The change in ulnar variance with grip

The effect of grip on ulnar variance was evaluated in 66 symptom-free wrists of 53 volunteers. Zero-rotation posteroanterior x-ray films were taken of each wrist before and after exertion of a grip force measured with a Jamar dynamometer. The volunteers were randomly divided into two groups. Group I subjects (35 wrists) were asked to exert a constant grip force of 11.3 kg. Group II subjects (31 wrists) were asked to exert a maximum grip effort, which resulted in a mean grip force of 30 kg (range, 22.8 kg to 53.6 kg). Group I demonstrated a mean increase in ulnar variance of 1.27 mm and group II showed a mean increase of 1.95 mm. The minimum increase in ulnar variance observed was 0.25 mm. The changes observed were statistically significant. The results confirm that a relative increase in ulnar variance occurs with grip. There may be an etiologic role for daily activities that involve repetitive grip and forearm rotation in development of the ulnar impaction syndrome.