Biodegradable and titanium osteosynthesis in maxillofacial surgery: in vitro and in vivo performances

Osteosynthesis systems, which consist of plates and screws, are applied to fixate bone segments in maxillofacial trauma and orthognathic surgery. Titanium osteosynthesis systems are currently widely used and accepted as the gold standard. However, their disadvantages include – among others – temperature sensitivity, tactile sensation of plates and screws, possible growth restrictions of the underlying bone, hampering of radiological imaging and radiotherapy, and accumulation of titanium particles in the surrounding tissues and different organs with potential mutagenicity. Biodegradable plates and screws may reduce removal rates in a second operation, while also avoiding most of the aforementioned disadvantages of titanium osteosyntheses. Biodegradable systems have, however, their own limitations including limited mechanical properties, palpability due to bulkiness, and possible foreign body reactions. To guide the evidence-based selection of osteosynthesis systems, the research described in this thesis aimed to compare the in vitro and in vivo performances of different biodegradable osteosynthesis systems as well as to compare the (clinical) performance of biodegradable and titanium osteosynthesis systems. It was concluded that biodegradable osteosyntheses are a viable alternative to titanium osteosyntheses when applied to treat maxillofacial trauma, with similar efficacy and significantly lower symptomatic osteosynthesis removal, but with higher perioperative screw breakage. For orthognathic surgery, biodegradable osteosynthesis also is a valid alternative to titanium osteosynthesis, but with longer operation times. It was shown that the biodegradable SonicWeld 2.1 mm system (poly[D,L-lactic acid]) had the most predictable degradation profile compared to other commonly used biodegradable systems. Furthermore, the SonicWeld 2.1 mm biodegradable systems had the most favourable mechanical properties for midface fracture fixation and osteotomies, and the Inion CPS 2.5 mm biodegradable system (poly[L-co-D,L-lactic acid-co-trimethylene carbonate]) for mandibular fractures and osteotomies. Finally, it was shown that the residents’ accuracy and reliability in applying torque to titanium osteosynthesis 1.5 mm screws were insufficient, but that both accuracy and reliability could be improved using a simple preclinical training model. These findings provide new insights into the biocompatibility, and biomechanical and degradation properties of (biodegradable) osteosynthesis systems that can be used for evidence-based selection and usage of such systems in maxillofacial surgery as well as to provide leads for future research.