560 MEP016 – Sex difference of muscle strength recovery after anterior cruciate ligament reconstruction in adolescent patients

AbstractBackground Several studies have shown that adult females demonstrated the less muscle strength and less improvement after anterior cruciate ligament reconstruction (ACLR) compared to male.Purpose To investigate the sex difference of muscle strength recovery after ACLR in adolescent athletes.Design Retrospective studySetting Clinical setting in youth sportsPatients Eighty-five females and seventeen males under 15 years of age were included in this study. Intervention All patients underwent primary unilateral ACLR using auto-semitendinosus tendon graft, and same postoperative rehabilitation protocol.Main Outcome Measurements Isokinetic peak torque during concentric knee extension and flexion with an angular velocity of 60 deg/sec were measured at pre- and post-operative 3, 6, 9, 12 and 24 months. The limb symmetry index (LSI), peak knee extensor and flexor torque normalized by body weight were compared by sex and post-operative time.Results There were no significant difference in LSI of knee extensor and flexor strength between males and females (figure 1). Knee extensor torque of males at 12 and 24 post-operatively were significantly larger than females in both sides. Compared to 3 months post-operatively, male extensor strength was significantly increased 6 to 24 months, however, females showed no change after 9 months post-operatively (figure 2). Knee flexor torque of males after 6 months post-operatively were significantly larger than females. Compared to 3 months post-operatively, male flexor strength was significantly increased 6 to 24 months, however, females showed no significant increase after 6 months post-operatively (figure 3).Discussion In this study, different effect of sex and post-operative time on knee strength was observed after ACLR in adolescent patients. Males showed continuous increase after 6 months postoperatively, and these were impact of maturation growth. However, female muscle strength showed plateau at 6 months, possibility limited adaptation to muscle training after ACLR. Download figure Open in new tab Download powerpoint Abstract 560 Figure 1 Limb symmetry index (LSI). (a) Knee extensor strength, (b) Knee flexor strengthDownload figure Open in new tab Download powerpoint Abstract 560 Figure 2 Peak knee extensor torque. (a) ACLR side, (b) Contralateral side, rANOVA *p<0.05 Tukey, t p<0.05 Mann-Whitney U testDownload figure Open in new tab Download powerpoint Abstract 560 Figure 3 Peak knee flexor torque. (a) ACLR side, (b) Contralateral side, rANOVA *p<0.05 Tukey, t p<0.05 Mann-Whitney U test