A Comparison of Functional Capabilities of Individuals With and Without Simulated Finger Disabilities: An Exploratory Study

Injuries to fingers remain the most pervasive nonfatal occupational injuries to the upper extremities in U.S. industries. It is logical to expect that work-related performance of individuals with finger disabilities (e.g., amputated fingers) will be inferior to those with all fingers intact and fully functional. However, the published literature does not provide any indication how much the functional capabilities of individuals with finger injuries differ from normal individuals. Knowledge of the nature and extent of decline in the functional capabilities of individuals with finger disabilities is necessary in order to make accommodations in the work place (including job, task, and equipment design), and meet ADA compliance. This laboratory investigation reports on the differences in the functional capabilities of individuals with and without simulated finger disabilities (amputations) when performing routine industrial tasks and standardized strength tests. Twelve male volunteers participated in the study. The finger disability simulated was of an extreme nature, and was defined as the loss of the use of four fingers in the preferred hand and the thumb in the nonpreferred hand. Subjects performed a variety of dexterity and strength exertion tasks. The dexterity tasks simulated finger dexterity in assembly work and manipulation of common hand tools and included: Modified Purdue Pegboard Test, O'Connor Tweezer Dexterity Test, Pennsylvania Bimanual Work Sample Test, and Hand-Tool Dexterity Test. The strength exertion tasks determined maximum volitional torque exertion capabilities when using common nonpowered hand tools, the psychophysical lifting strength, and standardized isometric arm, shoulder, back, and composite lifting strengths, and isokinetic lifting strength. Results indicated a significant reduction in performance for all dexterity tasks (p > 0.01). In comparison to normal individuals, the dexterity task performance times of individuals with finger disabilities increased by as much as 190%. The psychophysical lifting strength of the disabled was also significantly lower (<0.01), by as much as 35%. In contrast, reductions in standardized strength exertion capabilities of the disabled were smaller (between approximately 10% and 17%) and, for most tests, not significant (p ≥ 0.10). Strength exertion capabilities with hand tools reflected mixed results. While the torque capability of the disabled with both screwdrivers and wrenches went down, only the decline with screwdrivers was significant (p < 0.025). Overall, the results indicated that the performance of tasks that depended upon finger dexterity for completion, even those that required significant force exertions (e.g., psychophysical lifting strength exertion capability), declined significantly. While tasks that did not require appreciable dexterity and could be performed by the palm of the hand and thumb, or fingers, forming the two claws did not show a significant decline in capability. It is worth noting that the decline in capability in such cases, even though statistically insignificant, was very appreciable and of great practical consequence.