AN OBSERVATIONAL STUDY OF THE POSTERIOR THYROID ANATOMY – THE CRITICAL ZONE OF DISSECTION IN
THYROIDECTOMY
A dissertation submitted in the partial fulfilment of MS General Surgery (Branch I) examination of the Tamil Nadu Dr. M.G.R. Medical University, Chennai to be held in the year 2018
BONAFIDE CERTIFICATE
This is to certify that this is a bonafide work of Dr. Dennis Darren David
Submitted in partial fulfillment of the rules and regulations to Dr.
M.G.R Medical University, Chennai for the M. S. branch – I (General Surgery) examination to be held in the year 2018.
COLLEGE SEAL :
SIGNATURE : ________________________________________
DR. ANNA B. PULIMOOD PRINCIPAL
CHRISTIAN MEDICAL COLLEGE VELLORE, TAMIL NADU
BONAFIDE CERTIFICATE
This is to certify that the dissertation entitled “An observational study of the posterior thyroid anatomy – the critical zone of dissection in thyroidectomy” is a bonafide work of Dr. Dennis Darren David
submitted in partial fulfillment of the rules and regulations to Dr. M.G.R Medical University, Chennai for the M. S. branch – I (General Surgery) examination in the year 2018.
Name & Signature of the Research Guide: ____________________________
Dr. Pranay Gaikwad Professor and Head General Surgery Unit – I Christian Medical College Vellore, Tamil Nadu
Name & Signature of the Co-Guide:__________________________________
Dr. Paul MJ Professor
Endocrine Surgery
Christian Medical College Vellore, Tamil Nadu
DECLARATION
This is to declare that the dissertation entitled “An observational study of the posterior thyroid anatomy – the critical zone of dissection in thyroidectomy” in the Department of General Surgery is my own work under the guidance of Dr.Pranay Gaikwad, Professor and Head of General Surgery Unit I and Dr.Paul MJ, Professor of Endocrine Surgery, and submitted to the Dr.M.G.R Medical University in partial fulfillment of the rules and regulations for the M.S branch – I (General Surgery) examination to be held in the year 2018.
Dennis Darren David M. S. Post Graduate trainee Department of General Surgery Christian Medical College, Vellore
PLAGIARISM CERTIFICATE
ACKNOWLEDGEMENT
I thank God for the strength and for His presence throughout the study process and for making it possible to complete this research study.
I thank Dr.Paul MJ for the insight and expertise that assisted the research. I thank him for the special guidance, support and motivation he has extended to me during the study process.
I thank Dr.Pranay Gaikwad for the guidance he has offered to me.
I would like to express my sincere gratitude to the Faculty and Registrars from the Department of Endocrine Surgery for extending their helping hand in documenting every single anatomical detail intra-operatively that was required for the study. Without them, this study would have been impossible.
I thank Dr.Antonisamy for helping me with the methodology and sample size for the study. I am immensely grateful to Ms.Hepsy Chelliah from the Department of Biostatistics for helping me with the data analysis and results of the study, and for being prompt and available.
I thank Mr.Sudhakar from the Department of Biochemistry who provided assistance in processing PTH samples.
I thank Dr.Sasank K, my friend for assisting and supporting me specially during the start of this research.
I am grateful to my parents Mr. Ervin and Mrs. Rosemary David who have been my support and constant source of encouragement in all my academic pursuits. I thank my brother Mr. Kenneth David who has always
been my help in the most desperate times. A special thanks for helping me in the data analysis. I am grateful to my in-law’s for their moral support and prayers and boosting me from time to time. Finally, I want to thank God for my loving wife Mrs. Glory David for just being there for me all the time, for being my critique and specially for her valuable input, moral and technical support.
TABLE OF CONTENTS
CHAPTER 1 INTRODUCTION PAGE NO.
Abstract 17
Introduction 19
Justification of the study 20
Aim and Objectives 21
CHAPTER 2 LITERATURE REVIEW 22-39
Anatomy 23
Venous drainage 24
Arterial supply 24
Nerve supply 25
Recurrent laryngeal nerve injury 26
Parathyroid glands 29
Post-operative hypocalcemia 30
Tubercle of Zuckerkandl 33
Ligament of Berry 38
Indian studies 39
CHAPTER 3 METHODOLOGY 41-48
Study design 41
Inclusion criteria 41
Exclusion criteria 41
Outcome 42
Sampling and consent 42
Outline of the study 44
Variables 46
Data analysis 48
CHAPTER 4 DATA ANALYSIS AND FINDINGS 49
CHAPTER 5 DISCUSSION 82
CHAPTER 6 CONCLUSION 88
CHAPTER 7 BIBLIOGRAPHY 90
CHAPTER 8 APPENDICES 92
LIST OF FIGURES
FIGURE 1 PELIZZO CLASSIFICATION ... 34
FIGURE 2 MEASUREMENT OF TZ ... 37
FIGURE 3 GENDER ... 50
FIGURE 4 PATHOLOGY ... 50
FIGURE 5 PATHOLOGY ... 51
FIGURE 6 TYPE OF OPERATION ... 51
FIGURE 7 GRADES OF TZ ... 52
FIGURE 8 GRADE 0 TZ ... 53
FIGURE 9 GRADE 3 DISEASED TZ ... 53
FIGURE 10 INVOLVEMENT OF TZ BY DISEASE ... 54
FIGURE 11 GRADE 2 TZ ... 55
FIGURE 12 RELATIONSHIP OF TZ WITH RLN ... 56
FIGURE 13 RELATIONSHIP OF RLN TO TZ ... 56
FIGURE 15 RELATIONSHIP OF RLN TO LOB ... 57
FIGURE 16 NUMBER OF ITA BRANCHES ... 58
FIGURE 17 RELATIONSHIP OF ITA TO RLN (%) ... 59
FIGURE 18 VISUALISATION OF PARATHYROIDS (%) ... 59
FIGURE 19 PRESENCE OF DECOY FAT (%) ... 60
FIGURE 20 PVPC ON / OFF THYROID (%) ... 60
FIGURE 21 RELATIONSHIP OF SUPERIOR PARATHYROID WITH TZ 64 FIGURE 22 PARATHYROID RELATION TO TZ ... 64
FIGURE 23 LOCATION OF RIGHT INFERIOR PARATHYROID ... 67
FIGURE 24 LOCATION OF LEFT INFERIOR PARATHYROID ... 67 FIGURE 25 LOCATION OF INFERIOR PARATHYROID ... 68 FIGURE 26 ENCOUNTER OF RLN AFTER THYROID MOBILISATION 76 FIGURE 27 REASON FOR OBFUSCATION OF RLN ... 77
LIST OF TABLES
TABLE 1 COMPARISON OF GRADES OF TZ ... 38
TABLE 2 AGE ... 49
TABLE 3 INVOLVEMENT OF TZ BY DISEASE ... 54
TABLE 4 GRADE OF TZ ... 55
TABLE 5 VISUALISATION OF PARATHYROIDS WITH RELATION TO POST-OP HYPOCALCEMIA ... 62
TABLE 6 VISUALISATION OF PARATHYROIDS WITH RELATION TO POST-OP PTH ... 62
TABLE 7 INDIVIDUAL VISUALISATION OF PARATHYROIDS ... 63
TABLE 8 RELATIONSHIP OF PARATHYROID TO TZ ... 65
TABLE 9 RELATIONSHIP OF PARATHYROID TO SUPERIOR POLE .... 66
TABLE 10 PRESENCE OF DECOY FAT ... 68
TABLE 11 RIGHT SUPERIOR PVPC VS POST-OP CALCIUM ... 69
TABLE 12 LEFT SUPERIOR PVPC VS POST-OP CALCIUM ... 69
TABLE 13 RIGHT INFERIOR PVPC VS POST-OP CALCIUM ... 70
TABLE 14 LEFT INFERIOR PVPC VS POST-OP CALCIUM ... 70
TABLE 15 RIGHT SUPERIOR PVPC VS POST OP PTH ... 70
TABLE 16 LEFT SUPERIOR PVPC VS POST OP PTH ... 71
TABLE 17 RIGHT INFERIOR PVPC VS POST OP PTH ... 71
TABLE 18 LEFT INFERIOR PVPC VS POST OP PTH ... 72
TABLE 19 AUTOTRANSPLANTATION ... 72
TABLE 20 RIGHT SUPERIOR PARATHYROID AUTOTRANSPLANT VS
POST OP CALCIUM ... 73
TABLE 21 LEFT SUPERIOR PARATHYROID AUTOTRANSPLANT VS POST OP CALCIUM ... 73
TABLE 22 RIGHT INFERIOR PARA ATHYROID UTOTRANSPLANT VS POST-OP CALCIUM ... 73
TABLE 23 LEFT INFERIOR PARATHYROID AUTOTRANSPLANT VS POST OP CALCIUM ... 74
TABLE 24 PRE-OP PTH VS POST-OP CALCIUM ... 74
TABLE 25 PRE-OP PTH VS POST-OP PTH ... 75
TABLE 26 RLN ENCOUNTER VS NERVE PALSY ... 76
TABLE 27 REASON FOR OBFUSCATION ... 77
TABLE 28 RLN RELATION TO TZ ... 78
TABLE 29 ITA RELATION TO RLN ... 79
TABLE 30 RLN RELATION TO LOB ... 79
TABLE 31 PATTERN OF EXTRA-LARYNGEAL BRANCHING ... 80
TABLE 32 PRESENCE OF THYROID TISSUE IN LOB ... 81
TABLE 33 PRESENCE OF THYROID TISSUE IN LOB ... 81
LIST OF APPENDICES
A Institutional review board clearance letter ... 77
B1 Information sheet (English) ... 81
B2 Information sheet (Tamil) ... 83
B3 Information sheet (Hindi) ... 85
C1 Informed consent form (English) ... 87
C2 Informed consent form (Tamil) ... 89
C3 Informed consent form (Hindi) ... 90
D Proforma ... 92
ABBREVIATIONS
TZ – Tubercle of zuckerkandl RLN – Recurrent laryngeal nerve SP – Superior pole of thyroid LOB – Ligament of berry
PVPC – Parathyroid vascular pedicle complex ITA – Inferior thyroid artery
PTH – Parathyroid hormone LTF – Laryngotracheal fascia FFT – Fibrofatty tissue LN – Lymph node
CCND – Central compartment neck dissection MRND – Modified radical neck dissection TT – Total thyroidectomy
ABSTRACT
TITLE: An observational study of the posterior thyroid anatomy – the critical zone of dissection in thyroidectomy
AIM AND OBJECTIVES: To study the anatomical relationship of critical structures at the posterior surface of the thyroid and evaluate their role in post- operative complications.
METHODOLOGY: A total of 115 patients who underwent total thyroidectomy were recruited during the period of January 2017 to August 2017 in the Department of Endocrine Surgery at CMC Hospital.
RESULTS AND CONCLUSION: 115 patients who underwent total thyroidectomy were studied. There were 30 males and 85 females. The pathology was papillary cancer in 45 patients, nodular hyperplasia in 27.
Tubercle of zuckerkandl (TZ) was grade 1 in the majority on both sides (44/47). The right TZ was significantly larger (p value < 0.001) and more likely to be involved by disease (48.1% vs 33.7%). The RLN was most commonly found to be postero-medial to the TZ (84% on the right side and 85.3% on the left side). The branching of the nerve was symmetrical with one extra- laryngeal branch seen 15% and 2 branches in 12 (10%) patients bilaterally respectively. The RLN was superficial to the ligament of berry (LOB) in the
majority, 95.5% on the right and 92.6% on the left, the remaining were traversing through. There were 4 patients who had temporary RLN palsy but no significant correlation with risk factors could be determined.
The left superior parathyroid was visualized most frequently– 88.6%, and the left inferior the least to be visualized – 53.9%.
Decoy fat - the presence of misleading fatty tissue separate from the superior parathyroid gland which may increase the risk of parathyroid excision. 62%
patients had decoy fat on the right side and 49% on the left. We also studied the location of the parathyroid - vascular pedicle complex (PVPV) being ‘on thyroid’ or ‘off thyroid’ which had not been studied earlier. In 38.8% patients, the right inferior PVPC was “on thyroid. There was a significant association (p value 0.02) of PVPC being “on thyroid” (24.5%) in the left inferior parathyroid and hypocalcemia. Morever, the left inferior parathyroid was the least visualized (53.9%) in this study. There was also a significant association (p value 0.01) of PVPC being on thyroid (18.8%) in the right superior parathyroid and acute parathyroid insufficiency. In our study, autotransplantation was done in 16.5% of patients. There was a significant association (p value = 0.003) between autotransplantation done in the right superior parathyroid gland and hypocalcemia. The incidence of transient hypocalcemia was 11.3%. Familiarity with the nuances of posterior thyroid anatomy should decrease the chances of injury to nerves and parathyroids though this study could not demonstrate significance in view of the low risk of complications.Two new anatomical features to aid in safety of dissection were identified.
INTRODUCTION
The key to safe thyroidectomy lies in the detailed understanding of thyroid anatomy and careful dissection. This study was undertaken to understand the finer nuances of anatomy at the posterior surface of the gland, the critical zone of the dissection to promote safe thyroid surgery. Quoting from Crile, “Every student of surgery knows the general position of the recurrent laryngeal nerve and yet the greatest tragedies which follow thyroidectomies pertain to these structures. Even the surgeon who has had much experience in operations on the thyroid gland reviews the position of the recurrent nerves as an evil memory”(1). Hence to review and understand anatomy from generation to generation is important.
Though already studied by many authors, some of the details differ between studies and some have not been elucidated. The anatomical structures to be studied are the tubercle of zuckerkandl, the recurrent laryngeal nerve, the inferior thyroid artery, the ligament of berry, the superior parathyroid and inferior parathyroid gland. The complications associated with total thyroidectomy will also be studied in relation to the variations in anatomy.
JUSTIFICATION OF THE STUDY
In this study, the additional details not described in literature of potential importance that will be studied are –
1. Involvement of the tubercle with disease– gross appearance
2. Structures covering recurrent laryngeal nerve –tubercle of zuckerkandl, laryngotracheal fascia, fibrofatty tissue or lymph node– Often times it is these structures that obscure vision while dissecting the nerve causing nerve injury
3. Presence of thyroid parenchyma within the Berry ligament makes dissection difficult near the RLN entry to larynx with increased risk of injury
4. Parathyroid-vascular pedicle complex: Location of the gland and it’s vascular supply –on or off the surface of the thyroid gland –this may predict dysfunction of the gland after dissection
5. Presence of decoy fat separate from the parathyroid gland – which may be a risk factor for an inadvertent parathyroidectomy
AIM AND OBJECTIVES AIM-
To study the anatomical relationships of critical structures at the posterior surface of the thyroid and evaluate their role in post-operative complications.
OBJECTIVES-
PRIMARY OBJECTIVE
• To assess the relationship of the recurrent laryngeal nerve (RLN) with the Tubercle of zuckerkandl (TZ), Inferior thyroid artery (ITA) and ligament of Berry (LOB)
• To measure the size of the TZ, document the frequency of grades and presence of disease in TZ
• To document the pattern of branching in relation to the RLN and document extralaryngeal branching
• To study the anatomical variation of the parathyroid-vascular pedicle complex (PVPC) defined as ‘on thyroid’ or ‘off thyroid’, and to document presence of decoy fat
• To document the rate of encounter of nerve at the completion of full mobilization of the thyroid lobe and reason for failed encounter
SECONDARY OBJECTIVE
• To document post-operative complications of RLN injury and hypoparathyroidism and assess the above parameters as risk factors.
LITERATURE REVIEW
Total thyroidectomy is the total extracapsular removal of both the lobes, isthmus and the pyramidal lobe, leaving behind the parathyroid glands, intact recurrent and superior laryngeal nerves(2). Due to the vulnerability and variation of anatomy of the structures involved in this operation, adhesions and fixity to nearby structures, this used to be a morbid operation in the past (1). A thorough understanding of thyroid anatomy and its variations is the key to increasing safety of thyroid surgery(2).
Billroth had a 40% mortality for thyroidectomy for goiter before 1867 and 8.3% mortality during the anti-septic period, from 1877 to 1881. 10.5%
patients were tracheotomized. There were 25% unilateral nerve injuries and 4.5% bilateral nerve injuries in the latter group. The French academy of Medicine banned its practice in 1850 because the reputation of thyroid surgery was so poor, with a mortality rate of more than 20%
Janowski reported a 14% incidence of recurrent nerve injuries for goiter operations before 1885. Halstead later commented that the number was huge because routine laryngeal examinations were not done. It was Theodore Kocher who brought the operative mortality from 14.8% to 0.18% and an incidence of recurrent nerve injury comparable to surgeons as of today because of his meticulous surgical technique (1).
In 1938, Lahey reported more than 3,000 thyroidectomies operated by his team during a 3- year period. The recurrent laryngeal nerve was dissected in almost all the cases. He wrote that careful dissection would not increase but definitely decrease the number of injuries to the recurrent laryngeal nerves(3).
The recurrent laryngeal nerves are much softer compared to the peripheral nerves, and therefore the slightest direct or indirect pressure on the nerves interfere with nerve conduction. The nerve is exposed in the course of the operation, and the exposed nerve will be covered with scar formation which is capable of producing a block in the action current (1).
ANATOMY
The thyroid gland lies caudal to the larynx and encircles the anterior and lateral aspects of the upper trachea. It weighs approximately 20g. It consists of 2 lateral lobes joined anteriorly by the isthmus and may also have a superior extension known as the pyramidal lobe. The lower margin of the lobe is at the level of the 4th or 5th tracheal ring. Each lateral lobe of the thyroid is bordered by the trachea and esophagus on the medial surface, the carotid sheath on the posterior and lateral aspect, and the sternocleidomastoid and strap muscles namely sternohyoid, sternothyroid and superior belly of omohyoid. The isthmus is approximately 1.25cm in both transverse and vertical dimensions. Its size and position is often variable. The thyroid is covered by a thin capsule
derived from the pretracheal fascia. It is condensed to form the posterior suspensory or berry’s ligament near the cricoid cartilage and upper tracheal rings. There may be small masses of thyroid tissue within the vicinity of the lateral lobes, in the thyrothymic tract or superior to the isthmus along the line of the thyroglossal duct tract.
Venous drainage –
It is variable and drains through 3 veins namely superior, middle and inferior thyroid veins. The middle thyroid vein may be absent or conversely, may be several.
Arterial supply –
The arterial blood supply to the thyroid gland is primarily from the right and left superior and inferior thyroid arteries, derived from the external carotid arteries and thyrocervical trunk, respectively.
Superior thyroid artery — The superior thyroid artery is the first branch off the external carotid artery. It extends inferiorly to the superior pole of the thyroid lobe. In addition to supplying the thyroid, the superior thyroid artery is the primary blood supply to approximately 15 percent of superior parathyroid glands. The superior thyroid artery is a landmark for identification of the superior laryngeal nerve, which courses with the artery until approximately 1 cm from the superior thyroid pole(4).
Inferior thyroid artery — The inferior thyroid artery is a branch of the thyrocervical trunk which arises from the subclavian artery. The inferior thyroid artery courses posterior to the carotid artery to enter the lateral thyroid.
The point of entry can extend from superior to inferior thyroid poles. The inferior thyroid artery also supplies the inferior parathyroid glands and approximately 85 percent of superior parathyroid glands.
Thyroidea ima artery — A thyroidea ima artery is found in approximately 3 percent of individuals and arises from the aortic arch or innominate artery and courses to the inferior portion of the isthmus or inferior thyroid poles(2).
Nerve supply –
The recurrent laryngeal nerve is a branch of the vagus nerve , which turns back and runs superiorly into the neck as the motor nerve to the intrinsic muscles of the larynx. The left recurrent laryngeal nerve recurs around the ligamentum arteriosum and arch of the aorta. The right recurrent laryngeal nerve recurs around the subclavian artery before ascending into the trachea-oesophageal groove. The right nerve courses more obliquely as it is more lateral compared to the right nerve in the chest. Both the nerves cross the inferior thyroid artery on their way to the larynx. The whole of the intrinsic muscles of the larynx is
supplied by the recurrent laryngeal nerve except for the cricothyroid muscle which is supplied by the external branch of the superior laryngeal nerve.
Many variations of this relation have been described. The nerve may pass deep to, superficial to or within the branches of the inferior thyroid artery. The nerve continues superiorly and medially to enter the larynx along the posterior aspect of the cricothyroid muscle. The nerve is close to the capsule of the thyroid gland and may appear to be buried within the parenchyma. The nerve usually divides into 2 branches to supply the abductor and adductor muscles of the larynx. This division may occur at variable distances from the larynx, even prior to encountering the thyroid itself. The recurrent laryngeal nerve may lie anterior or lateral to the trachea-oesophageal groove and is at risk of injury during division of the thyroid veins. The most common position of the nerve is deep to the inferior thyroid artery. This is more common in the left side, as the right nerve runs anterior to the artery or between the branches of the artery.
Nearly 30 variations in the relationship of the recurrent laryngeal nerve and inferior thyroid artery have been described. In most cases, the nerve is often just about a few millmetres away from the inferior thyroid artery and ligament of berry, and also the thyroid. It is attached by fibrous tissue to the ligament of berry and is potentially the site of the greatest effect of traction on the nerve.
Recurrent laryngeal nerve injury –
It is interesting to note that it is in the last 2 cm of the extralaryngeal course of the nerve lies structures of importance such as the ligament of berry, the tubercle of zuckerkandl, the superior parathyroid gland and the nerve itself reveals its extralaryngeal branching here. Precise surgical technique and understanding of anatomy of this compact space is critical to successful thyroid surgeries.
The motor fibers responsible for the adduction and abduction of the vocal cords are located in the anterior branches of the nerve. The branching can be observed both, before and after crossing the inferior thyroid artery. It commonly occurs distal to the crossing of the inferior thyroid artery. Therefore if the superior approach is used, one of these branches may be injured.
Therefore Lekacos et al traced the branches to the trunk of the nerve in cases where the superior approach is used. Branched recurrent laryngeal nerves are a risk factor for both temporary and permanent nerve palsy. The relationship of the nerve to the inferior thyroid artery can vary as mentioned already.. Berlin observed that more than 80% of the nerves was deep to the inferior thyroid artery(5).
The most common sites where the nerve is at risk of injury are near the inferior thyroid artery, ligament of berry and at the inferior pole of the thyroid gland.
The cause for injury is presumed to be associated with stretching and compression at fixed points which causes neuropraxia, which is transient in most cases.
However, regardless of the cause of the palsy, permanent palsies are a debilitating complication. A permanent unilateral palsy will cause dysphonia, weakened cough, predisposition to aspiration, social and economic detrimental effects to the patient. A bilateral nerve palsy is potentially life-threatening which may necessitate a permanent tracheostomy at times. And therefore the key aim of thyroid surgery is to minimize the incidence of recurrent laryngeal nerve palsy(6).
In the case of immediate postoperative paralysis of the vocal cord, re- exploration of the wound and exploration of the nerve in its full course should be done and attempt to re-anastomosis should be made. But if continuity of nerve was ensured during the operation, re-exploration of the nerve is not needed. Only observation with regular follow-up is required and is expected to recover in the post-operative period by itself(7).
In Serpell et al’s study, he had revealed branching of the nerve in 64.5% with the help of intra-operative neuromonitoring(6). Casella et al noticed that the nerve had branches 25.7% on the right side and 22.9% on the left(8).
Besides nerve damage there are other causes of change in voice. They are important in affecting reported nerve palsy rates and include the type of surgery (primary/re-do), extent of surgery (lobectomy/subtotal/total
thyroidectomy), formal identification of the recurrent laryngeal nerve, ESBLN injury and surgical volume (high/low)(9).
PARATHYROID GLANDS
There are 4 parathyroid glands in close association with the thyroid gland. The number and positions of the glands may vary among individuals. Akerstrom et al described a 13% incidence of a supernumerary fifth parathyroid. The superior parathyroid glands are derived from the fourth branchial pouch and are in close association with the lateral lobes of the thyroid. They have a short line of descent and remain close to the lateral lobe of thyroid, along the posterior capsule in the region of the inferior thyroid artery. The inferior parathyroid glands are derived from the third branchial pouch and descend along the developing thymus. Therefore they have a long line of descent, and consequently their position is much more variable. An inferior parathyroid gland can be carried along with the thymus into the anterior mediastinum or the pericardium. Conversely, it may be left behind high in the carotid sheath. Most of the times the inferior parathyroid gland are found near the inferior pole of the thyroid within the capsule. They may also be found within clefts of thyroid tissue. Despite the variability in its anatomy, frequently there is a symmetric arrangement between the positions of the gland on either side. Symmetry of the superior glands is about 80% and in 70% of inferior glands(10).
There is a single arterial supply in 80% of the parathyroid glands, a dual supply in 15% and multiple arteries in the remaining. These arteries originate from the inferior thyroid artery in most cases, although in 20% of cases the superior thyroid artery supplies the superior parathyroid, sometimes associated with an anastomosing branch between the superior and inferior thyroid arteries(11).
Post-operative hypocalcemia-
Post-operative hypocalcemia is the most common complication following total thyroidectomy. The earliest symptom being perioral and acral paresthesias which if left untreated can become severe and manifest as carpopedal and generalized tetany. On examination one can elicit chvostek’s and trousseau’s sign. Chvostek’s sign is described as the twitching of facial muscles in response to tapping over the area of the facial nerve. There are 4 grades for chvostek’s sign.
Grade 1 – twitching of lip at angle of mouth Grade II – Grade 1 + twitching of ala nasi
Grade III – Grade II + twitching of lateral angle of eye Grade IV – twitching of all facial muscles
Trousseau’s sign is carpopedal spasm that results from ischemia, such as that induced by pressure applied to the upper arm from an inflated sphygmomanometer cuff. Chvostek’s sign is neither sensitive nor specific for hypocalcemia, since it is absent in about one third of patients with
hypocalcemia and is present in approximately 10% of persons with normal calcium levels. Trousseau’s sign, however, is more sensitive and specific. It is present in 94% of patients with hypocalcemia and in only 1% of persons with normal calcium levels(12).
The main cause of hypocalcemia is acute parathyroid insufficiency. This is due to intra-operative damage to the parathyroid glands by a combination of mechanical or thermal trauma, gland devascularisation or inadvertent removal, leading to reduction of the functional parathyroid parenchyma. According to Lorente-Poch et al, there is higher risk of injury and inadvertent excision if the parathyroid glands are not identified intra-operatively. The fewer identified glands, the higher risk of post-operative hypocalcemia and permanent hypoparathyroidism. Extensive surgery and parathyroid autotransplantation resulted in higher rates of hypocalcemia in Lorente’s study. The rate of permanent hypoparathyroidism was threefold higher among patients for whom autotransplantation was done. The incidence of post-operative hypocalcemia was higher when total thyroidectomy was for carcinoma than goiter. Permanent hypoparathyroidism rates were however similar after thyroidectomy for benign or malignant disease(13).
The rate of parathyroidectomy during thyroidectomy ranges from 9-19%. The current acceptable hypoparathyroidism rate following total thyroidectomy is 1- 2%. In Ebru’s study, the risk of transient hypocalcemia was significantly higher
in patients who underwent autotransplantation as compared to those who did not. There was no significant difference between the two groups in terms of development of permanent hypocalcemia. Thyroid cancer, substernal and recurrent goiter, Grave’s disease, thyrotoxicosis, lymphadenectomy, radicality of surgery and reoperation are reported as main risk factors for the development of transient and permanent hypocalcemia(14)(15).
Michie et al proposed that post-operative hypocalcemia was not only secondary to parathyroid damage and implicated bone absorption in patients with thyrotoxic osteodystrophy as the primary source of transient drops in serum calcium after thyroidectomy. In Donald’s study, transient hypocalcemia occurred in total thyroidectomy patients with an overall incidence of 28.2%.
The calcium levels were the lowest in the thyrotoxic group. The results of the study was consistent with their hypothesis that patients with grave’s disease were at an increased risk of developing post-operative hypocalcemia suggesting that an additional loss of calcium occurs in these patients(16). In Lorente’s study, post-operative hypocalcemia was observed in 42.3% patients.
Protracted hypoparathyroidism was reported in 18.4% and permanent hypoparathyroidism in 4.6%(13). In another study conducted by Puzziello et al, temporary hypocalcemia was reported in 37% out of which only 61% were symptomatic. 2% had permanent hypocalcemia. Puzziello also studied the relationship of hypocalcemia and the relative decrease in serum PTH. The study reported that the relative decrease in serum PTH (taken 2 hours post-
surgery) was greater in patients with hypocalcemia arising on the 2nd post- operative day than in patients who remained normocalcemic post-operatively.
The relative decrease in serum PTH in the normocalcemic group was 44%
whereas in the hypocalcemic group (serum calcium measured on the 2nd post- operative day) was 71%. The ROC curve for the relative decrease in PTH showed an excellent accuracy for predicting hypocalcemia compared with absolute decrease. A relative PTH >62% had a 100% sensitivity and specificity for predicting hypocalcemia on the 2nd post-operative day(17).
Ebru et al studied the rates of hypocalcemia post, hyroidectomy with and without parathyroid autotransplantation. Parathyroid autotransplantation was done in 7.9% of patients. And the reasons for autotransplantation were vascular impairment of the gland, not being able to dissect the parathyroid from the thyroid gland and a suspicious gland. The majority underwent autotransplantation due to vascular impairment. It was reported that 37% who underwent autotransplantation developed temporary hypoparathyroidism. The median calcium value was 7mg/dl and PTH value was 13pg/L(14).
TUBERCLE OF ZUCKERKANDL
The tubercle of Zuckerkandl is present in all thyroid glands. It is represented as a thickening where the ultimobranchial body fuses with the median thyroid process. When enlarged, it develops into a nodular process with the recurrent laryngeal nerve passing medial it into a fissure. This constant anatomic relation
is stressed in many studies that emphasize the use of the tubercle to locate the recurrent laryngeal nerve. Embryologically, the thyroid gland develops from two anlages: the larger median anlage and the paired, smaller lateral anlage.
The tubercle of Zuckerkandl may correspond to these lateral anlages, which may become the posterior and lateral parts of the thyroid lobes. The recurrent laryngeal nerve branches off the vagus nerve in the mesenchyme between the fourth and fifth pharyngeal pouches. It rejoins the pharyngeal cartilages running around the fourth aortic arch and is immediately covered by the thyroid tissue arising from the lateral anlages of the fourth branchial pouch.
This explains the constant anatomical relationship between the recurrent laryngeal nerve and the tubercle of Zuckerkandl.
Figure 1 Pelizzo Classification
Grade 0 – unrecognizable, Grade 1 – only a thickening of the lateral edge of the thyroid lobe, Grade 2 – smaller than 1cm, Grade 3 – larger than 1 cm (18)
The extent to which a tubercle is positively identified differs greatly in the few series reported in the medical literature, being: 7% for Page, 14% for Pelizzo(18), 55% for Hisham(19), 59% for Kaisha, 63% for Gauger, 66% for Gurleyik, 65% of grade 3 tubercles for Yalcin, 68% of grade 2 and 3 tubercles for Yun.
In Page et al’s series, 5 right tubercles of Zuckerkandl were distinctly recognised in 71 right lobectomies (i.e. 7 per cent of right-sided cases) and were very useful for locating the recurrent laryngeal nerve situated just beneath. In Gurleyik’s study, the RLN was medial to the TZ in 94% of the visualized TZ’s(20). In another study the RLN was posterior to the TZ in 96.2%(21).
According to Page, these differences in the frequency of discovery of a clearly visible tubercle of Zuckerkandl can be explained by several factors.
The first factor is the state of awareness of the thyroid surgeon, as the tubercle of Zuckerkandl is poorly described in the standard anatomical literature.
The second factor is the surgical procedure itself. The exposure and identification of a tubercle of Zuckerkandl is possible when the lateral lobe is exposed laterally after complete ligation of the superior pedicle, which was always our first-line procedure. In such cases, when the lobe is medially
displaced, the tubercle will appear as a small nodule, visibly distinct from the thyroid parenchyma. Cautious capsular dissection of the tubercle will then reveal the inferior laryngeal nerve immediately underneath. For lobectomies performed in the craniocaudal direction, with final ligation of the superior pedicle, the tubercle may not be clearly identified.
The third factor is related to the fact that, a well individualised tubercle of Zuckerkandl is not found as frequently as one might think. Moreover, in our experience, the tubercle was found only on the right side, whereas in theory it should be found bilaterally.
The fourth and final factor is that the existence of this tubercle also depends on the goitre itself. When a hypertrophic nodule involves the tubercle itself, the latter is particularly prominent (22).
Yalcin et al. have reported an incidence of grade 2 and 3 tubercles as 64%
and 65% in lateral lobes. Yun et al. have found grade 2 and 3 tubercles in 68% (right side 72% and left side 64%) of lateral lobes. (23).
Figure 2 Measurement of TZ
H = Height, W = Width
“The size of the exposed tubercle was measured based on the height and width by compass.
Height, H: apex of tubercle to groove between the tubercle and thyroid lateral margin;
Width, W: the longest length between upper and lower margin of the tubercle of zuckerkandl.
The grade was based on the classification method of Pelizzo et al. (18), in which
grade 0 = unrecognizable,
grade I = only a thickening of the lateral edge grade II < 10mm,
grade III > 10 mm.
(24).
“Chevallier et al. emphasized the tubercle of zuckerkandl as an anatomical landmark for the preservation of the superior parathyroid. The superior parathyroid is generally located in the cranial portion behind the recurrent laryngeal nerve and inferior thyroid artery, and the inferior parathyroid is located in the caudal portion of the tubercle of zuckerkandl in front of the recurrent thyroid artery and inferior thyroid artery”(8).
Studies Grade 0 Grade 1 Grade 2 Grade3
Gauger (%) 37 18 (1+2) - 45
Pelizzo (%) 23 8.6 53.8 14.4
Hisham (%) 19.8(0+1) - 25 55.2
Sheahan (%) 29(0+1) - 37 24
Pradeep (%) 0 65.2 25.1 9.5
Rajapakash(%) 20.6 36.2 30.6 12.5 Mehanna(%) 30.1(0+1) - 29.8 22.1
Irawati(%) 9.5 28.9 50.5 11
Yun (%) 10.7 7.9 43.5 37.9
Table 1 Comparison of grades of TZ
Ligament of berry –
Ligament of berry is the condensation of the pretracheal fascia with a layer of thyroid parenchyma at times on the posterolateral aspect of the thyroid
gland. It attches the thyoid gland to the cricoid cartilage and the upper tracheal rings. During thyroidectomy excessive medial rotation causes kinking of the RLN due to its close proximity to the LOB. At times the nerve is entrapped within the posterior fibres of the LOB(25).
INDIAN STUDIES
In Pradeep’s study, 64.3% nerves were deep to the inferior thyroid artery, 8.2%
passed in between the branches of the artery and the remaining were superficial to the artery. The RLN was medial to the TZ in 98% of his cases.
Majority of the RLN’s had a single branch (68.2% on the right side and 70.8%
on the left). However there were 2 or more branches in 31.4% on the right side and 29.2% on the left. More than 30% of the cases the RLN passed through the LOB (26).
Transient and permanent hypocalcemia occurred in 7.2% and 1.2%
respectiveluy in Gupta et al’s study. The incidence of temporary and permanent vocal cord palsies were 0.8% and 0.4% respectively in the same study(15). In Mohil’s study, 19% complained of change in quality of voice post-operatively.
Out of the 19%, direct laryngoscopy done post-operatively at 6 weeks revealed vocal cord palsy for 9%. Further evaluation by direct laryngoscopy revealed vocal cord palsy for 5% of patients. There was no permanent vocal cord palsy in the study(9). In M.K Bora et al’s study, the incidence of temporary nerve palsy was 2%.
Gangiti Kranthikumar et al studied the rates of hypocalcemia and recurrent laryngeal nerve palsy for patients who were undergoing completion thyroidectomy. It was found that 26.4% patients had recurrent laryngeal nerve palsy after initial surgery and no additional nerve injuries after the second surgery. There was temporary hypoparathyroidism in 24.5% of patients and permanent hypoparathyroidism in 16.6% of patients. Five out of 8 patients who had permanent hypoparathyroidism had undergone paratracheal nodal dissection(27). The incidences of grades of tubercle of zuckerkandl in Indian studies are included in table 1.
METHODOLOGY
The study was conducted in the Department of Endocrine Surgery, Christian Medical College, a tertiary care centre in Vellore, Tamil Nadu. This institute was established in the year 1990 and is now a 2700 bedded multispecialty hospital. The annual outpatients and inpatients handled is around 2.4 million and 1,40,000 respectively. Patients who underwent total thyroidectomy during the period of January 2017 to August 2017 in the Department of Endocrine Surgery were recruited in the study.
Study design:
An observational descriptive study was adopted.
Inclusion criteria:
All patients undergoing total thyroidectomy with or without nodal dissection
Exclusion criteria:
Patients with-
1. Previous thyroid surgery 2. Clinically fixed mass
3. Infiltrative mass on pre-operative imaging 4. Grossly extracapsular intra-operatively
Outcome:
The outcome studied was the anatomy of the posterior thyroid gland and the complications associated with the variations in anatomy.
Calculation of sample size:
The prevalence of the tubercle of zuckerkandl (TZ) varies from 7% to 72% taken from studies in the past 15 years. P was set to be 66 taken from a recent study published in 2012. With 10% precision(d) applied to the formula n = 4pq/d2,
N=4x66x34 / 10 x 10 N=90
Sampling and consent:
All patients who were posted for total thyroidectomy, who fulfilled the inclusion criteria were included in the study. An informed consent was taken from the patient prior to the procedure as per Institutional review board guidelines. Pre-operative Iced Serum Parathormone (PTH) was checked. Intra- operatively, the details of anatomy were filled in a proforma. The size of the tubercle of zuckerkandl was measured using a sterile flexible scale. Intra- operative photographs were taken to document the anatomy in select patients.
Post-operatively, complications of hypoparathyroidism and recurrent laryngeal nerve injury were assessed clinically and by checking post-operative serum
calcium and Iced Serum PTH on day 1. If day 1 PTH was >6pg/ml with normal calcium, no further test for calcium was done as per department protocol. If day 1 PTH < 6pg/ml, calcium was checked on consecutive days until it was normal or showed a rising trend. If there was post-operative voice change, the patient underwent a vocal cord examination 1 week post-operatively in the ENT OPD after discharge. Vocal cord examination was done either by indirect laryngoscopy or nasopharyngeal-laryngoscopy as decided by the ENT Surgeon.
The other details including demographic details, clinical examination, pre-op and post-op PTH and calcium values, imaging and histopathology details were obtained from the online clinical work station.
Outline of the study:
Patients posted for thyroidectomy
Inclusion criteria
- all patients undergoing total thyroidectomy
Exclusion criteria – 1.previous thyroid surgery
2. clinically fixed mass 3. infiltrative mass on pre-
operative imaging 4. Grossly extracapsular intra-
operatively
Patient consented
Pre-op PTH taken Patients presenting to Endocrine Surgery OPD
Intra-op findings noted, Photographs taken
Clinical assessment made to rule out hypocalcemia and voice change on Day 1 Post-op PTH and S.Calcium checked on Day
1
If symptoms of hypocalcemia present or Corrected S.Calcium < 8 or S.PTH < 8, patient is
started on oral calcium supplements and activated vitamin D3 and S.Calcium is re-
checked on Day 2
Patients with voice change are examined in the ENT OPD for vocal cord palsy
VARIABLES
The various variables studies were-
1. DEMOGRAPHY 1. Age
2. Gender 3. Pathology
2. ANATOMICAL DETAILS
Tubercle of Zuckerkandl (TZ) –
o The grades (size) of the tubercle of zuckerkandl(using a sterile flexible scale intra-operatively)
o Whether disease affects the TZ – gross appearance
Recurrent laryngeal nerve (RLN) -
o Relationship of the RLN with the TZ – medial, posterior or lateral o Relationship with berry’s ligament –superficialor through the
ligament and the distance from the ligament.
o Presence of the non-recurrent laryngeal nerve
o Number of extra-laryngeal branches
o Encounter rate at end of lobe mobilization without dissection for the nerve
o Obfuscating structure if not encountered – TZ,laryngotracheal fascia, fibrofatty tissue, lymph node
Inferior thyroid artery (ITA)
o Number of branches
o Branches relationship to the RLN – superficial, deep, between branches
Berry’s Ligament
o Presence of thyroid tissue in the ligament
Superior parathyroid gland
o Relationship to the TZ (or) the superior pole (SP) of the thyroid
o Presence of decoy fat separate from the parathyroid
o PVPC on or off thyroid surface and need for autotransplantation
Inferior parathyroid gland
o Location of the gland – whether it lies on the thyroid gland, thyrothymic tract or in an ectopic location
o Presence of decoy fat.
o PVPC on or off thyroid surface and need for autotransplantation
DATA ANALYSIS
All statistical analysis was done using Stata version 13.1.
o Descriptive statistics like frequencies, precntage and median were used to represent demographic and clinical variables
o Associations and correlations between demographic data, anatomical details and selected outcome were done using chi square test and pearson correlation test.
DATA ANALYSIS AND FINDINGS
There were 115 patients included in the study. Analysis was done with the help of the biostatistician.
DEMOGRAPHIC DETAILS AGE:
The median age was 44 years old, 19 being the youngest and 67 the oldest. There were 69 (60%) patients who were more than 40 years old.
Age Frequency Percentage
<30 22 19.1
30 - 40 24 21
40 - 50 35 30.4
>50 34 29.6
Table 2 Age
GENDER:
There was a female predominance overall, males 30 (26.1%) and females 85 (73.9%).
Figure 3 Gender
PATHOLOGY:
The majority of patients were diagnosed to have papillary thyroid carcinoma followed by nodular hyperplasia on histopathology. There was 1 patient with hurthle cell adenoma and 1 patient with poorly differentiated carcinoma. There was another patient with right lobe agenesis.
Figure 4 Pathology
26.1
73.9
0 10 20 30 40 50 60 70 80
male female
Gender (%)
BENIGN 51%
MALIGNANT 49%
PATHOLOGY
Figure 5 Pathology
TYPE OF OPERATION:
Out of 115 total thyroidectomies, 17 patients underwent central compartment node dissection, 11 patients underwent modified radical neck dissection (8 unilateral and 3 bilateral), 4 selective node dissection (3 unilateral and 1 bilateral).
45.2
2.6 0.9
34.8
6.1 6.1
0.9 2.6 0.9
Pathology(%)
76%
15%
9%
TYPE OF OPERATION
ONLY TT CCND MRND
PRIMARY OUTCOME -ANATOMICAL DETAILS
TUBERCLE OF ZUCKERKANDL:
The prevalence of TZ was 83.3% on the right and 77.4% on the left.
Grade 1 tubercles were the majority bilaterally. There were 44 (38.6%) and 47 (40.8%) patients with grade 1 tubercle on the right and left lobes respectively.
Figure 7 Grades of TZ
There were 40 (48.1%) tubercles on the right lobe and 27 (33.7%) tubercles on the left lobe involved by disease. 31 (77.5%) TZ on the right and 19 (70.3%) TZ on the left which were grade 3 was involved by disease and was statistically significant (p value <0.000).
16.7
38.6
29.8
14.9 22.6
40.9
23.5
13
0 5 10 15 20 25 30 35 40 45
0 1 2 3
Frequency of grades of TZ
right (%) left (%)
Figure 8 Grade 0 TZ
Figure 9 Grade 3 diseased TZ
Figure 10 Involvement of TZ by disease
Right Right involved by disease
Chi square
P value
TZ size Yes No
<10mm
>=10mm
9 29 16.8621 0.000*
43 66
Left Left involved by disease
Chi square
P value
TZ size Yes No
<10mm
>=10mm
8 41 17.1686 0.000*
19 12
Table 3 Involvement of TZ by disease
Also, the right TZ was significantly larger (p value <
0.001) and more likely to be involved by disease.
RIGHT LEFT
48.19 33.75
51.81
66.25
TZ involved by disease (%)
NO YES
Figure 11 Grade 2 TZ
Grade of TZ (Right)
Grade of TZ (Left) Chi square p value 0 & 1 2 & 3
0 & 1 49 14 11.55 0.001**
2 & 3 24 27
Table 4 Grade of TZ
RECURRENT LARYNGEAL NERVE:
The recurrent laryngeal nerve was found to be postero-medial to the tubercle of zuckerkandl in 84 (76.3%) patients on the right side and in 82 (75.9%) patients on the left side.
Figure 12 Relationship of TZ with RLN
18 (15%) patients had 1 branch on the right side and 19 (16.8%) patients had 1 branch on the left side. 12 (10%) patients had 2 branches bilaterally respectively.
Figure 13 Relationship of RLN to TZ
86.6 85.4
13.4 14.6 0
20 40 60 80 100
Right Left Right Left
Posteromedial Lateral
TZ relationship to RLN
Percentage
RLN lateral to TZ
Figure 14 Pattern of RLN branching
5(4.4%) and 8 (7.3%) patients had the right and left RLN going through the ligament of berry respectively. There was no non-recurrent laryngeal nerve in the study.
Figure 15 Relationship of RLN to LOB
1 2
18
12
19 12
RLN branching
Right Left
Left Right
92.66 95.54
7.34 4.46
RLN relationship to LOB
Super\icial Through
INFERIOR THYROID ARTERY (ITA) BRANCHING
The majority of patients had 2 ITA branches on both sides. 42 (39.6%) and 45 (43.2%) patients had 2 branches bilaterally respectively. The maximum number of branches found was 5 on the right side for a patient.
Figure 16 Number of ITA branches
With relation to the recurrent laryngeal nerve, the artery was superficial
bilaterally in the majority of the patients – 73 (65.7%) patients on the right and 78 (69.6%) patients on the left.
3
28
42
23
10 4 1
28
45
14 13
0 0 5 10 15 20 25 30 35 40 45 50
0 1 2 3 4 5
RIGHT LEFT
Figure 17 Relationship of ITA to RLN (%)
FREQUENCY OF VISUALISED PARATHYROID GLANDS:
The right and left superior parathyroids were visualized in 92 (81.4%) patients and 101 (88.6%) patients while the right and left inferior parathyroids were visualized in 73 (65.1%) patients and 61 (53.9%) patients respectively. The left superior parathyroid was visualized most frequently– 88.6%, and the left inferior the least to be visualized – 53.9%.
Figure 18 Visualisation of parathyroids (%)
NEW FINDINGS
PRESENCE OF DECOY FAT:
18.92 15.32
65.77
19.64 10.71
69.64
super\icial deep between branches
Relationship of ITA with RLN
left right
Right Left Right Left
Yes No
65.18 53.98 34.82 46.02
81.42 88.6
18.58 11.4
Visualized parathyroid
Inferior Superior
56 (62.9%) patients had decoy fat on the right side and 49 (50%) on the left.
Figure 19 Presence of Decoy fat (%)
LOCATION OF PARATHYROID VASCULAR PEDICLE COMPLEX:
The PVPC was situated off thyroid in the majority. The maximum number of PVPC “on thyroids” were on the right inferior parathyroid – 28 (38.8%). PVPV on the right superior parathyroid was 17 (18.8%) and left superior parathyroid was 15 (15.15%). The PVPC on thyroid for the left inferior parathyroid was 15 (24.5%)
Figure 20 PVPC on / off thyroid (%)
62.92 50
37.08 50
0 20 40 60 80
RIGHT LEFT
ABSENT PRESENT Presence of Decoy fat
Superior Inferior
Left Right Left
Off thyroid 15.15
81.11 84.85
24.59
61.11 75.41
PVPC - On / Off thyroid
Superior Inferior
SECONDARY OUTCOME – COMPLICATIONS AND RISK FACTORS
HYPOCALCEMIA AND ACUTE PARATHYROID INSUFFICIENCY There were a total of 13 (11.3%) patients who had hypocalcemia (S.Ca <8) and 33 (28.6%) patients with acute parathyroid insufficiency (PTH <
8) post total thyroidectomy.
The hypothesised risk factors for hypoparathyroidism were:
1. Visualisation of superior and inferior parathyroids
2. Location of superior parathyroid in relation to tubercle of zuckerkandl
3. Location of superior parathyroid in relation to superior pole of thyroid gland
4. Location of inferior parathyroid 5. Presence of decoy fat
6. Location of parathyroid vascular pedicle complex 7. Autotransplantation
8. Pre-op PTH
VISUALISATION OF PARATHYROIDS-
Out of the 13 patients who had hypocalcemia, all the 4 parathyroids were visualized in 5 patients, 3 parathyroids were visualized in 2 patients, 2 parathyroids in 2 patients and 1 parathyroid in 1 patient. There were no cases of hypocalcemia if the parathyroid was not visualized.
No. of parathyroids
identified
Post-op calcium Chi2
P value
<8 >8 Total
0 0 5 5 3.3132 0.507
1 1 4 5
2 5 24 29
3 2 34 36
4 13 99 37
Total 13 99 112
Table 5 Visualisation of parathyroids with relation to post-op hypocalcemia
Out of the 33 patients who had acute parathyroid insufficiency, all the 4
parathyroids were visualized in 16 patients, 3 parathyroids were visualized in 5 patients, 2 parathyroids in 10 patients and 1 parathyroid in 2 patient. In cases where none of the parathyroid was visualized, there was no parathyroid insufficiency, which was significant (p value 0.032).
No. of parathyroids
identified
Post-op PTH Chi2
P value
<8 >8 Total
0 0 5 5 10.5762 0.032
1 2 3 5
2 10 20 30
3 5 32 37
4 16 21 37
Total 33 81 114
Table 6 VIsualisation of parathyroids with relation to post-op PTH
Table 7 Individual visualisation of parathyroids
LOCATION OF SUPERIOR PARATHYROID WITH RELATION TO TZ- Majority of the superior parathyroid were superior to the tubercle of
zuckerkandl- 60 (72%) on the right and 60 (65%) on the left. There was no significant association of the location of the SP with relation to TZ and hypocalcemia or parathyroid insufficiency.
Post-op PTH <8 >8 Chi
square
P value Visualization of
parathyroid
Yes No Yes No
Superior Right identified 32 1 60 19 7.01 0.008
Left identified 28 5 72 8 0.61 0.435
Inferior Right identified 21 12 51 27 0.031 0.860
Left identified 20 13 40 39 0.930 0.335
Post-op Calcium <8 >8 Chi
square
P value Visualization of parathyroid Yes No Yes No
Superior Right identified 11 2 80 17 0.037 0.848
Left identified 12 1 86 12 0.230 0.631
Inferior Right identified 7 6 64 32 0.829 0.363
Left identified 7 6 52 45 0.000 0.987
Figure 21 Relationship of superior parathyroid with TZ
Figure 22 Parathyroid relation to TZ 19.2
8.43
72.2
24.1
9.8
65.9
Medial Lateral Superior
Parathyroid relation to TZ
Right Left
TZ Inferior parathyroid
Superior parathyroid
Post-op Calcium
<8 >8
Chi square P value Relationship of parathyroid to TZ
Right Medial 2 14
Lateral Superior
0 7
7 52
3.403 0.334
Left Medial 3 18
Lateral Superior
0 7
9 51
1.393 0.707
Post-op PTH
<8 >8 Chi square P value Relationship of parathyroid to TZ
Right Medial 7
1 22
9
1.881 Lateral
Superior
6 38
0.598
Left Medial Lateral Superior
5 2 18
17
1.255 7
41
0.740
Table 8 Relationship of parathyroid to TZ
LOCATION OF SUPERIOR PARATHYROID WITH RELATION TO SUPERIOR POLE OF THYROID –
The superior parathyroid was found posterior to the superior pole in the majority – 53.9% on the right and 51% on the left. There was no significant association of the location of the SP with superior pole and hypocalcemia or parathyroid insufficiency.
Post-op Calcium
<8 >8
Chi square P value Relationship of parathyroid to
superior pole
Right Medial 0 17
Lateral Posterior Superior
2 8 0
19 39 3
4.128 0.248
Left Medial 1 17
Lateral Posterior Superior
2 8 0
21 41 4
2.404 0.662
Post-op PTH
<8 >8 Chi square P value Relationship of parathyroid to
superior pole
Right Medial 5
8 16 0
12
0.325 Lateral
Posterior Superior
13 32 3
0.955
Left Medial Lateral Posterior Superior
4 4 17 0
15 20 32 4
4.381 0.357
Table 9 Relationship of parathyroid to superior pole
LOCATION OF INFERIOR PARATHYROID –
The right inferior parathyroid was situated on the gland in the right in 61%. The left inferior parathyroid was located on the gland in 48% and on the thyrothymic tract in 51% in the visualized glands. There were 2 ectopic located glands on the right. There was no significant association with location of
inferior parathyroid gland and hypocalcemia or parathyroid insufficiency.
Figure 23 Location of right inferior parathyroid
Figure 24 Location of left inferior parathyroid 36% 61%
3%
LOCATION OF RIGHT INFERIOR PARATHYROID
On The Gland Thyrothymic Tract Ectopic
48%
52%
LOCATION OF LEFT INFERIOR PARATHYROID
On The Gland Thyrothymic Tract
Post-op Calcium
<8 >8
Chi square P value Location of inferior parathyroid
Right On the gland 3 40
Thyrothymic tract Ectopic
4 0
21 2
1.659 0.436
Left On the gland 5 23
Thyrothymic tract 2 28 1.709 0.191
Post-op PTH
<8 >8 Chi square P value Location of inferior parathyroid
Right On the gland 12
8 1
31
0.476 Thyrothymic tract
Ectopic
18 1
0.788
Left On the gland Thyrothymic tract
8 12
20
0.675
19 0.411
Figure 25 Location of inferior parathyroid
PRESENCE OF DECOY FAT –
Decoy fat was present in 56 (62%) patients on the right and 49 patients (50%) on the left. There was no significant association with presence of decoy fat and hypocalcemia or parathyroid insufficiency.
Post Calcium <8 >8 Chi
square
P value Decoy fat Present Absent Present Absent
Right Left
4 6 51 27 2.437 0.119
6 5 42 42 0.080 0.777
Post PTH <8 >8 Chi
square
P value Decoy fat Present Absent Present Absent
Right 20 11 36 22 0.052 0.820
Left 15 12 34 36 0.380 0.537
Table 10 Presence of decoy fat
PARATHYROID VASCULAR PEDICLE COMPLEX ON / OFF THYROID- There was a significant association (p value 0.02) of left PVPC being on thyroid in the left inferior parathyroid and hypocalcemia. There was also a significant association (p value 0.01) of right PVPC being on thyroid in the right superior parathyroid and acute parathyroid insufficiency.
RIGHT SUPERIOR
PVPC POST-OP
CALCIUM
Chi2
P value
<8 >8 Total
ON THYROID 3 13 16 0.7354 0.391
OFF THYROID 8 78 73
TOTAL 11 78 89
Table 11 Right superior PVPC vs Post-op calcium
Table 12 Left superior PVPC vs Post-op calcium
LEFT SUPERIOR
PVPC POST-OP
CALCIUM
Chi2
P value
<8 >8 Total
ON THYROID 2 13 15 0.0113 0.915
OFF THYROID 10 71 81
TOTAL 12 84 96
Table 13 Right inferior PVPC vs Post-op calcium
Table 14 Left inferior PVPC vs Post-op calcium
Table 15 Right Superior PVPC vs Post op PTH
RIGHT INFERIOR
PVPC POST-OP
CALCIUM Chi2
P value
<8 >8 Total
ON THYROID 2 26 28 0.4233 0.515
OFF THYROID 5 37 42
TOTAL 7 63 70
LEFT INFERIOR
PVPC POST-OP
CALCIUM
Chi2
P value
<8 >8 Total
ON THYROID 4 10 14 4.8997 0.027
OFF THYROID 3 42 45
TOTAL 7 52 59
RIGHT SUPERIOR PVPC
POST-OP PTH
Chi2
P value
<8 >8 Total
ON THYROID 10 9 17 5.5166 0.019
OFF THYROID 21 52 73
TOTAL 31 59 90
Table 16 Left superior PVPC vs Post op PTH
Table 17 Right inferior PVPC vs Post op PTH
LEFT SUPERIOR PVPC
POST-OP PTH
Chi2
P value
<8 >8 Total
ON THYROID 7 8 15 3.2423 0.072
OFF THYROID 20 63 83
TOTAL 27 71 98
RIGHT INFERIOR PVPC
POST-OP PTH
Chi2
P value
<8 >8 Total
ON THYROID 11 17 28 2.0920 0.148
OFF THYROID 10 33 43
TOTAL 21 50 71
