Figure 1.
Musculotendonal structure of the human finger.
The musculotendonal structure of the human finger from posterior (dorsal) and lateral (radial) views (from Netter, 2002)
Figure 2.
Experimental setup for the measurement of 3D fingertip force and finger posture during maximum voluntary isometric pressing. The subjects' wrists were not touching the surface of the force plate while measurements were being conducted.
Figure 3.
The four finger pressing postures.
The four pressing postures, varying from flexed to fully extended, used in the experimental work. The segmental angles (θ1, θ2, θ3, θ4) are defined in Figure 4.
Figure 4.
Minimal Model of the finger without extensor mechanism.
Posterior (dorsal) and lateral (radial) views of the Minimal Model of the index finger without extensor mechanism. Four equivalent muscles (PF, PE, UI, RI) are considered to represent the actions of the finger flexor, extensor, lateral ulnar and lateral radial muscle groups respectively.
Figure 5.
Full Model of the finger with extensor mechanism.
Posterior (dorsal) and lateral (radial) views of the Full Model of the index finger with extensor mechanism (tendon network). In addition to the finger extensor muscle LE and flexor muscle FDP, the three major intrinsic muscles (UI, RI and LU) are included.
Figure 6.
Bone-to-bone contact force calculation results.
Calculated bone-to-bone contact forces (normalized by applied load) at the DIP, PIP and MCP joints obtained from both models for all finger postures. Based on measurement data from three typical trials (Trial 1, 3 and 6) for a representative subject (age: 25, weight: 75 kg, height: 1.72 m). The insets at the top show the measured 3D fingertip force vector for each posture.
Figure 7.
Percentage difference in bone-to-bone contact forces.
The differences between the calculated bone-to-bone contact forces at the DIP, PIP and MCP joints obtained from the two models for all finger postures. The means and standard deviations were calculated across all trials and all subjects. A ‘*’ indicates a significant difference between the results of the two models.
Table 1.
Statistical analysis of results from the Minimal Model.
Table 2.
Statistical analysis of results from the Full Model.
Figure 8.
Muscle force calculation results.
Calculated muscles forces (normalized by applied load) for the PE (LE), PF (PDF), RI (RI+LU) and UI muscles obtained from both models for all finger postures. Based on measurement data from three typical trials (Trial 1, 3 and 6) for a representative subject (age: 25, weight: 75 kg, height: 1.72 m). The insets at the top show the measured 3D fingertip force vector for each posture.
Figure 9.
Percentage difference in muscle forces.
The differences between the calculated muscle forces for the PE (LE), PF (PDF), RI (RI+LU) and UI muscles obtained from the two models for all finger postures. The means and standard deviations were calculated across all trials and all subjects. A ‘*’ indicates a significant difference between the results of the two models.