Objective

A criterion of the anterior cruciate ligament reconstruction (ACLR) success is the return to sport at the same level as before surgery. Return to sport (RtS) decision seems to be a key element in this success: if too early RtS exposes to risk of injury, too late RtS influences the motivation to return to the same level. Functional tests (Hop Tests) and isokinetic assessments (Isok Tests) are usually performed to guide this decision. However, a precise and objective biomechanical analysis of running pattern would be more similarly to the sport activity. In this context, our objective was to compare the running and sprinting biomechanical analysis, with the usual tests during return to sport.

Patients and methods

Sixteen patients practicing a pivot-contact competitive sport were included prospectively and assessed at 6, 9 and 12 months postoperatively after a first ACLR by: Hop Tests, a Star Excursion Balance Test (SEBT), concentric Isok Tests at 60°/s and 240°/s and eccentric 30°/s, and sprint and 12 km/h running biomechanical evaluation recordings on a instrumented treadmill. Correlation analyses were performed between all these parameters for each value, “healthy” side and side “operated”.

Results

Biomechanical stiffness of the lower extremity during running was correlated with the concentric isokinetic flexor strength ( r = 0.62 side “operated” and r = 0.56 side “healthy”). The sprint horizontal force was correlated with eccentric isokinetic strength ( r = [0.59 to 0.67]). The index of force application technique in the sprint were correlated with those of Hop Test ( r = [0.52 to 0.7]). There was no correlation for the variables “operated” and “healthy” to step length, or for SEBT variables.

Discussion/Conclusion

If the characteristics of the force application technique to the ground during the race could be estimated indirectly by Isok Tests and Hop Tests, only an instrumented treadmill analysis allows direct qualitative assessment of running pattern (step length symmetry). So, it seems that the association of these assessments is relevant in the decision to return to sport.