Bridging clinical and computational assessments: Standardizing kinematic reporting in modified mallet scale movements

Area of Science:

• Biomechanics
• Pediatric Orthopedics
• Rehabilitation Medicine

Background:

• Accurate shoulder kinematics assessment is vital for brachial plexus birth injury (BPBI) management.
• Current kinematic reporting methods lack standardization, impacting data reliability.
• The Modified Mallet Scale (MMS) is a key clinical tool for evaluating BPBI.

Purpose of the Study:

• To identify the optimal Euler sequence for reporting shoulder kinematics during MMS movements.
• To evaluate kinematic data discontinuities and amplitude coherence across different Euler sequences.
• To establish standardized reporting methods for improved clinical relevance in BPBI research.

Main Methods:

• Retrospective analysis of kinematic data from unaffected arms of ten children with BPBI.
• Utilized inertial measurement units for data collection.
• Quantified discontinuities (gimbal lock, phase angle) and evaluated amplitude coherence for ZXY, XZY, and YXY Euler sequences.

Main Results:

• The ZXY sequence exhibited gimbal lock in key MMS movements (M1, M2, M3).
• XZY and YXY sequences showed no gimbal lock, though YXY had phase angle discontinuities.
• Amplitude coherence analysis indicated XZY and YXY were most suitable for M1/M2, YXY for M3/M5, XZY for M4, and ZXY for M6.

Conclusions:

• The choice of Euler sequence significantly impacts the accuracy of MMS movement analysis.
• Movement-specific, standardized kinematic reporting is essential to reduce discontinuities and maintain amplitude coherence.
• Standardization will enhance clinical relevance and enable meaningful cross-study comparisons in BPBI evaluation.