Perils of intermaxillary fixation screws

Sir,

Intermaxillary fixation (IMF) screws, typically self-tapping, are easy and quick to use, seemingly safe, are compatible with plating systems, reduce buccal and gingival tissue trauma and are used to assist with open reduction and internal fixation (ORIF) of fractured mandibles.¹ However, there is limited literature on complications that may arise with their use.²

Hashemi and Parhiz³ studied 373 screws in 73 patients and found that 6.5% of screws damaged dental roots, of which 13 teeth required further treatment or extraction. Coburn et al.⁴ described complications in their 122 patient study including fracture of screws upon insertion and iatrogenic damage to teeth.

Of the complications noted, firstly, we further report the risk of root damage as shown in the panoramic radiograph (OPT) following ORIF (Fig. 1 ). We have also experienced failure at the IMF screw head-thread junction as in Fig. 2 , a complication also reported by Holmes² and Coburn⁴. Farr⁵ postulated that screw fracture at this junction might be created by the screw being placed partly into root dentine which would then require more force to insert the screw due to greater resistance, whilst this is a view that we share, we also propose that there can be, on occasion, mechanical weaknesses or faults at this junction. This unplanned separation may result in delays due to difficult intraoperative retrieval (if possible without further damage). The complications described have become more pertinent in the present climate, with greater reliance on IMF.

Fig. 1.

Panoramic radiograph depicts root dentine involvement of the LR6, LL6, UL5 and UR5.

Fig. 2.

Panoramic radiograph shows separation of the main screw thread body from the head in between the LL6 and LL5.

To avoid the problems outlined with IMF screws an alternative, in the form of MatrixWAVE™ MMF System, may be considered. This procedure can be performed under local anaesthetic. As compared to traditional wire fixation of an arch bar, the MatrixWAVE™ MMF System uses a modified arch bar, which is secured with screw fixation. It also uses shorter self-tapping screws compared to IMF screws, because there are more placed across the arch. Lastly, when securing the MatrixWAVE™ MMF System screws, they are not inserted up to the screw head-thread junction, thus allowing more space for wire and elastics to be applied on to these, as well as the cleats on the arch bar, so allowing a more even and accurate distribution of force.

In the current COVID-19 crisis, we are faced with difficult decision making where advice from health care bodies is to avoid ‘Aerosol Generating Procedures’ (AGP) where possible (such as drilling), along with limited theatre availability and usage. Avoiding AGP may help avoid general anaesthetic/intubation, hospital admission and exposure to potential COVID-19 viral infection, so reduce the stress on an already stretched system. In respect of fractured mandibles, both IMF screws and MatrixWAVE™ MMF System (or similar system), in particular, are proving more useful and a safer alternative for dentate mandibular fractures, at this time, but must be placed carefully.

Conflict of interest

We use Depuy Synthes fixation materials at North Manchester General Hospital.

Funding

No funding sources were used or required.

Ethics statement/confirmation of patient’s permission

Ethics approval not required. Patient permission obtained.