Validation of a multi-body optimization with knee kinematic models including ligament constraints

Area of Science:

• Biomechanics
• Motion Analysis
• Knee Kinematics

Background:

• Soft tissue artifact (STA) significantly compromises the accuracy of joint kinematics in motion analysis.
• Multi-body optimization (MBO) methods offer potential for STA compensation, but their in vivo validation remains limited.
• Existing MBO methods often use simplified constraints, leading to inaccurate kinematic estimations.

Purpose of the Study:

• To validate model-based kinematics from MBO methods against in vivo knee joint data.
• To compare the efficacy of three different ligament constraint types within MBO for STA compensation.
• To assess the accuracy of MBO-derived knee kinematics using intra-cortical pin measurements.

Main Methods:

• Employed multi-body optimization (MBO) incorporating three distinct ligament constraint strategies.
• Validated MBO-derived kinematics against in vivo knee joint motion data from three subjects using intra-cortical pins.
• Compared kinematic errors across MBO methods with no constraints, DoF coupling, null ligament variation, spherical, and anatomical ligament constraints.

Main Results:

• MBO methods with minimized or prescribed ligament length variations demonstrated marginal improvements over unconstrained and null ligament variation methods.
• Spherical joint constraints yielded errors below 2.2° for angles and 3.1mm for displacements.
• Minimized and prescribed ligament variations resulted in errors below 2.5° for angles and 4.1mm for displacements, generally lower than prior literature.

Conclusions:

• MBO methods show promise for compensating soft tissue artifacts in knee motion analysis.
• Anatomical ligament constraints offer potential for improved in vivo kinematic accuracy.
• Personalizing MBO models with subject-specific geometry is recommended for further accuracy enhancements.