Landing Biomechanics in Patients 2 Years After Augmented ACL Repair and 2 Years After Hamstring Autograft ACL Reconstruction Compared With Controls.

BACKGROUND

InternalBrace-augmented anterior cruciate ligament repair (ACL-IB) is believed to restore natural knee mechanics. However, there is a dearth of data on in vivo leg biomechanics after ACL-IB and comparability with gold standard surgery.

PURPOSES

To (1) investigate differences in sagittal and frontal landing biomechanics of the legs in patients after ACL-IB (Comparison I) and after anterior cruciate ligament reconstruction (ACLR; Comparison II), compare the involved legs with controls (Comparison III), and (2) identify leg differences that were greater than those typically observed in controls.

STUDY DESIGN

Cross-sectional study, Level of Evidence 3.

METHODS

A total of 29 patients who had ACL-IB, 27 sex- and age-matched patients who had ACLR, and 29 matched controls were asked to perform single-leg hops (SLH) for maximum forward distance 2 years postoperatively, assessed by marker-based motion analysis. Sagittal (hip, knee, and ankle) and frontal (hip and knee) plane angles and peak moments, joint work contribution, and peak vertical ground-reaction force and loading rates during landing were calculated. Differences between the involved and uninvolved legs in patients (paired tests) and between the involved legs in patients and the nondominant legs in controls (1-way analysis of variance) were analyzed. To determine whether these differences exceeded the typical variation seen in the control legs, we compared the overlap of the 95% CIs of the differences with the 95% CIs of the within-control differences (the nondominant versus dominant leg).

RESULTS

Patients who underwent ACL-IB (ACL-IB group) and ACLR (ACLR group) showed significant differences in their legs' SLH landing biomechanics. Only leg differences in the ACL-IB group were greater than those in in the control group (no overlap): smaller peak knee flexion angle (leg difference: -8.3° [95% CI, -13 to -3.7]; = -0.85; = .001; controls [95% CI, -1.7 to 4.2]) and lower peak knee flexion moment (-0.60 Nm/kg [95% CI, -0.72 to -0.31]; = -0.72; < .001; controls [95% CI, -0.06 to 0.35]) in the involved compared with the uninvolved leg; and lower peak knee flexion moment in the involved leg compared with control legs (-0.50 Nm/kg [95% CI, -1 to -0.07]; = -0.71; = .020).

CONCLUSION

Persistent differences in SLH landing biomechanics 2 years after ACL surgery suggest that ACL ruptures cause alterations that cannot be restored by augmented repair or reconstruction alone. The greater differences between the legs in the ACL-IB group than those typically seen within controls highlight the need for further research to understand the full potential or limitation of ACL preservation techniques.