Primary Mandibular Reconstruction: Analysis of 64 Cases and Evaluation of Interface Radiation Dosimetry on Bridging Plates

Abstract

The combination of a myocutaneous flap or free cutaneous tissue transfer with a three‐dimensional bendable reconstruction plate either of stainless steel or titanium has provided very satisfactory results in primary restoration of mandibular defects following surgical resections in irradiated patients or in those who require postoperative radiotherapy. Sixty‐four cases have been treated and evaluated prospectively using this technique. Fifty‐three of the patients had the soft‐tissue defect restored with a myocutaneous flap, 8 had a free cutaneous tissue flap, 2 were reconstructed with tongue flaps, and 1 closed primarily. The stainless steel plate of the A.O. type was used in 53 cases and the titanium plate system and hollow screws in the other 11 cases. A success rate of 78.9% was found with a median follow‐up of 384 days. Thirty of the 64 cases had preoperative irradiation and 15 were treated postoperatively. A plate failure rate of 23% was encountered in those treated with preoperative irradiation and in 20% with those having postoperative irradiation. Forty‐nine of the 64 patients or 76.5% experienced no perioperative complications. Five or 7.8% of the complications were minor. Ten patients or 15.6% experienced a major complication with one death due to a myocardial infarct. A radiation dosimetric model was employed using both stainless steel and titanium. The results from this study showed that, when using a parallel pair of beams, an excess dose of irradiation for the lowest energy cobalt‐60 is 13%, for 6 mV it is 15%, and for 18 mV it is 20%. The excess tissue dose, both for stainless steel and titanium plates, extends for about 0.2 mm for cobalt‐60, 1.1 mm at 6 mV, and for 25 mm at 18 mV. Patients with plates, therefore, can be treated safely with postoperative irradiation using either cobalt‐60 or 6‐mV energy.

Effects of implantable biomaterials on radiation dosimetry

“…9 Of the head and neck reconstructive materials which have previously been tested, stainless steel and Vitallium appear to have the greatest electron backscattering effect, with reports of dose enhancements from 15% to 36% in phantom tissue models using a 6MV energy radiation source. 1,2,4 The present investigation supports the use of cpt or tia in patients expected to undergo radiotherapy (as previously suggested by Delacroix 3 ) since these materials have a reduced effect on radiation dose distribution when compared with stainless steel. Still further reduction in adverse radiotherapy effects may be achieved through use of reconstructive devices of lower atomic number.…”

“…Studies have consistently found increased radiation dosage in front of (anterior to) and attenuated doses behind (posterior to) metallic plates. [1][2][3][4] These findings are explained by the ''interface effect'' which occurs when gamma rays cross the boundary between materials of different atomic number and subsequently cause scattering of secondary electrons. Changes in the fluence of secondary electrons produce radiation-dose enhancement on the side facing the beam (backscatter) and attenuation of the gamma rays on the interface side distal to the beam (transmission).…”

Increased plate and osteosynthesis related complications associated with postoperative concurrent chemoradiotherapy in oral cancer

“…Kin and Donoff 24 and Klotch and Prein 20 reported increased complication rates in irradiated fields, whereas others have reported no adverse effect. 22,25,26 According to Choi et al, radiation therapy does not impact local complication rates after free flap reconstruction for head and neck cancer. 25 In a study of 100 patients who underwent free fibula flap reconstruction of the mandible, 54% of 28 patients in the no radiotherapy group, 65% of 37 patients in the preoperative radiotherapy group, and 46% of 35 patients in postoperative radiotherapy group had complications of any severity.…”

“…Major complication rates range from 15% to 45% in these series. [20][21][22][23][24] These include fistulas, infection, loose hardware, and plate exposure. Contradictory reports exist in the literature on the role of radiation on plate and osteosynthesis related complications.…”

Prosthodontic guidelines for surgical reconstruction of the maxilla: A classification system of defects

“…This has been demonstrated with microvascular free flap reconstruction of the mandible. [23][24][25][26][27] Predictable implant placement in VBCFFs also allows for successful prosthetic rehabilitation. [28][29][30][31][32] Unlike mandible reconstruction, in which VBCFFs are necessary for discontinuity defects, limited defects of the palate can be reconstructed with a soft tissue free flap, provided that the native maxilla maintains the stable base necessary for function.…”