Bone Stress Injuries: A Holistic Evaluation

Stress fracture of the foot

Bone Stress Injuries

     Bone stress injuries (BSIs) refer to overuse injuries in which bones fail to withstand repetitive mechanical loads seen in weight-bearing activities such as running. This results in bone fatigue, localized bone pain and tenderness at the site of stress. BSIs are commonly seen in runners, endurance athletes, military recruits, but also in healthy people who have just started intense physical activity. BSI accounts for approximately 10% of all sport-related injuries and represents up to 20% of injuries treated in sports medicine clinics. Clinical presentation varies depending on severity. Initial findings may show radiographic evidence of periosteal edema and marrow edema; in more severe cases, stress fractures with visible fracture lines on X-ray may be present.

      Although severity can be assessed through imaging, it does not necessarily correlate with symptom severity; this can lead to an undiagnosed BSI. Early detection of a BSI is important for prompt management and treatment. Delay of diagnosis and chronic stress can lead to higher grades of injury that may require longer recovery periods, which can be frustrating for athletes. Therefore, in order to maximize an athlete's physiologic capacity to repair bone an adequate healing environment is needed which requires a full assessment from a nutritional, hormonal, and emotional standpoint as well as considering biomechanics, bone mineral density (BMD), and medication usage. The purpose of this article is to discuss the risk factors that contribute to bone stress injuries and how a holistic evaluation of BSIs can optimize management and healing in our athletes.

Risk Factors for BSIs

      In order to strategically approach and treat a patient who presents with a bone stress injury, it is important to have an understanding of contributing risk factors. Sudden changes in training intensity, low energy availability, previous stress injury, BMD, race, genetics, gender, biomechanics, hormone disruption, medications, nutrition, and exercise history are broadly considered to be risk factors for BSI at any age. Risk factors are mainly divided into biological factors and biomechanical factors.

Biological factors:

Biomechanical factors:

     One risk factor, the female athlete triad, demonstrates one important aspect of BSI, which is that the increased risk of BSI is multifactorial. There are some risk factors we can't avoid such as sex, genetics, anatomy, but most risk factors are in some way or another modifiable and/or manageable, which can aid in prevention.

Holistic Evaluation of BSIs

     When evaluating any form of BSI we must keep in mind that no two stress injuries behave alike. A holistic evaluation should consists of a thorough patient medical history, physical evaluation, radiographic imaging and laboratory testing. Therefore, when a patient presents with a BSI for the first time, assessment and treatment should be individualized to the patient, the causative activity, the anatomic site, and severity of the injury. Besides identifying and treating a stress injury, knowing what is predisposing the patient to such injury is equally important.

     The usual presentation of BSI is a patient initially reporting pain present during certain activities that without modification now describes an insidious progression of symptoms that may result in pain with daily activities. Patient's medical history should at least include patient demographics, medical conditions, medication history, exercise history, and dietary intake. On physical examination, there may be point tenderness with palpation on the affected bone site. Lower extremity stress injuries or fractures will reproduce pain with single-leg hop test, injury to the femoral neck is confirmed with log roll test, and fulcrum testing for long bone injuries. Imaging may show evidence of BSIs, but these can be easily overlooked. MRIs are effective for patients who are symptomatic with normal appearing X-rays. For patients, male or female, with recurrent stress injuries or fractures a complete laboratory work up should be done which can include vitamin D levels, serum calcium and phosphate levels, parathyroid hormone (PTH), thyroid-stimulating hormone (TSH), alkaline phosphatase, albumin, and pre-albumin. These tests are essential for assessing nutritional status and healing potential. In female athletes, further testing such as FSH, LH and estradiol levels may be warranted to assess if any underlying endocrine condition or energy imbalance is contributing to decreased BMD or recurrence of injury. 

     By presenting different cases scenarios involving BSIs, we can highlight the importance of a holistic approach to manage BSIs. 

1. The Fresh Recruit

Young male patient presents with a BSI that occurred during his basic training. When asked about his exercise history prior to basic training, he states that he had no physical training or conditioning prior to basic training. This fact is very importantto this case. Studies have shown that general fitness is a protective factor and that military recruits with higher activity levels before enlistment had fewer stress fractures during basic training. Reason is that as muscle fatigues, its capacity to absorb energy of an externally applied load diminishes resulting in higher stress and damage. Also, decreased energy availablity from, especially in male runners have been shown to be a key factor in low BMD most notable in the lumbar spine and radius. Knowledge of this patient's biomechanics, exercise history, and dietary intake can help prevent future BSIs.

2. The Alaskan Runner

A patient from Alaska presents with a BSI that occurred while running a 5 mile trail. He shares that the benefit of running in Alaska is that the scorching sun does not affect his training. It is well known that skin exposure to sunlight helps the body produce vitamin D which helps with calcium absorption and balance in the body. Therefore, lack of sun exposure may lead to vitamin D deficiency. Studies show that people with vitamin D deficiency have a higher risk of sustaining BSIs, while studies where vitamin D and calcium supplementation is given, there is a reduced incidence of BSIs. In cases like these, where vitamin D deficiency is suspected, determining serum 25(OH)D3 and calcium levels are appropriate. If lack of sun exposure is not a cause for vitamin D deficiency and low calcium, then other reasons such as malabsorption conditions (i.e. Celiac disease), kidney problems (i.e. renal failure), or endocrine dysfunction (i.e. hypoparathyroidism) may be explored.

3. The Female Triathlete

A female triathlete presents with a BSI after partcipatin in a recent triathlon. She states that during her training she had very few days of recovery in the month prior, her caloric intake was reduced significantly, and that her menstrual cycle became irregular to non-existent. This case is an ideal example of the female athlete triad - low energy availability, menstrual dysfunction, and low BMD - female athletes with one or more factors of this triad are at greatest risk. Studies show that inadequate caloric intake plus high intensity training may play a role in amenorrhea mostly due to low production of estrogen and progesterone. Low estrogen levels are also associated with decreased BMD, which is best seen in osteoporosis in post-menopausal women. Endocrine and nutritional state can disrupt the balance between bone formation and resorption thus predisposing female athletes, in particular, to BSIs and potential stress fractures. In cases such ase these, a dietary and exercise history together with an endocrine function evaluation such as FSH, LH, and estradiol levels may be a good approach.

Author
Ernesto P. Quinones Gonzalez Third year Medical Student at University of Medicine and Health Sciences (UMHS)

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