Residual Limb Health and Prosthetics

*Sashwati Roy, Shomita S. Mathew-Steiner and Chandan K. Sen*

#### **Abstract**

The residual limb of individuals with lower limb loss is dynamic tissue that is susceptible to both acute and chronic changes to limb volume and health over time. Changes in residual limb volume that affect socket fit may contribute to maladaptive gait patterns and deleterious changes to the socket/limb interface that increase harmful shear stress and contributes to residual limb skin injury. Current socket systems are static and lack the ability to provide end-users and prosthetists with patientcentric data about changes in socket fit over time. There is a need for objective clinical decision-making that results in greater prosthesis usage, improved residual limb health, and better comfort ratings for end-users. Among the socket systems available in the market, the elevated vacuum suspension system improves residual limb skin oxygenation, attenuates socket-induced reactive hyperemia and preserves skin barrier function. This suggests that such a system is compatible with imparting physiological benefits to the residual limb in people with lower limb amputations.

**Keywords:** amputation, prosthesis, residual limb health, transepidermal water loss, surface electrical capacitance, skin barrier, perfusion

#### **1. Introduction**

Prosthetics are artificial substitutes for body parts lost through congenital defects, injury (accident or combat-related) or disease. These devices can be worn on the outside of the body or surgically implanted and are made of a variety of materials that may serve a cosmetic and/or functional purpose. They have evolved from simple fiber-based appendages (ancient Egypt) to the sophisticated lower limb "blades" and bionic arms that enable amputees to transcend barriers to their activities. Prosthetics today are strong and light, made of aluminum, plastic or composite materials that are better molded to the patient limb. Furthermore, the advent of microprocessors, computer chips and robotic technology provide a range of motion that fits the lifestyle choices of the amputee.

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 overall success of the prosthesis [1, 2]. Plaster wraps or computer aided designs are the primary means to custom fit sockets to maximize socket performance and comfort without adversely affecting residual limb health (**Figure 1**). Currently, the lack of quantitative feedback to determine appropriate socket fit is a major drawback in this process. Prosthetists use anecdotal visual cues

combined with subjective verbal feedback from patients to minimize suspensiondependent movement between the socket and residual limb. This subjective information is used to revise socket parameters such as volume, geometry, and type of suspension to provide a "best" fit for the amputee. In day-to-day living, the volume of mature residual limb (>18 months postamputation [3]) are subject to short-term [4] and long-term [5, 6] changes in volume that compromise socket fit and performance.

More than 80% of amputations in the U.S. are the result of complications from vascular disease and diabetes [7, 8]. Less than 10% of lower-limb amputation results from trauma [9]. In the US, among those that live with a lower-limb amputation, a growing number of which are Service men and women [10–12], the limb volume changes adversely affect fit, performance, and residual limb health [6]—including skin breakdown and ulceration [13] (**Figure 1**) that can require surgical revision of the amputation. The requirement for surgical revision is known to be as high as 30% [14]. This review primarily focuses on skin health in the residual lower limb and the need for objective monitoring and evaluation of changes at the interface of the biological entity (limb skin) and the artificial entity (prosthetic limb) for sustained optimal limb health. Similar issues could apply to the residual upper limb.

#### **Figure 1.**

*(A) Prosthetists use a scanning device to digitize limb shape. (B) Digital model is modified to create a positive mold for socket fabrication tailored to the residual limb. (C) Tissue injury as a result of using a pin-locking suspension system. (D) Injury healed once the amputee was fit and began wearing an elevated vacuum suspension socket (EVS).*

**47**

**Figure 2.**

*each of these types of movements.*

*Residual Limb Health and Prosthetics*

**2.1 Components**

**2.2 Socket systems**

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

**2. Overview of the prosthetic lower limb**

artificial limb), the attachments and the control system.

time and leading to surgical interventions.

Service Members and veterans with limb loss.

There are two main types of prosthetics that replace a partial or complete loss of the lower limb and these include: (a) below the knee or transtibial (TT), where a prosthetic lower leg is attached to an intact residual upper limb, (b) above the knee or transfemoral (TF), where a prosthesis replaces the upper and lower leg and knee. Each of these types of prostheses is composed of key parts: the prosthetic limb, a socket (interface between the biological component (e.g., patients' body) and the

The piece that interfaces between the residual limb/body part and the artificial limb is called the socket and is typically molded around a plaster cast taken from the residual limb. A range of suspension systems are available for use on amputees and the choice of socket primarily depends on subjective information obtained by the prosthetist. The fit of a socket has to be precise or the artificial limb may cause discomfort or tissue damage resulting in the inability to wear the prosthesis for a

The most common systems in use are pin/shuttle lock, suction, and vacuum. The pin/lock system uses a padded liner with a pin on the end which is inserted into a shuttle lock built into the bottom of the connecting socket. A modification of this system is the lanyard, which connects the socket to the liner and limits shear and rotation. The suction system has a soft liner, a one-way valve and a sealing valve. Suction enables even adhesion to the interior surface of the socket and lowers the friction and shear. The vacuum system actively creates a seal around the socket and liner and enhances the adhesion of the limb to the socket, thereby regulating residual limb volume changes and promoting better circulation and reduced shear. The pin-lock is most popular but is associated with issues such as bell clapping (lateral displacement), pistoning (vertical displacement) (**Figure 2**) and distal tissue stretching (milking) which result in complications such as gait asymmetry, skin sores, and stump pain at the distal end. Suction and vacuum systems help minimize these complications and are currently popular (~95%) among

*Classification of residual limb movement within the socket. The timing and waveform profile are distinct in* 
