Medial Epicondyle Fracture of the Humerus

Medial epicondyle fracture of the humerus is an avulsion of the medial epicondylar apophysis, which carries the common flexor pronator origin and the anterior bundle of the ulnar collateral ligament. It occurs in children and adolescents, with a peak at 9 to 14 years, and boys are affected more often than girls.

It makes up about 10 to 12% of paediatric elbow fractures. An elbow dislocation accompanies it in about 30 to 60% of cases, and the fragment is trapped in the joint in about 15 to 18%.

Mechanisms are a valgus force with flexor contraction, traction on the ligament during a posterolateral elbow dislocation, and, in throwers, an acute avulsion on top of chronic apophysitis. A direct blow is rare.

The medial epicondyle ossification centre appears at 5 to 7 years and fuses at 14 to 17 years. Fractures are graded as undisplaced, minimally displaced (under 5 mm), displaced (5 mm or more), and incarcerated in the joint.

Complications are ulnar neuropathy (up to 10 to 16%), valgus instability, fibrous nonunion, loss of extension, myositis ossificans and, after trapped fragments, a mechanical block.

Pathophysiology.

The apophysis is weaker than the ligament and the flexor mass, so valgus load and muscle pull avulse the epicondyle rather than tearing the ligament. The pulled fragment can follow the dislocated joint and become trapped when the elbow reduces.

Fibrous union is common and often asymptomatic. Instability is a concern only when the ligament attachment is displaced enough to make the elbow valgus lax.

There is medial elbow pain, swelling and bruising, with tenderness over the epicondyle and pain on resisted wrist flexion and on valgus stress. Ulnar nerve symptoms (tingling in the ring and little fingers, weak grip) may be present.

A trapped fragment gives a mechanical block to extension. If the elbow dislocated and reduced spontaneously, the history of a "pop" with a fall may be the only clue. Check the ulnar nerve before any manipulation and again afterwards, and check pulses and capillary refill.

• Radiographs: anteroposterior and lateral views of the elbow. A missing medial epicondyle in its usual posteromedial position, or a fragment lying in the joint line that looks like a trochlear ossification centre, signals an incarcerated fragment.
• Compare with the other elbow when the ossification centres are in doubt.
• CT shows the true displacement and an incarcerated fragment, since radiographs underestimate displacement.
• Ultrasound or MRI in younger children with unossified apophyses.
• Valgus stress testing under fluoroscopy in theatre assesses instability when displacement is borderline.

Differential diagnosis.

• Normal ossification centres and medial condyle or lateral condyle fractures.
• Supracondylar fracture and elbow dislocation with other fractures.
• Ulnar collateral ligament injury and medial apophysitis in adolescent throwers.
• Flexor pronator strain.

Non-operative. Indicated for undisplaced and minimally displaced fractures (under 5 mm), in a stable elbow, without ulnar nerve dysfunction. Use an long arm cast or back slab with the elbow at 90 degrees, forearm pronated and wrist flexed to slacken the flexor mass, for 1 to 2 weeks. Begin movement by 2 to 3 weeks, because longer immobilisation causes stiffness.

Operative. Absolute indications are an incarcerated fragment, an open fracture, and an ulnar nerve entrapment or progressive deficit. Relative indications are displacement of 5 mm or more, a valgus unstable elbow, and high demand throwers.

• Open reduction and fixation through a medial approach, protecting the ulnar nerve: one 4.0 mm cannulated screw with a washer, or two smooth Kirschner wires or a tension band for small fragments.
• Incarcerated fragment: a closed extraction attempt under anaesthesia (valgus stress with wrist and finger extension and supination) is made in some centres, but failure or doubt means open removal and fixation.
• After surgery: back slab for 1 to 2 weeks, then active movement. Throwing resumes at 3 to 4 months.

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.
• Adolescents of adult size: paracetamol 1 g orally every 6 hours for up to 5 to 7 days (maximum 4 g daily; 3 g daily when weight is under 50 kg) and ibuprofen 400 mg orally every 8 hours with food for up to 5 days (maximum 1200 mg daily).

Monitoring. Radiographs at 1 week to detect displacement in cast treatment, at 3 to 4 weeks, and at 6 weeks. Ulnar nerve function at each visit. Range of movement and valgus stability at 6 weeks and 3 months. A fibrous union with a stable elbow needs no further treatment.

Referral and escalation. Refer all displaced fractures to paediatric orthopaedics within 1 week. Same day referral for an incarcerated fragment, ulnar nerve deficit, open fracture, a dislocated elbow that does not reduce, or neurovascular compromise.

Special groups.

• Throwers and gymnasts: lower threshold for fixation, because residual valgus instability limits return to sport.
• Adolescents close to skeletal maturity: the apophysis may fuse in a displaced position, so decide early.
• Kidney impairment: avoid ibuprofen.