Hand force profiles of women with hand osteoarthritis during sealed jar opening

Abstract

Purposes: Joint protection strategies are often recommended for individuals with hand arthritis. However, there is little research regarding their effectiveness or on the use of measures in evaluating the effects of joint protection strategies. The purposes of this study were to 1) evaluate the effects of the type of grasp, the hand grasping the lid, and the use of non-skid material on the hand forces acting upon a jar lid when breaking a jar's seal, 2) examine the hand forces requirements when opening a sealed jar and 3) investigate relationships between several measures of hand function and the actual hand forces used during the everyday task of opening a sealed jar in order to validate their use in measuring the effectiveness of joint protection strategies such as using a counterforce such as a table or opposing extremity and using a nonskid material.Methods: A novel jar device created by McGee, Nuckley, and Mathiowetz was used to gather measurements of grip force, compressive force down through the lid's axis of rotation (Fz) and compressive force perpendicular to the side of the lid (Fx/Fy) when attempting to open a `sealed jar'. The jar lid's torque requirement was set to 4.24 N*m, a torque commonly imposed by the manufacturer when creating a seal on larger diameter jars. Thirty-one women with hand osteoarthritis were asked to complete 16 jar opening simulations by alternating three different factors: hand turning the jar lid, position (supinated/vertical and oblique/diagonal), and use of a non-skid material. After each jar turning simulation, participants were asked to report their perceived level of pain and exertion using the 0 to 10 scales of the NRS and Borg CR10, respectively. Additional measures of hand function were quantified to determine if and to what extent they predicted success and the capacity to generate forces when opening a sealed jar.Results: The impact of arthritis on our sample's function was modest (AIMS2-SF2 Total Health Score; x = 10.62) and the distribution of arthritis between hands was not dissimilar. Use of the supinated grasp required less force/time in Fx [F(1,419)=30.5, p<.0001], Fy [F(1,419)=34.5, p<.0001], and Fz than power grasp [F(1,419)=23.5, p<.0001]. Participants used less grip force to twist the lid with their left hand than with their right hand [F(1,419)=21.7, p<.0001]. Participants also perceived their effort to be less when using their left hand, a supinated grasp, and non-skid material. Additionally, participants rated their pain as lower when using their left hand and when using a supinated grasp. Lastly, a left supinated grasp with a non-skid material was a significantly more successful strategy to open jars than was any other (&#967;2=9.4, p<.001). Across all approaches, participants who were successful used 149.2±6.2 N of grip force and 47.8±2.8 N of `compensatory' forces when opening the sealed jar. Perceived effort was a significant positive predictor of grip force across time and is a significant negative predictor of peak M(z). Palmar abduction of the stabilizing thumb was a significant positive predictor of torque and a negative predictor of grip forces. Total active motion of the stabilizing and turning thumbs was a positive predictor of grip force and an increase in pain from baseline was a significant negative predictor of grip force and a positive predictor of torque.Conclusions: The counterforce offered by the supinated `stabilizing' hand results in the use of fewer compensatory forces by the turning hand. The left hand requires less grip force to successfully open a sealed jar and pain as well as perceived effort were least among those who used a non-skid material when opening. This data supports that women with hand arthritis will know more success, perceive less pain and effort, use less grip force, and will more efficiently generate the forces required to break the seal of a large jar when using a left hand, supinated counterforce, and non-skid material. These findings validate the use of non-skid material to reduce hand forces with jar turning but only when combined with a supinated approach. Perceived effort, and a change in pain from baseline are strong predictors of the forces used during jar opening and thus should be considered when considering the effectiveness of joint protection strategies used by women with hand osteoarthritis when attempting to open sealed jars. Other measures of hand function were also predictive of the hand forces generated when opening a sealed jar and these factors should be considered during assessment and intervention planning.