Muscular modelling: relationship between postural default and spine overloading.

Area of Science:

• Biomechanics
• Musculoskeletal modeling
• Spinal load analysis

Background:

• Postural imbalances can significantly affect spinal biomechanics.
• Understanding muscle recruitment patterns is crucial for assessing spinal health.
• Previous models have limitations in personalized spinal load analysis.

Purpose of the Study:

• To develop and utilize a personalized muscular model for comparing spinal loads and muscle recruitment between an unbalanced subject and a normal volunteer.
• To quantify the impact of postural deficits on spinal loading and muscle activation.
• To explore potential compensatory mechanisms and their consequences on spinal health.

Main Methods:

• Data acquisition included sagittal X-rays, plantar foot pressure measurements, and MRI of the thoraco-lumbar region.
• A personalized muscular model was constructed using subject-specific data and muscular testing.
• External loads at the L3/L4 level were calculated, and simulations were run to assess muscle activation and joint compression.

Main Results:

• The unbalanced subject exhibited higher external spinal loads, particularly a greater flexion moment, due to postural deficits.
• Simulations revealed significantly higher erector spinae muscle group activation in the patient, leading to increased joint compression.
• Altering extensor muscle stress in the patient reduced joint compression but drastically increased shear and flexion moments.

Conclusions:

• The muscular model highlights that postural deficits lead to increased spinal loads and compensatory muscle activation.
• Higher muscle activation may result in joint compression and potential muscle fatigue.
• Alternatively, increased spinal loads without sufficient muscle compensation pose a significant risk of injury.