Background There is no consensus on the components of return-to-sport (RTS) testing following anterior cruciate ligament (ACL) reconstruction or whether passing RTS criteria can reduce a patient's risk of reinjury. Objectives To determine whether impartial, criteria-based RTS decisions are associated with less risk of a second ACL injury (either graft failure or contralateral ACL injury). Methods In this systematic review with meta-analysis, the authors conducted an electronic literature search in PubMed/MEDLINE, Embase, CINAHL, SPORTDiscus, and ProQuest Dissertations and Theses Global using database-specific vocabulary related to ACL reconstruction and return to sport. Individual study quality was assessed using the modified Downs and Black checklist, and overall quality of evidence was determined with the Grading of Recommendations Assessment, Development and Evaluation scale. Pooled risk difference (passed versus failed RTS criteria), injury incidence proportion, and the diagnostic accuracy of each RTS criterion were calculated. Results Four studies met the selection criteria. Overall, 42.7% (95% confidence interval [CI]: 18%, 69%) of patients passed RTS criteria, and 14.4% (95% CI: 8%, 21%) of those who passed experienced a second ACL injury (graft rupture or contralateral ACL injury). There was a nonsignificant 3% reduced risk of a second ACL injury after passing RTS criteria (risk difference, −3%; 95% CI: −16%, 10%; I2 = 74%, P = .610). The evidence rating of the Grading of Recommendations Assessment, Development and Evaluation scale was “very low quality,” due to imprecision and heterogeneity of the pooled risk difference estimate. Conclusion Passing RTS criteria did not show a statistically significant association with risk of a second ACL injury. The quality-of-evidence rating prevents a definitive conclusion on this question and indicates an opportunity for future research. Level of Evidence Prognosis, Level 2a-. J Orthop Sports Phys Ther 2019;49(2):43–54. Epub 30 Nov 2018. doi:10.2519/jospt.2019.8190

Background Hamstring injury is a prevalent muscle injury in sports. Inconclusive evidence exists for eccentric hamstring strengthening to prevent hamstring injuries. One reason for this discrepancy may be the influence intervention non-compliance has on individual study estimates, and therefore pooled estimates. Objective This systematic review aims to determine the effect of eccentric hamstring strengthening on the risk of hamstring injury and quantitatively explores the impact of intervention non-compliance on the precision, heterogeneity and strength of pooled estimates. Methods A computer-assisted literature search of Medline, CINAHL, Cochrane, EMBASE, AMED, SportDiscus and PEDro databases was conducted with keywords related to eccentric strengthening and hamstring injury. The search was conducted from the end of a previous comprehensive review forward (1 December 2008 to 31 December 2013). Randomeffects models were used for both main effects and a sensitivity analysis. Pooled estimate precision was measured with a confidence limit ratio (confidence limit ratio (CLR); upper limit divided by the lower limit) and heterogeneity was assessed with I 2 , Cochrane's-Q and τ 2 . A protocol was not registered for this review. Results Four out of 349 studies met the inclusion criteria. In main effects analysis, eccentric hamstring training did not reduce the risk of hamstring injury (risk ratio [RR]=0.59 ((95% CI 0.24 to 1.44)). This estimate was imprecise (CLR=6.0) with significant heterogeneity ( p value 0.02, 69.6% variation and t 2 =0.57). Subjects compliant with eccentric strengthening had a significant (RR=0.35 ((95% CI 0.23 to 0.55)) reduction in hamstring injuries. This estimate was precise (CLR=2.4) and homogenous ( p value=0.38, 2.8% variation and t 2 =0.007). Conclusions The null-biased effect in using intent-totreat methods from intervention non-compliance has a substantial impact on the precision, heterogeneity and the direction and strength of pooled estimates. Eccentric strengthening, with good compliance, appears to be successful in prevention of hamstring injury.

Physical activity did not change at 6 months, and a small to moderate improvement was found at 12 months postsurgery, despite large improvements in quality of life, pain, and physical function. Reasons for the lack of increased PA are unknown but may be behavioral in nature, as a sedentary lifestyle is difficult to change. Changing sedentary behavior should be a future focus of research in this subgroup.

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In the meta-analysis, graft augmentation or interposition appeared to provide a lower retear rate and improved ASES scores when compared with RCR alone. Future prospective, randomized, controlled, and appropriately powered trials are needed for more definitive recommendations.