Neo-natal castration leads to subtle differences in porcine anterior cruciate ligament morphology and function in adolescence

Abstract

Female adolescent athletes are at a higher risk of tearing their anterior cruciate ligament (ACL) than male counterparts. While most work related to hormones has focused on the effects of estrogen to understand the increased risk of ACL injury, there are other understudied factors, including testosterone. The purpose of this study was to determine how surgical castration in the male porcine model influences ACL size and function across skeletal growth. Thirty-six male Yorkshire crossbreed pigs were raised to 3 (juvenile), 4.5 (early adolescent), and 6 months (adolescent) of age. Animals were either castrated (barrows) within 1-2 weeks after birth or were left intact (boars). Post-euthanasia, joint and ACL size were assessed via MRI, and biomechanics were assessed via a robotic testing system. Joint size increased throughout age, yet barrows had smaller joints than boars (p<0.001 for all measures). ACL cross-sectional area (CSA), length, volume, and stiffness all increased with age (p<0.0001), as did ACL anteromedial (AM) bundle percent contribution to resisting applied loads (p=0.012). Boar ACL and AM bundle volumes were 18% (p=0.003) and 24% (p=0.004) larger than barrows across ages. However, CSA, stiffness, and bundle contribution were similar between boars and barrows (p>0.05). The barrows had smaller temporal increases in AM bundle percent function than boars, but these data were highly variable. Thus, early and sustained loss in testosterone leads to subtle differences in ACL morphology, but may not influence measures associated with increased injury risk, such as CSA or bundle forces in response to applied loads.