# Atypical Metatarsal Fractures: Report of Five Clinical Cases

## TL;DR

This paper reports five cases of atypical metatarsal fractures in women taking bisphosphonates, similar to known atypical femur fractures.

## Contribution

The study adds clinical evidence of atypical metatarsal fractures associated with bisphosphonate use, expanding the understanding of this condition beyond femur cases.

## Key findings

- All five patients had osteoporosis and were on bisphosphonate therapy.
- Imaging showed transverse metadiaphyseal fractures with lateral cortex thickening, matching criteria for atypical femur fractures.
- Fractures occurred with minimal or no trauma, suggesting drug-related bone brittleness.

## Abstract

Atypical fractures are well elucidated when they occur in the femur and are related to the use of bisphosphonates. Prolonged therapy with this drug leads to excessive suppression of bone remodeling, which makes the bone more brittle. In general, they are caused by minimal trauma or are atraumatic. This type of fracture is also reported in other bony sites, such as the metatarsus. Some reports and studies on atypical metatarsal fractures have been published, but further investigations are required to better understand this type of fracture and establish the proper diagnosis, treatment and conduct.

The present study is a report of five cases of patients who presented metatarsal fractures during therapy with bisphosphonates. All patients were female, had osteoporosis as a preexisting disease, were taking bisphosphonates, presented fractures that were either atraumatic or caused by minimal trauma, and the imaging examination showed a transverse meta-diaphyseal fracture of the fifth metatarsal shaft with thickening of the lateral cortex, image characteristics similar to the criteria used by the American Society for Bone and Mineral Research (ASMBR) to define atypical femur fractures.

Fraturas atípicas são bem elucidadas quando ocorrem no fêmur e tem relação com o uso de bifosfonatos. A terapia prolongada com esse medicamento leva a uma supressão excessiva do remodelamento ósseo, o que torna o osso mais quebradiço. Em geral, são fraturas atraumáticas ou causadas por trauma mínimo. Este tipo de fratura é também relatada em outros sítios ósseos, como o metatarso. Alguns relatos e estudos referentes às fraturas atípicas de metatarso já foram publicados, mas outras investigações são necessárias para que essa fraturas sejam mais bem compreendidas e recebam o devido diagnóstico, tratamento e conduta.

No presente trabalho, relatam-se cinco casos de pacientes que apresentaram fratura de metatarso durante terapia com bifosfonatos. Todos os pacientes eram do sexo feminino, tinham osteoporose como doença pré-existente, faziam uso de bifosfonatos, apresentaram fraturas atraumáticas ou causadas por trauma mínimo, e o exame de imagem revelou fratura metadiafisária transversa de eixo de quinto metatarso com espessamento do córtex lateral, características de imagem semelhantes aos critérios utilizados pela American Society for Bone and Mineral Research (ASMBR) para definir fraturas atípicas de fêmur.