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Reasons for failure of plate osteosynthesis: Not uncommonly, the management of plate fixation failure can pose a challenge for the surgeon. Therefore it is first necessary to recognize the underlying reason and to address it in the context of a correct therapy strategy. Peri-implant fractures at the end of the plate, screw breakage or loosening as well as plate breakage at the site of the initial fracture line can lead to failure of the plate fixation construct. Commonly, a secondary fracture at the end of the plate is caused by an adequate force impact in mostly younger male patients in an employable age. On the other hand, in geriatric patients brittle fractures due to a low impact in inadequate accidents are seen at an increasing rate resulting from a generalized fragility of osteoporotic bone. However, in most cases the mechanical failure of plate osteosynthesis is the result of plate breakage or screw loosening based on a delayed bone fracture union. Therapy: Numerous options for internal fixation are available to readdress the instability, ranging from additional plating through intramedullary nailing to conversion to endoprosthetic arthroplasty at an appropriate fracture location near a joint. The choice of treatment should depend on the type of plate failure as well as the individual bone quality. In cases of delayed fracture union, the surgical treatment should imperatively focus on measures to support fracture healing. [ABSTRACT FROM AUTHOR]

Introduction: Sacroiliac (SI) screws are used for osteosynthesis in unstable posterior pelvic ring injuries. In the cases of 'sacral dysplasia', in which the elevated upper sacrum does not allow a secure SI screw insertion into the S1 level, the S2 segment must be used to achieve stable fixation. The bone quality of the S2 segment is thinner compared to that of the S1 vertebra and may cause biomechanical weakness. An additional SI screw insertion into the S3 level may improve stability. With respect to the anatomical conditions of the posterior pelvic ring, there have been no anatomical investigations to date regarding SI screw placement into the third sacral segment. Materials and methods: CT raw datasets from 125 patients (ø59 years, ø172 cm, ø76 kg) were post-processed using Amira 5.2 software to generate 3D pelvic models. A program code implemented in C++ computed a transverse bone corridor for the first, second and third sacral segments for a typical SI screw diameter of 7.3 mm. Volume, sagittal cross-section, iliac entrance area and length of the determined screw corridors were measured. A confidence interval of 95 % was assumed ( p < 0.05). Results: The fully automatic computation revealed a possible transverse insertion for one 7.3-mm screw in the third sacral segment in 30 cases (24 %). The rate (60 %) of feasible S3 screw placements in the cases of sacral dysplasia ( n = 25) is significantly higher compared to that (15 %) of 'normal' sacra ( n = 100). With regard to the existence of transverse iliosacroiliac corridors as a function of sacral position in between the adjacent iliac bone bilaterally, a new classification of three different shape conditions can be made: caudad, intermediate minor, intermediate major, and cephalad sacrum. Gender, age, body height and body weight had no statistically significant influence on either possible screw insertion or on the calculated data of the corridors ( p > 0.05). Conclusion: SI screw insertion into the third sacral level deserves discussion in the cases of sacral dysplasia. Biomechanical and practical utility must be verified. [ABSTRACT FROM AUTHOR]