Craniofacial titanium implants and chronic pain: Histologic findings

Objective: To determine whether histologic features or histomorphometric outcomes of retrieved craniofacial percutaneous titanium implants could be found that could be related to chronic pain at the implant site in the temporal bone. Study Design: Histologic investigation and histomorphometric measurements of seven retrieved titanium implants with surrounding bone tissue. Setting: Tertiairy referral center. Patients and Methods: Four patients who had previously received percutaneous titanium implants for auricular prostheses (1 patient) and a bone anchored hearing aid (three patients) had chronic pain at the implant site despite conservative treatment. The implants were retrieved, sectioned, and ground for qualitative light microscopic inspection and quantitative measurement of the bone-to-metal contact and bone area. Results: Qualitative inspection of the sections of the implants demonstrated soft tissue zones at the interface, especially under the flange. Inflammatory cells were seen in the interface in all seven implants. In the implants with good bone-to-metal contact, the percentage of bone-to-metal contact rose with time. In the two implants with poor bone-to-metal contact, the soft tissue zones were more extensive, and slightly more skin reactions were observed than in the other implants while still in situ. Conclusion: A clear explanation for the chronic pain is not at hand. The only common histologic findings were the inflammatory cells present in the interface, but with varying density, and the presence of soft tissue zones. A variety of bone-to-metal was found among the retrieved implants.