Biomechanical evaluation of interfragmentary compression at tibia plateau fractures in vitro using different fixation...

Reliable osteosynthesis of intraarticular fractures depends on lasting interfragmentary compression. Its amount differs in the applied fixation method. The interfragmentary compression of cancellous and cortical lag screws and angle stable locking plates was quantified in an osteoporotic and non-osteoporotic synthetic human bone model.A split fracture of the lateral tibia plateau (AO/OTA type 41-B1.1) was mimicked by an osteotomy in right adult synthetic human tibiae with hard or soft cancellous bone. Specimens were fixed with either two 6.5 mm cancellous, four 3.5 mm cortical lag screws, or 3.5 mm LCP proximal lateral tibia plate preliminary compresed by a reduction clamp (n = 5 per group). A pressure sensor film was used to register the interfragmentary compression. One-way analysis of variance (ANOVA) with Bonferroni post hoc correction was performed for statistical analysis (p < 0.05).Interfragmentary compression under reduction clamp was 0.59 ± 0.12 MPa in the non-osteoporotic and 0.55 ± 0.14 MPa in the osteoporotic group. The locking plate itself maintained the compression in non-osteoporotic (0.53 ± 0.11 MPa) and osteoporotic bone (0.50 ± 0.14 MPa). Four 3.5 mm cortical lag screws provided a compression of 1.69 ± 0.65 MPa in non-osteoporotic bone, being not significantly different to the osteoporotic bone group (1.43 ± 0.47 MPa, P = 1.0). Two 6.5 mm cancellous lag screws showed a significantly higher compression in non-osteoporotic (2.1 ± 0.59 MPa) compared to osteoporotic (0.77 ± 0.21 MPa, P < 0.01) bone.Angle stable locking plates maintained the compression preliminarily applied by a reduction clamp. Two 6.5 mm cancellous lag screws are especially suited for non-osteoporotic bone, whereas four 3.5 mm cortical screws exhibited comparable compression in both bone qualities.