How Muscle and Tendon Properties Contribute to Functional Change Prior to and Following Knee Replacement

Overview

It is unknown how progressive physiological change in muscle and tendon contributes to loss of functional ability in patients undergoing total knee replacement between referral to surgery, and during post-surgery recovery. This study will use ultrasound and neurophysiological measures to evaluate progressive alterations of tissue to understand functional decline in men and women prior to and following knee replacement surgery. A group of healthy controls not undergoing knee replacement will also be studied to contrast changes in the patient group to normal changes over time. It is hypothesized that from the point of referral to surgery, patients will exhibit reductions in muscle and tendon size (atrophy) and reflex excitability that will be greater in the surgical compared with non-surgical leg, and these changes will precede observable losses in functional measures and strength. Secondly, it is hypothesized that following total knee replacement, muscle and tendon size, reflex activity, strength and functional measures will increase to a level below the pre-surgery values.

Osteoarthritis leads to degeneration of the articulating surfaces of the femur and tibia, with the end-stage intervention being replacement of these articulating surfaces using a total knee arthroplasty (TKA) surgical procedure. For patients undergoing TKA, there is a significant decline in functional abilities throughout the waiting period from surgical referral to the surgery date. Following the surgery, there is an improvement in function of these patients, but they do not reach the same functional level as healthy individuals who have not undergone TKA. To objectively measure functional abilities, various tests of strength, mobility and balance can be assessed. To date, no study has been conducted to evaluate how these objective measures of functional ability change throughout the pre-surgery waiting period and how this compares to levels following surgery. To gain a further understanding of the mechanisms behind these changes in function, physiological measures of muscle and tendon can be employed using electrical testing and ultrasound imaging. By evaluating changes in physiology alongside changes in function in TKA patients and healthy controls, we can gain a better understanding of the mechanisms underlying observable changes in function of patients undergoing TKA and how this compares to normal physiological changes in healthy controls. Patients undergoing total knee replacement will visit the laboratory on 5 separate testing occasions (1, immediately following referral for TKA; 2, midpoint between referral and surgery; 3, 2 weeks prior to surgery; 4, 6 weeks post-surgery; 5, 6 months post-surgery. At each testing session participants will begin by filling out questionnaires related to overall functional ability. They will then perform functional tests of the upper and lower body to gain measures of limb-dependent functional ability. Following functional measures, resting measures of muscle and tendon surrounding the knee and quadriceps muscle group will be obtained using a combination of ultrasound imaging and measurements at the skin surface. Participants will then be equipped will surface electromyography (sEMG) electrodes on the muscles composing the quadriceps and hamstrings muscle groups to measure muscle activity during the subsequent measures. Muscle reflex activity will be assessed through sub-maximal and maximal electrical stimulation of the femoral nerve via carbon stimulation electrodes placed on the skin surface. Participants will then perform three maximal voluntary contractions (MVC) requiring them to extend their leg as hard as possible against the force transducer. Stimulation will be applied prior to, during and following the MVCs to assess the level of muscle activation. From the MVCs, sub-maximal tracking tasks of 5,10,25,50 and 75% MVC will be established. Using the force displayed on a screen in front of the participants, they will be required to produce contractions up to these force levels and maintain the force level for 5 second in order to quantify force steadiness. During these sub-maximal tracking tasks, the ultrasound probe will be placed on the junction between the quadriceps muscle and tendon to record tendon elongation for quantification of tendon mechanical properties. These procedures will be preformed for the surgical leg of 30 patients undergoing TKA to compare inter-leg differences across time points, and 30 healthy control participants not undergoing TKA who are age-and sex-matched to the patient group will also perform these measures on their non-dominant leg using the same spacing between testing sessions. Measures will be compared between the surgical of patients and the non-dominant leg of healthy controls to evaluate differences over time in the patient group and how this compares to normal changes in a healthy population over the same period of time. This study will try and determine what measures of physiological change prior to surgery best predict optimization of patient function and improvement following surgery.