# Footnote 1
## 4 Discussion  
### Device Classification  
From the selected patents and scientific documentation, a new ankle/foot prosthesis classification has been created besides ESAR, CERS, and active, based on its components and prosthesis functions. ESAR prostheses are categorized into five different designs (see Figure 8). CERS and active categories are merged and divided into five different categories. There are some unique designs whose components cannot be grouped; these will be discussed individually. From the previous analyses, it can be determined that the general form for ESAR prosthesis is similar to the one illustrated in Figure 8A and mostly differs in form; sometimes, a single talon plate is aggregated, or the disposition of the plates may vary. In other cases, as in Figure 8B, the center of mass is moved, and the plates are rearranged. In the variation represented by Figure 8C, the foot plates are divided, so the prosthesis emulates aversion and inversion movements. In Figure 8D, some polymeric cushions are aggregated, replacing the use of extra plates. Figure 8E shows the usage of different types of damping systems (springs, actuators, etc.) that replace some plates. All of these designs use pyramid adapters as a connection between the prosthesis and transtibial components. There are some variations for ESAR prostheses that use a simple plate arrangement to adjust the return of energy (see Figure 9A). Other designs use a single spring bar that regulates the energy storage/release (see Figure 9B). For CERS prosthesis, the model by [PERSON] [129] (see Figure 10) considers a locking mechanism that preserves the energy storage in the spring. This energy is released upon the foot movement during the terminal stance. This impulse, in combination with the ESAR foot, provides necessary torque during the walk cycle. Figure 8: (**A**) General form of ESAR prosthesis, (**B**) Modified ESAR prosthesis, (**C**) ESAR with split plates, (**D**) ESAR prosthesis with cushions, (**E**) ESAR with damping system. Figure 7: Most productive countries for ankle/foot prosthesis literature. Active prostheses can be categorized by the components they use into three types: Multi-Array Prostheses (MAP), Low Powered Prostheses (LPP), and Controlled Adapative Stiffness (CAS). For MAP, the form is similar to the one shown in Figure 11. It uses an ESAR composite foot (E), and a DC motor (A), usually a 200 W Maxon(r) connected to a ball-screw transmission (C) that moves the linkage system (D) upward/downward and converts motor rotary motion into linear motion. In some cases, the motor is located instead of the spring (G) and connected to (C) using a timing belt. The linkage system (D) is in charge of connecting different mechanisms and allows plantarflexion and dorsiflexion movements; it may be composed of cables and/or pulleys, a bar mechanism, or crank sliders. F and G, depending on the prostheses, represent springs or actuators (pneumatic, electric, or hydraulic), for which torque varies from 100 to 140 Nm. Sometimes a parallel spring is aggregated due to the demanding torque requirements, and it aims to reduce the loads supported by the linkage system. Spring (G) saves energy during plantarflexion and dorsiflexion and supplements it during the swing phase. Housing (B) allocates all the electronic systems and provides stability to the system. The pyramid adapter (H) provides a connection between the transtibial components and the prosthesis. Some models have a lock mechanism, so the prosthesis could be used in a passive mode. See Figures 11-15. Figure 11: MAP active ankle–foot prosthesis. Figure 9: (**A**) Multiple plates prosthesis, (**B**) Single spring prosthesis by [PERSON] [74]. Footplate (C). Spring (E) is elongated using a Pulley system (F) connected to the Footplate (C). The pyramid adapter (I) provides a connection between the transtibial components and the prosthesis. Designs for this model use an external power supply that is not integrated into the main prosthesis body.