An analytical expression for the D.I.P.-P.I.P. flexion interdependence in human fingers

Area of Science:

• Biomechanics
• Human Anatomy
• Medical Engineering

Background:

• Empirical evidence confirms a strong correlation between distal interphalangeal (D.I.P.) and proximal interphalangeal (P.I.P.) joint flexion angles in human fingers.
• Existing research indicates that this interdependence differs between healthy individuals and those with pathologies.

Purpose of the Study:

• To derive an analytical expression quantifying the correlation between D.I.P. and P.I.P. joint flexion.
• To develop a model that can distinguish between normal and pathological finger flexion patterns.

Main Methods:

• A two-dimensional kinematical model was developed based on anatomical relationships to analytically express the D.I.P.-P.I.P. angle correlation.
• Numerical data from both healthy and pathological cases were used to parameterize the model.

Main Results:

• The analytical model allows calculation of the D.I.P. angle for any given P.I.P. angle.
• First-order differentiation of the model reveals the rate of change of D.I.P. flexion relative to P.I.P. flexion.
• The model accurately differentiates between healthy and pathological finger flexion patterns, with the rate of change serving as a key discriminatory feature.

Conclusions:

• Analysis of the derivatives of the D.I.P.-P.I.P. flexion behavior provides more pronounced and accessible information on differences between normal and pathological finger flexion compared to direct angular correlation.
• The developed analytical model enables precise calculation of the rate of change in D.I.P. angles, enhancing the analysis of finger joint mechanics in various conditions.