# Prosthesis Embodiment in Lower Extremity Limb Loss: A Narrative Review
## 2 Development of the Dimensions of Embodiment
### Proprioception and Oseoperception  
Proprioception is the conscious and unconscious intrinsic knowledge of the location of body parts, as well as the sensations of effort, force, torque, and heaviness [19]. In the context of the lower limbs, proprioception is vital to performing activities of daily life. As an example, walking requires coordinated movements of both feet such that when one foot contacts the ground, the contralateral foot must lift from the ground; how this all occurs in a smooth coordinated cycle speaks to the complexity and relative autonomy of these movements, in which proprioception plays a vital role [19].  
Studies of subjects with large-fiber sensory neuropathy, which typically leaves motor control intact but removes proprioceptive and tactile afferents, demonstrate the critical role  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Item \#** & **Question** & **Embodiment “Dimension”** \\ \hline
1 & The prosthesis is my leg. \\
2 & The prosthesis belongs to me. \\
3 & The prosthesis is a part of my body. \\
4 & I feel as if I was looking directly at my \\  & own leg, rather than at a prosthesis. \\
5 & It feels as if I had two legs. \\
6 & My body feels complete. \\ \hline  & The prosthesis is in the location \\
7 & where I would expect my leg to be, if \\  & it was not amputated. & (Location in [17], Anatomical \\
8 & The posture of the prosthesis \\  & corresponds to that of a real leg. \\ \hline  & **Walk with prosthetic for 30 s.** \\ \hline
9 & The prosthesis is moving the way I \\  & want it to move. \\
10 & I am in control of the prosthesis. \\ \hline \hline \end{tabular}
\end{table}
Table 1: The questions of the PEmbS-LLA test from [16].  
of this sense. These subjects struggle to make coordinated movements in the dark [19]. In a previous study, deafferenced subjects exhibited significant deviations compared to control subjects when attempting to draw a line that matches a displayed line, due to unintended motion reversals. These results indicate that compromised proprioception also compromises fine motor control, coordination, and ultimately, agency.  
Without proprioception, deafferenced subjects who lacked elbow coordination instead simultaneously contracted their elbow flexors and extensors to increase joint stiffness. This resulted in increased energy expenditure and reduced movement efficiency [19]. Furthermore, the absence of proprioceptive feedback contributes to maladaptive cortical plasticity. Preservation of proprioceptive neural pathways has been suggested to minimize neuroma formation, stabilize cortical representations of the limbs, and reduce phantom pain [20; 21]. As noted earlier, reduced residual limb pain and ease of movement are significant predictors of embodiment.  
Oosceointegration (OI) enables a phenomenon known as osseooperception (OP) that is similar to proprioception and that provides similar benefits. Oosceoperception refers to the perception of forces and loads experienced by the prosthesis through the direct connection between the prosthesis and residual bone [22]. Amputees using OI prostheses report a greater ability to perceive the type of surface on which they walk [23]. This enhanced sensory feedback allows users to accurately sense their position and posture and make adjustments to improve stability [24]. Furthermore, while vibrations can be transmitted through the socket in a traditional socket prosthesis, [PERSON] et al. showed that users of OI prostheses were much more sensitive to vibrations [25]. Increased sensitivity activates residual limb mechanoreceptors, further reducing sway and improving postural awareness and control [24].