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A. Ruspi1, F. Mina1, P. Adamo1, F. Temporiti1,2, F. Traverso1, N. Maffiuletti3, R. Gatti1,2
1Humanitas Clinical and Research Center - IRCCS, Milan, Italy, 2Humanitas University, Milan, Italy, 3Schulthess Clinic, Zurich, Switzerland
Background: Total knee arthroplasty (TKA) is effective in reducing pain, improving function and quality of life in patients with end-stage knee osteoarthritis. However, this type of surgery has been reported to reduce quadriceps muscular activity for several months after TKA. Quadriceps activation failure can be explained through spinal excitability modifications due to alteration of sensory feedback from damaged joint, but it seems also to depend on supraspinal mechanisms. Moreover, the mental representation of a motor task has been described as able to influence descending motor commands. However, quadriceps muscular activity pattern after TKA during different tasks has not been studied yet.
Purpose: The aim of this study was to investigate quadriceps muscular activity during different tasks in patients after TKA.
Methods: Fifteen patients scheduled for TKA and 15 age-matched healthy volunteers were asked to perform three isometric tasks in supine position with hips and knees extended at 0°: knee extension, hip flexion and hip flexion associated to contralateral hip extension. Participants were asked to execute the tasks maximally and their position was standardized using seatbelts in order to maintain the biomechanical context unchanged among the three tasks. Root-mean-square peak (RMS-peak) of rectus femoris, vastus medialis, and vastus lateralis was recorded using bipolar surface electromyography electrodes (FREEEMG, BTS, Italy) and normalized as percentage of RMS-peak of each muscle among the tasks. Patients were evaluated the day before surgery (T0), at one (T1) and three days (T2) after, whereas healthy subjects underwent a single evaluation session.
Results: Patients revealed higher RMS-peak for vastus medialis during hip flexion compared to knee extension at T1 (91.8±12.7 during hip flexion versus 72.2±22.2 during knee extension; p=0.003) and T2 (93.1±7.06 during hip flexion versus 80.6±20.1 during knee extension; p<0.05). Patients’ quadriceps activation pattern was different from healthy subjects, where vastus medialis activation was higher during knee extension compared to hip flexion both before and after surgery.
Conclusion(s): Higher muscular activity of vastus medialis was found in patients during hip flexion compared to knee extension. Quadriceps activation pattern was different from healthy subjects, where vastus medialis activity is higher during knee extension compared to hip flexion. These findings might be explained by cortical organization of voluntary movements after TKA. In particular, activity of muscles surrounding knee seems to be higher during tasks where the mental representation of damaged joint is not involved.
Implications: The current results could help clinicians to design specific interventions addressed to enhance the recovery of muscle strength in early phase after TKA through the improvement of neuromuscular function. In particular, a strength training consisting of exercises that exclude the mental representation of the involved joint might be beneficial in speeding up the motor and functional recovery after surgery.
Funding, acknowledgements: The authors did not receive any funding.
Keywords: Total knee arthroplasty, Quadriceps activation failure, Neuromuscular activity
Topic: Musculoskeletal: lower limb
Did this work require ethics approval? Yes
Institution: Humanitas Clinical and Research Center - IRCCS
Committee: Internal Ethical Committee of the Humanitas Clinical and Research Center
Ethics number: CLF19/02
All authors, affiliations and abstracts have been published as submitted.
