## 4 Discussion  
A feasibility study was performed in order to demonstrate the benefits of wearable monitoring during postoperative TAA recovery, and, to our knowledge, this research may be considered the first study that applied wearable inertial sensors to investigate the ankle's joint motions and kinematic outcomes after TAA surgery. In detail, this study reported early results of a consecutive series of patients with end-stage ankle OA before and after TAA surgery, using PROMs and an innovative assessment of used for ankle joint angles, plantar pressures and kinematic variables. TAA was proposed in order to preserve joint motion [16] and allow for a more physiological gait pattern. Innovative tools such as the baropodometric platform and inertial sensors can be used to assess the outcomes and reliability of surgical procedures [34; 35; 36; 37]. With regard to the PROMs, all but one showed a statistically significant improvement; however, PROM values were still low compared to those reported in the literature, potentially due to an early follow up, which in line with the literature [6; 38; 39; 40; 41; 42]. The physical examination showed no significant changes of the foot shape and alignment; however, the only study using these specific tests after TAA reported significant improvements with a longer follow up [7]. TAA surgery relieved pain and hypothetically helped to improve plantar support and gait [8; 38; 39; 40; 41; 42; 43]. Plantar pressure analysis with the baropodometric platform showed no significant changes in the evaluation of a static position. However, a more uniform plantar pressure distribution was observed throughout the feet, even if it was not statistically significance. In the dynamic evaluation, however, a significant increase in the mean pressure of the non-operated foot was recorded between the pre- and postoperative period, probably due to a compensatory mechanism acting to unload the operated foot. Indeed, the literature reported that the patient achieves a more balanced gait in relation to the gradual progress of rehabilitation [41; 44]. Although no significant changes between the pre- and postoperative period were reported, the dynamic evaluation after surgery showed a satisfied peak pressure distribution throughout the feet for many patients, which correlated with the findings reported in the literature, i.e., peak pressure is localized at the level of the calcaneus during the contact phase and at the level of the head of the I metatarsal bone during the intermediate and propulsive support phases [9; 11; 41; 45]. The inertial sensor parameters that improved early were those that are not fully affected by rehabilitation, such as stride and step length [8; 38; 39; 40; 42; 43]. Some studies showed that the gait pattern improved 12 months postoperatively, after the physical rehabilitation program's conclusion [8; 41; 42]. Generally, the outcomes became worse at a 3-month follow up, and then gradually improved significantly with a longer follow up, as shown in various studies [8; 38; 39; 40; 42; 43]. In our study, a few parameters of the patients showed significant changes between the pre- and postoperative period, which may be due to the very short-term follow-up period used. This was also the case regarding ankle inertial sensors measurements, which reported a significant reduction in both active and passive plantar flexion after surgery. Another crucial aspect to consider is the cost effectiveness of these tools. To accurately define this aspect, the cost of each evaluation should also be assessed. However, wearable sensor motion analysis and activity monitoring have been extensively utilized in numerous clinical settings thanks to their low cost and ease of application, even by non-experts. This approach often requires a similar or shorter time than administering a questionnaire, complements conventional clinical scores and provides additional diagnostic values or evidence of outcomes [46].