MANDIBULAR RECONSTRUCTION USING A TITANIUM PLATE - THE IMPACT OF RADIATION-THERAPY ON PLATE PRESERVATION

Purpose: To evaluate the soft tissue and bone tolerance of radiation t herapy (RT) in patients undergoing radical composite resection and man dibular reconstruction using a bridging titanium plate with myocutaneo us flap closure. Methods and Materials: From 1990 to 1994, 47 patients with primary or recurrent oral cavity or oropharyngeal carcinomas wer e treated with radical composite resection and mandibular reconstructi on using a bridging titanium plate with myocutaneous flap closure. Ele ven patients received no RT (no RT), 10 patients received RT greater t han 10 months from the time of surgery (remote RT), and 26 patients re ceived RT within 12 weeks of surgery (perioperative RT). The radiation dose to the reconstructed mandible ranged from 45 to 75 Gy (median 63 Gy). The effect of the titanium plate on the radiation dose was measu red using film dosimetry and soft tissue and bone-equivalent materials . The median follow-up was 17 months (range: 3-50 months). Results: La te complications included four patients with osteomyelitis or necrosis , two plate exposures requiring flap revision, one chronic infection, two cases of chronic pain, two fistulae, and one case of trismus and m alocclusion. The crude incidence of late complications by treatment wa s: (a) no RT: 3 of 11 patients (27%); (b) remote RT: 2 of 10 patients (20%); and (c) perioperative RT: 9 of 26 patients (35%). One patient i n the no-RT group lost the plate due to chronic pain. Five patients in the perioperative RT group also had plate loss, four due to osteomyel itis and/or necrosis, and one due to pain related to a recurrent tumor . No patients in the remote RT group had plate loss. The actuarial pro sthesis preservation rate at 2 years was 88% for the no RT, 100% for t he remote RT, and 57% for the perioperative RT groups (p = 0.05). Phan tom dose measurements showed that for parallel opposed 6 MV photon bea ms, there was no significant increase in the dose proximal or distal t o the plate in either a soft tissue- or bone-equivalent phantom. Concl usions: The impact of radiation therapy on plate preservation after ma ndibular reconstructive surgery using a titanium plate may be dependen t on the timing of RT relative to surgery. Significantly more mandibul ar reconstruction plates were lost when the involved mandible received RT in the perioperative period than when RT was delivered beyond 10 m onths from surgery or when no RT was given. The use of alloplastic imp lants such as titanium plates in conjunction with myocutaneous flap co verage for mandibular reconstruction is attractive because it allows i mmediate reconstruction of the defect and promotes a good functional a nd cosmetic result; however, administration of perioperative RT may re sult in a higher plate failure rate.