Forearm versus sternocleidomastoid parathyroid autotransplantation after total thyroidectomy with central neck dissection: a prospective randomized trial

Parathyroid autotransplantation is used when a parathyroid gland cannot be preserved in situ during thyroidectomy. The sternocleidomastoid muscle (SCM) is commonly used because it is accessible within the cervical operative field, whereas the forearm brachioradialis muscle (FA) provides an anatomically separate recipient site. Whether recipient-site selection is associated with differences in early postoperative systemic parathyroid function remains uncertain. In this prospective randomized controlled trial, 60 patients with papillary thyroid carcinoma requiring single-gland parathyroid autotransplantation were assigned to SCM or FA implantation (n = 30 per group). Systemic serum parathyroid hormone (PTH) was measured preoperatively and on postoperative days 1 (POD1) and 7 (POD7), and at 1, 3, and 6 months. Outcomes included POD1 systemic PTH, time to the first observed systemic PTH concentration ≥ 15 pg/mL, longitudinal PTH trajectories, hypocalcemic symptoms, pain, and graft-site complications. Mean POD1 PTH was higher in the FA group than in the SCM group, but the between-group difference was not statistically significant (21.53 vs. 13.74 pg/mL; P = 0.073). PTH concentrations were significantly higher in the FA group at POD7, 1 month, and 3 months (all P < 0.05), with no significant difference at 6 months. The median time to the first observed systemic PTH concentration ≥ 15 pg/mL was shorter in the FA group (log-rank P = 0.0017). Symptomatic hypocalcemia occurred in 2 of 30 patients (6.7%) in the FA group and 7 of 30 (23.3%) in the SCM group (P = 0.145). In exploratory analyses, POD1 systemic PTH was inversely correlated with age and positive central lymph node count in the SCM group but not in the FA group. FA allocation was associated with lower odds of POD1 PTH ≤ 14 pg/mL in an exploratory adjusted model (adjusted OR = 0.14, 95% CI 0.04–0.54; P = 0.005). Pain scores and graft-site complications were similar between groups. Forearm autotransplantation was associated with higher systemic PTH at POD7, 1 month, and 3 months and with earlier first observed attainment of systemic PTH ≥ 15 pg/mL in an exploratory analysis, whereas the POD1 difference was not statistically significant and 6-month biochemical outcomes were similar. Because systemic PTH reflects secretion from both preserved in situ glands and transplanted tissue, these findings do not establish graft-specific function or a recipient-site mechanism. Forearm implantation may be a feasible alternative to SCM implantation, but the findings require confirmation in larger studies with graft-specific measurements. Trial registration Chinese Clinical Trial Registry (ChiCTR2600128387; https://www.chictr.org.cn/ ). Registered on 20 July 2026. Retrospectively registered.