Yoeri Bemelmans

Physical activity after outpatient and fast-track knee arthroplasty 147 9 8]. Minimal information exists regarding the physical activity after TKA in anOS setting. Early experience with OS in patients operated for unicompartmental knee arthroplasty (UKA) showed promising results in terms of safety and efficiency [18]. Recently, Krenk et al. [20] reported on 20 patients operated for TKA and total hip arthroplasty (THA) following anenhanced recovery pathway. They found similar results in the postoperative physical activity in patients whowere discharged after amean of 2.6 days. However, with a substantial difference, this study captured changes within the early recovery phase up to 6 weeks postoperative compared to 6 days postoperative. Furthermore, patients in the OS pathway were compared with patients who followed the ERP as a control group. When comparing these pathways, both groups experienced a drop in physical activity during the first postoperative days after TKA, with a comparable improvement at 6weeks postoperative. Aparticular strength of this study is the assessment of physical activity over three time points, which allows a more detailed analysis of the activity of the different parameters into the early recovery phase. After hospital discharge, patients need to be encouraged to do their daily exercises in their home environment. With the use of the AM, we were able to objectively monitor if patients were physically active in their home environment during the first week and 6th postoperative week. On the other hand, this study and the results of Krenk et al. [20] demonstrate the need for follow-up beyond 6 weeks postoperative. This is of interest and needs attention in further research. Finally, this study does have some limitations. The most important limitation was the limited number of patients and power of this study. Nevertheless, this study was carried out in order to evaluate the daily physical activity in patients following OS after TKA, in an attempt to predict an appropriate sample size to design a performance of a full-scale research project [35]. A possiblemismatch in the study could be the potential selection bias. Patients were not individually randomly selected for one of the two pathways due to practical and financial consideration (e.g. limited number of AMs). Even thoughmedical comorbidities in both pathwayswere comparable, it resulted in equal physical activity up to six weeks postoperative. After surgery, patients did not change from one pathway to another. Conclusions This study demonstrates that the early physical activity parameters of patients undergoing TKA in the OS pathway were similar to patients who followed the standard ERP. Measurement with the AM is an added value for a more detailed and objective analysis of the physical activity during the early recovery phase in patients after TKA and provides more insight information rather than PROMs alone.