CBCT-Based measurement of lateral pterygoid muscle length in TMJ dysfunction

The lateral pterygoid muscle (LPM) plays a pivotal role in maintaining the stability of the temporomandibular joint (TMJ), especially the articular disc. A considerable number of patients afflicted with TMJ dysfunction may also experience LPM spasms, which can be challenging to discern through direct clinical examination. The objective of this study was to evaluate LPM length by measuring the distance between the origin and insertion points of the LPM with CBCT slices, a novel approach in the literature. The study encompassed a total of 498 TMJs and LPMs from 249 patients, including 59 males and 190 females. LPM lengths were measured on CBCT slices between the lateral pterygoid plate and fovea pterygoidea. Additionally TMJ movements were evaluated on conventional TMJ radiographs taken with the mouth open and closed. In all TMJs, the LPM length was found to be greater in males than in females (p < 0.0001). LPM length exhibited a significant increase in hypermobile joints, while it demonstrated a decrease in normal and hypomobile joints. In individuals with unilateral hypomobility, the LPM length on the hypomobile side was lower than the contralateral side (p < 0.05). While the muscle itself cannot be visually identified using CBCT due to its obscurity, the origins and insertions of the muscle can be clearly delineated. This allows for the measurement of distances between these points, thereby providing insight into the length of the muscle. The reduced length of the LPM in cases of hypomobile TMJs suggests the presence of LPM spasm. The study was conducted retrospectively on CBCT slices of individuals with TMJ dysfunction. No clinical interventions were performed on human participants within the scope of the study.