Introduction

Partial or complete finger amputations arising due of trauma, tumor, surgeries, or congenital anomalies are common forms of partial hand loss which may negatively impact the physical, emotional, and social well-being of an individual. (1) Prosthetic rehabilitation is non-invasive and often offers predictable esthetic results although function cannot be completely restored. An optimum residual stump with sufficient length, contours and compressibility allows superior esthetics and favorable retention. (2,3)

The most common methods of retention for a finger prosthesis are by use of tissue displacement and suspension. (4) Alternative techniques, such as adhesives, elastic bands, rings and implants have also been recommended in literature when stumps do not give appropriate retention. (5,6) This case report describes a low-cost and easy method to rehabilitate a partially amputated finger with a silicone finger prosthesis using a custom-made ring assembly as a retentive aid.

Case Report

A 24-year-old female reported to the department with a partially amputated left second finger. The patient's history revealed finger trauma from a cutting saw. Surgical reconstruction was not possible due to limited tissue availability and patient’s unwillingness for further surgery. Hence, prosthetic management was chosen. On examination, the tissues were healthy and all movements were intact in the affected finger (Fig. 1A). The diagnostic radiograph revealed a very thin proximal phalange. The soft tissue over the phalange was also flabby and easily compressible. So, the option of an implant as a retentive aid was ruled out. Therefore, the final treatment opted was to fabricate a prosthetic finger with a custom-made ring as a retentive aid.

Fig. 1- A. Preoperative photograph of finger defect, B. Soldered ring assembly as retentive aid

Impressions of the stump and adjacent finger were taken using irreversible hydrocolloid (Septodont Healthcare India Pvt. Ltd., Maharashtra, India) as the material does not compress the soft tissue. Impressions of the opposite index and second finger were also made. Working casts were obtained using type IV Gypsum (Kalrock, Kalabhai Karson Pvt. Ltd., Maharashtra, India). A custom-made silver dual ring component was planned as a retentive aid. It consisted of a tapered spring of length 6.5cm (Length and width within the dimensions of the second finger) soldered to another band type silver ring that could be worn over the adjacent index finger (Fig. 1B). The position of the rings was verified clinically and then soldered. Wax pattern was sculpted using donor technique simulating the anatomy of the second finger. Wax try-in was done and the retention was evaluated (Fig. 2A). A functional impression was made using a low viscosity polyvinyl siloxane impression material (Avue Gum Light body, Dental Avenue India Pvt Ltd, Haryana, India) and cast was poured using type IV Gypsum.

A custom-made detachable nail was fabricated. A putty index of the nail was made using condensation silicone putty (Zetaplus, Zhermack S.p.A., Rovingo, Italy). In order to match the patient's nail colour, auto polymerizing acrylic resin (DPI, Dental Products of India, Mumbai, India) and acrylic colours (Kokuyo Camlin Ltd., Mumbai, India) were used to fill the putty index. A mushroom-shaped button was made using clear self-cure acrylic resin and attached to the inner surface of the nail (Fig. 2B).

Fig. 2- A. Wax try-in, B. Customized acrylic nail, C. First part of the mold depicting blocked out ring, D. Color matching using Digital Spectrocolorimeter e-skin, E. Final finger prosthesis.

After attaching the nail portion to the wax pattern, the adjacent ring on the index finger was covered with condensation silicone putty to facilitate easy removal of the ring assembly during packing. The processing mold was fabricated using orthokal (Kalabhai Karson Pvt. Ltd., Maharashtra, India) (Fig. 2C), dewaxing was done and 1 mm uniform scrapping of the stump was carried out. Color matching of the patient's finger was performed using a Digital Spectrocolorimeter e-skin (Technovent Ltd., Bridgend, South Wales, UK) and a matching color recipe was obtained from the digital library of e-skin (www.spectromatch.com/sign-in/calculator) (Fig. 2D). Tin foil separating media (Separating Film, Technovent Ltd., Bridgend, South Wales, UK) was applied on the gypsum surface of the mold. Based on the colorant recipe, M511 platinum silicone (Technovent Ltd., Bridgend, South Wales, UK) and the pigments (e-skin color syringes, Technovent Ltd., Bridgend, South Wales, UK) were mixed for dorsal and ventral parts.

The packed mold was kept in a hot air oven for 1 hour at 90 degree Celsius to accelerate the vulcanization process. After deflasking, the prosthesis was retrieved and finished using silicone trimming wheels (5112, 5114, 5119, Technovent Ltd., UK). Extrinsic staining (Master Colors, Technovent Ltd., Bridgend, UK) was undertaken and the prosthesis was delivered to the patient (Fig. 2E). Another ring was used to hide the margins of the prosthetic finger. The patient was given instructions regarding the utilization and maintenance of the prosthesis.

Discussion

Because of the highly displaceable soft tissues and inadequate bone availability, conventional methods of retention were not feasible in this patient. The custom-made ring assembly offered adequate retention both from the affected and adjacent finger. Also, a spring type design was chosen to achieve moderate level of tissue compression. By 1mm uniform scrapping of the stump, sufficient space was gained for the silicone and the ring assembly was completely enclosed within the silicone. (7) This eliminated the need for any metal primer for the bonding between silicone and the silver alloy ring assembly. Because of the soldered ring assembly, movement of the prosthetic finger was majorly controlled by the adjacent index finger. A detachable custom-made acrylic nail matched the color of the patient’s nail and due to its mushroom shaped design, the nail could be easily enclosed within the silicone eliminating the need for any primers. Alternative prosthetic management could be fabrication of a gloved prosthesis enclosing the adjacent finger completely or by fabrication of a prosthetic finger with a silicone band that fits over the adjacent finger. (8) The advantage of the present technique includes a rigid mechanism of retention, reduced bulk of the prosthesis as well as controlled movement of the prosthesis along with the adjacent finger. (9)

Conclusion

Rehabilitation of a partially amputated finger is a challenging task for satisfying the psychological and esthetic needs of the patient. In the present case, the silicone finger prosthesis was customized to provide adequate comfort and functional ability to the patient.

References

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