Movement patterns of interosseus-minus fingers.

Area of Science:

• Anatomy
• Biomechanics
• Hand Surgery

Background:

• Intrinsic hand muscles, including interossei and lumbricals, are crucial for fine motor control and hand function.
• Understanding the specific roles of these muscles in movements like metacarpophalangeal (MCP) joint flexion and interphalangeal (IP) joint extension is vital for diagnosing and treating hand impairments.

Purpose of the Study:

• To investigate the movement patterns of MCP joint flexion and IP joint extension in fingers lacking interossei muscles (interosseus-minus fingers).
• To elucidate the functional contribution of lumbrical muscles in the absence of interossei.
• To determine the necessity of interosseus muscle activity for specific finger movements.

Main Methods:

• Studied movement patterns of isolated MCP joint flexion and isolated IP joint extension.
• Examined eighty fingers with intact extrinsic and lumbrical muscles but absent interossei muscles.
• Compared movement patterns to those observed in fingers with complete intrinsic muscle paralysis.

Main Results:

• Metacarpophalangeal flexion patterns in interosseus-minus fingers mimicked those of completely intrinsic-minus fingers, suggesting lumbrical inactivity during this motion.
• Isolated interphalangeal extension showed improvement in interosseus-minus fingers compared to totally intrinsic-minus fingers.
• Lumbrical muscle activity appears to mitigate extending forces at the MCP joint during IP extension.

Conclusions:

• Active participation of interosseus muscles is indispensable for executing isolated MCP flexion.
• Interosseus muscles are also necessary for effective isolated IP joint extension.
• Lumbrical muscles play a role in modulating MCP joint forces, particularly during IP extension.