ISB clinical biomechanics award winner 2025: Residual translational and rotational kinematics after combined anterior cruciate ligament and anterolateral ligament reconstruction during walking - A biplanar fluoroscopy analysis.
Oh J, Yoon S, Wang J, Koo S • Clinical biomechanics (Bristol, Avon) • 2026
Anatomical single-bundle anterior cruciate ligament reconstructions combined with anterolateral ligament reconstruction do not fully restore normal joint kinematics, with increased anterior translation and internal rotation persisting during walking, indicating residual instability.
Key Findings
Results
Operated knees exhibited significantly increased anterior tibial translation throughout a large portion of the stance phase compared with both contralateral and normal knees.
Anterior tibial translation was significantly increased during 17–85% of the stance phase in operated knees
Comparisons were made against both the contralateral (non-operated) knee and healthy control knees
Statistical significance was established at p < 0.05
Ten individuals who underwent combined reconstruction were compared against ten healthy controls
Statistical parametric mapping was used to identify time-continuous differences across the gait cycle
Results
Internal tibial rotation was significantly greater in operated knees during early stance compared with normal knees.
Increased internal tibial rotation was observed during 15–37% of the stance phase in operated knees
The difference was statistically significant (p < 0.05) compared with normal (healthy control) knees
The comparison with the contralateral knee did not reach the same level of significance over this interval
Biplanar fluoroscopic imaging was used to capture in-vivo tibiofemoral kinematics during treadmill walking
Results
Cumulative changes in internal-external rotation and anterior-posterior translation during early stance were significantly increased in operated knees compared with both contralateral and normal knees.
A cumulative-change analysis was employed in addition to statistical parametric mapping to quantify kinematic differences
Both rotational and translational cumulative changes were elevated in the operated knee group during early stance
Differences were significant relative to contralateral knees and normal control knees (p < 0.05)
This finding indicates residual dynamic instability even after combined ACL and ALL reconstruction
Conclusions
Combined single-bundle ACL and anterolateral ligament (ALL) reconstruction does not fully restore normal tibiofemoral kinematics during level walking.
Ten participants who underwent combined single-bundle ACL and ALL reconstruction were studied
Kinematics were assessed in vivo using a biplanar fluoroscopic imaging system during treadmill gait
Subject-specific 3D models were reconstructed using a statistical shape and intensity model with 2D–3D registration
Residual anterior translation and internal rotation persisted in operated knees despite the combined reconstruction procedure
Findings 'support rotational laxity of single-bundle techniques and suggest the potential need to address dynamic instability'
Methods
The study used biplanar fluoroscopy with subject-specific 3D modeling to measure in-vivo knee kinematics during treadmill walking.
A biplanar fluoroscopic imaging system captured dynamic motion during treadmill gait trials
Subject-specific 3D tibiofemoral models were reconstructed using a statistical shape and intensity model
2D–3D image registration was used to derive tibiofemoral kinematics from fluoroscopic images
Tibial kinematics were compared among three groups: operated knees, contralateral knees, and healthy control knees
Statistical parametric mapping was applied to evaluate continuous kinematic waveforms across the gait cycle
What This Means
This research suggests that even when surgeons repair a torn anterior cruciate ligament (ACL) combined with reconstruction of a secondary stabilizing structure called the anterolateral ligament (ALL), the knee does not move completely normally during everyday walking. Using high-precision X-ray imaging technology called biplanar fluoroscopy, researchers tracked the exact position of the shin bone (tibia) relative to the thigh bone (femur) in ten people who had undergone this combined knee reconstruction, comparing them to ten healthy individuals with no knee problems.
The study found that the reconstructed knees showed two persistent abnormalities during the stance phase of walking: the shin bone shifted too far forward (excess anterior translation) for most of the stance phase, and it also rotated inward (internal rotation) too much during early stance. These differences were statistically significant not only compared to healthy control knees but also compared to the patients' own non-operated knees, suggesting the abnormal motion is specific to the reconstructed side rather than a general characteristic of the individuals.
These findings matter because they indicate that the current combined single-bundle ACL plus ALL reconstruction approach, while an improvement over ACL reconstruction alone, still leaves patients with measurable joint instability during normal activities like walking. This residual instability could have implications for long-term joint health and the risk of re-injury. The results suggest that further refinements in surgical technique—potentially addressing dynamic rotational instability more directly—may be needed to fully restore normal knee mechanics after ACL injury.
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