BACKGROUND: In trauma surgery osteosynthesis aims on early mobilisation of the patient with quick reintegration to work, school and family. However, fracture fixation devices made of conventional titanium as well as of bioabsorbable poly-mers have several drawbacks in clinical practice. The former are associated with stress shielding phenomenons and have to be removed frequently (especially in paediatric trauma surgery), whereas the latter may cause adverse tissue reactions and exhibit limited mechanical properties. Therefore, we evaluated a newly devel-oped implant made of a magnesium alloy (Mg implants) which is supposed to combine excellent strength retention properties of metallic implants with biode-gradability of polymers. METHODS: In this comparative study, three different types of uncoated smooth cylindrical implants were used: novel Mg pins, new poly(lactic-co-glycolic acid) (PLGA) implants and conventional commercially pure titanium pins. All implants were placed transcortically in the middiaphysis of the femoral bone of 108 Spra-gue-Dawley rats. Pushout testing, microfocus computed tomography, fluorescent labelling, lightmicroscopic and exemplary scanning electron microscopic examination of the tested implants were performed after an implantation period of 1, 3 as well as 6 months to assess osseointegration. RESULTS: Pushout testing yielded highly significantly greater median maximum push out forces as well as ultimate shear strengths in Mg implants than in titanium and PLGA pins after each implantation period. Moreover, microfocus computed tomography revealed significantly higher mean bone-implant contact area in Mg implants than in titanium implants after 1 and 6 months of implantation and than in PLGA implants after 1 month. In addition, no local or systemic inflammatory reactions were observed in any of the investigated implant types. CONCLUSION: This study indicates that these novel biodegradable Mg implants are superior to new bioabsorbable PLGA and even to titanium pins with respect to both osseointegration and bone-implant interface biomechanics and thus may improve primary stability and advance fracture fixation.
Biomechanical and Radiological Evaluation of the Bone-Implant Interface of New Biodegradable Implants in Comparison to Conventional Titanium Pins - Findings in a Transcortical Rat Model
Lindtner, R. (Author). 2011
Student thesis: Diploma thesis