Anterior cruciate ligament reconstruction in adolescent patients: limb asymmetry and functional knee bracing

Boyi Dai, Robert J Butler, William E Garrett, Robin M Queen
American Journal of Sports Medicine 2012, 40 (12): 2756-63

BACKGROUND: Anterior cruciate ligament (ACL) reinjury rates are high in adolescent patients. Knee braces are commonly used after ACL reconstruction to prevent reinjury during return to sports.

HYPOTHESIS: Adolescent patients following ACL injury would demonstrate a decreased vertical ground-reaction force, knee extension moment, knee flexion angle, and knee flexion velocity on the surgical limb when compared with the nonsurgical limb during a side-cutting task. A functional knee extension-resistant brace would decrease the limb asymmetries.

STUDY DESIGN: Controlled laboratory study.

METHODS: Twenty-three adolescent patients 6 months after ACL reconstruction were recruited for this study. Three-dimensional kinematic and kinetic data were collected bilaterally (surgical, nonsurgical) during a 35° side-cutting task while the patient was wearing and not wearing a functional knee extension-resistant brace (nonbraced, braced) on the surgical limb.

RESULTS: The surgical limb demonstrated a significant decrease in peak impact vertical ground-reaction force (2.55 body weight [BW] vs 2.8 BW; P < .01), peak propulsion vertical ground-reaction force (2.15 BW vs 2.3 BW; P < .01), peak knee extension moment (0.13 BW × body height [BH] vs 0.17 BW × BH; P < .01), knee flexion angle at peak knee flexion velocity (27.8° vs 30.0°; P = .01), peak knee flexion angle (44.1° vs 48.5°; P < .01), and peak knee flexion velocity (571.3 deg/sec vs 640.1 deg/sec; P < .01) when compared with the nonsurgical limb during both nonbraced and braced conditions. Bracing increased the initial knee flexion velocity (42.4 deg/sec vs -40.2 deg/sec; P = .01) and decreased the initial knee flexion angle on the surgical limb (13.1° vs 15.7°; P < .01). Bracing also affected kinematics of the nonsurgical limb. Bracing did not decrease the asymmetry between surgical and nonsurgical limbs.

CONCLUSION: Adolescent patients 6 months after ACL reconstruction demonstrated significant kinematic and kinetic asymmetries between the surgical and nonsurgical limbs. The limb asymmetries persisted when the patients were wearing a functional knee brace. There were changes in the surgical knee kinematics with and without bracing, especially near initial ground contact.

CLINICAL RELEVANCE: The limb asymmetries are of concern with regard to injuring the graft or the contralateral limb when the patients return to sport.

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