Poster 219: Changes in Body Composition and Bone Mineral Density Following Arthroscopic Treatment of Femoral Acetabular Impingement in Collegiate Athletes: A Matched Cohort Study

OBJECTIVES: This study’s objective was to compare changes in body composition measurements (BCM) and bone mineral density (BMD) over 2 years between collegiate athletes following hip arthroscopy to treat labral tears due to femoral acetabular impingement syndrome (FAI) and matched uninjured collegiate athletes. METHODS: A retrospective matched cohort study compared BCM and BMD of NCAA Division I athletes who underwent hip arthroscopy as a treatment for symptomatic FAI (scope group) with a control group of athletes who did not have hip arthroscopy over 24 months. The control group was matched to the scope group by sex and sport at a ratio of 2:1. Inclusion criteria for the scope group included arthroscopic hip surgery between January 1, 2017, and May 1, 2019, labral repair, femoral head-neck reshaping osteoplasty to address an alpha angle > 55 degrees, and available preoperative and postoperative outcomes. Athletes who had open hip surgery, surgery to address athletic pubalgia, other lower extremity surgery during the postoperative period, or failure to complete preoperative or postoperative testing were excluded. Incoming athletes beginning August 1, 2017 who did not have hip surgery, and had available BCM and BMD outcomes were included as controls. Dual Energy X-ray Absorptiometry scanning was used to measure BMD, lean mass, and fat mass. The regions of interest included the trunk (comprised of the pelvis, spine, and ribs), and bilateral lower extremities (Figure 1A). A mixed-effects linear regression model was used to compare differences in the change of BCM and BMD between the control and scope groups at baseline and at 1- and 2-years. The interaction of group and time was treated as a fixed effect, and the individual athlete was treated as a random effect. A p- value < 0.05 was set as the threshold for statistical significance and all tests were two-tailed. RESULTS: A total of 20 athletes underwent hip arthroscopy during the study period. Three athletes were excluded due to insufficient pre- or postoperative data, and one athlete was excluded due to concomitant surgery to treat athletic pubalgia. Therefore, 16 NCAA Division I collegiate athletes (Figure 1B) were included in the scope group and 32 matched athletes were included as controls (Table 1). Relative to the control group, the scope group’s trunk BMD was significantly reduced at 1-year (β: - 0.052 grams/cm(2) [95% CI: -0.073 to -0.032]; p < 0.001; Figure 1C). At 2-years, the scope group’s trunk BMD change remained reduced compared to control, but this difference was no longer statistically significant (β: -0.020 grams/cm2; [ -0.051 to 0.011]; p = 0.20). No significant differences in the change in BMD of the legs were identified between groups at 1-year (β: -0.014 grams/cm(2) [-0.075 to 0.047]; p = 0.66) or 2-years (β: 0.057 grams/cm(2) [-0.038 to 0.155]; p = 0.24). Relative to control, the scope group demonstrated significant decreases in all of the regions comprising the trunk BMD at 1-year (Figure 1D), including the pelvis (β: -0.071 grams/cm(2) [-0.103 to -0.040]; p < 0.001), spine (β: -0.057 grams/cm(2) [- 0.092 to -0.023]; p = 0.002), and ribs (-0.027 grams/cm(2) [-0.053 to -0.002]; p = 0.035). Similarly, the trunk lean mass (Figure 1E) of the scope group decreased 1,903 grams relative to the control group (95% CI: -3052 to -746; p = 0.003) at 1-year, and 1,953 grams at 2-years (95% CI: -3009 to -892; p < 0.001). Lean mass estimates of the legs demonstrated a relative increase by 2-years in the scope group compared to controls (1196 grams [95% CI: 303 to 2090]; p = 0.011). Changes in fat mass of the trunk did not differ significantly compared to controls at 1-year (β: -394 grams [95% CI: -2417 to 1646]; p = 0.70) or 2-years (β: -1534 grams [95% CI: -3513 to 447]; p = 0.13). Similarly, changes in fat mass of the legs in the scope group did not differ significantly from the control group at 1-year (β: 582 grams [95% CI: -611 to 1780]; p = 0.34) or 2-years (β: -201 grams [95% CI: -1606 to 1217]; p = 0.78). CONCLUSIONS: Compared to matched control athletes, trunk BMD was significantly decreased 1-year after hip arthroscopy to treat FAI. BMD reductions were noted in the spine and ribs with the greatest reduction in BMD occurring in the pelvis. Similarly, a reduction in trunk lean mass was also noted in the scope group at 1 and 2 years. These same reductions in BMD and lean mass are not seen in the lower extremities of the scope group, however, suggesting postoperative rehabilitation restrictions alone are unlikely to account entirely for these findings. Taken together, the combination of the reduction in trunk BMD and the persistent reduction of trunk lean mass suggests significant alteration in the axial portion of the body following hip arthroscopy. These data may indicate a need for prioritizing early axial loading of the trunk through weight-bearing exercises, and incorporating core strengthening early postoperatively to improve lean mass. Ultimately, both bone health and lean mass are important considerations for hip arthroscopy, both when selecting patients preoperatively and managing them postoperatively.