From Morphology to Mechanics: Quantitative Evidence of Glenoid Fossa Depth Variation Shaping the Traumatic Response of the Mandibular Condyle.

OBJECTIVE: The depth of glenoid fossa is a critical anatomical determinant of how the mandibular condyle responds to traumatic force. However, its precise quantitative influence on condylar strain and displacement remains poorly defined. This study aimed to quantify the dose-response relationship between glenoid fossa depth and the biomechanical behavior of the mandibular condyle under traumatic loading. METHODS: An integrated approach was employed combining experimental mechanics via Digital Image Correlation (DIC) and personalized three-dimensional Finite Element Analysis (FEA). DIC was used to assess nine human mandibular specimens under a standardized 600 N axial load applied to the chin, following simulation of three glenoid fossa depths (7, 8.5, and 10 mm) using autopolymerizing resin. Real-time, full-field strain and displacement data on the condylar neck were captured using DIC. In parallel, personalized finite element models were constructed based on CBCT scans from 22 patients to correlate their individual fossa depth with the simulated condylar mechanical response. RESULTS: Both experimental and computational analyses demonstrated that increased glenoid fossa depth consistently reduced biomechanical strain and displacement at the condylar neck. DIC testing demonstrated that deepening the fossa from 7mm to 10 mm significantly decreased mean principal strain from 757.7 ± 113.0 to 355.3 ± 91.3 μm/m (P < 0.001) and coronal plane displacement from 0.159 ± 0.016 to 0.063 ± 0.016 mm (P < 0.001). This finding was corroborated by the FEA of the patient cohort, which revealed a strong, significant negative correlations between natural fossa depth and condylar neck strain (r = -0.68) and displacement (r = -0.76). CONCLUSION: Glenoid fossa depth is a key modulator of the mandibular condyle's response to traumatic loading. A deeper fossa enhanced osseous containment, which effectively disperses traumatic load, mitigates stress concentration and displacement at the condylar neck, and consequently, may lower the risk of fracture. These findings provide a quantitative biomechanical basis for using glenoid fossa depth as a potential imaging biomarker for fracture risk assessment. CLINICAL SIGNIFICANCE: This finding provides quantitative biomechanical evidence for understanding individual differences in condylar fractures, suggests fossa depth as a potential risk assessment indicator, and offers theoretical support for relevant clinical decision-making.