The importance of both the appearance and function of aesthetic prostheses are well documented, although not always consistently discussed with the individual who has an amputation or limb deficiency.^{1,2,3,4,5,6,7,8,9,10,11} In the past, this term referred almost exclusively to custom silicone prostheses or custom silicone coverings for mechanical hands. These were made to resemble the missing part of the upper limb in size, shape, and coloring. The highest quality solutions for such lifelike aesthetic restorations continue to be made of silicone because of its versatility and compatibility with human tissue.^4,10,12,13 However, the criteria for an “aesthetic” appearance have greatly expanded over the past decade, to include surface features that in no way resemble human skin. Beauty, in this case, is truly “in the eyes of the beholder”.

Recent changes have occurred in public perception and patient demand with respect to the ideal appearances of a prosthesis. Simultaneously, manufacturers have chosen to move away, at times, from making devices that “look real,” to making the devices have more functional grasping abilities, and incorporating features that make no attempt to resemble human skin. Although custom silicone restorations still feature prominently in the pantheon of what are considered “aesthetic” solutions among prosthetic devices, they are now joined by devices with customized surface characteristics that draw attention to, rather than away from, the fact that the person is wearing a prosthesis. A comprehensive treatment should consider the associated aesthetic implications, focusing on a patient’s ultimate acceptance and integration of their prosthesis.¹²

In the 1950s, French physician Jean Pillet noted that the loss of a single digit could profoundly affect an individual’s body image, self-esteem, and psychological status.⁸ Pillet established clinics around the world and pioneered the use of silicone prostheses that were sculpted and painted to match the characteristics of individual patients. Two decades later, Horst Buckner developed a new fabrication method to cover conventional prosthetic components, such as mechanical and electric hands, with lifelike silicone skin.¹⁴

As attitudes toward what defines functional aesthetic prostheses have changed, so have the materials, fabrication, and application techniques. In the 20th century, aesthetic functional prostheses were divided into two categories. The first was considered “high definition,” in which a great deal of time was spent in accurately duplicating the human appearance. The second was considered “low definition,” which was less costly and less realistic in appearance. Now, in the 21st century, more restoration options can be added using custom artwork, threedimensional (3D) scanning, hydrographic films, and other technologies.

For individuals who have had an upper limb amputation, the term function is often associated with grasp. However, activities that do not require active manipulation, including static prehension, support, stabilization, pushing, pulling, transferring proprioceptive inputs, and nonverbal communication, are extremely important.^{3,5,7,11,15,16,17}

A Dutch study divided the function of cosmesis or aesthetics into three categories: passive cosmesis (the appearance of the device), the cosmesis of wearing (the naturalness with which the individual who has had an amputation wears the device), and the cosmesis of use (the naturalness with which the individual who has had an amputation uses the device).¹¹ The appearance of the prosthesis carries subtle psychosocial implications. An aesthetic prosthesis balances the active and passive functional characteristics of the residual limb. For some wearers, the appearance of the sound side is duplicated; for others, the mechanical or robotic look of the prosthesis is emphasized.

Historically, the prosthetic management of finger and partial hand amputations was largely disregarded because of reduced prosthetic options resulting from space limitations. However, because the thumb and fingers comprise 90% of human arm function, the loss of one or more fingers can have a substantial effect on hand function.¹⁵ A single aesthetic prosthesis for an index finger actively functions in prehensile activities such as writing, grasping small objects, and typing on a keyboard⁷ (Figure 1). For a hand without a thumb or forefinger, even a nonmobile partial hand prosthesis provides opposition to the remaining fingers. For those with unilateral total hand amputation, an aesthetic, nonmobile functional hand prosthesis provides opposition to the sound hand while performing bimanual activities and aids with nonmanipulative tasks.

Individuals with more proximal upper limb amputations can take advantage of the entire surface of an oppositional prosthesis because its use is not limited to the terminal device. It is common to see a prosthesis user stabilizing a book against the forearm, sandwiching a grocery bag between their hip and the prosthesis, or pushing up from a chair by placing weight against the elbow componentry of the device. Fraser¹ noted that fewer than 25% of individuals used a terminal device for active manipulation, which can be overly emphasized as a determinant for good prosthetic use.

Because hand use is so important to humans, people with upper limb loss or difference usually face more scrutiny from those around them than do people with lower limb loss or difference, who can easily conceal their prostheses. Just as there are variations in an individual’s level of amputation, culture, vocation, avocational interests, sex, age, socioeconomic profile, and life stage, there are also varied psychologic responses to upper limb deficiency and amputation. An individual’s reaction to limb loss or difference does not necessarily correlate to the level of amputation.¹ Those reactions are also very likely to change over time and, for many, follow a similar course to the feelings of grief experienced after the death of a loved one.

Most often, someone with a new amputation or parents of a child with congenital limb difference prefer a prosthesis that greatly resembles the appearance of the missing body part. These prostheses allow the wearer to blend in and use the device without being seen as “other.” Within this spectrum, individuals face the phenomenon of the “uncanny valley,” a term used to describe the feelings of repulsion and rejection that are elicited by devices that approach, but ultimately fall short of human-like appearance.¹⁸ Frequently, as prosthesis users incorporate changes into an altered body image they may become more open to differently designed, less lifelike prostheses that meet other functional needs.

An alternate reaction that is becoming more common, especially in the United States, is for a person with limb loss or difference to choose a prosthesis with a mechanical or robotic appearance. This represents an opposing aesthetic need of the individual who has had an amputation recently to show that the changed state of their upper limb has become part of their new body image.

It is important to remember that the psychological considerations experienced by those affected by limb loss or difference are dynamic, with ever-changing requirements and desires. As Dr. Pillet noted, “Often the disfigurement is more pronounced in the mind of the amputee than others. However, the man who finds himself unable to take his hand from his pocket, even though it is very ‘functional’, may be as handicapped as if it were lost.”⁸

The need for rehabilitation therapy for individuals who have had an upper limb amputation must be recognized. Individuals with passive functional upper limb devices benefit from occupational and physical therapy. These therapies can improve overall body schema, strength, and the flexibility and range of motion of nearby joints. Therapies also reduce postoperative and phantom limb pain and help with desensitization, scar management, and edema control.

Often, therapy may be of greater value if the manipulation of small objects is deemphasized. Using the prosthesis in everyday situations involving supporting, stabilizing, pushing, pulling, holding, and facilitating balance can have better results.¹ Thus, training must not be limited to controlled prehension based on the erroneous assumption that fine motor activities require a terminal device. For a patient who has had a unilateral amputation, the prosthesis is typically used to assist with nondominant movements.²

van Lunteren et al¹¹ observed that many individuals who have had an amputation were taught direct grasp in clinical settings in which they used their terminal devices to pick up and hold an object. However, many users adopted indirect grasp approaches by picking up an object with their sound hand and transferring it to their terminal device. The individual who has had an amputation is best served by training protocols that teach not only targeted control of prosthetic componentry (terminal devices, wrists, elbows, and shoulders) but also the most efficient way to complete daily living, occupational, and avocational tasks (Figure 2).