Comparative study between lag screw and miniplate fixation for straight midline mandibular osteotomy

Abstract

The mandibular swing approach is a surgical approach for the resection of malignant lesions localized in the posterior oral cavity and oropharynx. We analyzed 15 years of experience with fixation of the straight midline mandibulotomy and compared two fixation methods: lag screws and miniplates. A total of 117 patients underwent a straight midline mandibulotomy during the study period; 85 had fixation with two lag screws and 32 with two miniplates. The overall complication rate was low and there was no significant difference in complication rate regarding the fixation method (9% for miniplates vs. 7% for lag screws). The most serious complication over the whole study period was non union, which occurred in only two patients, followed by orocutaneous fistula and infection. Radiotherapy did not cause serious complications and is not regarded as hazardous in midline mandibulotomy patients. We conclude that lag screw fixation is at least as safe as miniplate fixation, but because of better fragment compression, offers faster bone healing.

Neck dissection with en bloc surgical resection of the tumour in the oral cavity/oropharynx is a major procedure for the treatment of malignant carcinomas of the oral cavity and oropharynx. Mandibular resection is generally considered unnecessary when there is at least 1 cm of healthy tissue between the tumour and the bone. In these cases, a mandibulotomy is considered the preferred approach, as it provides excellent exposure of the posteriorly localized lesions, but with superior aesthetic and functional results compared with segmental mandibular resection. The mandibular osteotomy can be performed in a straight, notched, or stepwise fashion. Skin incisions can be a straight lip split incision or follow the natural prominence of the chin. Depending on the osteotomy site, the mandibulotomy can be posterior or anterior to the mental nerve. Anterior osteotomies are paramedian and midline, while the posterior osteotomy is a lateral mandibulotomy. The vertical ramus osteotomy with parasymphyseal osteotomy has been described for access to parapharyngeal space tumours as well.

Methods of fixation differ and include wire, wire combined with K-wire, or conventional miniplate fixation. Lag screw fixation was first introduced in maxillofacial traumatology in 1970 by Brons and Boering. In 1990, Dawson et al. introduced the use of lag screw fixation of the mandibulotomy site in those with oropharyngeal tumours. Other authors have subsequently suggested lag screw fixation as an alternative method for the fixation of the mandibulotomy site in patients with oral and oropharyngeal tumours.

The aim of this study was to analyze our experience of 15 years of fixation of the straight midline mandibulotomy in the mandible swing approach to the oral cavity and oropharyngeal tumours. This involved the comparison of two horizontally placed lag screws versus miniplate fixation of the straight midline mandibulotomy.

Materials and methods

A single-centre retrospective study was conducted of all patients with oral and oropharyngeal cancer treated surgically in our institution, with surgical access to the tumour via a mandibular swing approach. The study period was January 1997–September 2012. Data were collected from the department clinical oncology database and patient charts. All patients had histologically confirmed squamous cell carcinoma. They were reviewed for tumour type, TNM stage, tumour localization, method of reconstruction, radiotherapy, and follow-up. All complications regarding the fixation method (non union, local orocutaneous fistula, infection, osteonecrosis, hardware exposure) were noted in the patient’s chart by the attending physician, during the hospital stay or follow-up. The surgical technique for lag screw fixation of the midline mandibulotomy is described in full detail in a previous article by Uglešić et al. from 2004. When miniplates were used as the fixation device, two parallel 2.0-mm 4–5-hole miniplates were placed horizontally below the incisor roots ( Fig. 1 ). Before the osteotomy was made, the miniplates were placed and adapted to the bone, and holes for the screws were drilled. The choice between miniplate or lag screw fixation was operator-dependent and was based only upon the surgeon’s subjective preference. The treatment protocol did not differ between the two groups of patients; it was totally independent of the mandible fixation method.

Fig. 1
Postoperative orthopantomogram of the mandible with a straight midline mandibulotomy showing fixation with two parallel 2.0-mm miniplates.

Results

During the 15-year period, 1362 commando operations were performed. An en block resection with mandibular swing was performed in 117 patients. All mandibulotomies performed were straight midline cuts between the two mandibular incisors, and no lateral or paramedian mandibular osteotomy was done. The choice of fixation method depended completely on the operator’s personal preferences. Lag screw fixation was the method of stabilization of the mandibulotomy site in 85 patients ( Fig. 2 ). Marginal resection of the mandible was performed in combination with the swing approach in 10 patients. In the other 32 cases, the fixation was achieved with two parallel 2.0-mm miniplates. The patients were predominantly male (105 patients, 90%); only 12 (10%) patients were female. Patient age ranged from 32 to 80 years, with a mean age of 58.3 years. Details of the tumour localizations, TNM status, use of radiotherapy, reconstruction methods, and complications are shown in Table 1 .

Jan 19, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Comparative study between lag screw and miniplate fixation for straight midline mandibular osteotomy
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