Limitations of Transoral Thyroid Surgery
All scarless thyroid surgery techniques have limitations. In the transoral thyroid technique, its limitations are related to its design and partly the instruments. The placement and the location of the instruments can pose certain physical and mechanical limitations. The endoscopic instruments have innate limitations compared to the more advanced refined robotic instruments.
Transoral Thyroid Surgery is Technically Difficult for the SurgeonThe transoral thyroid surgery technique requires that the camera comes from the top over the head. This orientation presents the surgeon with an unfamiliar view of the thyroid and neck looking down from head of the bed. Everythying is upside down to the surgeon and this slows the process and prevents seeing some structures very well. As an example, during conventional open thyroid surgeries, main operating surgeon stands to the side of the patient’s neck and shoulder slightly looking up on the thyroid from the bottom.
In transoral technique, that few is flipped upside down. Such differences necessitate changes in the order and steps of thyroid surgery. Order of dissection is different and the way you find the main nerve for your voice function is also different. How you dissect the nerve and parathyroid glands are also different. All these differences and variables can effect the safety and outcome of the surgery. The bigger the thyroid mass, the more these visualization problems become.
Although the transoral endoscopic view provides ideal midline view of the thyroid with equal visualization of left and right sides of the thyroid gland, its unfamiliar view, the orientation, and steps pose limitations. Furthermore, based on the placement of the instrument through the mouth, certain cancer operations are not possible with transoral technique because the surgeon cannot get a good view of lymph nodes and other structures needed to makes sure all of the cancer has been removed. For this reason, Dr Suh almost always recommends robotic thyroid surgery for patients with cancer. During a robotic thyroid operation almost all neck structures are seen as good or BETTER than they are during an old-fashioned open neck operation that goes through a big neck scar.
For more aggressive or advanced thyroid cancers with cancer spread to the adjacent lymph nodes around the thyroid and next to the major vessels (Jugular vein and carotid artery), you will need an extensive lymph node surgery known as a modified radical neck dissection or lateral neck dissection. Transoral technique is not capable of performing such lymph node surgery compared to the robotic thyroidectomy.
Transoral Thyroid Surgery Limits the Number of Operating InstrumentsDuring transoral thyroid surgery, only three instruments are used, a camera and two other instruments. Robotic thyroid surgery has a big advantage over transoral thyroid surgery in that four instruments are used when the robot is used. Thus, having one less instrument for the surgeon to use limits certain maneuvers or dissection capabilities. As a general principle, surgeons rely on these instruments to expose and visualize the thyroid and all the other structures. If two instruments are required to provide access to the thyroid, there is no instrument to perform the operation. A separate instrument to actively dissect and cauterize the blood vessels or to divide the tissue is not availble because the two instruments are opening up the operative field and providing exposure to the thyroid.
There are a few "tricks" Dr Suh uses to overcome such limitations. For instance, a suture can be placed from outside through the skin and help to retract a muscle covering the thyroid gland. A fourth incision can be made at the armpit for a fourth instrument if needed. Lastly, transoral thyroid surgery is an endoscopic surgery, not a robotic surgery. Lack of articulating instruments which are used in robotic thyroid, endoscopic transoral surgery lacks the ability to perform a refined or delicate tissue dissection compared to robotic thyroid surgery. So any big or difficult operation is much better performed using the robotic scarless thyroid technique instead of the transoral scarless technique.
Transoral Thyroid Surgery Doesn't Allow Large Tumors to be RemovedSpecimen extraction can be challenging for large goiters in transoral thyroid surgery. Once the endoscopic resection has been completed, the specimen needs to be removed through the incision. In the transoral approach, the specimen needs to come through a narrow opening over the chin muscle and bony structure. Also, the mucosal incision in the oral cavity relatively small with limited ability to extend, and unlike the skin, it may be subject to tear and laceration. The incision opening can be dilated to facilitate the removal, but for larger specimens, the thyroid gland or the nodule may have to be fractured for easier extraction. A separate incision may be required for extraction as well.
These challenges need to be carefully managed and taken into consideration. Experience and expertise are very important especially in performing any kind of scarless thyroid surgery.