Abstract
Background
Optimal fixation for Herscovici type B and type C medial malleolar fractures because of debated due to differences in fragment size and loading conditions.Purpose
This study introduces the theoretical concept of Internal Fixation Bone Mass Index (IFBM) and compares three fixation methods under multidirectional loading.Study design
Biomechanical study using Synbone® artificial tibia models.Methods
Synbone® tibia models simulated type B (small fragment, n=27) and type C (large fragment, n=27) fractures. Three fixation methods-cannulated screws (CS, 4.0 mm), fully threaded cancellous screws (FTCS, 4.0 mm), and Kirschner wires (KW, 1.5 mm)-were tested under axial, transverse, and traction loading using an Instron® 5969 machine. IFBM was defined as A_implant/A_bone.Results
For type B fractures, KW showed a higher 2 mm displacement load under traction than CS (65 ± 11 N vs. 31 ± 9 N; post-hoc p = 0.008) and FTCS (65 ± 11 N vs. 36 ± 12 N; post-hoc p = 0.012), with no statistically significant difference under axial and transverse loading (ANOVA p = 0.231 and p = 0.501). For type C fractures, CS and FTCS showed higher stability than KW under transverse and traction loading (ANOVA p = 0.004 and p = 0.003); no statistically significant difference was detected under axial loading (ANOVA p = 0.167).Conclusions
Fixation performance differed by fracture type. KW showed favorable performance for type B fractures, whereas screw fixation (CS or FTCS) demonstrated superior performance for type C fractures. IFBM is a theoretical metric that requires clinical validation.