# Gamification of Upper Limb Rehabilitation in Mixed-Reality Environment
## 1 Introduction  
Upper extremity (UE) joint injuries are a significant concern because they can produce a limited range of motion inside the arm joints, which can hinder a person's ability to conduct day-to-day chores. In the emergency room, 20% of patients presented with injuries to their upper extremities [1]. These injuries can be painful and quickly elevated if individuals do not receive the proper treatment. Patients will continue to use their arms and hands until the discomfort and loss of movement become intolerable [2]. To help patients recover from these injuries, therapists, in general, create a personalized treatment plan that includes physical therapy, exercises, and stretches to boost their body's healing process. During each session, patients have to go through a series of activities, again and again, involving the upper extremity's injured part to keep joints and muscles from tightening up and becoming weaker. By monitoring their patients' activity in rehabilitation, therapists can ensure that their patients are making progress and benefiting from the treatment. However, the most common approaches to rehabilitation after such injuries have limitations that may slow the patient's progress. The motions used in today's treatmentsfor joint injuries rarely provide any additional stimulation to keep the patient engaged in the appropriate rehabilitation [3]. A patient's recovery might be delayed if they lose interest in their rehab because of monotony [4]. Most home-based rehabilitation programs also rely heavily on patient compliance with therapy sessions. Unfortunately, there are few efficient methods for occupational therapists, as most forms of rehabilitation therapy consist of just the most fundamental activities. In general, rehabilitation approaches for arm injuries of this nature are designed based on experiences from the prior. Therefore, there is a pressing need for an innovative approach to rehabilitation. One example is implementing sensor-based rehabilitation, a sort of therapy with various variations. For instance, Inertial Measurement Units (IMUs), a type of sensor that measures acceleration and rotation, are used to record the arm's motions and to follow the patient's rehabilitation progress [5]. There, however, the patient must correctly position the IMUs on the arm to measure certain variables, such as the range of motion at various joints. Surface electromyography (sEMG) is an additional form of sensor-based therapy. This type of therapy uses EMG sensors to monitor the electrical gradient along muscles as they contract to give treatment for various conditions. However, a slight change in the sensor's placement can affect its precision [5]. Neither of these methods offers a way to keep the patient engaged and motivated, damaging the patient's recovery. Due to these challenges in the field, we propose a new approach, a gamified Mixed Reality (MR)-based solution for upper extremity rehabilitation. This solution is fundamentally an MR application for the Microsoft HoloLens 2, including game levels comparable to a video game and an algorithm for measuring the ranges of motion of the various arm joint degrees of freedom. Gamification was chosen as the answer to this problem since research has shown that it can improve learning in various contexts by increasing engagement levels [6]. Choosing MR as the foundation has benefited the field of rehabilitation, especially gait rehabilitation [7], because it comes with spatial awareness, which gives more safety over the existing VR-based rehabilitation. The patient will be able to perform rehabilitation in the comfort of their own home due to the proposed solution's exceptional portability. The OT/clinicians can monitor the patient's engagement and progress in therapy by examining the information in real-time collected throughout each session. Furthermore, using a unique algorithm and input from the OT/clinician, the program is patient-specific and can adjust to the patient's individual needs.