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Research Article
Issue Date: January/February 2017
Published Online: December 02, 2016
Updated: January 01, 2021
Evaluation of Hand Forces During a Joint-Protection Strategy for Women With Hand Osteoarthritis
Author Affiliations
  • Corey McGee, PhD, OTR/L, CHT, is Assistant Professor, Programs in Occupational Therapy and Rehabilitation Science, University of Minnesota, Minneapolis; mcge0062@umn.edu
  • Virgil Mathiowetz, PhD, OTR/L, FAOTA, is Associate Professor, Programs in Occupational Therapy and Rehabilitation Science, University of Minnesota, Minneapolis
Article Information
Arthritis / Hand and Upper Extremity / Musculoskeletal Impairments / Special Issue: Research Articles
Research Article   |   December 02, 2016
Evaluation of Hand Forces During a Joint-Protection Strategy for Women With Hand Osteoarthritis
American Journal of Occupational Therapy, December 2016, Vol. 71, 7101190020. https://doi.org/10.5014/ajot.2017.022921
American Journal of Occupational Therapy, December 2016, Vol. 71, 7101190020. https://doi.org/10.5014/ajot.2017.022921
Abstract

OBJECTIVE. We evaluated whether a joint-protection strategy changes the mechanics of opening a sealed jar.

METHOD. Thirty-one adult women with hand osteoarthritis attempted to open a “sealed” jar instrument when using and not using nonskid material. Grip force, torque, success, and pain were recorded for each trial.

RESULTS. Participants used less grip force when twisting with their left hand. The greatest torque and success, yet the least amount of grip force across time, and pain was noted when the left hand turned the lid, the jar was held vertically, the right hand supported the base, and nonskid material was used.

CONCLUSION. Women with hand osteoarthritis should be educated to consider the hand they use and their approach when opening sealed jars. Use of nonskid material without additional reasoning may increase load on arthritic joints, pain, and dysfunction. Additional research on task kinematics and the kinetics of the stabilizing hand is needed.

The hand is the second most prevalent host to symptomatic osteoarthritis (OA; Centers for Disease Control and Prevention, 2011). People who most commonly have hand OA are postmenopausal women more than 55 yr old. Pereira et al. (2011)  reported that 43.9% of adults age 40 and older have hand OA, and Dahaghin et al. (2005)  reported that 67% of women have radiographically confirmed OA in at least one hand joint by age 55. Symptoms of hand OA include stiffness, pain, and decreased strength (Kjeken et al., 2005), which contribute to difficulties performing activities of daily living (Ye, Kalichman, Spittle, Dobson, & Bennell, 2011). Jar opening, wringing out clothes, and bottle opening are often the most difficult tasks for people with hand OA to execute (Kjeken et al., 2005).
Joint protection (JP) is “routinely used with all clients with . . . arthritis” (Boustedt, Nordenskiöld, & Lundgren Nilsson, 2009, p. 793). JP includes reducing joint stress to prevent “progressive deterioration” by “redistributing the forces in activity proportionately to the strength and vulnerability of the parts of the joints involved” (Cordery, 1965, p. 285). When used alone (Dziedzic et al., 2015) or with other interventions (Boustedt et al., 2009), JP enhances occupational performance and pain outcomes.
The European League Against Rheumatism’s task force on the management of hand OA acknowledged the need for arthritis rehabilitation effectiveness studies (Zhang et al., 2007) and stated that JP strategies, including “the avoidance of adverse mechanical factors” (p. 381), remain unproven. There is a paucity of research validating and identifying the best JP approaches for mechanistic changes in the hand. Further exploration of the effects of JP strategies on hand forces during common activities, such as opening a sealed jar, is needed. Our primary aims were to determine whether the use of a nonskid material by women with hand OA (1) alters hand force profiles during jar opening and (2) has a varied effect according to the hand turning the lid or the approach taken to holding the jar. A secondary aim was to explore whether pain and success in jar turning mirrored trends in force profiles.
Method
Design
A 2 × 2 × 2 experimental cross-sectional design was used to investigate within-subject differences in peak grip force profiles, integral of the grip force (IGF; i.e., grip force across time, or the area under a force–time curve), and torque when participants attempted to open a sealed jar. Three variables were studied: (1) the approach to grasping the jar, (2) the hand used to twist the lid, and (3) the use of a nonskid material to twist the lid. This study was approved by the University of Minnesota’s institutional review board (No. 0908M71484), and all participants provided informed consent before taking part in the study.
Participants
Participants were recruited through orthopedic, women’s health, and hand therapy clinics as well as community-based centers serving older adults. Recruits were eligible if they were female, older than age 18 yr, and met one of the following two criteria: (1) had radiographically confirmed hand OA or (2) had a combination of self-reported physician diagnosis and symptoms (i.e., achiness and stiffness) of hand OA (Szoeke et al., 2008). Recruits were excluded if they had one or more of the following seven characteristics: (1) an upper-extremity (UE) movement disorder (e.g., Parkinson’s disease, stroke, head injury, intentional tremor), (2) UE amputation, (3) hand joint arthroplasty, (4) trauma within the past 6 mo that increased nonarthritic symptoms, (5) hand or wrist conditions (e.g., carpal tunnel syndrome), (6) hand deformities that prevent the grasping of instruments, and (7) strength testing contraindications due to medical comorbidities.
Instrumentation
Participants completed 16 trials at attempting to break the seal on a force-sensing jar apparatus through counterclockwise twists. This instrument (i.e., the jar apparatus; McGee, Nuckley, & Mathiowetz, 2011) has good construct and ecological validity and excellent intratester reliability for the outputs used in this study. The jar’s lid had six force-sensing resistors and a six-axis load cell, allowing the jar to detect grip forces (i.e., forces on the jar lid during a power grasp measured in newtons) and the torque (measured in newton meters [Nm]) about the lid’s axis of rotation. During each trial, the torque required to turn the jar device was set through use of a torque limiter to replicate the actual torque required to open a sealed jar with an 83-mm diameter lid of 4.24 Nm (Soroka, 2002). Once the torque threshold was exceeded, the jar lid would rotate freely for 90° to simulate breaking the seal.
The jar-opening simulations (see Figure 1) consisted of two trials of three factors: (1) the approach (supinated stabilizing hand vs. oblique stabilizing hand), (2) the lid-gripping hand (right vs. left), and (3) the use or nonuse of nonskid material. The jar-grasping approaches were chosen because they are common approaches (Bush, Bix, Bello, & Fair, 2013). Participants were randomly assigned to predetermined sequences of the eight conditions.
Figure 1.
Oblique and supinated approaches with and without use of nonskid material.
Note. Only the left hand is depicted as the turning hand in these photos.
Figure 1.
Oblique and supinated approaches with and without use of nonskid material.
Note. Only the left hand is depicted as the turning hand in these photos.
×
Standardized procedures (McGee et al., 2011) were used for each jar-turning simulation. In a standing position, participants maintained standardized glenohumeral and elbow joint positions as well as hand placements to control for distal kinetic variance that might result from nonstandardized posturing. Between trials, 30 s of rest were offered.
Measures
Demographic information (i.e., race, age, self-reported hand dominance; see Corey, Hurley, & Foundas, 2001), disease impact, and maximum hand strength were recorded at baseline. Self-perceived impact of hand OA on daily living was characterized via the Arthritis Impact Measurement Scales 2—Short Form (AIMS2–SF; Ren, Kazis, & Meenan, 1999). Maximal voluntary contraction (MVC) grip strength of the dominant and nondominant hands was measured by the Jamar dynamometer and the B&L Pinch Gauge in accordance with standardized positioning and instructions (Mathiowetz, Weber, Volland, & Kashman, 1984).
Across all trials, the primary outcomes—grip force and opening torque—were recorded for a maximum period of 6 s. Secondary outcomes were success in breaking the seal and pain as measured with the Numerical Rating Scale (NRS; Downie et al., 1978). The NRS, a 0–10 scale of pain intensity, is commonly used in clinical practice and has high responsiveness to pain intensity changes (Ferreira-Valente, Pais-Ribeiro, & Jensen, 2011). An NRS rating of 0 indicates no pain, whereas a 10 indicates extremely strong or maximal hand pain. The first author was the sole evaluator of the outcomes because of the specialized training required to manage the instrumentation.
Statistical Analysis
MATLAB 155 (Version 7.9; MathWorks, Natick, MA) was used to compute grip force at peak torque of the jar lid, the IGF, and peak torque acting on the jar’s lid. NRS change scores (postbaseline) were calculated with IBM SPSS Statistics (Version 22; IBM Corp., Armonk, NY). Descriptive statistics and within-subjects comparisons (Student’s t, Cochran’s Q, and Wilcoxon signed-rank test) for baseline characteristics, hand force, torque, success, and pain were performed with SPSS. We used SAS (Proc Mixed, Version 9.4; SAS Corp., Cary, NC) to estimate the effect of and interactions among the three experimental factors on pain, peak grip force, IGF, and peak torque using a mixed-effects linear model with hands as the repeated factor and participants as the random effect. Post hoc within-subject comparisons of significant interactions were performed with Student’s t, using Bonferroni correction for multiple comparisons. Cohen’s d effect sizes for significant main and interaction effects were calculated and later interpreted (Cohen, 1988).
Results
Participants
Thirty-one women with hand OA participated. One woman was unable to complete eight trials with her left hand because of increased arthritic symptomatology during forearm pronation. The sample’s AIMS2–SF average total health score of 10.62 (standard deviation [SD] = 5.28) indicated that perceived health was mildly affected by the condition. Participants also reported mild disease impact on the Physical Functioning, UE Functioning, Social Interactions, and Affect subscales of the AIMS2–SF. See Supplemental Table 1 (available online at http://otjournal.net; navigate to this article, and click on “Supplemental”) for details on the sample’s characteristics.
On average, participants had OA in two digits in both the right and the left hand (mean [M] = 2.1, SD = 1.5, and M = 2.0, SD = 1.5 digits, respectively). Ninety percent had radiographically confirmed or self-reported thumb OA; the percentages for other digits were as follows: 45% index, 42% long, 23% ring, and 29% small. These percentages vary from reported distribution patterns in which index, middle, and small fingers are most often radiographically confirmed (Addimanda et al., 2012). This finding may be due to the large portion of the sample who were seeking occupational therapy for first carpometacarpal (CMC) OA at orthopedic clinics, which, when compared with interphalangeal hand arthritis, yields significantly worse hand function and symptomatology (p < .01; Bijsterbosch et al., 2010). The participants’ left hand had significantly more small finger proximal interphalangeal joints affected by OA than did their right (z = 2.00, p = .05). There were no other significant differences in the right–left distribution of joint involvement, the total affected joint counts, or maximum grip or pinch strength between right and left hands in our sample.
Force Outcomes
Grip Force at Peak Torque.
The average grip force when attempting to break the seal (i.e., at the time of peak torque) of the jar ranged from 129.8 (SD = 42.2) to 169.9 (SD = 58.6) newtons (N) in the left and right hands, respectively (Table 1). On average, the left hand used significantly greater force across all approaches and with or without nonskid materials (M = 134.0 N, SD = 6.1) than did the right (M = 158.1 N, SD = 6.2 N, p < .0001; see Tables 2 and 3). A lower peak grip force at the time of maximal torque is desirable, potentially indicating less stress applied to the joints.
Table 1.
Summary Statistics for Successful Turns, Grip Force, IGF, Pain Intensity, and Pain Change Across Four Approaches to Opening a Sealed 83-Millimeter Jar
Summary Statistics for Successful Turns, Grip Force, IGF, Pain Intensity, and Pain Change Across Four Approaches to Opening a Sealed 83-Millimeter Jar×
Approach ± Nonskid, Hand Used to Turn LidnTrialsTotal Successes, %Grip Force, N M (SD)IGF, N M (SD)Torque, Nm M (SD)Pain Intensity, NRS M (SD)∆ Pain M (SD)
Oblique
 Right306011 (18.3)142.9 (50.5)1,000.2 (341.4)3.2 (1.1)2.9 (2.4)2.2 (2.1)
 Left316219 (30.6)128.5 (39.7)905.8 (357.7)3.3 (1.3)2.9 (2.7)2.0 (2.2)
Oblique nonskid
 Right306016 (26.7)158.6 (49.7)1,072.6 (446.8)3.3 (1.1)3.4 (2.8)2.7 (2.6)
 Left316223 (37.1)129.1 (42.2)930.0 (378.5)3.6 (1.1)3.4 (2.5)2.4 (2.7)
Supinated
 Right306030 (50.0)169.9 (58.6)733.2 (324.5)3.9 (1.1)2.6 (2.3)1.7 (2.2)
 Left316235 (56.5)135.6 (56.8)762.8 (420.6)4.0 (1.0)2.4 (2.5)1.4 (1.9)
Supinated nonskid
 Right306043 (72.0)150.3 (56.5)633.2 (345.7)4.1 (1.0)2.6 (2.7)1.7 (2.5)
 Left316253 (85.5)136.2 (63.4)576.2 (320.5)4.3 (0.9)2.2 (2.2)1.3 (2.5)
Table Footer NoteNote. Successes = number of trials on which the jar lid seal was broken. Reports of pain are not specific to a hand. Pain intensity was reported after each trial by means of Change in pain = pain NRS score after each trial – baseline NRS score. IGF = integral of the grip force; M = mean, N = newtons; Nm = newton meters; NRS = Numerical Rating Scale; SD = standard deviation.
Note. Successes = number of trials on which the jar lid seal was broken. Reports of pain are not specific to a hand. Pain intensity was reported after each trial by means of Change in pain = pain NRS score after each trial – baseline NRS score. IGF = integral of the grip force; M = mean, N = newtons; Nm = newton meters; NRS = Numerical Rating Scale; SD = standard deviation.×
Table 1.
Summary Statistics for Successful Turns, Grip Force, IGF, Pain Intensity, and Pain Change Across Four Approaches to Opening a Sealed 83-Millimeter Jar
Summary Statistics for Successful Turns, Grip Force, IGF, Pain Intensity, and Pain Change Across Four Approaches to Opening a Sealed 83-Millimeter Jar×
Approach ± Nonskid, Hand Used to Turn LidnTrialsTotal Successes, %Grip Force, N M (SD)IGF, N M (SD)Torque, Nm M (SD)Pain Intensity, NRS M (SD)∆ Pain M (SD)
Oblique
 Right306011 (18.3)142.9 (50.5)1,000.2 (341.4)3.2 (1.1)2.9 (2.4)2.2 (2.1)
 Left316219 (30.6)128.5 (39.7)905.8 (357.7)3.3 (1.3)2.9 (2.7)2.0 (2.2)
Oblique nonskid
 Right306016 (26.7)158.6 (49.7)1,072.6 (446.8)3.3 (1.1)3.4 (2.8)2.7 (2.6)
 Left316223 (37.1)129.1 (42.2)930.0 (378.5)3.6 (1.1)3.4 (2.5)2.4 (2.7)
Supinated
 Right306030 (50.0)169.9 (58.6)733.2 (324.5)3.9 (1.1)2.6 (2.3)1.7 (2.2)
 Left316235 (56.5)135.6 (56.8)762.8 (420.6)4.0 (1.0)2.4 (2.5)1.4 (1.9)
Supinated nonskid
 Right306043 (72.0)150.3 (56.5)633.2 (345.7)4.1 (1.0)2.6 (2.7)1.7 (2.5)
 Left316253 (85.5)136.2 (63.4)576.2 (320.5)4.3 (0.9)2.2 (2.2)1.3 (2.5)
Table Footer NoteNote. Successes = number of trials on which the jar lid seal was broken. Reports of pain are not specific to a hand. Pain intensity was reported after each trial by means of Change in pain = pain NRS score after each trial – baseline NRS score. IGF = integral of the grip force; M = mean, N = newtons; Nm = newton meters; NRS = Numerical Rating Scale; SD = standard deviation.
Note. Successes = number of trials on which the jar lid seal was broken. Reports of pain are not specific to a hand. Pain intensity was reported after each trial by means of Change in pain = pain NRS score after each trial – baseline NRS score. IGF = integral of the grip force; M = mean, N = newtons; Nm = newton meters; NRS = Numerical Rating Scale; SD = standard deviation.×
×
Table 2.
Main Effects of Hand Use, Grasp Pattern, and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF
Main Effects of Hand Use, Grasp Pattern, and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF×
FactorM (SD)M (SD)Cohen’s d
Hand
LeftRight
Grip force, N158.1 (34.0)134.0 (33.4)***0.7
IGF, Ns781.0 (158.3)710.4 (159.9)**0.4
Torque, Nm3.6 (1.1)3.7 (1.1)*0.2
∆ pain2.1 (1.6)1.8 (1.6)*0.2
% success0.4 (0.4)0.5 (0.4)*0.4
Approach
ObliqueSupinated
Torque3.3 (1.1)4.0 (1.1)***0.6
Pain intensity, NRS3.2 (2.2)2.4 (2.2)***0.4
∆ pain2.3 (1.6)1.6 (1.6)***0.5
% success0.3 (0.3)0.7 (0.4)***1.1
Nonskid
YesNo
Torque3.7 (1.1)3.5 (1.1)***0.6
% success0.4 (0.4)0.6 (0.4)**0.4
Table Footer NoteNote. Reports of pain are not specific to a hand. Change in pain = pain NRS score after each trial – baseline NRS score. Pairwise comparisons (within rows) for significant main and interaction effects were performed with a Student’s t test. Effect sizes for significantly different interaction effects are described in the Results section in the article text. IGF = integral of the grip force; M = mean, Nm = newton meters; NRS = Numerical Rating Scale; Ns = newton seconds; SD = standard deviation.
Note. Reports of pain are not specific to a hand. Change in pain = pain NRS score after each trial – baseline NRS score. Pairwise comparisons (within rows) for significant main and interaction effects were performed with a Student’s t test. Effect sizes for significantly different interaction effects are described in the Results section in the article text. IGF = integral of the grip force; M = mean, Nm = newton meters; NRS = Numerical Rating Scale; Ns = newton seconds; SD = standard deviation.×
Table Footer Note*p < .05. **p < .01. ***p < .001.
*p < .05. **p < .01. ***p < .001.×
Table 2.
Main Effects of Hand Use, Grasp Pattern, and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF
Main Effects of Hand Use, Grasp Pattern, and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF×
FactorM (SD)M (SD)Cohen’s d
Hand
LeftRight
Grip force, N158.1 (34.0)134.0 (33.4)***0.7
IGF, Ns781.0 (158.3)710.4 (159.9)**0.4
Torque, Nm3.6 (1.1)3.7 (1.1)*0.2
∆ pain2.1 (1.6)1.8 (1.6)*0.2
% success0.4 (0.4)0.5 (0.4)*0.4
Approach
ObliqueSupinated
Torque3.3 (1.1)4.0 (1.1)***0.6
Pain intensity, NRS3.2 (2.2)2.4 (2.2)***0.4
∆ pain2.3 (1.6)1.6 (1.6)***0.5
% success0.3 (0.3)0.7 (0.4)***1.1
Nonskid
YesNo
Torque3.7 (1.1)3.5 (1.1)***0.6
% success0.4 (0.4)0.6 (0.4)**0.4
Table Footer NoteNote. Reports of pain are not specific to a hand. Change in pain = pain NRS score after each trial – baseline NRS score. Pairwise comparisons (within rows) for significant main and interaction effects were performed with a Student’s t test. Effect sizes for significantly different interaction effects are described in the Results section in the article text. IGF = integral of the grip force; M = mean, Nm = newton meters; NRS = Numerical Rating Scale; Ns = newton seconds; SD = standard deviation.
Note. Reports of pain are not specific to a hand. Change in pain = pain NRS score after each trial – baseline NRS score. Pairwise comparisons (within rows) for significant main and interaction effects were performed with a Student’s t test. Effect sizes for significantly different interaction effects are described in the Results section in the article text. IGF = integral of the grip force; M = mean, Nm = newton meters; NRS = Numerical Rating Scale; Ns = newton seconds; SD = standard deviation.×
Table Footer Note*p < .05. **p < .01. ***p < .001.
*p < .05. **p < .01. ***p < .001.×
×
Table 3.
Interaction Effects of Grasp Pattern and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF
Interaction Effects of Grasp Pattern and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF×
FactorApproach × Nonskid
Oblique + Nonskid, M (SD)Oblique – Nonskid M (SD)Supinated + Nonskid M (SD)Supinated – Nonskid M (SD)
IGF1,003.3 (295.8)a9,295 (309.5)a6,759 (319.3)c8,109 (291.4)b
Pain intensity, NRS34 (2.2)c30 (2.2)b24 (2.2)a25 (2.2)a
Table Footer NoteNote. For the Approach × Nonskid significant interaction, means that do not share a subscript letter (within rows) were significantly different (p < .05); means that share a subscript letter were not. IGF = integral of the grip force; M = mean; NRS = Numerical Rating Scale; SD = standard deviation.
Note. For the Approach × Nonskid significant interaction, means that do not share a subscript letter (within rows) were significantly different (p < .05); means that share a subscript letter were not. IGF = integral of the grip force; M = mean; NRS = Numerical Rating Scale; SD = standard deviation.×
Table 3.
Interaction Effects of Grasp Pattern and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF
Interaction Effects of Grasp Pattern and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF×
FactorApproach × Nonskid
Oblique + Nonskid, M (SD)Oblique – Nonskid M (SD)Supinated + Nonskid M (SD)Supinated – Nonskid M (SD)
IGF1,003.3 (295.8)a9,295 (309.5)a6,759 (319.3)c8,109 (291.4)b
Pain intensity, NRS34 (2.2)c30 (2.2)b24 (2.2)a25 (2.2)a
Table Footer NoteNote. For the Approach × Nonskid significant interaction, means that do not share a subscript letter (within rows) were significantly different (p < .05); means that share a subscript letter were not. IGF = integral of the grip force; M = mean; NRS = Numerical Rating Scale; SD = standard deviation.
Note. For the Approach × Nonskid significant interaction, means that do not share a subscript letter (within rows) were significantly different (p < .05); means that share a subscript letter were not. IGF = integral of the grip force; M = mean; NRS = Numerical Rating Scale; SD = standard deviation.×
×
Integral of the Grip Force.
The IGF ranged from 576.2 (SD = 320.5) to 1,072.6 (SD = 341.4) newton seconds (Ns). The highest IGF average amount was during the right nonskid oblique approach, whereas the left nonskid supinated approach had the smallest average grip power (see Table 1). An interaction between approach and nonskid material influenced the IGF used, F(1, 411) = 8.70, p = .003; the combination of a supinated approach and nonskid material yielded the smallest IGF when compared with all other possible interactions (p < .05; see Tables 2 and 3 and Supplemental Figure 1 [available online at http://otjournal.net; navigate to this article, and click on “Supplemental”]). A supinated approach + nonskid material had large IGF-reducing effects relative to oblique approaches with and without nonskid materials (Cohen’s ds = 1.1 and 0.8, respectively); the supinated approach without nonskid materials had moderate to small IGF-reducing effects relative to the oblique approaches with and without nonskid materials (Cohen’s ds = 0.7 and 0.4, respectively). A small IGF-reducing effect was noted when participants used the supinated approach with nonskid material relative to without (Cohen’s d = 0.4). A lower IGF is preferred because it implies a more efficient approach (Walker, 2007) and that less joint stress is applied during jar opening.
Torque.
Torque ranged from 3.2 (SD = 1.1) to 4.3 (SD = 0.9) Nm. The highest torque was noted during the left-hand nonskid supinated approaches, and the smallest torque was observed during the right-hand oblique approaches (see Table 1). The left hand produced more torque than the right, with a mean difference (MD) of 0.16 (SD = 0.07), t(41) = 2.47, p = .01. The supinated approach produced more torque than the oblique approach (MD = 0.70, SD = 0.07), t(41) = 10.07, p < .0001, and the use of nonskid material generated more torque than nonuse (MD = 0.23, SD = 0.07), t(41) = 3.53, p = .0005. These effects were small to moderate (see Tables 2 and 3).
Success
Success rates ranged from 18.3% to 85.2%. The right-hand oblique approach without nonskid material had the least success; the left-hand supinated approach with nonskid material had the highest (see Table 1). Three independent effects of hand, nonskid material, and approach on success were discovered: (1) A left-hand turn was more successful (95% confidence interval [CI] [40%, 68%]) than the right (95% CI [27%, 54%], p = .01), (2) the use of nonskid material resulted in greater success (95% CI [42%, 67%]) than nonuse (95% CI [26%, 54%], p = .001), and (3) the supinated approach had greater success (95% CI [53%, 79%]) than the oblique approach (95% CI [17%, 41%]). These effects were respectively small, moderate, and strong (Cohen’s ds = 0.39, 0.42, and 1.09; sees Tables 2 and 3 for details).
Pain
The average pain intensity score ranged from 2.21 (SD = 2.2) to 3.42 (SD = 2.5), with the highest pain intensity after a left oblique approach with nonskid material and the least pain intensity after a left supinated approach with nonskid material. The largest change in pain (M = 2.74, SD = 2.6) was when a right-hand oblique approach with nonskid material was used, whereas the smallest change in pain (M = 1.3, SD = 2.5) occurred when a left-hand supinated grasp with nonskid material was used (see Table 1).
Pain NRS scores were significantly higher, with more change, when an oblique approach was used than when a supinated approach was used, Fs(1, 411) = 25.98 and 23.77, ps < .0001, respectively. There were significantly larger pain increases when the right hand as opposed to the left was used, F(1, 411) = 3.88, p = .05. A nonskid material + oblique approach yielded significantly higher pain intensity ratings than any other combination (p < .05). Post hoc comparisons identified pain intensities to be different in all instances except for between the supination approaches. Although different, the relative effects of these combinations on pain intensity were small, with the largest effects on pain intensity noted when we compared the supinated + nonskid approach with that of the oblique + nonskid approach, and the smallest effects noted when we compared the two oblique approaches (see Tables 2 and 3).
Discussion
Effect of Nonskid Materials
The results of this study reveal that the use of nonskid material alone enhances hand torque acting on a jar lid. Across both hands and all approaches, nonskid material enhanced torque by roughly 6.1% and had a small significant effect on success. The effect of nonskid material, however, did not independently influence torque at peak torque or IGF but likely contributed to the development of downward compressive force that may have enhanced the frictional interplay of the hand and lid and necessitated less grip force. This assumption requires further exploration.
Effects of Approach
The supinated approach, independent of hand and nonskid material, produced the greatest torque. Although the pain-stabilizing effect of the supinated approach was small, the mean pain change of participants who used a supinated approach did not exceed the clinically significant change of 2 units on the NRS (Farrar, Young, LaMoreaux, Werth, & Poole, 2001), whereas the pain change of all oblique approaches did. Here, exceeding the clinically significant change is undesirable because it indicates that such an increase in pain would be of functional importance to the client.
Effects of Turning Hand
Although the sample was 90.3% right handed and the right hand’s maximum strength was slightly larger than the left’s, the left hand appeared to be better at generating torque. Because the arthritis distribution is similar across right and left joints, except for the small finger proximal interphalangeal, these results cannot be attributed to a higher right-hand joint count. An argument also cannot be made that the left hand generated less force across all factors because it was weaker; this hypothesis is not supported by the sample’s baseline hand-strength characteristics.
Participants’ baseline pain intensity had no effect on grip force at peak torque (p < .32). The lid-turning hand did, however, influence the pain experienced. Participants who twisted the jar lid with the left hand reported a smaller increase in pain than did those twisting with the right (MD = 0.31, SD = 0.16, p = .05). This difference may be explained by the left hand’s reduced grip force profile and inferred changes in the hand’s joint reactive forces, in particular the thumb, which constitutes 41% of the grip force profile during jar twisting (Shim, Huang, Hooke, Latsh, & Zatsiorsky, 2007), and the high prevalence of participants with first CMC OA. The left hand’s reduced grip force profiles are supported by the significantly greater safety margins (i.e., ratio of actual grip forces to those needed to prevent slippage) of healthy-handed participants when opening a simulated lid compared with closing it with the right hand (Shim et al., 2007).
The findings of Shim et al. (2007)  support ours, given that the right hand’s closing turn is analogous to (i.e., mirrors) the left hand’s opening turn. These differences are likely explained by Shim et al.’s additional conclusions that, when opening with the right hand, the thumb’s contributions to torque are inefficient relative to the grip force it exerts and, as a result, higher grip forces are needed to compensate. Although not explored by Shim et al., we speculate that this is explained by differences in frictional interplay between the thenar eminence and jar lid when opening (i.e., the thenar eminence and all of its surface area are perhaps more intimately connected to the lid when opening with the left hand than with the right).
Combined Effects of Hand, Approach, and Nonskid Material
The left-hand supinated approach with nonskid material resulted in an 85.5% success rate, the lowest pain intensity, and the least increased pain. This result may be due to the positive effects of nonskid material on torque, the reduced left-hand grip force requirements at peak torque, and the IGF-reducing effects of the supinated approach + nonskid material. We also speculate that, for participants with first CMC arthritis, the girth of the jar base stressed the stabilizing hand’s thumb into maximal palmar abduction when using the oblique approach, which resulted in increased pain and difficulty in providing the counterforce needed to rotate the lid independent of the base.
The first CMC joint compressive force in the left, supinated, nonskid approach was likely between 367.6 and 527.9 Ns, whereas it was projected to be between 638.1 and 916.5 Ns in a right, oblique, nonskid approach. This estimate is supported by the findings of Shim et al. (2007)  and the cadaveric work of Cooney and Chao (1977), in which for every 1 N of lateral pinch, the same pinch used in this experiment, between 9.3 and 13.4 N are acting on the first CMC joint. These findings are particularly striking given the high percentage of participants with first CMC OA and the projected between-approach differences in first CMC loads of up to about 400 Ns.
Although least painful, most efficient, and most successful, the left supinated grasp with nonskid material approach still required about 30.6 lb (136.2 N) of force, which was 60.4% of the participants’ left-hand MVC grip strength. Because frequent use of forces exceeding 15%–20% of MVC may be linked to the development of UE musculoskeletal disorders (Tanaka et al., 1994), nonskid materials may not suffice as a stand-alone JP approach. Instead, women with hand OA should also use a preferred approach, other JP strategies, or assistive jar opening devices.
Given that opening a jar is often part of meal preparation and is of importance to women with hand OA (Kjeken et al., 2005), these findings call into question the validity of the assumption that grip strength of 20 lb is enough to engage in daily activities (Terrono, Nalebuff, & Phillips, 2011). On average, our participants possessed MVC grip strengths 30 lb greater than this benchmark. In addition, participants exerted grips between 30.6 lb (136.2 N) and 38.2 lb (169.9 N) when attempting to break the seal. Although both MVC grip strength and grip forces during the task exceeded the recommended 20-lb threshold, many participants were unable to break the seal. Given the large forces required, there is a need for manufacturers to consider alternative jar design to mitigate risks.
This study had multiple limitations. Participants had mild symptoms with low effects on function per the AIMS2–SF Total Health Scale and were predominately right handed. Radiographic staging was not available to determine arthritis severity, but radiographic changes in hand arthritis do not often correspond with clinical symptomatology (Bijsterbosch et al., 2011). Although we evaluated the turning hand’s force and torque, we did not explore the effect of the stabilizing hand’s kinetics or wrist joint kinematics during the task. Participants did not rate pain in the stabilizing hand, only in the actively gripping hand.
Implications for Occupational Therapy Practice
These data support the use of nonskid materials yet challenge the belief that nonskid materials alone reduce hand forces. Occupational therapy practitioners should be aware of characteristics of different jar-opening strategies to enhance success, minimize pain, and reduce the grip forces of women with hand OA. For women with predominantly bilateral first CMC OA and symmetrical distribution of hand OA, turning the lid of a large-diameter sealed jar with the left hand in a pronated posture, stabilizing the base with a supinated right hand, and using nonskid material required the least amount grip force, yielded the highest success rate, produced more opening torque than all but the right supinated approach with nonskid material, required significantly lower grip force than all but one right-hand approach, and resulted in the least amount of pain intensity and a slight increase in pain. Nonskid material, particularly when used by the right hand using an oblique approach during opening, does not have the same hand force and pain-reducing effects and should be avoided. The use of nonskid material without additional strategies will likely increase loads on arthritic joints, pain, and dysfunction.
Suggestions for Future Research
Additional studies are needed to further evaluate these jar opening and other JP strategies in people with more severe hand OA and to evaluate compression forces in the gripping hand and all forces in the nonturning, stabilizing hand. Further research is also needed to further explore joint biomechanics given the various combinations of JP strategies evaluated in this study. Such studies could be conducted using three-dimensional analysis of the upper limbs along with inverse dynamics modeling. Finally, the strategies examined in this study should be evaluated in relation to all clinical measures, in various additional problematic gripping tasks (e.g., different-sized jars), and in regard to how they influence thresholds to successfully open real sealed jars.
Suggested citation. McGee, C., & Mathiowetz, V. (2017). Evaluation of hand forces during a joint-protection strategy for women with hand osteoarthritis (Suppl. Figure 1). American Journal of Occupational Therapy, 71, 7101190020. https://doi.org/10.5014/ajot.2017.022921
Suggested citation. McGee, C., & Mathiowetz, V. (2017). Evaluation of hand forces during a joint-protection strategy for women with hand osteoarthritis (Suppl. Table 1). American Journal of Occupational Therapy, 71, 7101190020. https://doi.org/10.5014/ajot.2017.022921
Acknowledgments
We thank Erica Stern for her assistance with study design and manuscript review; Will Thomas for his assistance with design, statistical analysis, and interpretation; David Nuckley for his assistance with design of the instrument and code writing for data cleansing; Mo Chen for his assistance with code writing for data cleansing; Sarah Braski, Michelle Kloke, Nina Moore, Katie Thomason, and Kim Stokke for their assistance with participant recruitment; Lisa Fitzpatrick for her help with editing; TRIA Orthopedics Center, University of Minnesota Orthopaedics, the University Orthopaedics Therapy Center, and the Volunteers of America, for their assistance with participant screening and recruitment; and the Minnesota Medical Foundation for partially funding the project. This article was presented at the 2015 Annual Conference of the American Society of Hand Therapists, Denver, Colorado.
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Figure 1.
Oblique and supinated approaches with and without use of nonskid material.
Note. Only the left hand is depicted as the turning hand in these photos.
Figure 1.
Oblique and supinated approaches with and without use of nonskid material.
Note. Only the left hand is depicted as the turning hand in these photos.
×
Table 1.
Summary Statistics for Successful Turns, Grip Force, IGF, Pain Intensity, and Pain Change Across Four Approaches to Opening a Sealed 83-Millimeter Jar
Summary Statistics for Successful Turns, Grip Force, IGF, Pain Intensity, and Pain Change Across Four Approaches to Opening a Sealed 83-Millimeter Jar×
Approach ± Nonskid, Hand Used to Turn LidnTrialsTotal Successes, %Grip Force, N M (SD)IGF, N M (SD)Torque, Nm M (SD)Pain Intensity, NRS M (SD)∆ Pain M (SD)
Oblique
 Right306011 (18.3)142.9 (50.5)1,000.2 (341.4)3.2 (1.1)2.9 (2.4)2.2 (2.1)
 Left316219 (30.6)128.5 (39.7)905.8 (357.7)3.3 (1.3)2.9 (2.7)2.0 (2.2)
Oblique nonskid
 Right306016 (26.7)158.6 (49.7)1,072.6 (446.8)3.3 (1.1)3.4 (2.8)2.7 (2.6)
 Left316223 (37.1)129.1 (42.2)930.0 (378.5)3.6 (1.1)3.4 (2.5)2.4 (2.7)
Supinated
 Right306030 (50.0)169.9 (58.6)733.2 (324.5)3.9 (1.1)2.6 (2.3)1.7 (2.2)
 Left316235 (56.5)135.6 (56.8)762.8 (420.6)4.0 (1.0)2.4 (2.5)1.4 (1.9)
Supinated nonskid
 Right306043 (72.0)150.3 (56.5)633.2 (345.7)4.1 (1.0)2.6 (2.7)1.7 (2.5)
 Left316253 (85.5)136.2 (63.4)576.2 (320.5)4.3 (0.9)2.2 (2.2)1.3 (2.5)
Table Footer NoteNote. Successes = number of trials on which the jar lid seal was broken. Reports of pain are not specific to a hand. Pain intensity was reported after each trial by means of Change in pain = pain NRS score after each trial – baseline NRS score. IGF = integral of the grip force; M = mean, N = newtons; Nm = newton meters; NRS = Numerical Rating Scale; SD = standard deviation.
Note. Successes = number of trials on which the jar lid seal was broken. Reports of pain are not specific to a hand. Pain intensity was reported after each trial by means of Change in pain = pain NRS score after each trial – baseline NRS score. IGF = integral of the grip force; M = mean, N = newtons; Nm = newton meters; NRS = Numerical Rating Scale; SD = standard deviation.×
Table 1.
Summary Statistics for Successful Turns, Grip Force, IGF, Pain Intensity, and Pain Change Across Four Approaches to Opening a Sealed 83-Millimeter Jar
Summary Statistics for Successful Turns, Grip Force, IGF, Pain Intensity, and Pain Change Across Four Approaches to Opening a Sealed 83-Millimeter Jar×
Approach ± Nonskid, Hand Used to Turn LidnTrialsTotal Successes, %Grip Force, N M (SD)IGF, N M (SD)Torque, Nm M (SD)Pain Intensity, NRS M (SD)∆ Pain M (SD)
Oblique
 Right306011 (18.3)142.9 (50.5)1,000.2 (341.4)3.2 (1.1)2.9 (2.4)2.2 (2.1)
 Left316219 (30.6)128.5 (39.7)905.8 (357.7)3.3 (1.3)2.9 (2.7)2.0 (2.2)
Oblique nonskid
 Right306016 (26.7)158.6 (49.7)1,072.6 (446.8)3.3 (1.1)3.4 (2.8)2.7 (2.6)
 Left316223 (37.1)129.1 (42.2)930.0 (378.5)3.6 (1.1)3.4 (2.5)2.4 (2.7)
Supinated
 Right306030 (50.0)169.9 (58.6)733.2 (324.5)3.9 (1.1)2.6 (2.3)1.7 (2.2)
 Left316235 (56.5)135.6 (56.8)762.8 (420.6)4.0 (1.0)2.4 (2.5)1.4 (1.9)
Supinated nonskid
 Right306043 (72.0)150.3 (56.5)633.2 (345.7)4.1 (1.0)2.6 (2.7)1.7 (2.5)
 Left316253 (85.5)136.2 (63.4)576.2 (320.5)4.3 (0.9)2.2 (2.2)1.3 (2.5)
Table Footer NoteNote. Successes = number of trials on which the jar lid seal was broken. Reports of pain are not specific to a hand. Pain intensity was reported after each trial by means of Change in pain = pain NRS score after each trial – baseline NRS score. IGF = integral of the grip force; M = mean, N = newtons; Nm = newton meters; NRS = Numerical Rating Scale; SD = standard deviation.
Note. Successes = number of trials on which the jar lid seal was broken. Reports of pain are not specific to a hand. Pain intensity was reported after each trial by means of Change in pain = pain NRS score after each trial – baseline NRS score. IGF = integral of the grip force; M = mean, N = newtons; Nm = newton meters; NRS = Numerical Rating Scale; SD = standard deviation.×
×
Table 2.
Main Effects of Hand Use, Grasp Pattern, and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF
Main Effects of Hand Use, Grasp Pattern, and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF×
FactorM (SD)M (SD)Cohen’s d
Hand
LeftRight
Grip force, N158.1 (34.0)134.0 (33.4)***0.7
IGF, Ns781.0 (158.3)710.4 (159.9)**0.4
Torque, Nm3.6 (1.1)3.7 (1.1)*0.2
∆ pain2.1 (1.6)1.8 (1.6)*0.2
% success0.4 (0.4)0.5 (0.4)*0.4
Approach
ObliqueSupinated
Torque3.3 (1.1)4.0 (1.1)***0.6
Pain intensity, NRS3.2 (2.2)2.4 (2.2)***0.4
∆ pain2.3 (1.6)1.6 (1.6)***0.5
% success0.3 (0.3)0.7 (0.4)***1.1
Nonskid
YesNo
Torque3.7 (1.1)3.5 (1.1)***0.6
% success0.4 (0.4)0.6 (0.4)**0.4
Table Footer NoteNote. Reports of pain are not specific to a hand. Change in pain = pain NRS score after each trial – baseline NRS score. Pairwise comparisons (within rows) for significant main and interaction effects were performed with a Student’s t test. Effect sizes for significantly different interaction effects are described in the Results section in the article text. IGF = integral of the grip force; M = mean, Nm = newton meters; NRS = Numerical Rating Scale; Ns = newton seconds; SD = standard deviation.
Note. Reports of pain are not specific to a hand. Change in pain = pain NRS score after each trial – baseline NRS score. Pairwise comparisons (within rows) for significant main and interaction effects were performed with a Student’s t test. Effect sizes for significantly different interaction effects are described in the Results section in the article text. IGF = integral of the grip force; M = mean, Nm = newton meters; NRS = Numerical Rating Scale; Ns = newton seconds; SD = standard deviation.×
Table Footer Note*p < .05. **p < .01. ***p < .001.
*p < .05. **p < .01. ***p < .001.×
Table 2.
Main Effects of Hand Use, Grasp Pattern, and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF
Main Effects of Hand Use, Grasp Pattern, and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF×
FactorM (SD)M (SD)Cohen’s d
Hand
LeftRight
Grip force, N158.1 (34.0)134.0 (33.4)***0.7
IGF, Ns781.0 (158.3)710.4 (159.9)**0.4
Torque, Nm3.6 (1.1)3.7 (1.1)*0.2
∆ pain2.1 (1.6)1.8 (1.6)*0.2
% success0.4 (0.4)0.5 (0.4)*0.4
Approach
ObliqueSupinated
Torque3.3 (1.1)4.0 (1.1)***0.6
Pain intensity, NRS3.2 (2.2)2.4 (2.2)***0.4
∆ pain2.3 (1.6)1.6 (1.6)***0.5
% success0.3 (0.3)0.7 (0.4)***1.1
Nonskid
YesNo
Torque3.7 (1.1)3.5 (1.1)***0.6
% success0.4 (0.4)0.6 (0.4)**0.4
Table Footer NoteNote. Reports of pain are not specific to a hand. Change in pain = pain NRS score after each trial – baseline NRS score. Pairwise comparisons (within rows) for significant main and interaction effects were performed with a Student’s t test. Effect sizes for significantly different interaction effects are described in the Results section in the article text. IGF = integral of the grip force; M = mean, Nm = newton meters; NRS = Numerical Rating Scale; Ns = newton seconds; SD = standard deviation.
Note. Reports of pain are not specific to a hand. Change in pain = pain NRS score after each trial – baseline NRS score. Pairwise comparisons (within rows) for significant main and interaction effects were performed with a Student’s t test. Effect sizes for significantly different interaction effects are described in the Results section in the article text. IGF = integral of the grip force; M = mean, Nm = newton meters; NRS = Numerical Rating Scale; Ns = newton seconds; SD = standard deviation.×
Table Footer Note*p < .05. **p < .01. ***p < .001.
*p < .05. **p < .01. ***p < .001.×
×
Table 3.
Interaction Effects of Grasp Pattern and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF
Interaction Effects of Grasp Pattern and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF×
FactorApproach × Nonskid
Oblique + Nonskid, M (SD)Oblique – Nonskid M (SD)Supinated + Nonskid M (SD)Supinated – Nonskid M (SD)
IGF1,003.3 (295.8)a9,295 (309.5)a6,759 (319.3)c8,109 (291.4)b
Pain intensity, NRS34 (2.2)c30 (2.2)b24 (2.2)a25 (2.2)a
Table Footer NoteNote. For the Approach × Nonskid significant interaction, means that do not share a subscript letter (within rows) were significantly different (p < .05); means that share a subscript letter were not. IGF = integral of the grip force; M = mean; NRS = Numerical Rating Scale; SD = standard deviation.
Note. For the Approach × Nonskid significant interaction, means that do not share a subscript letter (within rows) were significantly different (p < .05); means that share a subscript letter were not. IGF = integral of the grip force; M = mean; NRS = Numerical Rating Scale; SD = standard deviation.×
Table 3.
Interaction Effects of Grasp Pattern and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF
Interaction Effects of Grasp Pattern and Nonskid Material Use on Hand Pain, Force, Hand Torque, and IGF×
FactorApproach × Nonskid
Oblique + Nonskid, M (SD)Oblique – Nonskid M (SD)Supinated + Nonskid M (SD)Supinated – Nonskid M (SD)
IGF1,003.3 (295.8)a9,295 (309.5)a6,759 (319.3)c8,109 (291.4)b
Pain intensity, NRS34 (2.2)c30 (2.2)b24 (2.2)a25 (2.2)a
Table Footer NoteNote. For the Approach × Nonskid significant interaction, means that do not share a subscript letter (within rows) were significantly different (p < .05); means that share a subscript letter were not. IGF = integral of the grip force; M = mean; NRS = Numerical Rating Scale; SD = standard deviation.
Note. For the Approach × Nonskid significant interaction, means that do not share a subscript letter (within rows) were significantly different (p < .05); means that share a subscript letter were not. IGF = integral of the grip force; M = mean; NRS = Numerical Rating Scale; SD = standard deviation.×
×
Supplemental Material
Supplemental Material