D-67 Clinical Case Slide - Lower Extremity Issues II

Abstract

Wolff’s law states that tissue adapts in response to mechanical loads placed upon it. While clinicians typically evaluate athletes for symmetry, some sports require bilaterally asymmetric movement, which may result in bilateral differences in tissue adaptations. There is limited sports-specific data regarding bone mineral density (BMD) and therefore it is believed that asymmetric athletes might have a significantly different BMD in their asymmetrically loaded leg. PURPOSE: To determine if there are bilateral differences in hip BMD in track and field athletes competing in events which require asymmetric loading patterns. METHODS: Men’s and women’s NCAA Division I track and field, soccer, and lacrosse teams underwent hip DEXA scans. Bone mineral density of Ward’s triangle (BMDW) and of the femoral neck (BMDFN) were measured bilaterally. Track and field athletes competing in events where asymmetric lower extremity loading patterns are required (ASYM) were identified (e.g., those utilizing a “plant” leg, lead / trail leg, or running high speeds on a curve). These events were defined as jumping events, javelin, hurdles, pole vault, and the 200m. The asymmetric athletes were matched with non-asymmetric athletes (NON) based on similar age, height, and body mass. The absolute value of the difference in BMD measurements between the left and right hips was computed for each individual for both regions. Paired t-tests were used to compare bilateral differences for BMDW and BMDFN between asymmetric athletes and matched controls. RESULTS: 15 males and 19 females were included for each group. There were no significant differences in BMDFN between ASYM and NON for males (p = 0.794), females (p = 0.485), or combined (p = 0.473). There were no significant differences between groups in BMDW for males (p = 0.779), females (p = 0.446), or combined (p = 0.508). CONCLUSIONS: Lack of bilateral differences in BMD at two regions of the hip in ASYM compared to NON suggests that event-specific asymmetric movement is not sufficient stimulus to cause major adaptation in bone relative to general athletic participation. It remains possible that older athletes with greater event-specific experience may exhibit bilateral asymmetries. Clinicians do not need to consider event-specific movement when interpreting hip BMD in collegiate athletes.