**3. Residual limb health**

#### **3.1 Issues with prosthesis fitting**

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 provide a "best" fit for a patient.

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.

#### **3.2 Injuries of the residual limb**

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

#### *Prosthesis*

habits are common features of a vast majority of amputees who use a prosthesis resulting in at least one deviation or problem. The increased load or weight is often placed on the intact limb as a result of these deviations can cause discomfort or pain in the joints and lead to some form of degenerative joint disease or disability in extreme cases. Three of the most common secondary complications in lower-limb amputees due to compensatory and/or altered stresses are osteoarthritis, osteoporosis and back pain.

About 75% of patients with lower-limb prosthetics have skin problems [26, 27]. The lack of a normal pressure-distributing anatomy the residual limb is prone to issues such as elevated shear forces, stress risers, increased humidity, and prolonged moist contact within the prosthesis, which can contribute to ulceration. Ulcers or pressure sores, are the most common skin conditions in prosthetic users [24]

#### **Figure 4.**

*Laser speckle imaging (LSI) for skin perfusion. (A) Black box over transtibial amputee represents field of view (FOV) for perfusion mapping and quantification. (B) Representative perfusion maps acquired pre- and post-activity (over-ground walking) in sound and residual limb. (C) Perfusion was measured by laser Doppler flowmetry out-of-socket with liner on (O) and in-socket while resting with weight bearing on the residual limb (I) under SoC (black bar) and EVS (white bar) conditions. Data are mean perfusion units ± SE (shown as error bar). \*p<0.05 O vs I within gp at time point (reprinted with permission from Rink CL et al. [33]).*

**51**

**Figure 6.**

**Figure 5.**

*permission from Rink et al. [33]).*

*Residual Limb Health and Prosthetics*

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

**3.3 Preserving residual limb health**

and can vary in size and magnitude requiring prolonged recovery time out of the prosthesis, a new socket fitting and sometimes surgical interventions [26, 27].

Skin ulcers are typically the end result of vascular insufficiency and improper skin barrier function. Reperfusion of blood, as seen in reactive hyperemia, to nutrient- and oxygen-deprived tissue is another causative factor of tissue injury that contributes to ulcer formation [28]. In lower-limb amputation, this was identified

*Hyperspectral imaging for skin oxygen saturation. (A) Black box represents field of view (FOV) for qualification of tissue oxygen saturation (StO2) in residual limb. (B) Representative oxygen saturation map. (C) Reactive hyperemia quantified as percent changed in tissue oxygen saturation pre- and postactivity was determined in standard of care (SoC) (black bar) and EVS (white bar) socket systems at baseline and after 16 weeks of use (final). Data are mean ± SE (shown in error bar), \*p < 0.05 SoC vs. EVS (reprinted with* 

*Transepidermal water loss (TEWL) for skin barrier function. (A) Schematic of TEWL probe over the skin as it measures differences between relative humidity of ambient air and directly above skin. (B) Photograph of a TEWL measurement. (C) TEWL was measured 15 min after socket doffing in people with transtibial and transfemoral amputation (n = 10) under standard of care (SoC) (black bar) and EVS (white bar) conditions. Data shown are from areas of high stress and low stress combined. Data shown are from areas of high stress and low stress combined. Data are mean ± SE (shown as error bars). \*p < 0.05 SoC vs. EVS within time point. †p<0.05 baseline vs. final within prosthesis group (reprinted with permission from Rink et al. [33]).*

#### *Residual Limb Health and Prosthetics DOI: http://dx.doi.org/10.5772/intechopen.83819*

and can vary in size and magnitude requiring prolonged recovery time out of the prosthesis, a new socket fitting and sometimes surgical interventions [26, 27].
