Short Notes in Plastic Surgery

March 5, 2013

32. Fractures of the Zygoma

Filed under: Chapter 32 — ravinthatte @ 9:16 am

32. Fractures of the Zygoma

1.   Introduction: The bones that form the external and outer ring of the anterior orbit, namely the overhanging supra-orbital ridge of the frontal bone and the convex body of the zygoma, serve the purpose of protecting the eyeball, a vital organ of the body. The medial wall of the orbit is secure because of the bony projection of the nose (Figure 1). The arrangement came about in the process of evolution to preserve the valuable faculty of vision. These bones are therefore frequently fractured as they bear the brunt of external injuries and the globe is saved. The eyeball comes to get involved more often by penetrating injuries (by external objects) and rarely by fragments of these bones. It is interesting that the blood supply of the eyeball itself is extremely rich in the retina (the living organ) but is meager in the sclera and absent in the cornea, the latter two are therefore hardier in the game of survival. The eyeball in its central two thirds is mostly fluid, aqueous in front and vitreous posteriorly an arrangement which allows transmission of light. This helps the eyeball to become compressible, allowing it to spring back after episodes of sudden increased pressure (up to a point). Sometimes such sudden increases of pressure can be withstood by the eye but may break a bone in the orbit’s inferior wall aptly called the blow out fracture of the orbit. This fracture is dealt with in the next chapter. While this chapter is mainly devoted to an isolated (!) fracture of the zygoma, the exclamation mark is meant to indicate that frequently more than one bone in the face is fractured. Be that as may because the study of a few fractures of individual bones may serve to help in the understanding of the more complicated fractures, some localised fractures are dealt with as a preliminary.

2.   Applied and pathological anatomy: The zygoma articulates with the frontal bone on top, the temporal bone laterally (Figure 3), the greater wing of the sphenoid posteriorly and the maxillary bone medially (Figure 2).

The attachment to the frontal and maxillary bones are strong and therefore the zygoma is often referred to as a buttress bone. The other two attachments are weaker (with the zygomatic process of the temporal bone and behind with the sphenoid) and are thin. The zygomatico-temporal junction can suffer a green stick fracture or this area might buckle in creating a loose piece of bone (Figure 4).

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This area is very near the coronoid process of the mandible and therefore there might be difficulty in opening the mouth fully or this opening might be painful (Figure 3, 5 and 6).

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The injuries of the main body of the zygoma however can cause effects on the orbital cavity as well as the eye because it forms the lateral two thirds of the orbital floor as well as its lateral wall. Sub-conjunctival hemorrhage is common and a scleral flame might be visible. Because the lateral canthal ligament is attached to the zygomatic bone any fracture which will separate the bone from all its attachments will in all likelihood cause an inferior descent of the bone aided by the pull of the massetor which is attached to the outer surface of the zygoma (Figure 7,8).

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This will result in the eyeball losing its horizontal plane and if the displacement is severe, the eyeball might be skewed enough to cause diplopia and the lower eyelid will hang below the level of its opposite fellow. The inferior surface of the zygoma also forms the roof of the maxillary antrum together with the maxilla and fractures of the zygoma can result in a tear in the antral mucosa leading to extra-vasated blood entering the antral cavity seen on an x-ray as an opacity (Figure 10,11).

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Of its attachments the maxillary end may show a fracture in the maxilla as well where small fragments might be present. The infra-orbital nerve emerges on to the face here, may be contused and causes anaesthesia of a part of the lower eyelid and on the lateral surface of the nose (Figure 9).

3.   Diagnosis: Sub-conjunctival hemorrhage, a scleral flame, a flattened cheek (Figure 19-22), bony crepitus, a hanging lower eyelid, a change in the horizontal axis of the eyeball, more severe forms of dystopia and the inability to open the mouth are some of the tell-tale signs of signs of a fracture of the zygoma. Several of these features might not be apparent immediately after the event due to peri-orbital swelling (oedema or haematoma) but will become obvious to the discerning eye in one or two days. Intra-oral palpation with a finger in the upper lateral sulcus of the cheek together with a bi-manual examination and a comparison with the sulcus of the opposite cheek will reveal the difference in the bony contour. There was a tendency in the past either not to treat the fractures because they did not really affect life as such unless there was diplopia or dysarthria of the TM joint. There was also a tendency to treat these fractures by blind methods through small incisions with the help of elevators. For example, both the zygomatic arch as well as the body of the zygoma could be leveraged (in to its normal position?) by introducing instruments through a small incision in the temporal fossa then to insinuate it under the temporal fascia to leverage the bone or bones to hear what was called a click (Figure 12,13, 14)!

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The only useful, available view by way of an x-ray was the Water’s view which when executed expertly did show excellent images but post-operative confirmation of the success of the leverage was rarely done by way of an x-ray. Over the years as anaesthesia became safer techniques of imaging (including 3-d reconstruction) have been revolutionized and specialization in smaller anatomical areas came about, most fractures of the zygoma are now treated by an open method after arriving at an accurate diagnosis by computerized tomography. Stainless steel wires have now been replaced with mini plates and screws. Though wires are equally effective, they are harder to apply and have to be tightened with difficulty.

4.   Access for fixation of fractures at the fronto-zygomatic area is usually through an incision just lateral to the upper eyebrow (Figure 15).

Slide7

A small incision suffices. A similar small incision over the temporal arch will reveal the fractures at this site. Both these areas are easily accessible though covered by dense fascia. The approach to the body of zygoma is either through the sub-ciliary approach or rarely by a transconjunctival approach in the depths of the fornix of the lower eyelid. The orbicularis oculi muscle drapes the bone and has to be carefully split when the incision is sub-ciliary (in the direction of the fibres) or has to be retracted when the bone is approached through the conjunctiva. In either approach the orbital septum is not opened and is retracted to approach the zygomatic bone. These three incisions allow a more effective anatomical restoration by leverage or with the help of a clamping forceps. The eyeball can be gently retracted and gives an excellent view of the floor of the orbit and a safe and effective intra-osseous fixation can be performed. Sizeable pieces of loose bone can be reattached and also fixed but bone dust and small sized debris is extracted particularly at the zygomatico-maxillary junction. In closed fractures non-union is virtually unknown. In fact this propensity to unite rapidly and firmly means that the diagnosis and a proper treatment of this fracture needs to be done quickly because a mal-united fracture is very difficult to treat and might mean that consequences such as diplopia do not revert to normal and aesthetic results are poor.

5.   In the recent past, a bicoronal scalping flap has been used to expose most of the zygomatic bone and gives a far better access to its superior and lateral aspects and reduction of the fracture becomes that much easier (Figure 17).

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In the event the sub-ciliary incision can be that much smaller and only over the site of the zygomatico-maxillary fracture. An intra-oral approach is also very effective (Figure 18) and a combination of these two incisions coronal and intra-oral have the added merit of concealing the scars. That non-union is rare in this condition has already been mentioned but if the fractures are compound and / or have occurred because of penetrating injuries, infection is always a possibility and this can lead to a non-union. Infection in this area has an effect on the peri-orbita and a thorough debridement, removal of loose pieces of bone, a very close scrutiny for foreign bodies by way of magnifying glasses, administration of suitable antibiotics, all help. Occasionally, a strategically placed drain is kept to not allow the peri-ocular space to be occupied by an inflammatory exudate and later formation of a pocket of pus which may lead to adhesions and restrictions of the movements of the eyeball.

6.   The photographs reproduced below show that the real proof of a properly reduced fracture of the zygoma can be ascertained only by what is a worm’s eye view. Figure 19 clearly shows a scleral flame and a peri-orbital hematoma. Figure 20 shows a depression below the eye notwithstanding the swelling. The depression is shown by a red arrow. Figure 21 is a good comparison of the frontal view in this patient but Figure 22 is the clincher where you can compare the two convexities of the body of the zygoma and come to the conclusion that the fracture is now in its natural place.

Slide9

Important note: While dealing with any fracture of the face and certainly around the orbit a thorough neurological and ophthalmic examination including acuity of vision is very important not only from the point of view of what effects the original injury has caused elsewhere but also from the medico-legal point of view.

The compiler of these notes is grateful for the illustrations provided by Arunesh Gupta, Nisheet Agni both from Mumbai and Parag Sahasrabuddhe from Pune. The other diagrams have been produced by Photoshopping a skull borrowed from the Department of Plastic Surgery at the Lokmanya Tilak Hospital in Mumbai.

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