Correlations of skeletal anomalies of the lower limbs and the mandibular ramus lengths
Authors: Vasilyeva Maria , Perevezentsev Grigory 
Published: August 2024

Introduction: The musculoskeletal system of the human body and its anatomical units closely interact with each other. Despite the emergence of modern diagnostic methods in medicine, in particular in dentistry, the acceptance by doctors of the fact that patients are indicated for diagnosis of systemic disorders of the musculoskeletal system is mostly denied. Before proceeding with radical treatment, occlusal and postural disorders should be taken into account as the main etiological factors of TMJ dysfunction.
Purpose: To study correlations between developmental anomalies of the mandibular ramuses and differential lower limb lengths in adult patients.
Materials and methods: 136 patients with facial asymmetry and TMJ problems were diagnosed, and the correlation between the mandible ramus lengths and the parameters of the lower limbs and pelvis was analyzed. The following were used for diagnosis: radiography of the lower limbs, computerized optical assessment of posture topography using the DIERS Formetric 4D motion complex, cone-beam computed tomography (CBCT) of the joints.
Results: According to the radiologist's report of 136 patients in the study group, anatomical shortening of one lower limb (ALLD - anatomical leg length discrepancy) was detected in 83 patients, which amounted to 61%. Of these, 31 (37.3%) patients had anatomical shortening of the right extremity, and in 52 (62.7%) cases the left extremity was shorter than the right one. According to the results of CBCT assessment of the patients, 89 patients showed predominance of the length of the left mandibular ramus, and 47 patients showed an increase in the length of the right ramus. Based on the results of quantitative evaluation of digital CBCT sections of the mandibular ramuses in patients of the study group, it was revealed that in 54 (65.1%) patients the left mandibular ramus was shorter than the right one, and in 29 (34.9%) cases the right mandibular ramus was shorter than the left one. According to the results of the postural DIERS Formetric analysis of all patients with ALLD, torsion and rotation of the pelvis were slightly expressed (from 0 to 2°), which confirms the representativeness of the sample. 31 (37.3%) patients had left pelvic tilt, and 52 (62.7%) had right pelvic tilt; this data correlates with X-ray findings.
According to the results, shortening of the mandibular ramus and ALLD were observed on the same side of the body in 96.4% of cases. The remaining 3.6% of cases of the correlation discrepancy are related to the secondary acquired pathologies, injuries, and surgeries of the lower limbs.
Conclusion: Based on the methods of modern evidence-based medicine, assessment of occlusal-postural disorders, we can conclude that there is a direct correlation between the lengths of the mandibular ramuses as well as the lower limb lengths in cases of anatomical differences in the length of the lower limbs. We conclude that shortening of the mandibular ramus and ALLD are observed on the same side of the body in most cases. This is due to the translation of the head towards to the long leg in order to maintain the vertical position and the static-dynamic balance of the body. We would like to note separately that the minimum parameters of pelvic torsion and rotation, as well as the pronounced values of the pelvic tilt (skew), directly determine the presence of anatomical shortening of the lower limb. The greater the pelvic tilt, the more pronounced are the deformities of the TMJ condyles and the shortening of one mandibular ramus.