Histometric and histological analysis of bone to screw contact between metallic and absorbable 2.0 fixation system: a pilot study in dogs

The use of internal fixation systems (IFS) to treat fractures and osteotomies in the facial skeleton is well described at literature, however this is the first study to approach differences between buccal and lingual cortical sides for bone to screw contact. The purpose of the present study was to compare by a histological and histometric analysis, the bone to screw contact and histological interface of both absorbable and metallic systems. Twelve mongrel male dogs were subjected to unilateral osteotomy and divided into two groups (absorbable and metallic). Bone fragments were stabilized with two 4-hole plates with semi-rigid fixation. At 2 and 18 weeks, three dogs were killed and plates place were removed with each screw type been analyzed (monocortical and bicortical). Histometric analysis showed the following statistical significant differences for total bone to screw contact: monocortical absorbable experimental 2 weeks group (0.00%; 0-0.036) versus monocortical metallic experimental 2 weeks group (33.30%; 0.252-0.435), p = 0.0002, U = 4; monocortical absorbable experimental 18 weeks group (0.00%; 0-0) versus monocortical metallic experimental 18 weeks group (14.50%; 0.077-0.233), p = 0.0009, U = 14; monocortical absorbable control 18 weeks group (0.00%; 0-0) versus monocortical metallic control 18 weeks group (30.53%; 0.270-0.360), p = 0.0039, U = 0; monocortical metallic experimental side 2 weeks group (33.30%; 0.252-0.435) versus monocortical metallic experimental side 18 weeks group (14.50%; 0.077-0.233), p = 0.0042, d.f. = 1, F = 10.2121; bicortical absorbable experimental 18 weeks group (6.42%; 0.033-0.109) versus bicortical metallic experimental 18 weeks group (14.87%; 0.080-0.202), p = 0.0357, d.f. = 1, F = 5.0722; and bicortical absorbable control 2 weeks group (7.09%; 0.054-0.082) versus bicortical metallic control 2 weeks group (14.49%; 0.139-0.153), p = 0.0009, d.f. = 1, F = 21.3660. It is concluded that Inion system did not promote osteolysis at distance from plate to screw union, however this can implicates a higher permanency time in bone (AU)