Hand prosthesis: An art of reconstruction

Introduction:

"It is the God given right of every human being to appear human".

Any kind of deformity, facial or elsewhere may cause psychological and emotional disturbance to the patient as well as social annihilation. Both function and form are important attributes of the hand. The active function of the hand is represented by its prehensile activities in grip, grasp, transferring and absorbing forces.1

Nowadays the amputation of one or more fingers of the hand, as the consequence of trauma or congenital absence of one or more phalanxes, carries a serious reduction of hand function and social dysfunction for the patient.2 Currently, many injuries and traumatic amputations of fingers can be rescued by microsurgery through reimplantation. However, in some cases, reconstruction is either not advisable or partially successful.3 It is in this group of patients that prosthesis can be provided and may offer great psychological help.4

Esthetic prostheses for the hand can offer psychological, functional and rehabilitative advantages. By restoring the natural appearance to the hand, prosthesis eliminates the trauma caused by constant reminder of the handicap and, thus offers true psychological therapy.5 Thus, the purpose of this report is to describe a simple technique for fabrication of acrylic resin hand prosthesis for a patient after an accident at work to provide motor skills recovery and diminished social discrimination.

Case report:

A patient was attended in the clinic for rehabilitation of the left hand with missing middle finger, ring finger and little finger including the respective metacarpal bones (fig 1,2).

When multiple fingers are missing, extensive skin coverage must be considered. It was preferred to fabricate partial hand prosthesis for multiple finger loss, with the uninjured fingers left free, because they can apply more force and use the hand for a variety of activities. Upon examination, the remaining stump was found to be stable and rehabilitative process was possible using conventional hand prosthesis.

Technique:

An impression of the remaining stump was made using the irreversible hydrocolloid material (Neocolloid; Zhermack: Kab dental supplies) (fig 3).

To maintain a natural appearance, the prosthesis was sculpted with each joint slightly flexed. Wax pattern was hollowed from inside to make the final prosthesis light in weight. Later it was placed in warm water so that the fingers were shaped to mimic the natural opposing hand when it is held at rest. Borders were merged with the skin adjacent to the defect site (fig 4).

For retention of the prosthesis, two loops made of orthodontic wire were embedded into the hollow part of the wax pattern. These loops were used to engage the Velcro strap. Additional retention was achieved through a finger ring which engaged the index finger.

The wax pattern was then tried on the patient. The fit, stability, borders and retention of the pattern were evaluated along with shape and size of the pattern. The anatomic lines were then checked to improve esthetics. Using lost wax technique a three piece mould using type III dental stone was made to fabricate the prosthesis (fig 5).

Heat polymerizing clear acrylic resin (DPI – Heat cure; Dental products of India ltd) was intrinsically pigmented according to the skin color of the patient. Color matching of the under surface was done first as this tends to be lighter than the top surface. For finger nails, acrylic resin was pigmented to mach the patient's natural nails. Both the halves of the flask were closed; light pressure was applied to remove excess flash. The resin was processed at slow curing cycle of polymerization. When the moulds were sufficiently cool, the prosthesis was carefully removed. The fit and shade was evaluated on the patient. Extrinsic coloring was done to match the exact color of the patient and have life-like appearance. Careful coloration is crucial for maximal patient acceptance. The patient was wearing the prosthesis under a variety of light sources (fig 6, 7). To achieve an enhanced realistic appearance, the nail and nail bed were shaped with trimmer according to the nails of the natural fingers. The prosthesis was inserted and the patient was instructed in home care and prosthesis maintenance.

Discussion:

Finger reconstruction, especially of proximal phalanx, requires complex surgical procedures with specific functional and cosmetic requirements. Furthermore, even when these techniques offer several advantages whenever fingers are amputated or mutilated, it is very limited in amputation of the proximal phalanxes of the second and third finger because the transposed digital finger may reveal itself too short and consequently not functional at all.

Our patient was not willing for any reconstructive surgical correction. Considering the age, general health and economic status of the patient, we were oriented towards the non invasive technique which would solve the aesthetic need of the patient. For these reasons, prosthetic rehabilitation was introduced and a number of materials and technique have been developed to be used in this process. The acrylic resin and silicone are the most common materials used for rehabilitation. Although silicone has texture and flexibility similar to the skin, provides a more comfortable and better capacity for skin – prosthesis linkage. However, this material is more difficult to pigment and degrades due to color instability when exposed to ultraviolet rays.6

On the other hand, even though acrylic resin is a very hard material and slightly uncomfortable to the patient, but there are added advantages such as easily characterized, presents great durability, cost effective, relined or repaired easily and intrinsic and extrinsic color matching is best achieved.

Among the sculpture techniques there is the analogous finger technique, which is performed by moulding and sculpture of another person finger or can also be carried out based on anatomical reproduction.7,8

Currently, the methods for prosthesis retention to the remaining part of the finger include ring, double ring, adhesives and osseointegrated implants.4,9Although the patients frequently require optimal reconstruction of the hand in cases of injury or amputation, prosthetic devices recover only basic functions of the hand. Minute finger control requires considerable mechanical engineering that encompasses an efficient motor drive and adequate power supply which renders possible prototypes for hand prostheses in everyday performance.10

Bone anchoring is another alternative method used since 25 years in oral surgery; it was first described by Branemark11,12 as an alternative technique to dental prosthesis. For many years it was treatment of choice for teethless patients until Lundborg13 in 1993, started the use of osseointegrated implants to anchor prosthesis of long bones of the leg. Later this technique was applied to retain the maxillofacial prostheses. The limitations of this procedure are, it requires preservation and normal functioning of the metacarpal phalanx joint and the presence of an adequate consistency of the bone to allow implants anchoring. The major complications are: lack of osseous integration of the implant, but is very rare, detachment of the prosthesis or lack of acceptance by the patient.4,14

CONCLUSION:

Good suspension alone is not sufficient for patient   acceptance   of hand prosthesis. For many patients, a high level of cosmesis is paramount. Characteristics such as a pleasing shape, thin margins, lifelike finger nails, realistic color, contours, and detail are essential for patient satisfaction. This level of restoration is most successful when hand prostheses are individually sculpted and colored in situ under variety of lighting conditions.

References:

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