THE EFFECT OF FLEXOR DIGITORUM PROFUNDUS ON GRIP STRENGTH: A STUDY EXAMINING THE FUNCTIONAL EFFECTS OF SINGLE-DIGIT FDP AVULSION

Introduction Closed avulsion of the Flexor Digitorum Profundus (FDP) from distal phalanx most commonly affects the ring finger when an extensive force is applied to a finger in active flexion. Whilst it is undoubtably reasonable to provide treatment for those who present with symptoms, there may be a cohort of people who sustain an avulsion without noticing. This study aims to quantify the effect of ring finger FDP avulsion on overall grip strength to determine the functional effect of a missed injury Method Right handed volunteers, with no abnormality on examination were included (N= 42). Proximal muscle group action was excluded. Grip strength was tested using a Jamar dynamometer with and without splinting of the ring finger to block flexion at the DIPJ and repeated six times alternately to mitigate the effects of fatigue Results Most subjects showed a small (0.3–3kg) change in their average grip strength with the splint (N= 29). Some showed a dramatic change in their grip strength (6–11.4) (N=6) others showed no change or slight improvement with the splint (−3–0) (N=7). Data were not normally distributed (kolmogorov-smirnov p=0.023). A wilcoxon signed rank test showed a statistically significant difference in performance with, compared to without, the splint, mean 2.34kg reduction (−3.3 − 11.4) (p Discussion Horton et al have examined the quadriga effect and shown that the individual strength of other digits is reduced when one FDP is isolated. This implies overall grip strength should be reduced; our data supports this assertion. However despite splinting, the majority of subjects were still within the normal range of power for age. Larger scale studies are required to assess the functional effect of repair vs conservative management