Short, thick neck phenotype as an anatomical determinant of thyroidectomy complexity: A prospective single-center observational study

Background: Neck configuration is a key determinant of thyroidectomy difficulty, yet it lacks a simple, reproducible definition for research, risk stratification, and operative planning. A short, thick neck is intuitively associated with limited exposure and longer operative times, but evidence has been largely anecdotal. Methods: In a prospective single-center observational cohort, 843 consecutive adults undergoing primary total thyroidectomy (2019–2024) had preoperative neck phenotype assessed by anesthetists using neck circumference (NC) and cervicomental height (CMH). A Difficult Neck Phenotype Index (DNPI = NC/CMH) was derived. Associations with operative time, exposure maneuvers, Thyroidectomy Difficulty Scale (TDS), and postoperative complications were examined using multivariable models adjusting for BMI, thyroid volume, Graves' disease, malignancy, and retrosternal extension. Results: Mean NC, CMH, and DNPI were 372 ± 41 mm, 200 ± 27 mm, and 3.88 ± 0.67, respectively. Higher DNPI correlated with longer operative time (Spearman ρ = 0.41, p < 0.001) and increased use of exposure maneuvers (partial strap division, long retractors, lateral incision extension), as well as greater blood loss and drain placement, independent of clinical confounders. An exploratory DNPI cut-off of 4.1 was associated with operative time > 75th percentile with an AUC of 0.78 (95% CI 0.71–0.84), sensitivity 76.3%, and specificity 68.5%. Postoperative morbidity was low, and DNPI was not an independent predictor of RLN injury, hypocalcemia, cervical hematoma, or wound complications. Conclusions: DNPI is an exploratory, internally derived morphometric marker that operationalizes neck phenotype and was independently associated with intraoperative complexity in total thyroidectomy. In a high-volume specialist setting, difficult neck phenotype was associated with greater technical demand and resource use without a detectable increase in short-term morbidity, although power for rare events was limited. External, validation across populations, techniques, and institutional volumes is warranted.