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Muscle strategies and mechanical loading in patients with osteoarthritis

Ghazwan, Aseel 2017. Muscle strategies and mechanical loading in patients with osteoarthritis. PhD Thesis, Cardiff University.
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Abstract

Osteoarthritis (OA) is a chronic degenerative joint disease frequently affecting the knee. The cause of OA remains unclear. It is known that mechanical loading is a key contributing factor to the initiation and progression of knee OA. The overall aim of this work was to investigate mechanical loading at the knee in terms of external moments, muscle co-ordination, muscle forces and knee contact forces (KCF) during gait in Non-pathological subjects (NP), subjects with medial knee OA listed for high tibial osteotomy surgery (pre-HTO), and subjects with late-stage OA listed for total knee replacement (pre-TKR) using musculoskeletal modelling and dynamic simulations of motion. This was achieved through four objectives. Objective 1: Examine alternative methods of normalization that effectively reflect muscle activity as compared to Maximal Voluntary Contraction (MVC). Rationale: Patients with compromised function due to disease or injury are unable to maximally contract their muscles during MVC tasks. The current study finds an alternative method that is comparable to the MVC in reflecting muscle activity for level gait, whilst having good repeatability. Hypothesis: Activities of daily living (ADL) give a representative and repeatable measure of muscle activity during different ranges of motion. Methods: EMG data were recorded from knee muscles in 10 NP subjects during ADL and different methods of normalization were tested. Intra- and inter-individual variability were calculated to determine reliability. Results: ADLs are proposed and demonstrated in this work as a useful measure in EMG normalization. Objective 2: Determine if there is a trend in co-contraction index and OA progression. Rationale: People with OA tend to walk with high muscle co-contraction to compensate for joint instability. For long-term joint integrity, this could increase in the net knee compressive contact load and may contribute to the progression of OA. The current study explores how the coordination between quadriceps, hamstrings and gastrocnemii are affected in pre-HTO and pre-TKR compared to NP. Hypothesis: Increased co-contraction of knee muscles to compensate for joint laxity in OA patients. Methods: EMG signals from seven peri-articular knee muscles were processed to create a linear envelope. The co-contraction index (CCI) was calculated for muscle pairs across the knee. Results: CCI was a useful marker of OA progression, where an increase in lateral CCI reflected progression from NP to pre-HTO. Increase in medial CCI could potentially differentiate the severity of knee OA. Objective 3: Examine if activation patterns, used to stabilize the knee joint, change with OA progression. Rationale: Varying individual muscular control strategies depend on strength and coordination, and contribute to joint stability and loading. It is important to understand the changing role of muscles in the mechanical loading of joints with degenerative joint disease. The purpose of this study was to estimate quadriceps, hamstrings and gastrocnemius forces in patients with OA progression. Hypothesis: The knee joint is stabilized by the external knee adduction moment (KAM) that should be balanced by the internal moment produced by muscle forces and joint loading. In OA, lateral and medial muscles use different strategies to IV counterbalance the high external KAM. Methods: An EMG-driven model was used to estimate muscle forces. Results: Compared to NP, OA subjects exhibited altered muscle forces in relation to applied external moments at the knee joint. Objective 4: Estimate knee contact force (KCF) in patients with OA progression. Rationale: Assessment of muscle forces and joint loading is essential to fully understand altered loading mechanisms associated with the progression of OA. Hypothesis: Changes in muscle strategies would be different between groups and can have a significant effect on the magnitude of the knee joint loading. Methods: Gait biomechanics (moments, muscle forces and joint loading) were calculated by OpenSim. Results: Differences in the patterns and magnitudes of the KCF waveforms provide information on gait changes associated with the progression of knee OA.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Electromyography; EMG normalization; Muscle co-contraction; Muscle forces; Knee loading; Osteoarthritis.
Date of First Compliant Deposit: 10 January 2018
Last Modified: 28 May 2019 14:21
URI: http://orca-mwe.cf.ac.uk/id/eprint/107997

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