title: Assessment of quadriceps muscle weakness in patients after total knee arthroplasty and total hip arthroplasty: methodological issues.
abstract: The aim of this exploratory study was to verify whether the evaluation of quadriceps muscle weakness is influenced by the testing modality (isometric vs. isokinetic vs. isoinertial) and by the calculation method (within-subject vs. between-subject comparisons) in patients 4-8months after total knee arthroplasty (TKA, n=29) and total hip arthroplasty (THA, n=30), and in healthy controls (n=19). Maximal quadriceps strength was evaluated as (1) the maximal voluntary contraction (MVC) torque during an isometric contraction, (2) the peak torque during an isokinetic contraction, and (3) the one repetition maximum (1-RM) load during an isoinertial contraction. Muscle weakness was calculated as the difference between the involved and the uninvolved side (within-subject comparison) and as the difference between the involved side of patients and controls (between-subject comparison). Muscle weakness estimates were not significantly affected by the calculation method (within-subject vs. between-subject; P>0.05), whereas a significant main effect of testing modality (P<0.05) was observed. Isometric MVC torque provided smaller weakness estimates than isokinetic peak torque (P=0.06) and isoinertial 1-RM load (P=0.008), and the clinical occurrence of weakness (proportion of patients with large strength deficits) was also lower for MVC torque. These results have important implications for the evaluation of quadriceps muscle weakness in TKA and THA patients 4-8months after surgery.
authors.affiliation: Neuromuscular Research Laboratory, Schulthess Clinic, Zurich, Switzerland; Institute of Human Movement Sciences and Sport, ETH, Zurich, Switzerland.
authors.forename: S P
authors.initials: SP
authors.lastname: Lauermann
authors.affiliation: Neuromuscular Research Laboratory, Schulthess Clinic, Zurich, Switzerland; Institute of Human Movement Sciences and Sport, ETH, Zurich, Switzerland; Laboratory of Human Motricity, Education, Sport and Health (LAMHESS) - EA 6309, University of Nice Sophia Antipolis, Nice, France.
authors.forename: K
authors.initials: K
authors.lastname: Lienhard
authors.affiliation: Neuromuscular Research Laboratory, Schulthess Clinic, Zurich, Switzerland.
authors.forename: J F
authors.initials: JF
authors.lastname: Item-Glatthorn
authors.affiliation: Neuromuscular Research Laboratory, Schulthess Clinic, Zurich, Switzerland; INSERM U1093 - Cognition, Action and Sensory Plasticity, University of Burgundy, Dijon, France.
authors.forename: N C
authors.initials: NC
authors.lastname: Casartelli
authors.affiliation: Neuromuscular Research Laboratory, Schulthess Clinic, Zurich, Switzerland. Electronic address: nicola.maffiuletti@kws.ch.
authors.forename: N A
authors.initials: NA
authors.lastname: Maffiuletti
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D053581:Muscle Strength Dynamometer; D018908:Muscle Weakness / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D015203:Reproducibility of Results; D019415:Torque
keywords: Dynamometry; Joint replacement; Muscle strength; Quadriceps femoris