Zygoma Fracture During Zygomatic Implant Installation
Is it possible we have zygoma fracture with zygomatic a implant installation?
During the osteotomy for the installation of the zygomatic implant, the surgeon must triangulate his vision taking in account the position of the implant in the region of the alveolar ridge, the relation with noble structures (as the orbital cavity and infraorbital nerve), and the ideal position in the area of the body of zygoma.
After the total mucoperiosteal detachment, the bone surface often does not provide us the detailed guidance of where it will be the maximum availability of the bone in the region of the body of zygoma. Not rare, the osteotomy falls immediately into the maxillary sinus, and keeping the drill in this direction, it could follow to the infratemporal fossa, without the zygomatic bone being drilled.
Using this feeling and judgment, paying attention to the zygomaticomaxillary bone region's external topography, we can decide to go with "a safer" positioning, doing the osteotomy in a more external area concerning the body of zygoma.
It anticipates the exit of the zygomatic implant in the body of zygoma, becoming it identifiable and would prevent the entrance of the implant in the infratemporal fossa.
However, this approach can bring some significant problems concerning the external cortical of the zygoma. It could become too thin.
I already had cases where this thin cortical cracked; however, the zygomatic implant kept stable, and the immediate load was kept successfully. Nevertheless, I had a case where the worst-case scenario just happened. Let's see the case.
The zygomatic implants were planned in the 3D model. Once in the perfect position achieved, the zygomatic implants' size was reduced to the initial drill size.
After that, the virtual 3D model is "drilled," and we have the "Virtual Osteotomized Prototype." The perfect position guide where we should put os osteotomies.
With that prototype in hand, we can study the whole path of the drill during the osteotomy. In this case, we could understand how the challenge would be this case. The drills were slightly passed through the infratemporal fossa, and, at the same time, a thin outer zygomatic bone cortical was left.
Under along the osteotomy view, it is possible to check the zygoma external cortical bone after the "virtual zygomatic implant drilling."
There was a complete zygoma external cortical breaking, and the implant anchorage was lost. The bone fragment was totally separate from the zygoma, like a piece of bone graft harvested from the mandibular ramus.
Situations like that can happen in any case, even though in cases of the bulk zygomatic bone. Just keep the initial osteotomy too displaced toward the external cortical and use a zygomatic implant much thicker than the osteotomy size.
If the zygomatic bone is thin, even though the osteotomy passing throws the central area from the internal and external cortical, the cortical fragility is unavoidable. In such situations, our planning must foresee this condition and adjust our planning to keep the outer cortical the most robust possible, preventing its embrittlement and possible breaking. Guess how I found this out?
In this case, the patient of low height and presented a zygomatic bone extremely thin. In the virtual planning, the complexity of the case was noticed, where the installation of 4 zygomatic implants would be necessary (Allon4 Zygoma / Quad Zygoma).
Immediately after the end of the osteotomy, I realized the challenge (and the problem) that I was facing to install this implant. I started the installation to identify any sudden increase in the installation torque to prevent compression in the cortical. As the implant was being installed, I made a counterclockwise torque movement for the implant itself to function as if it were a screw male. That way, I could have better control of the insertion torque.
When I just left about 5 mm for the implant's total insertion, what I feared most occurs— a complete breaking of external cortical of the body of zygoma and the implant's total run down. The zygomatic implant lost its insertion completely.
The bone segment of the zygomatic bone's external cortical bone was wholly detached, like detaching a bone block of the mandibular ramus region.
In front of such a challenge, the ask is - what to do? Fix the segment with microplates and screws? Abort the procedure?
Although all these options came to my mind, I have opted for another one. Reinstall the implant passing through the infratemporal fossa.
With the drilling more internal than the previous one, the drill transfixed the infratemporal fossa. During the drilling in this region, it is normal to notice some degree of facial soft tissue trepidation because the drill is being conducted through the muscle, fascia, and fatty tissue. Such segments of the soft tissues can also adhere to the drill's groove after its removal.
After passing for this region, the drill initiates the perforation in a more posterior area of the zygomatic bone, going into the zygomatic arch's direction.
Although this approach is suitable in extreme situations, such situations are not perfect conditions. Therefore, there is a substantial reduction in the amount of bone insertion of the zygomatic implant, leading to an expressive loss in the insertion torque value.
It is essential to notice that the more posterior the zygomatic implant's head is located, the more significant is the trend towards increasing the bone anchorage. That happens because, in such conditions, the osteotomy will pass through zygoma from anterior to posterior.
In my case, the anchorage happened, however, as expected, with a low torque concerning a normal situation. It was one of the rare cases of zygomatic implants in which I chose to bury the implants and wait 3 months. After this period, the implants were reopened, and the prosthesis was finished without any issue.
What lesson have I learned?
In the case of the thin zygomatic bone, we should always make a plan to maintain as much as possible the integrity of the outer cortical. Even when an optimal thickness of zygomatic bone exists, we can plan to displace the osteotomy toward the internal cortical to keep the outer cortical free of damage.
Practically we could accept the following.
A positioning equidistant or slightly toward the outer cortical can lead to a cortical breaking of the external one. You can completely lose the zygomatic implant's insertion and must have to make new osteotomy in a possible but not ideal position.
However, with a dislocated positioning more for the inner cortical, what will happen in the worse of the hypotheses? The zygomatic implant can pass partially through the infratemporal fossa and return immediately toward the more posterior part of the zygoma body. It will promote an anchorage in 4 cortical, and the high torque will be kept.
What is the possibility of you to understand this concept without using virtual planning 3D? Zero.
The virtual planning allows you to understand the complexity and individuality of each case. It lets you comprehend the zygoma and the path of the drill along the bone and optimize the surgical perceptions that happen in advance.
This concept that you've just learned could take years or until decades of practice to be understood, but it is possible to comprehend it with the virtual planning since your first surgeries.
That's the reason I keep saying to my students. Put a lot of effort into planning your zygomatic implant cases. It worth it. You will know accurately where it will be the osteotomy, and you will have a smart prototype in your hands (virtually osteotomized prototype).
All these tools and knowledge are fully available to everyone. It is worth investing a little time and devotion that the results certainly will be priceless for the surgeon but mainly for the patients.
If you want to learn this kind of approach to zygomatic implant click here to know our training.
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