Fifth metatarsal base fracture in children

This page concerns fractures of the base of the fifth metatarsal, not three equivalent diagnoses: after a sprain or inversion injury, well-localised pain over the bony prominence on the outer border of the foot may indicate such an injury. Site of the fracture line, skeletal age, displacement and sport practised all change treatment and timing.

What it is

The base of the fifth metatarsal is the prominence felt on the outer border of the foot, behind the little toe, where the peroneus brevis tendon inserts. In the growing child an ossification centre (apophysis) is also present there and can be mistaken for a fracture on X-ray.

Three different pictures occur in this small area, and telling them apart matters because it changes immobilisation, weight-bearing and return-to-sport timing:

• Iselin's apophysitis: gradual-onset overload pain in the growing athlete, without acute trauma;
• an avulsion fracture of the base: the most common after an inversion injury, with a small fragment separating proximally;
• a Jones fracture: involves the metaphyseal-diaphyseal zone just distal to the base, with a less favourable blood supply and its own clinical behaviour.

When to have it assessed

Typical signs after an injury are sharp pain on the outer border of the foot, swelling, difficulty bearing weight, and tenderness over the bony prominence. This is often mistaken for an ankle sprain, but in a sprain the tender point lies over the ligament in front of the lateral malleolus, not over the bone. Persistent refusal to bear weight, marked swelling, extensive bruising or pain not improving over some weeks deserve assessment; visible deformity, an open wound or cold, pale toes require emergency care.

What we look at

Assessment starts clinically, palpating the fifth metatarsal base, the peroneal tendon, the ankle ligaments and the rest of the midfoot, so that lateral pain is not automatically equated with a base fracture. A foot X-ray in several views establishes where the line runs: an ossification centre has smooth margins parallel to the metatarsal, while a fracture has irregular, transverse margins. When doubt persists or pain continues despite a normal X-ray, a repeat radiograph or MRI/CT may be considered, guided by the specific clinical question.

Treatment

Most fifth metatarsal base injuries in children heal without surgery: protection with a rigid brace, a walker boot or a cast, weight-bearing graded on symptoms, and a progressive return to activity. There are no universal timings — a minimally displaced avulsion fracture in a young child and a Jones-zone fracture in a competitive adolescent do not follow the same pathway even if the initial pain looks similar. Surgery is a minority option, considered for significantly displaced or joint-involving fragments, for delayed or non-union, and in some Jones-zone fractures in the athletic adolescent, where slower healing is more likely.

Follow-up and return to sport

Clinical and radiographic reviews continue until healing is documented. Recovery also includes regaining ankle and foot mobility, strengthening the peroneal muscles and calf, and a controlled progression from walking to running to sport-specific movements. Return to sport follows clinical and radiographic criteria, not a preset date.

When it is not a fracture

Gradual-onset outer foot pain in a young athlete without a clear injury more often points to Iselin's apophysitis, a benign, self-limiting overload condition, or to an ankle sprain or peroneal tendinopathy. See also paediatric injuries and fractures and paediatric sports traumatology.