Proximal fifth metatarsal fractures

Bone Stress Injuries at the Ankle and Foot

Bone stress injuries (BSIs) are a frequent finding in athletes, particularly of the foot and ankle. A BSI is caused by recurring microtrauma to the cortical or trabecular bone exceeding the repair capacity of normal bone. The most frequent fractures at the ankle are low risk, characterized by a low risk for nonunion. These include the posteromedial tibia, the calcaneus, and the metatarsal diaphysis. High-risk stress fractures have a higher risk for nonunion and need more aggressive treatment. Examples are the medial malleolus, navicular bone, and the base of the second and fifth metatarsal bone.Imaging features depend on the primary involvement of cortical versus trabecular bone. Conventional radiographs may remain normal up to 2 to 3 weeks. For cortical bone, early signs of BSIs are a periosteal reaction or the "gray cortex sign," followed by cortical thickening and fracture line depiction. In trabecular bone, a sclerotic dense line may be seen. Magnetic resonance imaging enables early detection of BSIs and can differentiate between a stress reaction and a fracture. We review typical anamnestic/clinical findings, epidemiology and risk factors, imaging characteristics, and findings at typical locations of BSIs at the foot and ankle that may help guide treatment strategy and patient recovery.

Classification of avulsion fractures of the fifth metatarsal base using three-dimensional CT mapping and anatomical assessment: a retrospective case series study

Background

To clarify the injury mechanism of the avulsion fracture of the fifth metatarsal combining 3-dimensional (3D) fracture mapping with anatomical measurements.

Methods

Two hundred twenty-two patients with the avulsion fractures of the fifth metatarsal base, who were admitted to our hospital from August 2015 to August 2020. The computed tomography (CT) scans were used to generate the 3-D images of all mapped fracture lines for the avulsion fractures of the fifth metatarsal base were compiled in an overall 3D image. The fifth metatarsal base of 8 unpaired lower limbs of adult Asian frozen cadaveric specimens were also dissected to observe and measure the specific locations of the attachment points of the peroneus brevis, lateral band of the plantar fascia, and peroneus tertius to the fifth metatarsal base.

Results

Based on the type of fracture line produced and the specific locations of the attachment points of the tendons or fascia, the avulsion fractures of the fifth metatarsal base can be classified into three types: type I predominantly involves the action of the lateral band of the plantar fascia; type II predominantly involves the action of the peroneus brevis; type IIIA involves the joint action of the peroneus brevis and lateral band of the plantar fascia with one fracture line, and type IIIB involves the joint action of the peroneus brevis and lateral band of the plantar fascia with two fracture lines.

Conclusion

The lateral band of the plantar fascia and peroneus brevis play a major role, either separately or together, in avulsion fractures of the fifth metatarsal base. With this knowledge, we propose a novel classification based on the injury mechanism, which can serve as a reference for clinical treatment and diagnosis.

Level of evidence

Level III, retrospective case series.

Fractures of the Base of the Fifth Metatarsal Bone: A Critical Analysis Review

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Fractures of the proximal fifth metatarsal (PFMT) are one of the most common foot injuries, accounting for 61% to 78% of all foot fractures, but full consensus on their classification, diagnosis, and treatment has not yet been reached.

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The most commonly accepted classification is that of Lawrence and Botte, who divided the location of PFMT fractures into 3 zones with respect to their healing potential.

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Avulsion fractures of the tuberosity of the base (zone 1) generally heal well, and nonoperative treatment is commonly recommended.

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Internal fixation may be considered for displaced fractures that extend into the fourth-fifth intermetatarsal joint (zone 2) as well as for nondisplaced fractures in athletes or high-demand patients, with the aims of reducing the healing time and expediting return to sport or work.

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Stress fractures of the proximal diaphysis (zone 3) are preferably treated operatively, particularly in the presence of signs of delayed union. With nonoperative treatment, supportive measures such as ultrasonography or external/extracorporeal shockwave therapy have been demonstrated to have limited potential for the enhancement of fracture-healing.