Rehabilitation volume, psychological readiness, and motor function are important factors for a successful return to sport after anterior cruciate ligament reconstruction: A 2-year follow-up cohort study.

Objectives: To find contributors to return to sport success or time until return to sport in individuals after an anterior cruciate ligament reconstruction.

Design: Cohort study.

Methods: Secondary analysis of the data of two intervention studies.

Participants: We included adults < 36 years of age with a tendon autograft anterior cruciate ligament reconstruction who were active in any type of sport prior to the injury and aiming to return to sport. All participants were prospectively monitored for 24 months.

Interventions: At the end of the individual post-surgery rehabilitation and re-injury prevention programmes, self-report- and objective functional outcomes were quantified.

Main outcome measures: The potential return to sport success (return to the same type of sports, frequency, intensity, and quality of performance as pre-injury), secondary injuries, and all rehabilitation and training measures were prospectively monitored. To determine the contributing factors, Cox regressions for traits and baseline factors and a logistic mixed model, which also included prospective time-dependent factors, were calculated.

Results: 203 participants were included; 104 (51 % of the total sample and 68 % of the full cases) successfully returned to their sporting activity. The median duration until return to sport was 302 days (interquartile range was 114 days). Contributing factors were the type of working (blue- vs. white collar: odds ratio for return to sport = 0.51 [95 % confidence interval = 0.29 to 0.90]) and the athletic status (elite vs. non-elite: odds ratio = 2.28 [1.03 to 5.03]). Prospectively, higher rehabilitation volumes until the end of the rehabilitation were predictive for return to sport success: the odds ratio per additional hour of rehabilitation was 1.004 [1.001 to 1.006]. Functional abilities such as the normalised knee separation distance during drop jump landing (odds ratio = 0.961 [0.924 to 0.999]) were predictive at a later stage, at the end of the re-injury prevention. Psychological readiness for return to sport was predictive at most of the timepoints: those who were confident to return to sport were more successful to return to sport at the end of the rehabilitation (odds ratio = 1.029 [1.004 to 1.056]) and at the end of the re-injury prevention (odds ratio = 1.038 [1.004 to 1.073]).

Conclusions: The most important factors for a successful pre-injury-level return to sport after anterior cruciate ligament reconstruction were the exercise volume, psychological readiness and functional hop/jump abilities. Whilst the impact of these modifiable factors was robust against multilevel modelling, the impact of athletic and working status vanishes when the prospective factors are included.