Ankle Avulsion Fracture
An avulsion fracture occurs when a fragment of bone is pulled away at the attachment site of a ligament or tendon. This is usually caused by traumatic traction, which may result from either:
Repetitive loading over time.
A single high-load event, such as a forceful injury.
Mechanism of injury:
Avulsion fractures occur because tendons and ligaments can tolerate greater tensile forces than the attached bone. When the force exceeds the bone's capacity, a bone fragment is pulled away at the attachment site.
Common locations:
Avulsion fractures can occur at several sites in the body, but some areas are more commonly affected:
Ankle region:
Commonly around the malleolar region where ligament attachments can avulse a bone fragment.
Foot:
Often at the base of the fifth metatarsal.
They may also occur in the talus and calcaneus³.
Clinically Relevant Anatomy of Fifth Metatarsal Avulsion Fractures
The fifth metatarsal, which is commonly involved in avulsion fractures, consists of three main regions:
Tuberosity: The most lateral and proximal region of the bone.
Metaphysis: The intermediate section connecting the tuberosity and the shaft/head region.
Head: The distal end of the bone, forming part of the articulation with the adjacent toe.
Tendon and muscle attachments:
Peroneus Brevis:
Attaches to the lateral aspect of the tuberosity.
This muscle can exert substantial traction on the tuberosity during inversion movements, which may produce an avulsion fracture under high load.
Peroneus Tertius:
Attaches dorsally to the proximal metaphyseal region.
It is less directly involved in typical avulsion fractures but contributes to dynamic foot movement.
Mechanism of injury:
Inversion injuries:
A common cause of avulsion fractures at the tuberosity.
Traction from peroneus brevis creates considerable force on the tuberosity when the foot inverts, causing a bone fragment to detach.
Epidemiology and Etiology of Avulsion Fractures
Epidemiology:Avulsion fractures account for approximately 5–6% of all fractures treated in primary care.
Fifth metatarsal:
The annual incidence of fifth metatarsal fractures is approximately 67 per 100,000 people⁴.
This is a common site for avulsion fractures, especially in connection with inversion injuries of the foot.
Etiology:
Typical causes:
Inversion injury: Injuries that create traction at the plantar aponeurosis attachment.
Twisting injury of the ankle and foot: May produce avulsion fractures at several locations, including the fifth metatarsal.
Mechanism of Zone 1 injury:
During inversion of the foot, peroneus brevis or the lateral band of the plantar fascia pulls on the tuberosity and causes an avulsion fracture.
This may occur with or without involvement of the tarsometatarsal joint.
Lawrence and Botte Classification of Proximal Fifth Metatarsal Fractures:
Zone 1 (Tuberosity fracture):
Cause: Traction from peroneus brevis or the lateral band of the plantar fascia during inversion of the foot.
Location: The tuberosity of the fifth metatarsal, often close to the tarsometatarsal joint.
Treatment and prognosis: Good outcomes are generally achieved with conservative treatment.
Zone 2 (Metaphyseal-diaphyseal fracture):
Cause: Forced forefoot adduction combined with plantarflexion of the hindfoot.
Location: The junction between the metaphysis and diaphysis, extending into the fourth-fifth intermetatarsal articulation.
Treatment and prognosis: Often requires more extensive management, with a moderate to good prognosis.
Zone 3 (Proximal diaphyseal fracture):
Cause: Chronic overload or repetitive stress, such as prolonged weight-bearing.
Location: Distal to the articulation between the bases of the fourth and fifth metatarsals.
Treatment and prognosis: May require surgery; healing is slower and the risk of complications is higher.
Clinical Features and Presentation of Avulsion Fractures
Avulsion fractures differ from ligament ruptures in both symptoms and management. Although non-operative treatment often gives good results for lateral ligament ruptures, conservative treatment of some avulsion fractures may not provide satisfactory results⁶.
Symptoms and signs:
Symptoms of an avulsion fracture can resemble those of an ankle sprain, making the conditions difficult to distinguish without imaging such as X-ray or MRI.
Pain:
Occurs immediately after the injury, usually in the ankle or foot.
Pain is often localized to the lateral aspect of the foot or over the fifth metatarsal.
Swelling:
Substantial swelling may develop rapidly in the injured area.
Bruising:
Visible discoloration may develop shortly after the injury.
Functional impairment:
Difficulty walking or bearing weight through the injured ankle or foot.
Tenderness on palpation:
Localized tenderness over the fracture site, particularly at the tuberosity of the fifth metatarsal.
History and mechanism of injury:
The injury history often resembles an ankle sprain and is commonly related to plantarflexion and inversion of the foot.
Typical triggering activities include sport or sudden twisting movements.
Differentiation from ankle sprain:
With an avulsion fracture, pain and tenderness are often more focal and localized to the fracture site, such as the tuberosity of the fifth metatarsal.
Imaging is required for a definitive diagnosis and to distinguish an avulsion fracture from ligament injury.
Differential Diagnoses and Diagnostic Procedures for Fifth Metatarsal Avulsion Fractures
Differential diagnoses:
Jones fracture:
Occurs as a fracture in the proximal fifth metatarsal at the metaphyseal-diaphyseal junction.
May be related to repetitive loading of the lateral foot and biomechanical or alignment factors.
Jones fractures have a greater risk of delayed union or non-union and may require surgery, unlike many Zone 1 avulsion fractures.
Dancer's fracture:
A fracture involving the fifth metatarsal, typically associated with inversion or twisting mechanisms.
It often heals well with conservative management depending on location and displacement.
Stress fractures:
Result from chronic repetitive loading, commonly affecting the shaft or proximal diaphyseal region of the fifth metatarsal.
Mid-shaft fractures:
Fractures occurring in the diaphysis of the fifth metatarsal, which may be related to direct trauma or high loading.
Diagnostic procedures:
X-ray:
First-line imaging for confirming the diagnosis, although small fractures or associated injuries accompanying an ankle sprain may occasionally be missed.
Further imaging:
MRI or CT scan: Recommended for more detailed assessment of injury extent, including bone injury or soft-tissue involvement.
Bone scan: May be used to identify stress-related lesions.
Outcome measures
Olerud Ankle Score:
A standardized tool used to measure functional recovery of the ankle following injury.
Examination:
History:
Assess the mechanism of injury, immediate pain level, and swelling.
The Ottawa Ankle Rules can be used to identify areas of pain and determine the need for radiography.
Palpation:
Identify areas of maximal tenderness to localize the specific injury site.
Medical treatment:
Conservative treatment:
Indication: When the fracture fragment is not significantly displaced.
Measures:
Use of a walking boot or cast for 4–6 weeks for immobilization.
Crutches may be recommended to limit weight-bearing when necessary.
Surgical treatment:
Indication: Displaced fractures or when more than 30% of the cubometatarsal joint is involved.
Procedures:
The bone fragment may be excised or fixed using osteosynthesis hardware.
Physiotherapy Management of Avulsion Fractures
Rehabilitation after an avulsion fracture often resembles management after an ankle sprain, with attention to both movement dysfunction and associated impairments. The treatment plan should be individualized to the patient's specific needs⁸ (Level of evidence: 2B).
Importance of appropriate management:
Inadequate management can lead to prolonged functional limitation.
Most fractures heal well, but restoration of full function requires recovery of:
Normal arthrokinematics.
Lower-limb strength.
Proprioception.
Functional movement appropriate to the patient's activities or sport.
Rehabilitation phases:
1. Acute phase (approximately 2 weeks postoperatively):
The focus of this phase is to reduce pain, inflammation, and edema while minimizing muscle atrophy.
Interventions:
Passive range-of-motion exercises to maintain mobility.
Cryotherapy to control swelling and pain.
2. Recovery phase:
Begins once the goals of the acute phase have been achieved and can be divided into three subphases:
Weeks 0–6:
Active range-of-motion exercises for the toes and metatarsophalangeal (MTP) joints.
Isometric exercises for the ankle dorsiflexors, plantarflexors, invertors, and evertors.
Active ankle movement can gradually be introduced from around week 2 when permitted by healing and medical restrictions.
Weeks 6–8:
Active and passive exercises for the ankle and subtalar joints.
Isometric and isotonic strengthening exercises.
Proprioceptive training for balance and strengthening of proximal musculature.
Weeks 8–12:
Strengthening of the dorsiflexors, plantarflexors, invertors, and evertors, together with the long toe flexors and extensors.
Full weight-bearing exercises are introduced gradually as tolerated and permitted.
3. Functional phase (from approximately 6–8 weeks postoperatively):This phase focuses on restoring full function and progressing toward sport- or activity-specific training.
Interventions:
Strength and conditioning for the lower extremities.
Improved neuromuscular control and balance.
Activity- or sport-specific exercises to prepare for return to normal function or competition.
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