JMIR Publications

ABSTRACT

Background:

Application of spinal orthoses and local vibration in the treatment of hyperkyphosis is a developing concept. Further research is needed to determine the impact of leaf springs and local vibration techniques on the neuromusculoskeletal system.

Objective:

To evaluate the effect of the simultaneous application of a leaf spring and a programmed local vibration system in a spinal orthosis on thoracic kyphosis angle and trunk flexor and extensor muscles' function.

Methods:

We used a soft thoracolumbar orthosis as a basis for a parallel leaf spring bar made by AISI 1075 steel with (45cm×2cm×2mm) dimensions. We added and evaluated two local vibration systems with predefined force, Probe displacement and programmed frequency. Each local vibration unit was positioned alongside the spinal column, at a distance of 12 cm, while wearing the orthosis. Then one person used the orthosis. We assessed thoracic kyphosis and trunk flexor/extensor muscle function (isometric, isotonic, and isokinetic) before and after a four-week intervention.

Results:

Results indicated that each vibration unit caused an on-body displacement of 3 to 6 mm and a free displacement of 1 cm, operating at 8 Hz with a force of 20 N, current of 300 mA, and voltage of 12 V over an area of 12.56 cm². Each session lasted 10 seconds with a 5-minute rest, totalling 12 repetitions. After 4 weeks, the thoracic kyphosis angle decreased from 47.24 to 45.81 degrees. In isometric tests, extensors improved strength by 22.2% to 50%, while flexors decreased torque by -24.1% to -26.5% but achieved faster force generation (-50% half-peak time). Isotonic concentric tests showed extensors improving power by 66.7% to 100% and efficiency, with flexors experiencing reduced power output (12.5-14.3%) but better control (40% decay time). In isotonic eccentric tests, flexors increased peak power by 44.4% and decreased average power (-16.7%), while extensors maintained baseline power but improved efficiency by 20%. Isokinetic tests revealed flexors improved peak torque by 233% and work capacity by 200%, while extensors increased by 66.7% with efficient torque development (55.2% time to peak).

Conclusions:

This study demonstrated the feasibility of a semi-rigid thoracolumbar orthosis with integrated programmable vibration in the management of hyperkyphosis. This system achieved good user acceptance and a reduction in thoracic kyphosis. Extensor muscle performance and modified flexor activation patterns improved. Muscle-specific responses warrant targeted rehabilitation approaches, and the solenoid system delivers effective mechanical stimulation while maintaining comfort. These results support further development of combined biomechanical-neuromuscular orthotic interventions for spinal rehabilitation. Clinical Trial: This study was the first phase of the first author thesis project protocol that received approval from the ethics committee of the University of Social Welfare and Rehabilitation Sciences in January 2023. The approval code was (IR.USWR.REC.1401.217).This thesis project protocol received approval from the ethics committee of the University of Social Welfare and Rehabilitation Sciences, with an approval code (IR.USWR.REC.1401.217) in January 2023. The protocol for RCT of this thesis was subsequently approved by the Iranian Registry of Clinical Trials on February 14, 2023, with the registration reference code IRCT20190811044505N2.