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Buck S.1, Edin B.2, Strong A.1, Häger C.1
1Umeå University, Community Medicine and Rehabilitation, Umeå, Sweden, 2Umeå University, Integrative Medical Biology, Umeå, Sweden
Background: Movement control is critically dependent on exteroceptive and proprioceptive information. Reduced sensorimotor control of the knee has been demonstrated after injury of the anterior cruciate ligament (ACL), and it is suggested to be due to a reduction in proprioceptive acuity. Independent of whether poor sensorimotor control causes injuries or results from injuries, prevention and rehabilitation of ACL injuries require proper functional assessments. Various such test have been proposed in research, but their implementation and evaluation still represent clinical challenges. There is thus a pronounced need for improved clinical discriminative knee function tests related to proprioceptive ability.
Purpose: To develop and evaluate a functional obstacle clearance test that targets the proprioceptive ability of the lower extremity and allows discrimination of ACL-deficient from healthy legs.
Methods: We developed a paradigm in which participants step repeatedly over an obstacle and the foot clearance is measured. Ten healthy controls and 4 ACL-injured persons (subacute stage), all aged 18-27 years, have so far successfully performed the test. Participants wore custom-made goggles occluding downward vision, and stood behind an obstacle with the leading foot on a 2 cm elevated platform, while the lagging foot was parallel but on the floor. Participants placed the leading foot on a plastic obstacle hurdle (either 13% or 18% of participant height, respectively) in front of them. After a 3 seconds memorizing period, the participants returned the leading foot to the starting position on the platform, and then stepped over the obstacle with instructions of having as little clearance as possible between foot and obstacle. All participants performed 8 trials on each leg with obstacle heights presented in an unpredictable order. 8 high-speed cameras (Oqus, Qualisys AB, Sweden, 240Hz), recorded reflective markers on the whole body while two video cameras filmed all trials. Kinematics were processed in Qualisys track manager (Version 2.11) and then exported to Visual 3D (6DOF model, C-motion Inc. Maryland, USA). Means, standard deviations and coefficients of variation (CV) were calculated for the following variables: foot clearance in relation to the obstacle (mm), knee flexion (deg) at crossing and step length (m). Mann Whitney U-test/ANOVAS were used to compare data between groups.
Results: According to the preliminary analyses, the variation of foot clearance of the lagging leg (CV) was as hypothesized larger in the injured leg of the ACL-group compared to non-dominant leg of controls. Moreover, the 4 ACL-subjects showed a larger CV for the foot clearance of the injured leg compared to the non-injured. For step length and knee flexion angle at crossing, preliminary data suggest that the ACL-group also have a larger variation of their injured lagging leg compared to non-injured controls.
Conclusion(s): Our test seems to capture sensorimotor control deficits of the knee after ACL-injury as indicated by the variation estimate.
Implications: This functional test shows promising potential to be implemented in the clinics to estimate proprioceptive deficits and guide rehabilitation but require further validation and appropriate technological development.
Funding acknowledgements: Swedish Scientific Research Council, Umeå University, Västerbotten county council, Swedish National Centre for Sports Research; Umeå School of Sport Sciences
Topic: Musculoskeletal: lower limb
Ethics approval: Regional Ethical Review Board in Umeå, dnr 2015/6731M
All authors, affiliations and abstracts have been published as submitted.
