Background: Release for full activity and return to sport after anterior cruciate ligament reconstruction (ACLR) is often dictated by time from surgery and subjective opinion by the medical team. Temporal guidelines for return to sport may not accurately identify impaired strength and neuromuscular control, which are associated with increased risk for second injury (contralateral and/or ipsilateral limb) after ACLR in athletes.
Hypotheses: Athletes undergoing ACLR and returning to sport would demonstrate functional deficits that would not be associated with time from surgery.
Study design: Controlled laboratory study.
Methods: Thirty-three male (n = 10) and female (n = 23) athletes with unilateral ACLR, who were cleared by a physician to return to their sport after surgery and rehabilitation, performed the single-legged vertical hop test for 10 seconds on a portable force plate. Matched teammates of each patient were recruited to serve as sex-, sport-, and age-matched controls (CTRL; n = 67). Maximum vertical ground-reaction force (VGRF) was measured during each single-limb landing. Single-limb symmetry index (LSI) was calculated as the ratio of the involved divided by uninvolved limb, expressed as a percentage.
Results: The single-limb vertical jump height LSI was reduced in the ACLR group, 89% (95% confidence interval [CI], 83%-95%), compared with the matched CTRL group, 101% (95% CI, 96%-105%; P < .01). The LSI for VGRF normalized to potential energy achieved during flight of the hop was increased in ACLR at 112% (95% CI, 106%-117%) relative to the CTRL group at 102% (95% CI, 98%-106%; P < .01). Linear regression analysis indicated that time from surgery was not associated with limb symmetry deficits in the ACLR group (P > .05; R (2) = .002-.01).
Conclusion: Deficits in unilateral force development (vertical jump height) and absorption (normalized VGRF) persist in an athlete's single-limb performance after ACLR and full return to sports. These symmetry deficits appear to be independent of time after reconstruction.
Clinical relevance: On the basis of these results, clinicians should consider assessment of single-limb power performance in the decision-making process for return-to-sport release. Persistent side-to-side asymmetries may increase the risk of contralateral and/or ipsilateral injury.