Abstract
Anterior cruciate ligament deficiency (ACLD) affects the performance of walking in some patients (non-copers) while copers are able to minimize the effects via proper musculoskeletal compensations. Since many daily activities are more challenging than level walking, e.g., obstacle-crossing, it is not clear whether copers are able to cope with such a challenging task. A successful and safe obstacle-crossing requires not only sufficient foot clearance of the swing limb, but also the stability of the body provided mainly by the stance limb. Failure to meet these demands may lead to falls owing to loss of balance or tripping over obstacles. The purpose of the current study was to identify the motor deficits and/or biomechanical strategies in coper and non-coper ACLD patients when crossing obstacles of different heights for a better function assessment.
Ten coper and ten non-coper ACLD patients were recruited in the current study. The non-coper ACLD subjects were those who had not been able to return to their pre-injury level activities, had at least once giving way during the last six months and their Lysholm knee scale was less than 70 [1]. Each subject walked and crossed obstacles of heights of 10%, 20% and 30% of their leg lengths at a self-selected pace. Kinematic and kinetic data were measured with a 7-camera motion analysis system (Vicon, Oxford Metrics, U.K.) and two force plates (AMTI, U.S.A.). The leading and trailing toe clearances were calculated as the vertical distances between the toe markers and the obstacle when the toe was directly above the obstacle. Joint angles of both limbs, and joint moments of the stance limb, were calculated. Peak extensor moments at the knee during stance phase and the corresponding joint angles were extracted for statistical analysis. A 3 by 2, 2-way mixed-model analysis of variance with one between-subject factor (group) and one within-subject factor (obstacle height) was performed (α=0.05). SAS version 9.2 was used for all statistical analysis.
Compared with the copers, significantly reduced leading and trailing toe clearances were found in the non-coper group (P<0.05). The non-copers showed significantly decreased peak extensor moments (P<0.05) and flexion angle at the affected knee during the stance phase before leading limb crossing (P<0.05).
Distinctive gait patterns were identified in coper and non-coper patients with unilateral anterior cruciate ligament deficiency during obstacle crossing. During the stance phase before the un-affected leading limb crossing, the non-copers showed significantly reduced flexion and peak extensor moments at the affected knee (i.e., quadriceps avoidance), primarily owing to the impaired stability at the affected knee. The significantly reduced leading and trailing toe clearances in the non-coper group indicate that the non-coper ACLD patients are at a higher risk of tripping over the obstacle, and may have difficulty in regaining balance owing to the unstable ACLD knee. Advanced rehabilitation program or reconstruction of the ACL is suggested for the non-coper group.
