The Impact of Radiotherapy on Extra-Oral Implants for the Rehabilitation of Craniofacial Defects and Optimal Timing for Placement

Implant-retained prostheses are a viable option for reconstructing craniofacial defects for reasons as diverse as ablative oncological surgery, trauma and congenital deformity.  Implant success is determined by a variety of factors but radiotherapy in particular has emerged as a significant predictor in many large studies with success rates of 58-78.8% quoted for irradiated implants compared with 94-97% for non-irradiated implants^{1, 2}. We sought to audit our own experience at the Queen Elizabeth Hospital Birmingham, UK in terms of the impact of radiotherapy on implant success and the optimal timing for placement in relation to radiation exposure.

We conducted a retrospective audit of all implants placed for prosthetic rehabilitation of craniofacial defects (orbital, nasal and auricular) at University Hospitals Birmingham between 2005 and 2015.

A total of 190 cases were performed over the audit period. In the 167 (87.9%) case notes available for review, 451 implants were placed (mean 2.7 implants/patient). Patients had a mean (SD) age of 63.2 (19.7) years and male to female ratio of 2.0:1. Auricular prostheses accounted for 222 (49.2%) implants, whilst 131 (29.0%) implants were placed for orbital prostheses and 98 (21.7%) for nasal prostheses. The commonest reasons for requiring maxillofacial prosthetics were ablative surgery following cutaneous squamous cell carcinoma in 51 (30.5%) cases, basal cell carcinoma in 27 (16.2%) cases and malignant melanoma in 19 (11.4%) cases.

From the patients audited, 54 (32.3%) received radiotherapy, accounting for 175 (38.8%) implants. Of these, 66 (37.7%) implants were placed in already irradiated bone, with 109 (62.3%) being exposed to radiotherapy after placement. Univariate analysis revealed that failure rates were significantly higher for those implants being placed in bone which was irradiated (either before or after placement) when compared with implants placed in non-irradiated bone (10.9% vs. 2.2%, chi-square test p=0.0002). This was echoed in a Kaplan-Meier survival analysis using a log-rank test, demonstrating a significant difference between the two groups (p<0.001). There was minimal difference in the failure rates returned when comparing implants placed pre- and post-radiotherapy and this difference was not found to be statistically significant on univariate analysis (10.6% vs. 11.0%, chi-square test p=0.9338) and survival analysis (p=0.96).

Our findings are in keeping with previous literature on the subject with the principle observation that radiotherapy exposure adversely affects success rates in extra-oral implants for maxillofacial prostheses. There appeared to be little difference in outcomes in terms of whether implants were placed pre- or post-radiotherapy. We work closely with our Maxillofacial Prosthetists and tend to place implants at the time of ablative oncologic surgery. Placement at the time of the initial ablative surgery appears to have no detrimental effect on outcome as an independent variable when compared with delayed placement at a second subsequent operation (failure rate 6.0% vs. 5.9%, Fisher’s exact test p=1.00). The current work would appear to support this practice regardless of whether or not the patient goes on to require adjuvant radiotherapy.

References

1. Parel SM, Tjellstrom A. The United States and Swedish experience with osseointegration and facial prostheses. Int J Oral Maxillofac Implants 1991; 6: 75-79
2. Visser A, Raghoebar GM, van Oort RP, Vissink A. Fate of implant-retained craniofacial prostheses: life span and aftercare. Int J Oral Maxillofac Implants 2008;23(1):89-98