Applying a follower load delivers realistic results for simulating standing.

Area of Science:

• Biomechanics
• Spinal Mechanics
• Finite Element Analysis

Background:

• Accurate simulation of lumbar spine loading during standing is essential for understanding spinal health.
• Previous experimental and numerical studies have used various loading methods, but their in vivo relevance is unclear.

Purpose of the Study:

• To compare intersegmental rotations, intradiscal pressures, and facet joint forces for different loading modes simulating standing.
• To identify the loading mode that most closely replicates in vivo measured data.

Main Methods:

• Utilized a validated finite element model of the lumbar spine (L1-L5/S1).
• Investigated six distinct load application modes to simulate standing.
• Compared calculated intersegmental rotations and intradiscal pressures against published in vivo data.

Main Results:

• Intersegmental rotations varied significantly across loading modes (up to 8 degrees at one level, 2.2–19.5 degrees overall).
• A follower load of 500 N demonstrated the closest agreement with in vivo intervertebral rotation data (3.3 degrees difference).
• Intradiscal pressures showed minor variations; facet joint forces ranged from 0 to nearly 80 N.

Conclusions:

• Applying a follower load of 500 N is the most accurate method for simulating standing in finite element models of the lumbar spine.
• This loading mode yields results for intervertebral rotations and intradiscal pressures that align well with in vivo measurements.