# Prosthesis Embodiment in Lower Extremity Limb Loss: A Narrative Review
## 1 Introduction  
Each year in the United States, approximately 150,000 patients undergo lower-limb amputation [1]. For these individuals, prosthetic devices serve as vital tools that restore mobility and independence in everyday life. \"Prosthesis embodiment\" refers to the process by which users mentally integrate these artificial limbs into their body [2; 3]. It is the point beyond which a prosthetic device ceases to be perceived merely as an assistive device, but instead as part of a patient's self and identity. Research indicates that the degree of embodiment is directly related to continued regular use and satisfaction with the prosthesis [4], indicating that the more a user feels that the prosthesis is part of their body, the more likely they are to continue using it. Consequently, loss of embodiment often leads to prosthesis abandonment, as patients choose to discontinue using their devices.  
Prosthesis abandonment presents a significant clinical concern. Among lower limb amputees who decide against using their prosthesis, the majority (up to 74%) rely on wheelchairs for mobility, often for decades [5]. When wheelchair use does not meet patient needs and functional capacity, this can be associated with morbidity such as decreased mobility, poor posture, pain, fatigue, pressure ulcers, and increased dependence on personal assistance [6].  
It is commonly noted that the clinical standard of care for limb amputation surgery has not changed significantly in the last two centuries, and prosthesis abandonment remains an afterthought. This review builds on previous work on the definition and measurement of embodiment [2; 3] and asks the following questions for lower-limb amputees:  
* What interventions are available to improve embodiment and reduce abandonment?
* What dimensions of embodiment should be included in the standard of care for lower-limb amputation surgery?  
Recent decades have seen rapid advances in lower limb prostheses, becoming sophisticated mechatronic systems that can be directly anchored to the user's skeletal system and even restore sensation, such as proprioception and cutaneous sensation, to the missing limb. With this new generation of devices, there has been an evolution in goals within the community, moving toward offering integrated devices that users accept as part of themselves as they interact with the external world. This research outlines the landscape of available interventions pertaining to embodiment and explores the mechanisms through which they do so.  
However, much is yet to be understood, such as why some users prefer futuristic appearing prosthetics while others prefer natural appearing prosthetics [7]. Furthermore, many interventions are early in development and have not been thoroughly tested. In addition, the lack of a common evaluation framework limits generalizability. Future research should address these concerns in a systematic review by clinicians and clinician-scientists when making formal recommendations on the standard of care for lower-limb amputees.  
This review is structured as follows. Section 2 provides an overview of prosthesis embodiment and how to quantify prosthesis embodiment. These ideas inform Section 3, which describes the review's search strategy. Section 4 describes clinical interventions in development for improving prosthesis embodiment in lower-limb amputees. Finally, Section 5 highlights the future work required for a systematic review.