Stress fractures in the lower extremity

Abstract

Stress fractures are fatigue injuries of bone usually caused by changes in training regimen in the population of military recruits and both professional and recreational athletes. Raised levels of sporting activity in today's population and refined imaging technologies have caused a rise in reported incidence of stress fractures in the past decades, now making up more than 10% of cases in a typical sports medicine practice.

Background information (including etiology, epidemiology, clinical presentation and treatment and prevention) as well as state of the art imaging of stress fractures will be discussed to increase awareness amongst radiologists, providing the tools to play an important role in diagnosis and prognosis of stress fractures. Specific fracture sites in the lower extremity will be addressed, covering the far majority of stress fracture incidence.

Proper communication between treating physician, physical therapist and radiologist is needed to obtain a high index of suspicion for this easily overlooked entity. Radiographs are not reliable for detection of stress fractures and radiologist should not falsely be comforted by them, which could result in delayed diagnosis and possibly permanent consequences for the patient. Although radiographs are mandatory to rule out differentials, they should be followed through when negative, preferably by magnetic resonance imaging (MRI), as this technique has proven to be superior to bone scintigraphy. CT can be beneficial in a limited number of patients, but should not be used routinely.

Introduction

Using the term stress fracture may be confusing, as it has different meanings in contemporary literature. Most authors use it to indicate fatigue fractures, where others use it in its proper meaning, indicating a group of fractures made up of fatigue fractures and insufficiency fractures (including pathologic fractures). In this article it is used as a substitute for fatigue fractures.

Stress fractures belong to the wide spectrum of overuse injuries. Due to their strenuous training activities, military recruits and competitive athletes are primarily affected and have been subject of most articles written about stress fractures. However, the increase in participation of recreational athletes in major sports events (i.e. marathon running), often pushing their limits, have led to an increase of stress fractures in this population as well. Increased incidence has subsequently increased understanding of stress fracture mechanism and behavior, resulting in recognition of low and high risk sub categories.

In 1855, the Prussian military physician Breithaupt was the first to describe the stress fractures in the metatarsals of soldiers, now commonly referred to as a march fracture, depicting clinical setting and symptoms [1]. Forty years later, only 2 years after the discovery of roentgen and its clinical application, Stechow reported on radiographic identification of metatarsal stress fractures [2]. The diagnosis remained a solely military one until Pirker reported on the first stress fracture diagnosed in an athlete, a transverse femoral shaft fracture, in 1934 [3]. Devas was the first to report a large series of stress fractures in athletes in 1956 [4]. Since then, stress fractures have been increasingly reported upon in medical literature in both clinical and research settings.

This paper intends to increase radiologists’ awareness of stress fractures and to give a compact overview of background on stress fractures. The clinical picture and symptoms of stress fractures will be described and special attention will be given to the imaging options available for early diagnosis of the condition, as this has significant implications for treatment and outcome, which are also briefly discussed. Although stress fractures can occur in almost any bone, 95% of stress fractures occur in the lower extremity. Therefore, stress fractures of the lower extremity are the focus of this paper.