The aim of this study was to quantify the contribution of contralateral coronoidectomy to intraoperative mouth opening in patients with severe unilateral temporomandibular joint (TMJ) ankylosis by measuring the incremental gain achieved after each surgical step. Seven consecutive patients (six Sawhney type IV and one type III) underwent gap arthroplasty followed sequentially by ipsilateral and contralateral coronoidectomy.

Mouth opening was measured intraoperatively after each surgical step and at 1-year follow-up. Statistical analysis was performed using the Friedman test for repeated measures and the Wilcoxon signed-rank test for paired comparisons.

Median preoperative mouth opening was 0 mm (IQR 0–0), increasing to 20 mm (IQR 5–22) after gap arthroplasty, 28 mm (IQR 25–30) after ipsilateral coronoidectomy, and 45 mm (IQR 40–46) after contralateral coronoidectomy. Overall differences between surgical stages were significant (p < 0.001). Contralateral coronoidectomy provided a median additional gain of 17 mm (p = 0.022), with further improvement observed in every patient.

At 1-year follow-up, median mouth opening was 43 mm (IQR 42–45), with no recurrence or major complications. These findings provide quantitative evidence supporting the contribution of contralateral coronoidectomy to achieving functional mouth opening during the surgical management of severe unilateral TMJ ankylosis.