No abstract

The appearance of the skin is dependent on the optical properties of the various layers of tissue and the presence of pigments. In order to reproduce the lifelikeness of the skin in developing digital prostheses, a multiple layered moulding technique was utilised. The prosthesis was moulded in two coloured layers, an outer layer and an inner layer. Four combinations of multiple coloured layers and two single coloured layers varying in their optical properties and base colours were assessed. In two groups an additional intermediate layer of detailed colours was added between the two layers, to enhance the creaselines, nails, blood vessels, and other features. All prosthesis were moulded to a total thickness of 0.6 mm. This method of moulding was based on the anatomical characteristics of the epidermal and dermal layers of the skin and their optical characteristics. The aim was to determine which combination of multiple layers gave the best outcome and made the prosthesis look lifelike in appearance. The appearance and lifelikeness of the prostheses were qualitatively assessed by a panel of assessers divided according to their vocation. The study showed that the best combination for moulding the prosthesis in multiple layers was to have the outer layer translucent and the inner layer opaque. An intermediate layer should be incorporated to enhance the more prominent surface features and the nails. The base colour of the inner layer should be darker than the outer layer to allow the intermediate layer to have a reflective background.

The wide range of skin tones in the Asian population presents a challenge when colour-matching hand and finger prostheses. It requires that the prostheses be custom-made to better match the wide variations. We have developed a finger and hand prosthesis using a multi-layered moulding technique incorporating a colour-matching procedure capable of reproducing the colour tones and life-like appearance of the skin. Between 1990–1994, we have fitted these prostheses to a total of 109 patients. In evaluating the colour-match of their prostheses, 84% of the patients fitted with hand prostheses and 78% of those fitted with finger prostheses had a good to excellent match. This paper discusses some of the challenges we face in colour-matching hand and finger prostheses in the Asian population.