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

TL;DR

This study compares leg biomechanics in patients who had two different types of ACL surgery and finds that both show lasting differences compared to healthy controls.

Contribution

The study provides new empirical evidence on long-term biomechanical outcomes of ACL-IB compared to ACLR and controls.

Findings

Patients who underwent ACL-IB showed greater leg differences in knee flexion angle and moment than controls.

Both ACL-IB and ACLR patients had significant biomechanical differences in landing mechanics two years post-surgery.

ACL-IB patients had lower peak knee flexion moment in the involved leg compared to control legs.

Abstract

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.

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.

Cross-sectional study, Level of Evidence 3.

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 t 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).

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]; d = −0.85; P = .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]; d = −0.72; P < .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]; d = −0.71; P = .020).

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.

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