Abstract
Reconstructing segmental mandibular defects in children of deciduous dentition is a challenge. The authors treated a 23-month-old girl with a segmental mandibular defect secondary to tumour resection. Considering the unpredictable negative impacts of the autogenous bone grafting method on the musculoskeletal system of the donor sites, which was growing rapidly at this age, the authors applied transport disc distraction osteogenesis (TDDO) to reconstruct the mandible discontinuity. To the best of the authors’ knowledge, this is the first time TDDO has been used for mandible reconstruction in such a young patient with deciduous dentition. Aesthetics and function were restored satisfactorily at the end of treatment. The facial appearance and occlusion were stable through the 35 month follow-up, possibly due to the growth of the regenerated bone parallel with the rest of the maxillofacial skeleton. The satisfactory reconstruction also contributed to the patient’s physical and psychological development. The success of mandible reconstruction with TDDO in this study casts new light on the management of segmental mandibular defect in children with deciduous dentition.
It is imperative to reconstruct the profile and functions of paediatric segmental mandible defects effectively to avoid hurting the patients’ psychiatric and physical development. Mandible reconstruction is more complicated in very young pre-school patients than in adults. Autogenous vascularized bone grafting is often the first choice for adult mandible reconstruction due to its predictable effect. For pre-school patients whose musculoskeletal system is undergoing rapid growth, this technique may cause unpredictable damage to donor sites during bone harvesting. Vessel anastomosis in very young patients also requires more skill than in adults; increasing the risk of failure.
Transport disc distraction osteogenesis (TDDO), which does not require bone harvesting, is another option for mandible reconstruction. Despite the effectiveness of TDDO in adults and teenagers, there are few clinical reports of TDDO in patients with deciduous dentition. The authors present the case of a 23-month-old girl with mandible ameloblastoma who was reconstructed using TDDO following tumour ablation.
Clinical case
A 23-month-old girl presented with a painless bony expansion in her left mandible ( Fig. 1 a ). Panoramic radiography confirmed a large radiolucent lesion in the left mandible distal to the first deciduous molar and extending to the lower two-thirds of the ramus ( Fig. 1 b). The tooth germs of the second deciduous molar and the first permanent molar were included in the lesion. Initially diagnosed as an odontogenic cyst, the lesion was just enucleated and the bone cavity was packed with iodoform ribbon gauze, which was regularly changed before healing. The lesion was diagnosed pathologically as ameloblastoma. Segmental mandibulectomy was therefore necessary to obtain sufficient surgical margins and a discontinuity defect was expected. Immediate reconstruction was planned to alleviate aesthetic and functional damage and potential negative effects on the patient’s physical and psychological development. After having been informed of the extent of bone resection, as well as the advantages and disadvantages of autogenous bone grafting and TDDO, the parents finally agreed with the authors to apply TDDO to the patient’s mandible reconstruction.
The extent of resection and aspects of TDDO such as transport-disc size and distraction length were decided preoperatively through simulated surgery on a solid model of the mandible which was manufactured based on CT scanning. A plastic guiding plate was also pre-manufactured to assist in positioning the distraction device in the later operation ( Fig. 2 ). Under general anaesthesia, the left mandible was exposed through the sub- and retro-mandibular approach ( Fig. 3 ). Periosteum beyond the safe surgical margin was preserved to maintain osteogenecity. Mandibulectomy was performed 0.5 cm away from the anterior and posterior walls of the bone cavity with a Gigli saw. The opening of the oral mucosa was closed well with sutures. The osteotomy line for the transport disc was decided by accurately loading the internal distraction device (Cibei Med, Cixi, China) on the mandible stump with the assistance of the prefabricated plastic guiding plate. A bone block of 16 mm × 10 mm was subsequently osteotomized as the transport disc ( Fig. 4 a and b ). It was crucial to avoid lacerating the soft tissues on the medial side of the transport disc. The distraction device was replaced on the transport disc and the mandibular stumps, with the distraction activation arm submandibularly placed. After a 7 day latency period, distraction was started at a rate of twice 0.4 mm/day and continued for 58 days ( Fig. 5 a ). Satisfactory calcification in the distraction gap had already been indicated by radiography after 4 months of consolidation ( Fig. 5 b).
The distraction device was removed at the end of 6 months to ensure high-degree calcification of the distraction area ( Fig. 5 c). When the distraction device was removed it was found that the distraction area was fully ossified and the transport disc was completely fused with the posterior mandibular stump ( Fig. 6 ).
No complication was found in the whole treatment period. The girl has been followed up periodically for 35 months, with no signs of tumour recurrence. The midline of the mandible shifted left by 2.0 mm at the end of treatment and did not change thereafter. With fair occlusion and a normal optimal interincisal opening in the last 35 months ( Fig. 7 a and b ), she has eaten a regular diet and her speech is pronounced clearly. Her facial appearance was satisfactory to both her parents and the authors ( Fig. 8 ). As demonstrated in the latest CT scan, the height and width of the reconstructed mandible were acceptable and the shape was roughly symmetrical ( Fig. 9 ). Her physical condition (judged by weight and height) is within the normal range and her behaviour is no different from that of other Chinese girls her age.
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