STAGING AS A SURGICAL PREDICTOR: T3 VERSUS T4A ORAL SQUAMOUS CELL CARCINOMA AND ITS DETERMINANTS FOR NECK DISSECTION EXTENT AND SHOULDER RANGE OF MOTION

Abstract

Background: The primary tumour (T) stage in oral squamous cell carcinoma (OSCC), classified per the American Joint Committee on Cancer (AJCC) TNM 8th edition, governs the extent of surgical resection and neck dissection and is a key determinant of postoperative shoulder morbidity. The transition from T3 to T4a represents a surgically and functionally decisive threshold, yet its differential effect on shoulder range of motion (ROM) across all seven motion planes has not been systematically characterised. Objectives: To compare shoulder ROM across seven domains — flexion, extension, abduction, horizontal abduction, horizontal adduction, internal rotation, and external rotation — between T3 and T4a OSCC patients undergoing neck dissection, and to contextualise these findings within the published literature on spinal accessory nerve (SAN) morbidity and neck dissection extent. Materials and Methods: A prospective observational study was conducted on 9 OSCC patients — 3 with T3 disease (33.3%) and 6 with T4a disease (66.7%) — staged according to AJCC 8th edition TNM classification. Shoulder ROM was measured using standardised goniometry across seven planes preoperatively and at postoperative days 1, 2, 3, 10, and 30. Between-group comparisons were performed using one-way ANOVA (F-test), with statistical significance defined as p<0.05. Results: T4a patients recorded higher pre-operative baseline ROM values across all seven domains. Statistically significant between-group differences were observed in: extension (day 10, p=0.049; day 30, p=0.007), horizontal abduction (day 10, p=0.000), horizontal adduction (day 1, p=0.012; day 10, p=0.000), internal rotation (pre-op, p=0.036; day 3, p=0.000; day 30, p=0.000), and external rotation (days 1–10; p=0.003–0.044). Contrary to expectation, T3 patients demonstrated worse absolute post-operative ROM, attributable to lower pre-operative baselines. Conclusion: T stage in OSCC represents a surgically and functionally decisive threshold of post-operative shoulder ROM trajectories. The paradoxical finding of greater absolute ROM deficits in T3 patients reflects pre-operative baseline differences, underscoring the importance of baseline-adjusted longitudinal analysis. Six mechanistic pathways explain T4a's theoretical predisposition to greater morbidity. Early structured rehabilitation targeting all seven ROM planes is mandatory for both stages. A larger prospective cohort is required to establish definitive T-stage-specific ROM norms.