# Effect of an Innovative Biofeedback Insole on Patient Rehabilitation after Total Knee Arthroplasty
## 2 Materials and Methods
Therefore, it is possible to train patients to reach a \"permitted load\" range that can be defined in advance by medical or physical therapy staff according to the patients' needs. The system also has a rechargeable battery with a half-life of about 40 h, roughly corresponding to 5 days of use during the immediate TKR post-operative period. The battery can be recharged by means of as USB cable similar to the ones used for mobile phones. Figure 1: The insole. The device is composed of the insole containing the weight sensors, which is connected with a band to the electronic bio-feedback display. The display is then attached to the patient leg with a Velcro strap. The enrolled patients were evaluated at time 0 (pre-surgery, upon hospital admission) with the insole to confirm their ability to reach complete weight bearing. They were also instructed on its functioning, modeling capacity, and calibration. On the fourth day post-op, the patients were transferred to our clinic's rehabilitation ward and evaluated again by the physical therapist and physiatrist team. Evaluations were carried out at 5, 10, 15, and 30 days post-op using the Numerical Rating Scale (NRS, from 0 to 10) to assess pain; the Knee Score System (KSS, updated 2011), including both the comprehensive objective standard evaluation and the functional component, each with a score of 0-100 ([PERSON] et al., 2010); and the Western Ontario McMaster Universities Index Osteoarthritis (WOMAC), translated into Italian ([PERSON] et al., 2010). Furthermore, using the Tinetti scoring system ([PERSON] et al., 2010; [PERSON] et al., 2010), we assessed gait and weight bearing during the dynamic phase to verify the patients' ability to reproduce a correct PWB motor pattern. We later interviewed the patients regarding their inside compliance with the NRS, concerning ease of use, absence of complications, and pain with daily use ([PERSON] et al., 2010). The standard rehabilitation protocol used in our clinic to treat patients after TKR includes immediate non-weight bearing mobilization with Kinetec (0-60\({}^{\circ}\) ROM) and standing upright from the second day post-surgery with partial and progressive weight bearing, starting from 50% of the patients' body weight to 90% at discharge (using a double scale in the static bipodalic position to help patients find the correct bearing). Rehabilitative programs always include foot pumping during the first day, lower limb massage therapy, pharmacologic therapy with 100 mg ketoprofen infusion once per day (to prevent heterotopic ossification), stair climbing, and proprioceptive exercises. For the study group, we requested they stand up from the second day post-op with the insole, and we planned their weight bearing at 30-50% of the body weight. This would then increase according to the following scheme: 40-60% from the 4 th day, 50-70% from the 7 th day, 60-80% from the 10 th day, and 80-90% from the 15 th day until discharge (day 30). The paired \(t\)-test was used for numerical variables. Null hypotheses of no difference were rejected if two-sided \(p\)-values were less than 0.05. Data were analyzed statistically using Matlab (MATLAB and Statistics Toolbox Release 2012b, The MathWorks, Inc., Natick, MA, USA). Figure 2: How the insole and the display should be worn by the patient.