Lateral Condyle Fracture of the Humerus

Lateral condyle fracture of the humerus is a physeal fracture of the distal humerus in children that runs through the growth plate and exits through the joint surface. It is therefore intra-articular, and it is unstable when displaced. Most are Salter-Harris type IV injuries.

It is the second most common paediatric elbow fracture after the supracondylar fracture, accounting for about 10 to 20% of elbow fractures in children. The peak age is 5 to 8 years, with a range of 2 to 12 years, and boys are affected more often than girls.

The usual mechanism is a fall on the outstretched hand with a varus force on the extended elbow, so that the common extensor origin avulses the condyle. A valgus force driving the radial head into the capitellum is the other mechanism.

Displacement is graded by the widest gap on any view: under 2 mm is minimal, 2 to 4 mm is moderate, and over 4 mm is marked and often rotated. Milch type I fractures exit lateral to the trochlea and keep the elbow stable. Milch type II fractures exit through the trochlear groove and the elbow can subluxate.

Complications are nonunion, cubitus valgus with tardy ulnar nerve palsy, malunion, fishtail deformity, lateral spur formation, avascular necrosis of the trochlea and capitellum, premature physeal closure, and stiffness.

Pathophysiology.

The common extensor origin pulls the fragment distally and rotates it. Synovial fluid washes out the fracture haematoma and impairs union, which is why displaced fractures treated in a cast so often fail.

The blood supply to the fragment runs through the posterior soft tissue attachments. Stripping them during surgery risks avascular necrosis, so exposure is kept anterolateral.

In young children the epiphysis is largely cartilage, so the bony fragment on the radiograph is smaller than the true fragment and true displacement is underestimated.

The child holds the elbow flexed after a fall, with lateral elbow pain, swelling and bruising. There is tenderness over the lateral condyle, reduced flexion, extension and forearm rotation, and sometimes crepitus. Deformity is usually less obvious than in a supracondylar fracture.

Elbow instability or a palpable subluxation suggests a Milch type II injury. Check radial pulse, capillary refill and the median, anterior interosseous, radial and ulnar nerves. Check for forearm swelling, skin breaks and other injuries of the same limb. An injury that does not fit the history in an infant should prompt a safeguarding assessment.

Imaging:

• Radiographs: anteroposterior, lateral and 45 degree internal oblique views of the elbow. The oblique view shows the largest gap. Look for the Thurston-Holland metaphyseal flake and a posterior fat pad.
• Measure the widest gap on any view. Over 2 mm is the usual threshold for surgery.
• Minimal displacement in a young child: ultrasound, MRI or arthrography under anaesthesia to show whether the articular cartilage hinge is intact. An intact hinge means a stable fracture.
• Arthrography at surgery confirms articular congruity after reduction.
• Comparison views and a skeletal survey when non-accidental injury is suspected.

Differential diagnosis.

• Supracondylar fracture and medial epicondyle fracture.
• Radial neck fracture and Monteggia fracture dislocation.
• Elbow dislocation and capitellar fracture.
• Transphyseal separation of the distal humerus (under 3 years, may be non-accidental).

Aims are an anatomical articular reduction, stable fixation and preservation of the posterior blood supply.

By displacement.

• Under 2 mm with an intact cartilage hinge: long arm cast with the elbow at 90 degrees and the forearm neutral to pronated for 4 to 6 weeks. Radiographs at 5 to 7 days and 10 to 14 days detect late displacement, which needs surgery.
• 2 to 4 mm: arthrography or MRI. If the hinge is intact, a cast with the same close review is possible. A disrupted hinge or increasing gap needs percutaneous pinning.
• Over 4 mm, rotated, or Milch type II: open reduction and fixation through an anterolateral approach, or closed reduction with percutaneous pinning when arthrography shows the joint surface reduced to within 2 mm.
• Fixation: two or three smooth Kirschner wires of 1.6 to 2.0 mm, divergent, crossing the fracture and engaging the medial cortex. Screws are used only in older children with a large metaphyseal fragment.
• After surgery: long arm cast for 3 to 4 weeks, wires removed in clinic at 3 to 4 weeks when early healing shows, cast discontinued at about 6 weeks, then mobilisation. No contact sport for 3 months.
• Late presentation over 3 weeks: undisplaced fractures are fixed in situ. Displaced fractures presenting late are a specialist decision, because reduction after weeks carries a risk of avascular necrosis. Established nonunion with valgus or ulnar nerve symptoms needs fixation or osteotomy with ulnar nerve decompression.

Analgesia.

• Paracetamol 15 mg/kg orally every 4 to 6 hours as needed for up to 5 days (maximum 75 mg/kg daily and not exceeding 4 g daily); reduce the dose and extend the interval in hepatic impairment or malnutrition.
• Ibuprofen 10 mg/kg orally every 6 to 8 hours with food for up to 5 days (maximum 40 mg/kg daily and not exceeding 2400 mg daily), from 3 months of age; avoid with dehydration, NSAID-sensitive asthma or renal impairment.
• Severe pain at presentation: intranasal fentanyl 1.5 microgram/kg once (maximum 100 microgram a dose, one repeat after 10 minutes if needed), with continuous monitoring of sedation, oxygen saturation and respiratory rate.

Reduction under sedation. Ketamine 1 to 2 mg/kg intravenously over 1 to 2 minutes as a single dose (a further 0.5 to 1 mg/kg after 10 minutes if needed; 4 to 5 mg/kg intramuscularly without access), given by a clinician skilled in paediatric airway care with continuous oximetry and capnography, after fasting. Avoid with raised intracranial pressure, psychosis or acute upper airway infection.

Pin site infection. Flucloxacillin 12.5 to 25 mg/kg orally four times daily (maximum 1 g a dose) for 5 to 7 days, reviewed at 48 to 72 hours; stop if jaundice or raised liver enzymes appear. With penicillin allergy, clarithromycin 7.5 mg/kg orally twice daily (maximum 500 mg a dose) for 5 to 7 days, checking interacting drugs.

Monitoring. Radiographs at 5 to 7 days and 10 to 14 days for cast treatment, at 3 to 4 weeks before wire removal, and at 6 weeks for union. Carrying angle and range of movement at 3, 6 and 12 months. Annual review to skeletal maturity if growth disturbance appears. A persistent gap at 6 to 8 weeks indicates nonunion.

Referral and escalation. Refer every fracture with 2 mm or more of displacement to paediatric orthopaedics on the same or next day. Same day referral for open fracture, neurovascular compromise, a tense forearm suggesting compartment syndrome, an unstable elbow (Milch type II), or suspected non-accidental injury.

Special groups.

• Infants and young children: ultrasound or MRI is needed because the epiphysis is cartilaginous; transphyseal separation can mimic this fracture.
• Safeguarding: an unexplained fracture in a child under 3 years needs a child protection assessment.
• Kidney impairment: avoid ibuprofen; reduce morphine and fentanyl doses and extend intervals.
• Region specific: delay in presentation after traditional bone setting is common and leads to nonunion and avascular necrosis, so ask about prior treatment.