Quadriceps and hamstring muscles strength differences in adolescent and adult recreational athletes 6 months after autograft bone-patellar-tendon-bone anterior cruciate ligament reconstruction: A retrospective study.

Abstract

Knee muscle strength recovery after anterior cruciate ligament reconstruction (ACLR) is crucial for a safe return to sport (RTS) but it is poorly described in the adolescent population. Therefore, we compared the knee muscle strength at 6 months post-surgery in adults and adolescents. We hypothesized a greater muscular strength in adolescents 6 months after ACLR. This was a retrospective analysis of 55 adolescents (13-18 years old) and 76 adults (19-39 years old) who underwent ACLR with autograft bone-patellar-tendon-bone (BPTB), subjected to isokinetic tests 6 months after surgery. The following outcomes were analyzed: (1) the maximum torque of hamstrings (H) and quadriceps (Q) during flexion and extension at 30°/s normalized by body weight; (2) hamstrings to quadriceps strength ratio (HQ ratio); (3) injured to uninjured leg muscle strength ratio (limb-symmetry index, LSI). Both adults and adolescents produced lower Q torque with the injured leg compared with uninjured, but similar H torque. In adolescents, the injured Q torque and the Q-LSI were higher compared with adults. In both populations, the Q-LSI was lower than the H-LSI and the HQ ratio in the injured leg was higher compared with uninjured. Adolescents showed a lower HQ ratio in injured legs. At 6 months after ACLR both adolescents and adults did not recover Q strength in the injured leg. However, adolescents showed larger Q strength compared with adults. The HQ ratio analysis showed that 6 months after surgery both groups are not ready for a safe RTS.