Malunion - Cubitus Varus and Cubitus Valgus

Long Answer - Orthopaedic MBBS Exam

Definition

Normal Carrying Angle

• Bailey and Love's Short Practice of Surgery, p. 505

CUBITUS VARUS

Definition and Deformity

Cubitus varus deformity of left elbow (Campbell's Operative Orthopaedics, 15th Ed)

Aetiology

• Most commonly follows a malunited supracondylar fracture of the humerus in children
• It is the most common angular deformity after supracondylar fracture
• Not primarily due to growth arrest - it is the result of malunion of the distal fragment in varus tilt
• Varus tilting of the distal fragment (medial tilt/collapse) is the single most important cause
• Medial comminution, medial column instability, and inadequate reduction/pinning lead to this collapse

Mechanism of Coronal Tilting

Mechanism of coronal tilting leading to cubitus varus: A - Impaction medially; B - Tilting of fragment medially; C - Horizontal rotation (Campbell's, 15th Ed)

Clinical Features

• Obvious medial angulation of the forearm (gun-stock deformity)
• Most noticeable in full extension
• Tenderness over the lateral collateral ligament complex
• Prominent tendon of the medial head of triceps
• Usually good cosmesis is the primary concern - function is generally NOT significantly impaired in uncomplicated cases

Complications of Cubitus Varus

1. Lateral elbow instability / Posterolateral rotatory instability (PLRI) - the mechanical axis, olecranon, and triceps line of pull are all displaced medially; the repetitive external rotation torque stretches the lateral collateral ligament complex
2. Tardy ulnar nerve palsy - cubitus varus deformities can also rarely be associated with this
3. Snapping of the medial head of triceps over the medial epicondyle
4. The link to elbow instability in adulthood has been documented up to 51 years after the original childhood injury
5. Signs: positive posterolateral rotatory apprehension test, positive lateral pivot shift, posterolateral rotatory drawer test

• Campbell's Operative Orthopaedics, 15th Ed 2026, p. 1776

Remodelling

• 100% remodelling has been shown in children younger than 5 years
• Only minimal remodelling occurs after age 8 years - surgical correction becomes necessary

Treatment

1. Lateral closing wedge osteotomy - easiest, safest, most stable, most commonly used; corrects coronal and (if placed obliquely) sagittal plane deformity; also allows axial rotational correction
2. Medial opening wedge osteotomy with bone graft
3. Oblique osteotomy with derotation

Three-dimensional osteotomy for correction of cubitus varus. Medial and posterior tilt corrected; distal fragment compacted with external rotation using wedge of humeral cortex (Campbell's, 15th Ed)

1. Lateral incision; tourniquet inflated
2. Insert 2 K-wires into lateral condyle before osteotomy (just distal to planned distal cut)
3. Make closing wedge osteotomy laterally, leaving medial cortex intact initially; cuts angled in sagittal plane if sagittal correction needed
4. Weaken medial cortex with drill holes; apply valgus stress with forearm in pronation and elbow flexed to complete osteotomy
5. Advance K-wires from lateral condyle into medial cortex of proximal fragment
6. Fixation tailored to age: K-wires + screws for younger children; plate-and-screw for adolescents

• Campbell's Operative Orthopaedics, 15th Ed 2026

CUBITUS VALGUS

Definition

Aetiology

• Nonunion of lateral condylar fractures is actually more often responsible for cubitus valgus than simple malunion of supracondylar fractures
• Because the normal carrying angle naturally increases from childhood to adulthood, an increase in valgus is less cosmetically noticeable than varus reversal

Clinical Features

• Increased carrying angle on inspection
• May be well tolerated for years
• The critical late complication is tardy ulnar nerve palsy

Tardy Ulnar Nerve Palsy - The Classical Complication

• Develops years (5-20 years) after the original fracture
• Progressive weakness of ulnar-innervated intrinsic muscles (interossei, hypothenar, medial two lumbricals)
• Clawing of the ring and little finger (claw hand - more pronounced in ring and little fingers)
• Loss of sensation on the medial 1.5 fingers and medial palm
• Wasting of hypothenar eminence and dorsal interossei
• Positive Froment's sign (flexion of IP joint of thumb on paper-holding test)
• Positive Wartenberg's sign (little finger abduction)
• Campbell's Operative Orthopaedics, 15th Ed 2026; S Das Manual on Clinical Surgery, 13th Ed

Treatment

1. Anterior transposition of the ulnar nerve (subcutaneous, intramuscular, or submuscular) - relocates the nerve to prevent further stretching
2. Medial epicondylectomy - partial or complete removal of the medial epicondyle
3. In situ decompression - for mild/early cases

• Medial opening wedge osteotomy or lateral closing wedge osteotomy of the distal humerus to restore normal carrying angle
• Often combined with nerve transposition

Comparison Table: Cubitus Varus vs Cubitus Valgus

Key Exam Points (High-Yield)

1. Cubitus varus = gun-stock deformity - result of malunion of supracondylar fracture (medial tilt of distal fragment); primarily a cosmetic problem but late PLRI can occur
2. Cubitus valgus = tardy ulnar nerve palsy - the feared late complication; caused most often by malunion/nonunion of lateral condyle fracture, not supracondylar
3. Cubitus varus is NOT primarily due to growth arrest - it is malunion
4. The carrying angle is normally 9-14°; measured with elbow extended and forearm supinated
5. Remodelling of varus: complete below age 5, minimal above age 8
6. Osteotomy of choice for cubitus varus: lateral closing wedge osteotomy (most stable, safe, commonly used)
7. Tardy ulnar nerve palsy: traction neuropathy from stretching of the ulnar nerve over years in cubitus valgus; treatment is anterior transposition ± correction of deformity