Stress fracture site linked to osteopenia in young, female athletes

Atypical stress fractures—in the femur, acetabulum, sacrum, spine, or ribs—are more likely to occur in young, athletic women with underlying bone mineral density (BMD) abnormalities, according to the results of a paper presented at the 2009 Annual Meeting.

Lead investigator Pamela Sherman, MD, said this finding has important implications for treating low bone density in young women.

“Defining the site of stress fracture as a reliable indicator of abnormal bone density provides an invaluable clinical tool for diagnosing osteopenia, which is an otherwise silent issue in apparently healthy young women,” asserted Dr. Sherman.

“Detecting early signs of low bone density,” she continued, “allows for disease prevention through a global treatment plan of education, nutritional support, restoration of menstrual cycles, and activity modification.”

Studying BMD and fracture site
A cohort of 73 female patients between the ages of 15 and 45 was treated for stress fractures at a single institution during a 2-year period.

Dr. Sherman noted that the impetus for the study was an earlier, retrospective study of women with a history of stress fracture that was conducted over a 4-year period (1994–1998). That study found that women younger than age 40 who had cancellous bone fractures were more likely to have low bone density as defined by dual energy X-ray absorptiometry (DXA) scan.

Based on previous studies, researchers determined the most common fracture sites. Forty-five of the patients had typical stress fracture sites below the knee (29 tibia, 9 metatarsal, 3 fibula, and 4 calcaneus). Twenty-eight patients had atypical stress fracture sites above the knee (7 femoral neck, 7 femur, 7 pubic rami, 2 spine/pars, and 2 rib fractures, 1 lesser trochanter, 1 acetabulum, and 1 sacrum).

Each patient received a nutritional consultation and evaluation, underwent a DXA scan, and completed a written questionnaire at enrollment that focused on exercise background, activity level, physical characteristics, and menstrual history. Three subsequent questionnaires completed 6 weeks, 3 months, and 6 months after the study began ascertained ongoing difficulties with basic activities of daily living (secondary to the fracture), ability to return to exercise, and current general health.

Researchers measured BMD using the World Health Organization’s criteria for osteopenia (more than one standard deviation below the bone density of a normal woman of the same age). In addition, the investigators assessed patients for the presence of eating disorders and eating disorder risk factors and determined body mass index (BMI), any history of menstrual irregularities, and calcium intake.

Results
Using student t-tests, researchers found a significant difference in the study groups in both spine and femoral BMD statistical analysis (Table 1). Osteopenia was more common among patients with atypical fracture sites than among those with typical fracture sites.

Dr. Sherman said that “significant but weak” associations exist between BMD and BMI at all three sites of BMD measurement (spine, femur, and forearm).

“In this study, 30 percent of patients with a BMI greater than 23 had low bone density, as did 39 percent of patients with a BMI of 20 to 23,” said Dr. Sherman. “Fifty-two percent of those with a BMI lower than 20 had low bone density.”

In addition, researchers found a correlation between patients who were diagnosed with a history of or current eating disorders and lower spine BMD (Table 2).

“Based on our findings, we recommend that anyone presenting with a stress fracture at an atypical site above the knee should be referred for a DXA scan to rule out occult compromised bone health,” said Dr. Sherman. “Early diagnosis of low bone density may be treated with proper calcium and vitamin D supplementation, review of adequate dietary intake, and potential available or future pharmacological agents.”

Dr. Sherman authored “Atypical stress fracture sites predict underlying bone health issues in athletic females” with Jennifer Rogers-Stevane, MD; Deborah Saint-Phard, MD; Terry Karl, MS, RD, CDN; Lisa Callahan, MD; and Jo A. Hannafin, MD, PhD. None of the authors reported conflicts.

Jennie McKee is a staff writer for AAOS Now. She can be reached at mckee@aaos.org