Using Ferguson mouth gag to improve the visibility and surgical access in TMJ surgery (Arakeri’s TMJ Technique)

We thank you for the opportunity to respond to the comments and suggested alternate method of viewing the temporomandibular joint (TMJ).

The space between the lower limit of the root of the zygomatic prominence (ZP) and the lower middle limit of the sigmoid notch (SN) can be quite small Fig. 1 . The authors suggest the use of the Ferguson mouth gag (FMG) Fig. 2 , together with the rubber tubing. However, one may not negotiate the beaks of the FMG into such a small space. Hence forceful wedging of the FMG may become necessary. In addition, the FMG is designed for a clasp knife type of grip action, which requires excessive forces. This is unlike our use of a 701 SS WHITE carbide bur on a straight hand piece to place the holes necessary for the K Wires, can be used in a pen grip fashion, for accuracy and controlled pressure.

Fig. 1
Illustrates the space between the central lower limit of the sigmoid notch and the lower limit of the zygomatic arch in a middle-aged human dry skull.

Fig. 2
Ferguson mouth gag.

The authors describe the need to angulate the FMG infero-medially to engage the SN and supero- laterally to engage the ZA. We feel that this often results in slippage and a much greater risk of outward fractures of the ZA and the condylar neck can fracture due to forces exerted by the FMG. In addition, to properly place the FMG, wider dissection may be required to expose the coronoid notch.

Our experience with the FMG whilst usable proved fairly cumbersome, especially with respect to crowding of the surgical field, its bulkiness, the design of the beaks and the excessive forces transmitted to open the beaks. The beaks of the FMG are at the same plane when placed vertically or horizontally whereas the sigmoid notch and the zygomatic prominence are on different saggital planes ipsilaterally. This would necissitate manoeuvring the beaks, which would result in angulation of the FMG with the vectors of force directed superiorly, inferiorly laterally and medially. This could result in further damage such as injury to structures medial to the sigmoid notch.

Perhaps a modified lengthening of a single beak of the Doyen gag that have large semicircular arcs maybe a better alternative to the FMG ( Fig. 5 ). Firstly, the large semicircular arc would clear the surgical field and secondly, it is designed for use with finger pressure. The use of a modified FMG as described for the Doyen gag can be useful in treating medially displaced condylar fractures as well as temporomandibular joint ankylosis where there is bony fusion to the arch and or temporal bone.

The authors implied some concern about possible brain injury from drilling and placement of the K wires. The bony distance from the outer surface of the zygomatic prominence (ZP) to the root of the zygomatic process of the frontal bone is about 1 cm as shown in Figs. 3 and 4 , when viewed from the skull base and the vertex. The cutting length of the 701 bur is about 3 mm long with a 0.6 mm diameter tip. Thus when placing a 2 mm pilot hole on the ZP for the K wire, there is sufficient distance from the brain and a safe distance for the placement of a secure K wire. Our technique also allows for a 5–10 degree margin of error in placing the K wires, thus negating the need for repeated drilling.

Feb 5, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Using Ferguson mouth gag to improve the visibility and surgical access in TMJ surgery (Arakeri’s TMJ Technique)

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