A novel stability-based EMG-assisted optimization method for the spine. (August 2018)

• Record Type: Journal Article
• Authors: Samadi, S; Arjmand, N
• Is Part Of: Medical engineering & physics. Volume 58(2018)
• Page Start: 13
• Page End: 22
• Publication Date: 2018-08
• Subjects: Spine -- Electromyography (EMG) -- Stability -- Biomechanical model -- Forces -- Muscle stiffness; Biomedical engineering -- Periodicals; Biomedical Engineering -- Periodicals; Physics -- Periodicals; Génie biomédical -- Périodiques; Biomedical engineering; Electronic journals; Periodicals; 610.28
• DOI: 10.1016/j.medengphy.2018.04.019
• Languages: English
• ISSNs: 1350-4533

Abstract

Highlights: A novel stability/EMG-driven (SEMG) model of the thoracolumbar spine was developed. SEMG model computed muscle forces and spinal loads during various static tasks. Predictions were compared with those of the traditional EMG-driven (TEMG) model. SEMG model predicted task-dependant larger global muscle forces and spinal loads. SEMG model predicted L4-L5 intradiscal pressures in agreement with in vivo data. Abstract: Traditional electromyography-assisted optimization (TEMG) models are commonly employed to compute trunk muscle forces and spinal loads for the design of clinical/treatment and ergonomics/prevention programs. These models calculate muscle forces solely based on moment equilibrium requirements at spinal joints. Due to simplifications/assumptions in the measurement/processing of surface EMG activities and in the presumed muscle EMG-force relationship, these models fail to satisfy stability requirements. Hence, the present study aimed to develop a novel stability-based EMG-assisted optimization (SEMG) method applied to a musculoskeletal spine model in which trunk muscle forces were estimated by enforcing equilibrium conditions constrained to stability requirements. That is, second-order partial derivatives of the potential energy of the musculoskeletal model with respect to its generalized coordinates were enforced to be positive semi-definite. Fifteen static tasks in upright and flexed postures with and without a hand load at different heights were simulated. The SEMG model predicted different muscle recruitments/forces (generally larger global and local muscle forces) and spinal loads (slightly larger) compared to the TEMG model. Such task-specific differences were dependant on the assumed magnitude of the muscle stiffness coefficient in the SEMG model. The SEMG model-predicted and measured L4-L5 intradiscal pressures were in satisfactory agreement during simulated activities.