Function and form are important attributes of the hand, which may be affected by congenital abnormalities, disease, and, most commonly, trauma.1–3 Traumatic amputation of the fingers represents a serious insult resulting in dramatic impairment of hand function.4 A prosthesis can be provided to patients for whom surgical reconstruction is not possible for psychological, financial, functional, and rehabilitative reasons. By restoring the natural appearance of the hand, a prosthesis eliminates the constant reminder of the disability and offers true psychological therapy.2 Fabrication of an artificial finger is challenging and requires artistic and technical expertise to provide a lifelike appearance.
A precisely fitting replica can improve function by restoring length and providing opposition for the remaining digits, maintaining sensitivity through a thin lamina, protecting the sensitive residual finger, and transmitting pressure and position sense for activities such as writing or typing.2,5 Retention is an important determinant in the success of the prosthesis, which depends on vacuum effect and length of the residual digit.3,6 This case series describes modifications in the procedure of making a finger prosthesis to help to provide good aesthetics with less labor and skill requirements plus saving time and finances and providing adequate retention.
A 15-year-old adolescent girl reported to the Department of Prosthodontics for rehabilitation of her right amputated index finger that had been lost 1 year back in a road traffic accident at the proximal phalanx. The remaining part of the finger was asymptomatic with no signs of infection (Figure 1A).
A 40-year-old man reported to the Department for rehabilitation of his right amputated index finger that had been lost 2 years back in a road traffic accident at the proximal phalanx. The residual digit was asymptomatic with no signs of infection (Figure 1B).
The residual digit was lubricated with a thin layer of petroleum jelly (Vaseline, Hindustan Unilever Ltd., Mumbai, India) to facilitate removal of the impression without tearing. A cylinder of modeling wax (Modeling wax no 2, Hindustan Dental Products, Delhi, India) providing 4-mm space for impression material was made, and an impression of the residual finger taken with putty consistency addition silicone (3M ESPE AG, Germany) and poured in dental stone (Type3 Labstone, Kalabhai, Karson Pvt Ltd Mumbai, India; Figures 2 and 3). This residual digit mold was scraped 1 mm uniformly in the area designated for contact with the prosthesis. Markings were made on the residual digit cast to differentiate dorsal and ventral aspects, which would help in orientation of the wax pattern.
An impression of the patient's counterpart normal digit was also made in a similar cylinder of modeling wax, in the natural slightly flexed position with a thin mix of irreversible hydrocolloid (Zelgan 2002, Dentsply Pvt Ltd., Gurgaon, Haryana, India) providing vent holes to record an undistorted impression, and poured in molten wax. This pattern was gradually hollowed with a carver while still soft from the attachment side and slowly adapted on the modified residual digit mold to achieve a natural position. Carving was done to obtain normal lateral curvature of the finger in a relaxed position.
The pattern was then transferred to the patient's hand and evaluated for size, shape, retention, and minute details such as creases and whorls (Figure 4). On achieving satisfactory results, the pattern was flasked, so that dorsal and ventral halves of the finger were obtained in separate flask parts to achieve better characterization with different shades of silicone (Multisil Epithetic, Bredent Gmbh and Co.KG Seden, Germany). Dewaxing was done routinely, and the silicone was colored intrinsically to match different shades of the patient's skin in natural daylight between 11:00 am and 1:00 pm.
The appropriately matched silicone was layered into its location. Even the fingernail was created with silicone and pigmented to match the natural nail as problems have been encountered with artificial nails in the adaptation to their bed. Processing was done as per the manufacturer's instructions, followed by removal and trimming of excess material. The fit and shade of the prosthesis were evaluated on the residual digit, and extrinsic coloration was applied on required areas. An adjustable split finger ring was used to better the retention by its compressible nature (Figure 5A and B). The patient was instructed to avoid prolonged contact with water, sunlight and corrosives.
If at least 1 cm of mobile phalanx remains, the use of digital prostheses can provide excellent aesthetics and produce a stable point for light grasping.7 The mold was scraped by 1 mm to take advantage of the compressibility of the residual digit and create a prosthesis with better retention and fit through the superb elasticity of silicone combined with suctional retention.8 Care should be taken that this arbitrary scraping is not excessive to avoid creating a constricting prosthesis that may cause ischemia and associated complications. A decorative split finger ring was placed at the margin of the finger prosthesis to divert attention from the junction and to improve retention by its compressible nature. Although a solitary impression of the amputated finger was made to conserve material and money without affecting the prognosis, the impression of the normal counterpart helped in duplicating minute details in a simple manner, saving time without requiring great skill.
All modifications contributed to fabrication of an aesthetically and functionally acceptable prosthesis without the invasiveness involved in an implant or magnet-retained prosthesis. Because an adhesive was not required, problems of compliance were reduced. The method of achieving suctional retention by overlapping the residual finger is useful when some part of the phalanx remains. In cases of a shorter residual finger, adhesives or other retentive devices may be required to hold the prosthesis.
Hollowing out the solid wax finger is cumbersome and needs multiple alterations during adaptation to the residual finger, as the overlapping part has to be kept very thin to avoid looking unaesthetically bulky. Earlier, various materials such as acrylic resins and polyvinyl chloride were used to fabricate a finger prosthesis but were rejected because of suboptimal appearance and lack of stain resistance.8 Acrylic resins are uncomfortable because of lack of flexibility, although they are cheaper. The overall durability and resistance of silicone is superior to any other material currently available for finger restorations with the functional benefit of the gentle, constant pressure applied by the elastomer helping to desensitize and protect the injured tip. Over time, scar tissue contained within the silicone prosthesis becomes more pliant and comfortable.8
Modifications were made in the conventional technique to improve retention and to reduce the expenditure, time, and labor involved in producing a comfortable, aesthetic prosthesis.
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Keywords:© 2011 American Academy of Orthotists & Prosthetists
finger prosthesis; traumatic amputation; silicone; phalanx; split finger ring