**2.3 The socket/limb interface**

The importance of the socket/limb interface has been highlighted in several published reports. The primary concerns reported from prosthesis users include the fit of the artificial limb and comfort. A study by Klute et al., identified that the time-consuming prosthesis fitting process can contribute to excess pressure and friction on the residual limb, resulting in skin and deeper tissue damage and related pain and discomfort [15]. The outcome of this study emphasized the need for a fitting process that included objective measures to complement and improve user feedback.

Several studies employing radiological [15–17], acoustic [18], and optical [19] approaches have been used to analyze the movement of the residual limb within the socket of lower limb systems. These have numerous shortcomings primarily related to lack of clinical translatability and testing capability in a limited range of movements. The LimbLogic® vacuum system developed as a result of a Veterans Affairs (VA) grant funded collaborative work with Ohio Willow Wood was commercialized for clinically relevant quantification of prosthetic socket performance. Elevated vacuum suspension (EVS) [20, 21] (**Figure 3**) creates subatmospheric pressure between the prosthetic socket and liner worn over the residual limb. Studies performed with this system identified that variances among individuals may be a result of different gait styles, tissue types, residual limb geometries, prosthesis weight distribution, and socket fit. The results demonstrated that elevated vacuum pressure data provide information to quantify initial socket fit and monitor changes from an initial set point. The correlation between displacement and vacuum pressure fluctuation was dependent on socket fit. In general, higher vacuum pressure settings resulted in the lower amounts of displacement and vacuum pressure fluctuation within each socket fit condition. However, the rates of decreases created distinct trends in the data that correlated to particular fit conditions.

Therefore, the effectiveness of lower limb prosthesis is largely measured by its ability to minimize in-socket movement of the residual limb, conserving residuum health. Movement of the residual limb within the prosthetic socket contributes to increased risk of skin ulceration [22]. Technological advancements in residual limb scanning and socket manufacturing have empowered prosthetists to design and

#### **Figure 3.**

*Elevated vacuum suspension schematic and probe measurement points. (A) Illustration of test socket with recess for in-socket silicone probe holder. (B) Residual-limb measurement sites. Green and yellow indicate measurement sites of high and low stress, respectively. LDF = laser Doppler flowmetry, TCOM = transcutaneous oxygen measurement (reprinted with permission from Rink et al. [20]).*

**49**

*Residual Limb Health and Prosthetics*

performance.

**3. Residual limb health**

**3.1 Issues with prosthesis fitting**

provide a "best" fit for a patient.

**3.2 Injuries of the residual limb**

*DOI: http://dx.doi.org/10.5772/intechopen.83819*

fit customized sockets that account for unique amputee residual limb shape and volume. However, unlike the rigid socket that is fixed in geometry and volume, the morphometry of the residual limb is dynamic. Mature residual limbs experience diurnal changes in volume of up to 2% [4] because of a number of factors including activity level, ambient environment, body composition, dietary habits, and hormones [6]. Furthermore, chronic remodeling of a mature residual limb can result in even greater (~10%) volume changes over the course of weeks [23] and months [5]. Thus, socket fit and residual limb movement in the socket are subject to time-dependent changes. Because socket movement increases risk of residuum dermal injury and ulceration [22], there is a clear need to evaluate the efficacy of using a socket monitoring system that can quantify residual limb movement inside the socket to aid in the socket fitting process. Such a system has the potential of minimizing risk to residual limb health [6] while maximizing functional

Achieving a comfortable and functional connection between an amputee and their prosthetic limb is critical to the success of the prosthesis. Therefore, the socket system is the most significant component for the overall rehabilitative success of the prosthesis [24, 25]. Socket comfort is achieved by appropriately loading and off-loading the residual limb, where the optimal biomechanical performance of the prosthesis is achieved by transfer motions of the residual limb without loss or excess motion to the prosthesis. In an effort to maximize socket performance and comfort without adversely affecting residual limb health, a prosthetist custom fits a socket for every patient using plaster wraps or computer aided design. Currently, this process suffers from a lack of quantitative feedback to determine appropriate socket fit. Prosthetists aim to create a comfortable and intimate socket interface, but current approaches are limited as they rely on anecdotal visual cues along with subjective verbal feedback from the patient. Prosthetists then use this information to revise socket parameters such as volume, geometry, and type of suspension to

In light of the subjective inputs that currently inform prosthesis form, fit, and therefore function, there is a clear need to provide objective measures to optimize prosthesis fitting and provide continual feedback to both end-user and prosthetist as the residual limb volume and shape are susceptible to change over time. Under the current paradigm of prosthetic socket fitting, inadequate and/or misinformation communicated to the prosthetist can lead to sub-optimal fit and comfort of the prosthetic system. This contributes to repeat clinical visits to rectify areas of discomfort, or in more extreme cases rejection of the prosthesis and preference toward other assistive devices such as wheelchairs. Two surveys administered to lower limb prosthesis users indicated a high prevalence of skin sores or irritation occurring within the socket, with fit likely being a contributing factor [24, 25]. If left unresolved, such limb health issues may necessitate disuse of the prosthesis.

Most amputees have an active and satisfying quality of life with a majority that wear a prosthesis at least 7 h a day to aid in mobility and everyday living. An improper fit or alignment, lack of adequate gait training and development of poor *Residual Limb Health and Prosthetics DOI: http://dx.doi.org/10.5772/intechopen.83819*

*Prosthesis*

feedback.

conditions.

**2.3 The socket/limb interface**

The importance of the socket/limb interface has been highlighted in several published reports. The primary concerns reported from prosthesis users include the fit of the artificial limb and comfort. A study by Klute et al., identified that the time-consuming prosthesis fitting process can contribute to excess pressure and friction on the residual limb, resulting in skin and deeper tissue damage and related pain and discomfort [15]. The outcome of this study emphasized the need for a fitting process that included objective measures to complement and improve user

Several studies employing radiological [15–17], acoustic [18], and optical [19] approaches have been used to analyze the movement of the residual limb within the socket of lower limb systems. These have numerous shortcomings primarily related to lack of clinical translatability and testing capability in a limited range of movements. The LimbLogic® vacuum system developed as a result of a Veterans Affairs (VA) grant funded collaborative work with Ohio Willow Wood was commercialized for clinically relevant quantification of prosthetic socket performance. Elevated vacuum suspension (EVS) [20, 21] (**Figure 3**) creates subatmospheric pressure between the prosthetic socket and liner worn over the residual limb. Studies performed with this system identified that variances among individuals may be a result of different gait styles, tissue types, residual limb geometries, prosthesis weight distribution, and socket fit. The results demonstrated that elevated vacuum pressure data provide information to quantify initial socket fit and monitor changes from an initial set point. The correlation between displacement and vacuum pressure fluctuation was dependent on socket fit. In general, higher vacuum pressure settings resulted in the lower amounts of displacement and vacuum pressure fluctuation within each socket fit condition. However, the rates of decreases created distinct trends in the data that correlated to particular fit

Therefore, the effectiveness of lower limb prosthesis is largely measured by its ability to minimize in-socket movement of the residual limb, conserving residuum health. Movement of the residual limb within the prosthetic socket contributes to increased risk of skin ulceration [22]. Technological advancements in residual limb scanning and socket manufacturing have empowered prosthetists to design and

*Elevated vacuum suspension schematic and probe measurement points. (A) Illustration of test socket with recess for in-socket silicone probe holder. (B) Residual-limb measurement sites. Green and yellow indicate measurement sites of high and low stress, respectively. LDF = laser Doppler flowmetry, TCOM = transcutaneous oxygen* 

*measurement (reprinted with permission from Rink et al. [20]).*

**48**

**Figure 3.**

fit customized sockets that account for unique amputee residual limb shape and volume. However, unlike the rigid socket that is fixed in geometry and volume, the morphometry of the residual limb is dynamic. Mature residual limbs experience diurnal changes in volume of up to 2% [4] because of a number of factors including activity level, ambient environment, body composition, dietary habits, and hormones [6]. Furthermore, chronic remodeling of a mature residual limb can result in even greater (~10%) volume changes over the course of weeks [23] and months [5]. Thus, socket fit and residual limb movement in the socket are subject to time-dependent changes. Because socket movement increases risk of residuum dermal injury and ulceration [22], there is a clear need to evaluate the efficacy of using a socket monitoring system that can quantify residual limb movement inside the socket to aid in the socket fitting process. Such a system has the potential of minimizing risk to residual limb health [6] while maximizing functional performance.
