Hard and soft tissue changes and long-term stability after vertical height reduction genioplasty using biodegradable fixation

The aim of this work was to analyse the stability of vertical height reduction genioplasty using biodegradable material, as well as to determine vertical changes of hard and soft tissues during this procedure. Forty patients underwent vertical height reduction genioplasty using two types of biodegradable fixation (Biosorb FX^® or OSTEOTRANS-MX^®), combined with mandibular setback surgery. We assessed lateral cephalographs over time (pre-operation; immediately post-operation; 3 months, 6 months and 12 months post-operation). We found a mean vertical difference of 0.22 mm (standard deviation (SD) = 0.49 mm) at the menton point immediately post-operation, compared with 12 months post-operation. And there was no statistical significance(P > 0.05). The chin hard tissue remained stable from the immediate post-operation period to 1 year post-operation, and the chin soft tissue remained stable from 3 months to 1 year post-operation. The regression equation describing the replacement of hard tissue with soft tissue change, between pre-operation and 12 months post-operation is y = 0.590x + 0.885 (R² = 0.300, P < 0.001). We confirm that the use of biodegradable fixation is a stable method, in terms of skeletal tissues, and a relatively stable method, in terms of soft tissues. In vertical height reduction genioplasty, soft tissue does not reflect 100% of the vertical tissue reduction in hard tissues. This data may influence establishment of surgical treatment objectives.