Skin-crease Thyroidectomy
Condition: Thyroid Nodule
MeSH terms: Thyroid Nodule
Study type: Observational

Summary: 
      We performed a retrospective observational-analytic study. Anatomical measurements were
      performed on 118 participants during an ultrasound exam, and demographic data was collected
      from their medical files. The data was stratified according to age, sex, patient's body mass
      index (BMI), and height.
    

Detailed description: 
      Approval - Ethical Considerations The study was approved by the Institutional Review Board
      (NHR-014417). Study Design In this retrospective observational-analytic study we analyzed the
      anatomical relation between the cricoid cartilage, thyroid gland isthmus, and the superficial
      second neck crease. We reviewed patient data from between November 2016 and August 2018. The
      data was collected during ultrasound exams of 118 subjects who underwent assessment of the
      thyroid gland. Patients who had any neck surgical procedure prior to the test, patients with
      abnormalities in the anterior neck, and patients without clear second crease were excluded.

      During the examination, patients were lying supine with their head in mild extension, in the
      same manner that is practiced during a thyroidectomy. The assessment and collection of data
      was performed by the senior author (OR) who routinely performs both this preoperative
      examination and thyroid surgeries in the medical center. The precise location of the cricoid
      cartilage and the thyroid isthmus was determined using ultrasound. The main parameters were
      the distances between the thyroid isthmus superior border and the second neck crease, and the
      distance between the cricoid cartilage superior border and the second neck crease. These were
      measured with a ruler with ultrasound imaging guidance (Figure 1).

      Several neck creases can be observed in normal adults. The first upper crease runs
      horizontally roughly along the thyroid notch and hyoid bone. A second lower neck crease runs
      parallel to it approximately at the height of the cricoid and this is the crease the
      measurements in our study relate to. Occasionally there is a third prominent skin crease
      around 2-3 finger breadths above the clavicle. Other less prominent horizontal neck creases
      can be present.

      Demographic variables, such as age, sex, BMI, and height, were collected from medical records
      and used for result stratification either as continuous variables or divided into sub-groups
      according to accepted divisions.

      Sample size calculation The hypothesis was that the second neck crease is superficial to the
      thyroid gland isthmus superior border (0 cm horizontal distance). A vertical distance of 0.5
      cm and more was considered significant difference in the location.

      Statistical analysis Distance between the thyroid isthmus or the cricoid cartilage and the
      second neck crease were described by means, standard deviation, and range. Age, sex, BMI, and
      height were analyzed as quantitative variables with the measures mentioned above. The
      continuous variants were also grouped for a clearer presentation of the results. The BMI
      variant was categorized into accepted ranges: underweight (below 18.5 kg/m2), normal weight
      (18.5 to 25 kg/m2), overweight (25 to 30 kg/m2), and obese (over 30 kg/m2). BMI sub-groups
      and sex variables were described by frequencies and percentages.

      The distances were compared among sub-groups using ANOVA, Kruskal-Wallis test, Independent
      sample t-test, and Wilcoxon rank sum test. The choice between those tests was according to
      the number of sub-groups, the group's sample size, and the distribution of the data in each
      sub-group.

      A correlation between age, BMI, height, and the distance was tested by Pearson's correlation
      coefficient test or Spearman's correlation coefficient test. The choice between those tests
      was according to the sample size and the score's distribution. If the variable was defined as
      ordinal sub-groups, Spearman's correlation coefficient test was used.
    

Intervention name(s): Ultrasound of the Neck
Intervention type(s): Diagnostic Test
Intervention description(s): Anatomical measurements were performed on participants during an ultrasound exam
Observational model: Case-Only
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        The data was collected during ultrasound exams of subjects who underwent assessment of the
        thyroid gland.