Mylène Jansen

140 Chapter 7 care’ and ‘harm to other leg’ appear to be relevant for increasing user-friendliness for patients. The 3 patients who were treated with both the CD and DD device generally rated user- friendliness higher for the DD device, but there was clearly a lot of variation between their answers. Comparison of these outcomes should be interpreted with care, and only considered suggestive. Besides the fact that the group of patients that were treated with both devices is limited in size, data is likely to be influenced as a result of the period between the treatments. This study had several limitations. First, this evaluation of user-friendliness would ideally have been performed in a randomized study. However, this was considered unethical by the responsible ethical committee due to the fact that the DD device was already available in clinical practice at the start of the study, which is why the current study setup was chosen. Second, the number of patients evaluated in this study was limited. Once further introduction of the DD device is established and more data becomes available, further evaluation is recommended to see if the current findings hold. Although longitudinal clinical and structural results with the DD device are expected to be similar to results seen in patients who received treatment with the CD device, this should be evaluated as well. Lastly, the patient questionnaire that was used to evaluate user-friendliness was not a validated questionnaire. Due to a lack of validated outcome measures relevant for evaluating the CD against the DD device, the current questionnaire was made based on demands and wishes as judged by the multidisciplinary team of patients, clinicians and medical device experts before development of the DD device. As such, the current questionnaire does incorporate aspects that are considered important by key users, but using a validated patient questionnaire would have been preferable. In conclusion, the DD device provides a surgical instrument intended for KJD which reduces surgery time and improves user-friendliness compared to the CD device. Furthermore, it was demonstrated that incorporating patients as end-users in the development process of the DD device increases insights in user-friendliness, which potentially may further reduce treatment burden and facilitate implementation in regular care. Taken together, the DDdevice contributes to implementation of KJD for severe knee OA at a relatively young age.