Low Bone Mineral Density in Male Athletes Is Associated With Bone Stress Injuries at Anatomic Sites With Greater Trabecular Composition Adam S. Tenforde, * y MD, Allyson L. Parziale, z BS, Kristin L. Popp, § PhD, and Kathryn E. Ackerman, z|| MD, MPH Investigation performed at Boston Children’s Hospital, Boston, Massachusetts, USA Background: While sports participation is often associated with health benefits, a subset of athletes may develop impaired bone health. Bone stress injuries (BSIs) are a common overuse injury in athletes; site of injury has been shown to relate to underlying bone health in female athletes. Hypothesis/Purpose: This case series characterizes the association of type of sports participation and anatomic site of BSIs with low bone mineral density (BMD), defined as BMD Z-score \–1.0. Similar to female athletes, it was hypothesized that male ath- letes who participate in running and sustain BSIs in sites of higher trabecular bone content would be more likely to have low BMD. Study Design: Cohort study; Level of evidence, 3. Methods: Chart review identified 28 male athletes aged 14 to 36 years with history of 1 lower-extremity BSI who were referred for evaluation of overall bone health, including assessment of lumbar spine, hip, and/or total body less head BMD per dual-energy x-ray absorptiometry. BMD Z-scores were determined via age, sex, and ethnicity normative values. Prior BSIs were classified by anatomic site of injury into trabecular-rich locations (pelvis, femoral neck, and calcaneus) and cortical-rich locations (tibia, fibula, femur, metatarsal and tarsal navicular). Sport type and laboratory values were also assessed in relationship to BMD. The asso- ciation of low BMD to anatomic site of BSI and sport were evaluated with P value \.05 as threshold of significance. Results: Of 28 athletes, 12 (43%) met criteria for low BMD. Athletes with a history of trabecular-rich BSIs had a 4.6-fold increased risk for low BMD as compared with those with only cortical-rich BSIs (9 of 11 vs 3 of 17, P = .002). Within sport type, runners had a 6.1-fold increased risk for low BMD versus nonrunners (11 of 18 vs 1 of 10, P = .016). Laboratory values, including 25-hydroxy vitamin D, were not associated with BMD or BSI location. Conclusion: Low BMD was identified in 43% of male athletes in this series. Athletes participating in sports of running and with a history of trabecular-rich BSI were at increased risk for low BMD. Keywords: RED-S; female athlete triad; BMD; male athletes Sports participation is associated with many health bene- fits, including improved muscle mass and bone strength. 24 However, a subset of athletes of both sexes may experience adverse health consequences associated with sports partici- pation, including development of bone stress injuries (BSIs). BSI is a form of overuse injury to bone that is characterized by localized bone pain and tenderness as a result of struc- tural fatigue. These injuries exist on a continuum of sever- ity, with mild injuries resulting in periosteal edema and with more severe injuries showing varying degrees of mar- row edema and evidence of stress fracture. The medical con- cern is that this form of injury may eventually progress to a full fracture if not appropriately treated. Prior research in runners has identified annual incidence rates of BSIs of approximately 5% in adolescent runners and 20% in colle- giate runners. 26,28 In rates of stress fracture by athletic *Address correspondence to Adam S. Tenforde, Department of Phys- ical Medicine and Rehabilitation, Harvard Medical School, Spaulding Rehabilitation Hospital, 1575 Cambridge Street, Cambridge, MA 02138, USA (email: atenforde@partners.org). y Department of Physical Medicine and Rehabilitation, Harvard Medi- cal School, Spaulding Rehabilitation Hospital, Cambridge, Massachu- setts, USA. z Division of Sports Medicine, Boston Children’s Hospital, Boston, Massachusetts, USA. § Division of Endocrinology, Massachusetts General Hospital and Har- vard Medical School, Boston, Massachusetts, USA. || Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA. One or more of the authors has declared the following potential con- flict of interest or source of funding: K.L.P. receives research support from the Department of Defense (W81XWH-15-C-0024). The American Journal of Sports Medicine 2018;46(1):30–36 DOI: 10.1177/0363546517730584 Ó 2017 The Author(s) 30