The Effect of Ring Finger Distal Interphalangeal Joint Stiffness on Grip Strength: A Simulated Study in Normal Participants.

Background: Pain of the hand distal interphalangeal joints may result from trauma, osteoarthritis or inflammatory arthritis. When symptoms are not controlled by non-operative means, surgical arthrodesis may be performed, resulting in complete stiffness of the joint and possible weakening of grip strength. This study aims to quantify the effect of a stiff ring finger distal interphalangeal joint on overall grip strength. Methods: One hundred participants were screened to exclude upper limb pathology. A Jamar dynamometer was used to assess overall hand grip strength. A splint was used to prevent distal interphalangeal joint flexion, thus replicating a fused distal interphalangeal joint. Participants were tested with and without the splint and the results compared. The mean of three grip strength tests was taken. Results: The participants included 55 females. Mean age was 31 (18-60 years). 76 participants had a reduction in grip strength with splinting, with a significant difference seen (p < 0.05) on Wilcoxon signed rank test. The median reduction in grip strength with splinting was 1.67 kg. However only 10 participants (10%) had a grip strength loss of greater than 6.5 kg, which is the minimal clinically important difference. Conclusions: This study found a significant loss in overall hand grip strength when the ring finger distal interphalangeal joint was stiffened. However, despite this significant change, only 10 (10%) participants experienced a reduction of greater than 6.5 kg. This is the level of weakness felt to be required to reduce function. Thus our results suggest that 90% of patients with a stiff ring finger distal interphalangeal joint are unlikely to have a clinically identifiable functional reduction in grip strength as a result.