Overview
Definition:
Parathyroid autotransplantation is a surgical procedure where parathyroid glands, typically removed during thyroid or parathyroid surgery, are reimplanted into a different location within the body
This is primarily done to preserve parathyroid function and prevent postoperative hypoparathyroidism.
Epidemiology:
The incidence of needing autotransplantation is directly related to the complexity and extent of thyroid and parathyroid surgery
It is a common adjunct in total thyroidectomy, especially when parathyroid glands are devascularized or inadvertently removed
Rates vary based on surgeon experience and patient factors.
Clinical Significance:
Preserving parathyroid function is critical to avoid symptomatic hypocalcemia, which can lead to severe neuromuscular excitability (tetany), cardiac arrhythmias, and long-term complications like osteodystrophy
Autotransplantation is a key strategy to mitigate these risks in patients undergoing extensive neck surgery.
Indications
Surgical Indications:
Primary indications include inadvertent removal or devascularization of parathyroid glands during total thyroidectomy, completion thyroidectomy, or extensive parathyroidectomy for hyperplasia or large adenomas.
Risk Factors For Hypoparathyroidism:
High risk of permanent hypoparathyroidism due to multiple gland involvement, substernal goiters requiring extensive dissection, reoperative neck surgery, or suspected adherence of glands to surrounding structures.
Failure Of Conservative Measures:
When intraoperative assessment suggests significant risk of ischemia to the native glands, even if technically preserved.
Preoperative Preparation
Patient Evaluation:
Thorough assessment of calcium and parathyroid hormone (PTH) levels
Review of previous neck surgery and imaging
Identification of any existing symptoms of hypocalcemia.
Informed Consent:
Discussing the rationale for autotransplantation, potential risks, benefits, and alternatives
Explaining the procedure, including gland harvest, preparation, and implantation site.
Anesthesia Considerations:
General anesthesia is typically employed
Careful monitoring of electrolytes and calcium levels during the perioperative period.
Procedure Steps
Gland Identification And Harvest:
Careful identification of all four parathyroid glands
If devascularized or deemed at high risk of ischemia, glands are meticulously harvested with their blood supply intact.
Gland Preparation:
The harvested glands are typically minced into small fragments (approximately 1-2 mm cubes) to maximize surface area for vascularization
They are kept in a sterile, cold saline solution.
Implantation Sites:
Common sites include the sternocleidomastoid muscle (most common and preferred due to good vascularity and ease of access), the forearm muscles (brachioradialis or pronator teres), or the subcutaneous tissue of the neck.
Implantation Technique:
Small incisions are made at the chosen implantation site, and the parathyroid fragments are placed into muscle pockets or subcutaneous tissue
Care is taken to ensure good contact with the host tissue for vascular ingrowth.
Wound Closure:
Standard surgical closure of the implantation site and neck incision.
Postoperative Care
Monitoring Of Calcium Levels:
Frequent monitoring of serum calcium and ionized calcium levels, typically every 6-12 hours in the immediate postoperative period
PTH levels may also be monitored.
Calcium And Vitamin D Supplementation:
Prophylactic oral calcium and calcitriol (active vitamin D) supplementation is usually initiated
Doses are adjusted based on serum calcium levels and symptoms.
Symptom Assessment:
Close observation for signs and symptoms of hypocalcemia, such as paresthesias (tingling), muscle cramps, Chvostek's sign, Trousseau's sign, and in severe cases, seizures or laryngospasm.
Wound Care:
Standard surgical wound care, including dressing changes and monitoring for infection or hematoma at the neck and implantation sites.
Complications
Early Complications:
Graft failure leading to symptomatic hypoparathyroidism and hypocalcemia
Hematoma formation at the implantation site
Infection at the implantation site
Seroma formation.
Late Complications:
Late graft failure or insufficient function leading to chronic hypocalcemia
Hyperparathyroidism secondary to overgrowth of the transplanted tissue (rare)
Chronic wrist pain or numbness if implanted in the forearm.
Prevention Strategies:
Meticulous surgical technique to preserve blood supply
Careful gland handling and preparation
Appropriate site selection with good vascularity
Close postoperative monitoring and timely adjustment of calcium and vitamin D supplementation.
Prognosis
Factors Affecting Prognosis:
The success rate of parathyroid autotransplantation is generally high, with reported functional rates between 50-90%
Factors influencing success include the number of glands transplanted, the amount of viable parathyroid tissue, the quality of the implantation site's vascularity, and the overall health of the patient.
Outcomes:
Most patients achieve adequate parathyroid function, avoiding the need for lifelong calcium and vitamin D supplementation
Some degree of supplementation may be required long-term in a subset of patients
Functional assessment is typically done by monitoring PTH levels and calcium levels with minimal or no supplementation.
Follow Up:
Long-term follow-up is essential to monitor for graft function
This includes periodic assessment of serum calcium levels and PTH levels, especially if the patient experiences recurrent symptoms of hypocalcemia or requires adjustments in supplementation
Routine imaging of the implantation site is usually not necessary unless symptoms suggest recurrence or complication.
Key Points
Exam Focus:
Understand the indications for autotransplantation
Recall the most common implantation sites and their rationale
Differentiate between early and late complications
Recognize the importance of postoperative calcium and vitamin D management.
Clinical Pearls:
When in doubt about parathyroid gland viability during thyroidectomy, err on the side of caution and consider autotransplantation
Mincing the glands increases vascular engraftment surface area
The sternocleidomastoid muscle is a reliable implantation site due to its rich blood supply.
Common Mistakes:
Failure to identify all four parathyroid glands
Inadequate preservation of blood supply to the harvested glands
Impantation into poorly vascularized tissue
Inadequate or delayed postoperative calcium/vitamin D supplementation
Not adequately monitoring calcium levels postoperatively.