Grip strength characteristics using force-time curves in rheumatoid hands.

Area of Science:

• Rheumatology
• Biomechanics
• Orthopedics

Background:

• Rheumatoid arthritis (RA) commonly affects the hands, leading to deformities that impair function.
• Grip strength is a critical measure of hand function, but its assessment in RA can be complex.
• Force-time curves offer a detailed analysis of grip dynamics beyond simple strength measurements.

Purpose of the Study:

• To investigate the impact of various rheumatoid hand deformities on grip strength using force-time curve analysis.
• To correlate specific deformities with quantitative measures of grip strength, endurance, and disability.

Main Methods:

• Studied 43 patients (10 men, 33 women) with established rheumatoid arthritis affecting their hands.
• Analyzed force-time curves from 86 hands, categorizing deformities into ulnar deviation, swan neck, boutonnière, and combined types.
• Assessed grip strength (peak force, average force), grip duration, and area under the curve (AUC).

Main Results:

• Hands with combined deformities exhibited the weakest grip strength (34.7 N) and shortest grip duration (22 sec).
• Swan neck deformity significantly reduced grip magnitude (49.8 N) and sustainability (15 sec), more so than boutonnière deformity (82.7 N).
• Hands with only ulnar deviation deformities demonstrated the strongest grip (90.8 N).
• Area under the curve (AUC) was the best predictor of disability, as assessed by the Patient Evaluation Measure.

Conclusions:

• Specific rheumatoid hand deformities have distinct and significant impacts on grip strength and endurance.
• Force-time curve analysis, particularly AUC, provides valuable insights into functional impairment and disability in RA hands.
• Understanding these relationships can inform targeted interventions and management strategies for RA patients.