The importance of utilising a set of commonly accepted outcome measures that are validated is paramount so that the natural history of the disease as well as treatment success can be monitored at both the patient and population level to enable meaningful comparisons between treatment modalities. Therefore, there is an urgent need for a common consensus regarding the reporting of outcomes data collected in high quality studies.
Patient reported outcome measures
PROMs, although subjective, are critical measures of treatment efficacy as patient perceived benefit is the ultimate goal of treatment. They should, therefore, supplement data derived from physical measures as they provide the context of the impact on function for the individual. PROMs including functional measures have gained prominence with the current emphasis on patient centred clinical practice. Yet, no publication of collagenase injections used PROMs as an outcome and only 15 publications reporting surgical outcomes used function PROMs. Only one RCT reported outcomes using function PROMs [
24].
The DASH questionnaire is a 30-item self-rated region-specific disability and symptom scale outcome measure. It was the most commonly used function outcome measure but may lack the sensitivity to detect significant improvement following surgical or injection treatment for DD due to a ‘flooring effect’, that is relatively low pre-treatment scores resulting in a reduced potential for improvement [
24]. It is difficult to be certain whether this represents a genuine problem as only 6 studies reported pre-treatment DASH scores, although all showed comparatively low values. The normal mean value for the DASH questionnaire reported by the American Academy of Orthopaedic Surgeons [
110] was 10.10 (+/- 14.68 SD). All publications reporting pre- and post-operative data showed a reduction in post-operative scores, indicating an improvement in function compared with pre-operative levels, but this reached significance in only two studies [
22,
23]. A difference of 15 points is considered to be the minimal clinically important difference (MCID) indicating an improvement [
111]. However, the exact figure is controversial and may vary according to the upper limb disorder being considered. No studies achieved a MCID equal to or more than 15 points and only two studies showed a MCID of 10 points [
22,
25], which may in part be attributed to the relatively low pre-treatment scores. Additionally, caution is advised when applying MCIDs due to difficulties with variation over time of in the patients’ perception of their disability [
112]. Thus, whilst the evidence for assessing the outcomes of interventions for DD using DASH indicates that it may be useful, further work is necessary to determine the level of change that is considered meaningful.
The Michigan Hand Outcome Questionnaire (MHQ) is a 37-item region-specific outcome measure that includes 6 sub-scales of activities of daily living, hand function, pain, cosmesis, patient satisfaction and overall function [
31]. The MHQ has been shown to detect change in function following surgery for DD [
23,
25] and to correlate with changes in fixed flexion deformity [
25]. The MHQ focuses on the hand as compared with the DASH, which assesses entire upper limb function. Furthermore, unlike DASH, the MHQ assesses the functional impact on each hand separately; this may be especially relevant to conditions such as DD that can affect both hands to varying extents. It also includes questions that may be of greater relevance for people with DD. For instance, aesthetics are a construct in the MHQ not included in the DASH and may be relevant for some patients with DD, for example when shaking hands [
3] or when presenting the hand with the palm uppermost as when receiving coins.
Whilst the MHQ may appear to be more suitable than the DASH to assess DD outcomes it is lengthy, comprising 74 questions, and may not always be completed. Short versions of the DASH and MHQ have recently become available. The Quick-DASH was used by one study [
66] but it is not clear if it is prone to a flooring effect when used for DD. The use of the short MHQ has not yet been reported in outcomes studies for DD. Pain, which is included in both the DASH and MHQ, is seldom reported by people with DD [
113] and may reduce the sensitivity of both tools.
The PEM has been shown to be sensitive to change when used for patients with scaphoid fractures or carpal tunnel syndrome [
114]. In a study of 100 patients with various conditions affecting the hand [
115], including 15 who had DD, patients were able to complete it more rapidly than the DASH or MHQ. A sub-analysis of the results for the patients DD has not been published. Therefore, it is not possible to assess the sensitivity to change in the context of DD.
While there are a number of other hand function questionnaires, these have either been validated for use with specific conditions such as the ABILHAND for rheumatoid arthritis, chronic stroke and systemic sclerosis [
116] or do not assess the area affected by DD, such the Patient Rated Wrist Evaluation (PWRE) [
117]. Disease-specific hand function questionnaires are generally considered to be desirable as they focus on activities that specifically affect the study population, usually having been developed with patient participation. An example that has been shown to be sufficiently sensitive to change is the Boston questionnaire for carpal tunnel syndrome [
118]. Recently the Unité Rhumatologique de Affections de la Main scale (URAM) questionnaire [
15] and Southampton Dupuytren’s Scoring System [
119] have been developed as disease specific questionnaires, but have not yet been validated by other investigators.
An alternative approach is to ask individual patients to identify their most restricted activities and when applied to DD, significant improvement in median scores were reported [
22].
Patient satisfaction
Methods used to report patient satisfaction varied, with no single measure used consistently. Studies reported overall satisfaction or satisfaction with surgery but did not explore the relationship with hand function. One study of collagenase injection [
78] correlated satisfaction with treatment and improved range of motion at 30 days after the last injection.