitus varus: Lateral closing wedge osteotomy (supracondylar) - most common
7. Baumann's angle on AP X-ray: reduced in cubitus varus (normal 9-26°; also described as angle between humeral shaft axis and lateral condylar physis/growth plate - normally 64-81° in some conventions - confirm the version used in your textbook)
8. Cubitus varus - although historically "cosmetic only," now known to cause posterolateral rotatory instability and secondary fractures
9. Carrying angle: 10-15° normally (slightly more in women)
10. The carrying angle disappears on pronation or full flexion