By Piriya Mahendra, medwireNews Reporter
A single-stage, surface-mounted implant designed using the principles of the intraosseous transcutaneous amputation prosthesis (ITAP) is an effective bone anchor for an external prosthesis but may not produce good cosmetic outcomes in complex craniofacial reconstruction, researchers say.
Norbert Kang (Royal Free Hospital, London, UK) and co-authors say that the novel implant for extra-oral craniofacial defects addresses the problem of excessive soft-tissue mobility at the skin-implant interface. It also provides a biological seal that prevents the entry of bacteria, they add.
"ITAP represents a new approach to the design of bone-anchored implants and is the first implant specifically designed to achieve osseo-cutaneous integration whereby the skin is encouraged to adhere directly to the implant," the researchers explain.
However, although all patients in the study were either satisfied or very satisfied with the implant overall, they gave it low scores for cosmetic quality. Indeed, they gave the implant a score of 6 for overall satisfaction, but a score of 11 for cosmetic quality on a Likert scale of 1-25, where a score of 1 represents excellent satisfaction and 25 represents poor satisfaction. The retention system was given a mean score of 9 for ease of use.
The implants were manufactured by incorporating a porous flange structure coated with hydroxypatite to encourage soft-tissue integration. These were inserted into the cranial facial skeleton at a number of different sites in six adult patients.
A total of 16 implants were inserted using a one-stage procedure and followed up for periods of between 18 months and 7 years.
The findings revealed that one implant loosened at 3 months. This implant underwent multiple episodes of infection and was replaced with a new ITAP implant 4 years later. The authors report that the replacement was stable and uninfected at an 18-month follow up.
Another patient experienced a few minor episodes of superficial infection in the first year after insertion, but none thereafter. The episodes of infection in the first year did not require antibiotic treatment.
One patient died during follow up, but this was unrelated to the implant surgery.
The authors say that the final measure of success when designing such implants should be a patient who is able to return to normal social interaction with a high quality prosthesis. "Sadly we were unable to achieve this for every patient," they write.
Kang et al conclude that although they have no plans to continue using craniofacial ITAP implants, the information gained from the current analysis may be useful when designing similar bone-anchored implants in future.
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