Femoral loads during passive, active, and active–resistive stance after spinal cord injury: a mathematical model

Clin Biomech (Bristol, Avon), 2004 · DOI: 10.1016/j.clinbiomech.2003.12.005 · Published: March 1, 2004

Spinal Cord Injury Bioinformatics Biomechanics

Simple Explanation

This study uses a math model to estimate how much force is on the thigh bone when people with spinal cord injuries stand. The model looks at standing with support, with some muscle use, and with muscle use against resistance. The goal is to see how these different ways of standing affect bone compression and shear forces, which can help prevent bone problems after spinal cord injury.

Study Duration

Not specified

Participants

Two subjects (one male with SCI, one able-bodied female)

Evidence Level

Mathematical model based on experimentally derived parameters

Key Findings

1
Active-resistive stance resulted in maximal distal femur compression estimates of ~240% of body weight.
2
Quadriceps force estimates peaked at 190% of body weight with active–resistive stance.
3
The distal femur shear force estimates never exceeded 24% of body weight with any form of stance.

Research Summary

The purpose of this study was to estimate the loading environment for the distal femur during a novel standing exercise paradigm for people with spinal cord injury. A static, 2-D model was developed to estimate the external forces; the activated quadriceps forces; and the overall bone compression and shear forces in the distal femur during passive, active, and active–resistive stance. These results support our hypothesis that active–resistive stance induces the highest lower extremity loads of the three stance paradigms, while keeping shear to a minimum.

Practical Implications

Understanding Lower Extremity Forces

The model allows clinicians to better understand the lower extremity forces resulting from passive, active, and active–resistive stance in individuals with spinal cord injury.

Designing Effective Interventions

The findings help in designing exercise programs that maximize compressive loads on bone while minimizing shear forces, potentially promoting osteogenesis and preventing osteoporosis.

Future Research Directions

The study highlights the need for future research to determine the optimal loading dose necessary to prevent musculoskeletal deterioration following SCI.

Study Limitations

1
Standard anthropometric body segment values were based on uninjured subject populations, however, persons with spinal cord injury may have altered body composition
2
Issues such as spasticity and contracture were not considered in this model.
3
Two of the model parameter values (μgr and dx) were derived experimentally from two subjects.

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