Tengman E.1, Schelin L.1,2, Häger C.K.1
1Umeå University, Department of Community Medicine and Rehabilitation, Section for Physiotherapy, Umeå, Sweden, 2Umeå University, Umeå School of Business and Economics (USBE), Department of Statistics, Umeå, Sweden
Background: Knee muscle weakness is one of the main dysfunctions following a rupture of the anterior cruciate ligament (ACL), and the weakness can prevail decades after injury as we have earlier reported (Tengman et al 2014). Assessment of the maximal concentric isokinetic quadriceps strength is traditionally used to evaluate knee muscle strength. However, recent research indicates that deficits may be more evident during other parts of the movement than the maximum torque. New statistical methods (functional data analysis, FDA) enable comparisons of the whole torque-time profile and have to our knowledge not been applied before in these contexts.
Purpose: The aim was to investigate, using FDA, isokinetic torque curves in concentric/eccentric quadriceps and hamstrings strength more than 20 years after ACL injury. This was done in two cohorts, treated with physiotherapy either in combination with surgery or without surgery, and the strength profiles were compared to non-injured age- and gender-matched controls. In previous analyses we have analyzed peak torque. We are here addressing analyses of the whole torque curve (10-90˚ of knee flexion) which provides information about the whole torque-time profile.
Methods: A Kin-Com® dynamometer (90°/s) was used to measure torque in quadriceps and hamstrings during both concentric and eccentric contractions in 70 persons with a unilateral ACL injury; 33 (21 men, age 46±5yrs) were treated with physiotherapy and ACL reconstruction (ACL-R) and 37 (23 men, 48±6yrs) with physiotherapy alone (ACL-PT). Comparisons were made to 33 (21 men, age 47±5yrs) age- and gender-matched controls. Six repetitions were performed and the maximal repetitions were analysed with FDA, providing information about torque as a function of the movement path throughout the whole range of movement. Torque curves were compared between the three groups and between legs.
Results: ACL-PT had strength deficits in concentric (80-43˚ of knee flexion) and eccentric (52-76˚ of knee flexion) quadriceps strength and eccentric hamstrings strength (whole range) compared to controls and to the non-injured leg. ACL-R, showed no strength deficits compared to controls, while the injured leg had lower concentric and eccentric quadriceps strength during the whole torque curve compared to the non-injured leg.
Conclusion(s): Strength deficits throughout the whole motion, and not only for peak values, are still evident 20 years post ACL injury. ACL-PT showed strength deficits compared to controls and their non-injured leg while ACL-R were deficient only in comparison to their non-injured leg. The FDA analysis indicates that the deficit exists not only at the event of peak torque. FDA may be used to better understand strength deficits after an ACL injury which may be of meaningful clinical value.
Implications: New statistical methods enable advanced analyses of isokinetic strength profiles. Such knowledge for physiotherapists can facilitate improved evaluation of strength following ACL injury and planning of better individually-tailored strength training programmes.
Funding acknowledgements: Swedish Scientific Research Council, Umeå University, Västerbotten-county-council, Swedish National Centre for Research in Sports; Umeå School of Sport-Sciences, Ingabritt&Arne Lundbergs-foundation
Topic: Sport & sports injuries
Ethics approval: The project was approved by the Regional Ethical Review Board in Umeå, Sweden (dnr 08-211M).
All authors, affiliations and abstracts have been published as submitted.
