Endoscopic parathyroidectomy

The description of the endoscopic parathyroidectomy covers all aspects of the surgical procedure used for the management of primary hyperparathyroidism. Operating room set up, position of patient and equipment, instruments used are thoroughly described. The technical key steps of the surgical procedure are presented in a step by step way: first trocar insertion, working space creation, enlarging of working space, Dissection of parathyroid glands, freeing of adenoma, extraction. Consequently, this operating technique is well standardized for the management of this condition.

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Endoscopic   parathyroidectomy

Authors
F Rubino
Abstract
The description of the endoscopic parathyroidectomy covers all aspects of the surgical procedure used for the management of primary hyperparathyroidism.
Operating room set up, position of patient and equipment, instruments used are thoroughly described. The technical key steps of the surgical procedure are presented in a step by step way: first trocar insertion, working space creation, enlarging of working space, Dissection of parathyroid glands, freeing of adenoma, extraction.
Consequently, this operating technique is well standardized for the management of this condition.
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2001-11
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WeBSurg.com, Nov 2001;1(11).
URL: http://www.websurg.com/doi-ot02en158.htm

Endoscopic   parathyroidectomy

1. Introduction
Improved reliability in preoperative imaging techniques (high-resolution ultrasonography and sestamibi scan) as well as the development of intraoperative assays to confirm normalization of parathyroid hormone (PTH), have led to changes in the treatment of primary hyperparathyroidism.
Today, more surgeons are comfortable with unilateral exploration, which allows for smaller incisions, shorter operative times and the use of sedation instead of general anesthesia in some instances.
Laparoscopic procedures were initially limited to body areas with pre-existing cavities; access to potential spaces has extended the spectrum of minimally invasive endoscopic surgery.
Since the first report of an endoscopic parathyroidectomy in 1996 (Gagner), video-assisted techniques have been applied to surgery of the neck, and several series have documented the feasibility of these approaches for parathyroid and thyroid diseases.
The advantages of minimally invasive surgery for endocrine diseases of the neck consist of reduced postoperative discomfort and improved cosmetic results (Miccoli and Monchik, 2000). Due to the magnification of the laparoscope, minimally invasive video-assisted surgery of the neck is also thought to decrease the incidence of recurrent nerve injuries (Naitoh et al., 1998).
The endoscopic approach includes constant gas insufflation and four trocars placed on the anterior aspect of the neck. Other authors subsequently described technical variations of this endoscopic technique.
The endoscopic approach to the neck requires the creation of a virtual cavity with a much smaller working space than in conventional neck surgery. This can result in a limited view of cervical structures and can compromise visualization of classic anatomical landmarks.
Switching the endoscope from one trocar to another may be needed during the procedure requiring quick reorientation of the surgeon with the anatomical landmarks. An essential element involved in a successful endoscopic parathyroidectomy is the surgeons’ ability to appreciate normal and abnormal anatomy of the neck from different angles of view, in a way they may have never seen before with the naked eye.
2. Cervical anatomy
• Generalities
Most individuals have four parathyroids situated on the posterolateral capsule of the thyroid gland. But the number may vary from two to six. More than four parathyroid glands may be found in 5% of cases.
Characteristically the glands are yellowish-red or yellowish-brown. Minute blood vessels in the pedicle of the gland may help differentiate them from other tissues. The parathyroid glands vary greatly in size, shape, number, and location.
• Parathyroid glands
• Lower
1. Thyrothymic ligaments
2. Thymus
In 61% of cases, the lower parathyroid glands are situated at the level of the inferior poles of the thyroid gland, on its posterior, lateral or anterior aspects. In 26% of cases, they are situated in the thyrothymic ligaments or on the upper cervical portion of the thymus. More rarely, they are situated at the level of the middle third of the posterior aspect of the thyroid gland (Ackerstrom et al., 1984).
• Upper
The upper parathyroid glands are generally located on the posterior aspect of the middle third of the thyroid lobes, approximately 1 cm above the crossing of the inferior thyroid artery and the recurrent nerve. Often, when the parathyroids are difficult to find, it is helpful to trace the course of the inferior thyroid artery and its branches.
• High and low ectopias
1. High ectopias
2. Low ectopias
Anomalies of migration of the parathymus are responsible for high or low ectopias of the lower parathyroid glands. High ectopias along the carotid sheath from the angle of the mandible to the lower pole of the thyroid gland do not exceed 2% (Ackerstrom et al., 1984). Low ectopias, found in 3.9% to 5% of cases, derive from delayed separation of the parathyroids from the thymus. Inferior parathyroids may thus be located in the anterior mediastinum, usually in the thymus.
• Vasculature
About 80% to 86% of the blood supplying the superior parathyroid glands and 90% to 95% of the blood supplying the lower parathyroid glands originates from the inferior thyroid artery. However, superior thyroid arteries contribute significantly to the parathyroid blood supply. Sufficient parathyroid blood supply is ensured by collaterals between thyroid vessels and neighboring esophageal and tracheal arteries.
3. Indications
Indications
Laboratory evidence of primary hyperparathyroidism associated with successful localization of a solitary parathyroid adenoma by technetium Tc 99m sestamibi scintigraphy and/or ultrasonographic scanning.
The quick PTH assay (QPTH) is promoted by some as being a useful adjunct in improving specificity and will probably become more widely used in assessing successful removal of the primary pathological features.
Since the neck offers a limited working space for endoscopic maneuvering, the ideal candidate is a thin patient with a moderately enlarged gland (1-2 cm).

Relative contraindications
- evidence of multiple gland disease;
- likelihood of hyperplasia of the parathyroids or multiple gland disease;
- history of nephric disease, family history of parathyroid disease, or suspected multiple endocrine neoplasia syndrome;
- goiter;
- previous neck surgery or irradiation of the neck;
- lithium-associated PHPT;
- abnormal neck structure (skeletal or soft tissue);
- obesity (as a short, wide neck can limit maneuverability).

Absolute contraindications
- preoperative evidence or suspicion of parathyroid carcinoma: the endoscopic approach may lead to inadequate staging.
The removal of a parathyroid carcinoma through a small incision or through an endoscopic trocar or cannula involves a risk of rupture with potential cell spillage, leading to disease recurrence.
4. Operating room
• Patient
After inducing general endotracheal anesthesia, the patient is placed on the operating table in the supine position with the neck slightly extended and rotated towards the side contralateral to the lesion to maximize access to the ipsilateral neck. A donut is used to stabilize the head.
• Team
1. Surgeon
2. First assistant
3. Anesthesiologist
4. Scrub nurse
During the first step of the procedure (creation of the working space), the surgeon stands on the side of the table opposite the affected parathyroid gland and the assistant stands opposite the surgeon.
For the remainder of the procedure, both the surgeon and the assistant stand on the side of the lesion. For instance, in the case of left parathyroidectomy, the assistant who maneuvers the camera stands on the surgeon’s right side.
The scrub nurse stands on the side of the table opposite the surgeon.
• Equipment
1. The main monitor is placed on the side of the table opposite the affected gland.
2. A second monitor is placed on the side of the affected gland and is used by the assistant during the first step of the procedure.
Laparoscopic and video units are usually placed behind the surgeon.
5. Trocar placement
• Anatomical landmarks
Anatomical landmarks are outlined with a marking pen on the skin, including the sternal notch, the midline, the anterior border of the sternocleidomastoid muscle (SCM), and the external jugular veins.
• Trocar insertion
Unlike the peritoneal cavity, the neck region offers no natural working space.
Trocar insertion must be performed carefully. The first trocar is inserted using an open technique, while the other trocars are inserted under direct visual guidance.
It is mandatory to have a clear view of the area where the trocar is being inserted.
Placement of trocars is performed progressively as the cavity is created by use of insufflation and instruments.
Tip:
In order to minimize the risk of injury to vessels or to the trachea during trocar insertion, the tip of the trocar should be directed towards the endoscope.
• Optical trocar A
Above the sternal notch, slightly to the side of the midline, a 0° 5 mm endoscope is inserted along the avascular space formed by the anteromedial border of the ipsilateral SCM.
The 0° endoscope is then replaced by a 30°, 5 mm endoscope, which is used for the remainder of the procedure.
• Three other trocars
They are then inserted under direct vision:
- one 2-3 mm trocar (B) at the midportion of the ipsilateral SCM;
- one 2-3 mm trocar (C) at the midline;
- one 2-3 mm trocar (D) superolaterally, along the anterior border of the SCM.
6. Instruments
• Operating devices
1. Curved scissors
2. Dissector
3. Grasper
4. Hook dissector
5. Biopsy forceps
6. Kelly clamp
7. Suction-irrigation device
Dedicated instrumentation (2-3 mm in diameter and 18-20 cm in length) is required for this procedure.
• Retracting device
5 mm peanut swab
7. First trocar insertion
• Skin incision
1. Incision
A 5 mm skin incision is made at the sternal notch just above the insertion of the sternocleidomastoid muscle (SCM). A blunt-tipped Kelly clamp is used to enter the subplatysmal space under direct vision. Blunt dissection is performed to create a space along the anterior border of the ipsilateral SCM where trocar A is inserted using an open technique.
• Leakage-free trocar site
1. SCM
2. Strap muscles
3. Platysma muscle
4. Middle cervical fascia
A purse-string suture (2.0 silk) is placed around the incision in order to minimize gas leakage from the first trocar site. The purse-string should be placed in the subcutaneous tissue, since placing the purse-string transcutaneously seems to increase the risk of keloids. Carbon dioxide is insufflated to a pressure of 12 mm Hg. A 5 mm 0° endoscope is inserted through trocar A.
The following anatomical structures can be observed:
- laterally: SCM (medial edge);
- medially: strap muscles (sternohyoid and sternothyroid muscles);
- superiorly: platysma muscle;
- inferiorly: middle cervical fascia.
8. Working space creation
• Dissection of working space
1. Skin and platysma muscle
2. Pretracheal muscles
3. SCM
The working cavity is then created by carefully moving the endoscope in an in-and-out fashion, under 12 mm Hg CO2 insufflation. The landmark that guides this part of the dissection is the medial border of the SCM. Once the lower medial border of the SCM is recognized, the endoscope is gently advanced towards the avascular edge of the muscle below the platysma muscle, just above the cervical fascia and the strap muscles in order to create a small cavity.
Once an adequate working space is obtained, the insufflation pressure is decreased to 8-10 mm Hg for the remainder of the procedure.
• Variation and danger
• Variation
Alternatively, at the time of the initial open dissection, the strap muscles may be identified and separated in the midline, and the space above the thyroid gland entered directly.
In this case, the anterior surface of the thyroid is visualized and the first trocar inserted at the sternal notch. Two trocars are then inserted laterally and one in the midline of the anterior surface of the neck. A plane lateral to the thyroid gland is created and an angled 30/45° endoscope is inserted through the trocar at the sternal notch.
The anatomy of the region is viewed caudad to cephalad:
- medially: thyroid gland (posterolateral aspect of the thyroid lobe);
- superolaterally: strap muscles (medial edge);
- inferomedially: trachea.
• Danger
1. SCM
2. Internal jugular vein
Care should be taken to avoid insertion of the trocars through the fibers of the SCM to avoid injury of the internal jugular vein or the common carotid artery.
Rarely, an external jugular vein or smaller venous vessels such as subplatysmal or subcutaneous veins, or anterior cervical veins may be injured during trocar insertion. These types of vascular injuries may be concealed by the tamponade effect of insufflation or the trocar itself during the operation. Therefore, these types of injuries may only be revealed at the end of the operation when the trocars are removed and the neck is desufflated.
9. Enlarging/working space
• Dissection of the common carotid artery
This operative step is performed to enlarge the working cavity and insert trocars B and C. The common carotid artery is identified and dissected cephalad using a combination of blunt dissection and gas insufflation. This enables easy separation of structures, minimizing the need for sharp dissection. It also prevents mild bleeding from small vessels and helps maintain a clear endoscopic view. This step permits enlargement of the plane that lies lateral to the thyroid and medial to the carotid artery.
At this point, the following structures should be identified:
- laterally: SCM;
- inferiorly: common carotid artery;
- medially: lateral edge of the strap muscles.
Tip:
1. Muscle SCM
If the source of moderate bleeding is a small venous vessel, hemostasis can be effectively achieved by crushing the vessel with the jaws of the grasper for approximately one minute. In addition to the advantage of reducing the risk of electrical injury, this method also avoids the switching of instrumentation in and out of the neck, thereby decreasing the risk of traumatic injury to neighboring organs.
• Inserting the last trocar
The newly created space allows for the insertion of trocar D above the medial-upper portion of the SCM. The 2-3 mm 30° endoscope is then inserted through this trocar and the anatomy of the region is viewed cephalad to caudad.
The following anatomical structures can be recognized:
- laterally: medial border of the SCM;
- inferolaterally: common carotid artery;
- inferomedially: thyroid, trachea and esophagus;
- superomedially: lateral border of strap muscles;
- superiorly: platysma muscle.
• Visualization of the thyroid gland
The space between the lateral border of the strap muscles and the medial edge of the carotid artery is enlarged. Strap muscles are retracted anteromedially in order to visualize the lateral aspect of the thyroid lobe. The thyroid lobe is then gently retracted medially to provide further exposure of the area, exposing the loose connective tissue posterolateral to the thyroid lobe.
10. Dissection/parathyroids
• Retraction of the thyroid gland
When performing dissection of the posterolateral aspect of the thyroid gland, a 3 mm endoscope should be placed through trocar D while a 5 mm peanut swab is introduced through trocar A and used to retract the thyroid lobe medially. Positioning the endoscope through the superolateral trocar makes it possible to approach the recurrent laryngeal nerve and the parathyroid glands frontally, and can assist in the dissection of the base of the neck or the superior mediastinum in cases where the surgeon needs to search for ectopic parathyroid glands.
• Approaching the parathyroid glands
1. Inferior thyroid artery
2. Adenoma
Dissection directed medially on the posterolateral aspect of the thyroid gland enables the identification of the recurrent laryngeal nerve and parathyroid glands. Either an inferior view or a lateral view with a switch of the endoscope is used. The inferior thyroid artery is a useful landmark for locating the recurrent laryngeal nerve. As the artery passes medially behind the thyroid gland, it crosses the recurrent laryngeal nerve in front, behind or on both sides.
At this point, classical anatomical landmarks, as in conventional surgery, lead to the dissection of the parathyroid glands. The superior parathyroid glands are most often found at the level of the upper two thirds of the posterior thyroid capsule. Enlarged parathyroid glands may sometimes be easily identified without the need for extensive dissection of other structures.
In most cases, the inferior thyroid artery or its branches lead to the inferior parathyroid glands.
• Visualization of the parathyroids
The magnification provided by the endoscope permits good visualization of the structures. The vasa nervorum that runs along the recurrent laryngeal nerve can be easily recognized. This helps in the identification and preservation of the nerve. Parathyroid glands are also clearly visualized and their blood supply can be easily identified. The endoscopic approach allows the surgeon to search for glands located deeply in the tracheoesophageal groove or further down in the superior mediastinum.
• Dangers and variations
• Electrocautery
Bleeding from a middle thyroid vein may considerably hinder the view of the structures. Such bleeding can be difficult to manage endoscopically. The use of cautery is to be avoided since the small working space may lead to inadvertent contacts between endoscopic instruments, potentially resulting in the spreading of energy and injury to the nervous and vascular structures.
To prevent injury to the nerve, the surgeon should minimize or avoid clip application in the close vicinity of the nerve or when the nerve is not yet identified. The use of bipolar coagulation or ultrasonic energy for hemostasis is preferable due to their limited lateral spread. The nerve should also be separated from the thyroid gland before the gland is retracted medially or manipulated, in order to avoid stretching and axonal damage.
• Non-recurrent nerve
In approximately 1% of cases, the right recurrent nerve is non-recurrent and originates in a superior level of the vagus nerve. It therefore has a lateral course and is susceptible to injury. If anatomic interruption of the nerve is observed intraoperatively, conversion to open surgery and reanastomosis should be performed using the operative microscope and 10.0 polypropylene sutures.
• Vein ligation
If needed, the middle thyroid vein can be ligated using 5 mm clips or a 5 mm ultrasonic scalpel introduced through trocar A. In order to perform this step, a 3 mm endoscope is inserted through trocar D on the anterior border of the SCM. This maneuver allows for safer medial retraction of the thyroid lobe and can facilitate exposure of the deeper tissue planes.
• Recurrent nerve
It is easier to identify the recurrent laryngeal nerve close to the site where the inferior thyroid artery crosses the lateral border of the lower pole of the thyroid gland. The nerve or one of its branches may pass behind, between or in front of the branches of the artery.
11. Freeing adenoma
• Dissection of the affected gland
When the parathyroid adenoma is identified, it must be carefully handled to avoid damaging the parathyroid capsule with consequent risk of spillage and disease recurrence.
The parathyroid gland can be retracted bluntly by pushing it medially with the closed tip of a grasper, better exposing it. While retracting maneuvers provide tension, curved scissors or a curved hook dissector are used to dissect the gland away from surrounding structures and loose areolar tissue, until complete mobilization is achieved and the vascular pedicle of the gland is clearly identified.
• Clipping the pedicle
When the parathyroid adenoma is completely freed and the vascular pedicle circumferentially dissected by using a curved dissector or a right-angled dissector, a clip applier is introduced through trocar A. After placing two 5 mm clips proximally and one distally, a 2-3 mm scissors is introduced through trocar B to divide the pedicle between the clips.
Alternatively, a 5 mm ultrasonic scalpel can be passed through trocar A and used to coagulate and divide the parathyroid vascular pedicle.
12. Extraction
A small extraction bag is fashioned by removing the thumb portion of a surgical glove and placing a purse-string. It is introduced through the 5 mm trocar. The specimen is placed into the bag and the purse-string is pulled to ensure tight closure of the bag during the extraction. The free tails of the purse-string are then grabbed and pulled through trocar A with a grasper. The trocar is then removed and the bag is extracted through the port site incision which may need to be slightly enlarged to accommodate the specimen.
13. End of the procedure
After extraction of the specimen, the optical trocar is reinserted at the sternal notch and exploration of the working cavity is carefully performed to check for hemostasis and integrity of the neck structures. Routine use of drains is unnecessary. The neck is then desufflated and the trocars are removed.
Two blood samples are obtained 10 and 20 minutes after the ligature of the parathyroid pedicle and quick PTH assay (QPTH) is performed to check that a decrease of least 50% in baseline hormonal levels is achieved intraoperatively.
The specimen is submitted for frozen section analysis to confirm extraction of parathyroid adenomatous tissue.
If the results of QPTH and frozen section analysis are consistent with successful removal of parathyroid adenoma, the operation ends and the skin incision is closed. Sterile adhesive strips are used to close the incisions at the 2-3 mm trocar sites, while the 5 mm incision can either be closed by sterile adhesive strips or by using a subcuticular 4.0 absorbable suture. The latter is recommended in case the incision was enlarged to accommodate the specimen during extraction.
14. Postop period
A test for possible bleeding at the end of parathyroidectomy should be performed. The patient’s head can be tilted down and the lungs hyperinflated by the anesthesiologist to increase intrathoracic pressure as well as blood pressure in the neck veins. Patients should be monitored for several hours after surgery, possibly with their head and shoulders elevated 10° to 20° to maintain a negative pressure in the veins. Vocal cord dysfunction should be ruled out with laryngoscopy during extubation.
After extubation, the patient should be monitored for a few hours to ensure that recovery from anesthesia is uneventful and that there are no other possible sequelae of neck carbon dioxide insufflation. Continuous end-tidal monitoring is suggested during the operation. Arterial blood gas determination may be necessary during the first few postoperative hours in patients who develop hypercarbia intraoperatively, since it has been shown that increased values of PaCO2 may persist as long as 2 hours after desufflation.
Patients should have one determination of serum calcium and magnesium levels during the first 12 hours postop, and then at least once a day for the following 2-3 days to check for possible hypoparathyroidism.
15. Complications
Immediate complications
Our experience in the animal model suggests that insufflation of CO2 at 15 and 20 mm Hg may cause a significant increase in central venous pressure as well as in intracranial pressure. Insufflation pressure up to 10 mm Hg proved to be safe both in experimental studies and in most published clinical series (Rubino et al., 2000).
Pneumothorax and pneumomediastinum may occur during neck dissection under gas insufflation. It is essential to avoid dissecting too low towards the base of the neck. Subcutaneous emphysema has been reported to follow gas insufflation for endoscopic neck surgery. In our experience, it seems to be due both to high levels of insufflation pressure and to the method used for the initial dissection. It may also be caused by the development of pneumomediastinum. Subcutaneous emphysema might also play an important role in the mechanism of production of hypercarbia because it increases the total gas exchange area.
Severe acidosis and hypercarbia may theoretically have a negative inotropic effect on myocardial cells and may produce a decrease in peripheral vascular resistance. Despite this potential risk, no significant hemodynamic complications have been described in the literature.
Reducing the level of insufflation pressure may reduce the passage of gas in the subcutaneous tissue. The creation of a working space below the strap muscles may also thicken the anatomical barrier for absorption of CO2 in the subcutaneous tissue.
If a bilateral recurrent laryngeal nerve injury has occurred during the operation, obstruction of airways and anoxia may occur immediately after extubation.
Sustained supraventricular tachycardia has been reported during endoscopic neck surgery (Gottlieb et al., 2000).

Early complications
Skin necrosis is a potential complication when the initial dissection is not correctly directed under the platysma muscle. In this case the superficial layer is too thin, and small vessels could be compressed under gas insufflation resulting in ischemia of the skin.
Temporary laryngeal nerve paresis has been reported following endoscopic neck surgery. Postoperative hoarseness may be caused by several mechanisms. Hoarseness that occurs 2 to 5 days following surgery is most likely caused by edema in the operative fields and is self-limiting.
Postoperative hypocalcemia may occur during the first few days after a parathyroidectomy; however, symptomatic hypocalcemia is unlikely if unilateral exploration was performed.

Late complications
Long-term hoarseness (up to 6 months) may be the result of stretching of the nerve with consequent axonal damage, but with preservation of the nerve. In this case, new axons grow and the hoarseness may resolve. Permanent hoarseness may be caused by inadvertently cutting or ligating the recurrent laryngeal nerve. When vocal cord dysfunction lasts for more than one year, it is most likely permanent.
Cosmetic results of endoscopic thyroidectomy are usually excellent. However, keloids, although rare, may form within the surgical scar above the sternal notch.

Follow-up
Follow-up of patients undergoing endoscopic parathyroidectomy should include an outpatient visit within the first 10 days post-op to monitor wound healing. As for any patient undergoing parathyroidectomy for primary hyperparathyroidism, routine follow-up should be performed to allow for early detection of persistent or recurrent hyperparathyroidism.
16. Conclusion
Endoscopic parathyroidectomy is feasible and safe. This minimally invasive approach has the potential to decrease morbidity and permits an earlier return to work. Cosmetic results are certainly improved with respect to the conventional open approach. However, larger experience and comparative studies are needed to assess its specific role in the management of parathyroid diseases. Technical difficulties may be overcome as experience increases and specific instrumentation becomes available. Experience in preoperative management of hyperparathyroidism and detailed knowledge of cervical anatomy remain the key for successful treatment of primary hyperparathyroidism.
17. Reference
Akerstrom G, Malmaeus J, Bergstrom R. Surgical anatomy of human parathyroid glands. Surgery
1984;95:14-21.
Gagner M. Endoscopic subtotal parathyroidectomy in patients with primary hyperparathyroidism. Br J
Surg 1996;83:875.
Gottlieb A, Sprung J, Zheng XM, Gagner M. Massive subcutaneous emphysema and severe
hypercarbia in a patient during endoscopic transcervical parathyroidectomy using carbon dioxide
insufflation. Anesth Analg 1997;84:1154-6.
Miccoli P, Monchik JM. Minimally invasive parathyroid surgery. Surg Endosc 2000;14:987-90.
Naitoh T, Gagner M, Garcia-Ruiz A, Heniford BT. Endoscopic endocrine surgery in the neck. An initial
report of endoscopic subtotal parathyroidectomy. Surg Endosc 1998;12:202-5; discussion 206.
Rubino F, Pamoukian VN, Zhu JF, Deutsch H, Inabnet WB, Gagner M. Endoscopic endocrine neck
surgery with carbon dioxide insufflation: the effect on intracranial pressure in a large animal model.
Surgery 2000;128:1035-42.