Patients

The study was part of a larger study aimed at describing clinical and functional consequences of hand osteoarthritis, and was approved by the regional ethics committee.¹⁸ Participants were recruited among patients previously referred to a rheumatology outpatients department. Of those agreeing to participate in the larger study, the first 100 were consecutively included in the present study. Inclusion criteria were age between 50 and 70 years, ability to communicate well in Norwegian, and osteoarthritis of the hand according to the classification criteria of the American College of Rheumatology.¹⁹ Exclusion criteria in the present study were functional problems mainly related to diseases other than osteoarthritis, or cognitive deficits affecting the interview or scoring processes.

Sample and data collection

The study employed a cross sectional design. The data collection comprised a comprehensive clinical examination by a rheumatologist, including recording of sociodemographic data and disease related factors, and completion of several self reported health status questionnaires. Within three weeks after this examination, the patients completed an interview with an occupational therapist, addressing activity limitations and participation restrictions. Following the interview, hand function was evaluated according to previous recommendations concerning core outcomes for clinical trials in hand osteoarthritis, by measuring joint mobility, grip strength, pinch strength, and pain.^20–,²²

Assessments

The variables collected were categorised according to the dimensions of the ICF model,¹² (fig 1⇓).

• Download figure
• Open in new tab
• Download powerpoint

Figure 1

 The International Classification of Functioning, Disability and Health (ICF) was used to organise potential explanatory variables in the study.

Personal factors

Age, disease duration, comorbidity, and self efficacy were grouped as personal variables.

Self efficacy is concerned with people’s judgements of their capabilities to execute given levels of performance and to exercise control over events,²³ and was measured using the function subscale in the Arthritis Self Efficacy Scale (ASES).²⁴ This subscale contains nine statements on function with which the patient may agree or disagree. The scores are expressed as values between 10 and 100, a score of 10 representing the lowest possible level of self efficacy.

Impairment variables

The impairment variables are measures of limitations or problems in body function or structure related to the disease.¹² The most important clinical characteristics of hand osteoarthritis are pain and reduced joint mobility and grip force. The following measures were chosen to reflect these characteristics at the impairment level.

Joint mobility of both hands was measured as follows:

• flexion deficit of digits II-V as the distance in mm from the distal palmar crease to the distal point of the digits;

• extension deficits of digits II-V as the distance in mm from the distal point of the nailbed of the extended fingers to a table where the patients rested their hand in a supinated position;

• opposition deficit of digit I as the distance between the tip of the thumb and the base of digit V;

• radial abduction of the thumb as the angle between the metacarpal bones of the thumb and the digit II parallel to the plane of the palm.^25,26

For both hands, grip strength and three pod pinch strength (thumb, index and long finger) were measured in Newtons (N) by the Grippit electronic instrument,^27,28 with the subjects sitting in a standard position with the elbow in 90° flexion and the wrist in a neutral position. Force recordings are displayed on the Grippit electronic unit every 0.5 seconds while the 10 second grip is in progress. The mean of the 20 registrations was recorded.

Immediately following each assessment of grip force, pain was measured on a 100 mm visual analogue (VAS) scales ranging from 0  =  no pain to 100  =  maximal pain, by asking the patient to mark the amount of pain experienced during the resisted motion in respectively grip strength and pinch strength for each hand.

Activity and participation variables

Activity limitations are the difficulties an individual may have in executing a task or action, while participation restrictions are the problems an individual may experience in involvement in life situations.¹² According to the ICF, one way of differentiating between activity and participation is to designate all detailed domains as activities and the broad category headings as participation.¹²

We therefore considered the physical disability scale of the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) to be a measure of hand related activity limitations.^3,18,29 In AUSCAN the patients rate their problems with performing the following nine activities on a scale of 0 (no problems at all) to 4 (extremely difficult): opening a new jar, carrying a full pot, picking up large heavy objects, fastening jewellery, turning taps/faucets on, doing up buttons, wringing out washcloths, peeling vegetables, and gripping and turning a round doorknob or handle. The mean score of the nine items constitutes the final AUSCAN function score.

The Canadian Occupational Performance Measure (COPM) was used to describe and measure the qualitative and quantitative aspects of activity limitations and participation restrictions as perceived by the individual.³⁰ During a semistructured interview, the patients identify their problems within three areas of self care, productivity, and leisure, and rate the importance of each problem on a scale from 1 (not important at all) to 10 (extremely important) in order to make priorities. Finally, the patients rate the most important activities (up to five) for performance and satisfaction with performance on scales from 1 (not able to do it, not satisfied at all) to 10 (able to do extremely well, extremely satisfied). Total performance and satisfaction scores are calculated by dividing the sum of the scores by the number of problems. The psychometric properties of the COPM have been established in many groups of patients, among them those with rheumatoid arthritis,³¹ osteoarthritis,³² ankylosing spondylitis,³³ fibromyalgia,³⁴ and chronic pain.³⁵

Data analysis and statistics

The qualitative data were analysed as follows: first the patients’ statements concerning activity problems and participation restrictions during the COPM interview were read through, then codes were identified to describe the data, after which the codes were combined into broader categories.³⁶ Frequency counts on responses were undertaken where appropriate.

Proportion and frequency counts were also calculated for categorical variables, while mean and standard deviation were computed for continuous variables. Differences between the right and the left hand were examined by paired samples t tests. Correlations between the COPM scores, the AUSCAN score, and the impairment variables were examined by Pearson correlation coefficient.

Three hierarchical regression analyses were conducted. The AUSCAN score, an indicator of hand related activity limitations, served as the dependent variable in the first model, while the COPM performance score and the COPM satisfaction score served as the dependent variables in the two other models, as indicators of activity limitation and participation restrictions.

According to the ICF model, a blockwise analysis was used to calculate the explanatory power of the independent personal and impairment variables on the dependent variable. To do this, the following variables were entered into the model in two blocks (fig 1⇑):

• Block 1 (personal factors): age, disease duration, comorbidity, and the self efficacy function score.

• Block 2 (impairment variables) (all measures are for the right hand): grip force in pinch grip, pain during resisted motion (pinch grip), and mobility restrictions digits I-V (computed as the sum of the three mobility deficit measures).

Before conducting the regression analyses, possible colinearity of the independent variables was examined using the variance inflation factor. Further on, distribution of the residuals was examined for normality. As recommended when small samples are involved, we chose a conservative approach in presenting the results from the regression analyses, using the adjusted R² values.³⁷ We used SPSS for Windows (version 11.0) for the statistical analyses. Probability (p) values below 0.05 were considered significant.

Sample

Of 100 consecutively approached patients, 94 attended the baseline assessments. Two of these were excluded because of functional problems mainly related to cerebral palsy (n = 1),and cognitive deficit (n = 1). As sex is known to affect pain and function,⁷ and there were only five men among the included participants, it was decided to exclude these from the further analyses. The demographics of the 87 final female patients are presented in table 1⇓. Although the inclusion criterion was hand osteoarthritis, more than half of the patients also had osteoarthritis in other joints, with the knees being the most commonly affected joints.

Activity limitations and participation restrictions

The patients listed a total of 801 occupational performance problems in the COPM interviews, and prioritised 361 of these. As the COPM interviews were oriented towards revealing activity limitations and participation restrictions in general, the patients described the problems they experienced in their daily life regardless of whether these were caused by osteoarthritis of the hands or of other joints.

The most commonly described problems were related to the categories “household management” (337 reported problems), “functional mobility” (119 reported problems), “personal care” (102 reported problems), and “active recreation” (68 reported problems)(data not shown). The most frequent reported hand related activity problems were “wringing out wash cloths”, “opening jars”, and “opening bottles” (fig 2⇓). The mean AUSCAN score was 1.80, indicating that this group of patients has moderate problems with performance of hand related activities (table 1⇑).

• Download figure
• Open in new tab
• Download powerpoint

Figure 2

 The 14 most commonly described and prioritised hand related activity problems reported by 87 women in COPM interviews, given in rank order from the most often prioritised to the least often prioritised. COPM, Canadian Occupational Performance Measure.

Impairment of hand function

As shown in table 2⇓, hand mobility was restricted for all digits. With respect to flexion or opposition, the deficit was largest for digits I, II, and III, while the extension deficit was largest for the third and fourth digits. Compared with control values, grip strength was reduced to less than 60% of normal.²⁷ Unfortunately, reduction of pinch strength could not be calculated, as normative values are not yet available for the Grippit instrument. Resisted motion was painful for both grip and pinch.

There were significant differences between the right and the left hand in extension deficits for the III, IV, and V fingers, abduction of the thumb, and grip strength. Although the impairments were most severe in the right hand, the grip was stronger in this hand.

Associations among personal factors, impairment, activity limitations, and participation restrictions

The hierarchical multiple regression models are presented in table 3⇓. The personal variables were entered as block 1 and accounted for 18% of the variation in the AUSCAN function score. The contribution of this block was significant (p<0.002).

The impairment variables were added into the model as block 2, and constituted the greatest contribution to the explanation of the dependent variable, with an additional 37% (p<0.001). The most important variables were grip force in pinch grip (p<0.01), and pain during resisted motion (pinch grip) (p<0.01). The final model (with two blocks) explained a total of 55% of the variation in the AUSCAN function scores (p<0.001).

However, repeating the analysis with the COPM performance score and the COPM satisfaction score as dependent variables revealed different results (table 3⇑). In these analyses, the block with personal factors constituted the greatest and significant contribution to the explanation of the dependent variables. The model with the COPM performance score as dependent variable had an explanatory power of 32% (p<0.001), with self efficacy function as the most significant variable (p = 0.004), while the model with the COPM satisfaction score had an explanatory power of 39% (p<0.001), with disease duration, comorbidity, self efficacy function, and hand power in pinch grip as the four significant variables.

Conclusions

Hand osteoarthritis has considerable functional consequences in terms of pain, reduced hand mobility, reduced grip force, and problems in many domains of activity and participation. Regression analyses showed that hand related activity limitations seem to be closely associated with hand impairment, while performance and satisfaction within a broader spectrum of activity and participation are more influenced by personal factors. As a consequence, rehabilitation programmes should be both multidisciplinary and multidimensional, aiming at reducing hand impairment, improving occupational performance, and enhancing the self efficacy and coping strategies of the individual.