A SIMULATION OF HAND IMPAIRMENTS - EFFECTS ON UPPER EXTREMITY FUNCTION AND IMPLICATIONS TOWARD MEDICAL IMPAIRMENT RATING AND DISABILITY DETERMINATION

Objectives: To determine whether simulation of significant impairment of the hand will have a predictable impact on degree of functional los s at the wrist and hand. Design: Single subject repeat measures using before-after trial comparisons and healthy volunteer subjects. Setting : Occupational therapy section of a large academic medical center. Oth er Participants: Twenty adult volunteer student subjects from an occup ational therapy education (OTE) department were included. All were bet ween ages 18 and 43 years, right hand dominant, and in excellent gener al health. There were 19 women and 1 man, reflecting gender distributi on of the OTE student body. Intervention: A simulated fusion of the ca rpometacarpal (CMC) joint of the thumb was achieved by immobilization in an individually fabricated splint designed to maximally restrict mo tion at the first CMC joint. Impairment ratings (baseline vs splinted) according to the AMA Guides were obtained by Greenleaf testing, and u pper extremity function was quantitatively assessed before and after s plinting. Main Outcome Measures: Measures of upper extremity function included grip and pinch strength, wrist torque, and speed of performan ce on the Valpar Small Tools test, Jebsen Hand Function test, and an e xploratory measure, the Functional Life Activity Test (FLAT). Results: Significant impairments were achieved for all subjects after splintin g and according to Greenleaf testing. Splinting resulted in significan t reductions in grip and pinch strength, wrist torque, and significant slowing of performance on the Valpar, Jebsen, and FLAT tests. Regress ions of degree of impairment on degree of functional loss after splint ing, and according to each of the above measures, were not significant . Conclusions: Impairment of the hand was simulated to a mild-to-moder ate degree as measured according to the AMA Guides. This imposed signi ficant reductions in motion at key joints of the wrist and hand as wel l as significant reductions in grip and pinch strength and wrist torqu e. A corresponding and significant slowing of performance on a variety of measures of upper extremity function of an industrial and nonindus trial nature was also seen. However, and for the first time, correlati on and regression reveals that it is not possible to predict degree of functional loss attributable to degree of impairment for the hand. IL thus appears that, for mild-to-moderate clinical impairments, the ass ociated impairment rating is a poor estimator of functional loss at th e hand and should be used cautiously, if at all, as a criterion for di sability determination. (C) 1997 by the American Congress of Rehabilit ation Medicine and the American Academy of Physical Medicine and Rehab ilitation.