Abstract
Biomechanical changes after anterior cruciate ligament reconstruction (ACLR) may be detrimental to long-term knee-joint health. We used pattern recognition to characterise biomechanical differences during the landing phase of a single-leg forward hop after ACLR. Experimental data from 66 individuals 12-24 months post-ACLR (28.2 ± 6.3 years) and 32 controls (25.2 ± 4.8 years old) were input into a musculoskeletal modelling pipeline to calculate joint angles, joint moments and muscle forces. These waveforms were transformed into principal components (features), and input into a pattern recognition pipeline, which found 10 main distinguishing features (and 8 associated features) between ACLR and control landing biomechanics at significance alpha =0.05. Our process identified known biomechanical characteristics post-ACLR: smaller knee flexion angle; less knee extensor moment; lower vasti, rectus femoris and hamstrings forces. Importantly, we found more novel and less well-understood adaptations: smaller ankle plantar flexor moment; lower soleus forces; and altered patterns of knee rotation angle, hip rotator moment and knee abduction moment. Crucially, we identified, with high certainty, subtle aberrations indicating landing instability in the ACLR group for: knee flexion and internal rotation angles and moments; hip rotation angles and moments; and lumbar rotator and bending moments. Our findings may benefit rehabilitation and assessment for return-to-sport 12–24 months post-ACLR.
Highlights
The single-leg hop-for-distance is routinely used in the evaluation of individuals after surgery to reconstruct a ruptured anterior cruciate ligament[26,31] (ACL)
For each variable retained after Parallel Analysis (PA), median of 4 principal components accounting for an average of 98.5% of the total variance was retained (Table 1)
This was reduced to 10 main features (Table 2) comprising 3 principal components of muscle forces (Fig. 1), 4 of joint angles (Fig. 2), and 3 of joint moments (Fig. 3)
Summary
The single-leg hop-for-distance is routinely used in the evaluation of individuals after surgery to reconstruct a ruptured anterior cruciate ligament[26,31] (ACL). During single-leg landing tasks, ACL-reconstructed (ACLR) individuals have shown altered biomechanics at the hip, knee and ankle[12,15,25,27,45] when landing on the involved knee. ACLR individuals have demonstrated smaller peak knee flexion angles[20,27,28,38,45] and smaller peak knee extensor moments[12,20,27,28,38] compared to controls and/or the uninjured limb. These findings are based on discrete data points in the landing phase determined a priori, and do not take into account the whole temporal waveforms of these biomechanical variables.[4]
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