IntroductionAdequate migration and differentiation of mesenchymal stem cells is essential for regeneration of large bone defects. To achieve this, modern graft materials are becoming increasingly important. Among them, electrospun nanofiber scaffolds are a promising approach, because of their high physical porosity and potential to mimic the extracellular matrix (ECM).Materials and MethodsThe objective of the present study was to examine the impact of electrospun PLLA nanofiber scaffolds on bone formation in vivo, using a critical size rat calvarial defect model. In addition we analyzed whether direct incorporation of bone morphogenetic protein 2 (BMP-2) into nanofibers could enhance the osteoinductivity of the scaffolds. Two critical size calvarial defects (5 mm) were created in the parietal bones of adult male Sprague-Dawley rats. Defects were either (1) left unfilled, or treated with (2) bovine spongiosa, (3) PLLA scaffolds alone or (4) PLLA/BMP-2 scaffolds. Cranial CT-scans were taken at fixed intervals in vivo. Specimens obtained after euthanasia were processed for histology, histomorphometry and immunostaining (Osteocalcin, BMP-2 and Smad5).ResultsPLLA scaffolds were well colonized with cells after implantation, but only showed marginal ossification. PLLA/BMP-2 scaffolds showed much better bone regeneration and several ossification foci were observed throughout the defect. PLLA/BMP-2 scaffolds also stimulated significantly faster bone regeneration during the first eight weeks compared to bovine spongiosa. However, no significant differences between these two scaffolds could be observed after twelve weeks. Expression of osteogenic marker proteins in PLLA/BMP-2 scaffolds continuously increased throughout the observation period. After twelve weeks osteocalcin, BMP-2 and Smad5 were all significantly higher in the PLLA/BMP-2 group than in all other groups.ConclusionElectrospun PLLA nanofibers facilitate colonization of bone defects, while their use in combination with BMP-2 also increases bone regeneration in vivo and thus combines osteoconductivity of the scaffold with the ability to maintain an adequate osteogenic stimulus.

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Open reduction and internal fixation (ORIF) with locking plates or primary arthroplasty remains a controversial issue in the management of complex proximal humerus fractures. Aim of this study was to evaluate the surgeon- and patient-based outcome of patients older than 65 years who underwent ORIF using locking plate fixation of a 3- or 4-part fracture of the proximal humerus. Twenty-seven patients older than 65 years were treated with locking plate fixation (PHILOS, Fa. Synthes, Umkirch, Germany). At an average follow-up of 44 months, the clinical and the subjective outcome were evaluated, and complications were analyzed. The mean age- and gender-related Constant score was 70% (30–100%) compared with 92% (47–108%) of the contralateral non-injured shoulder. The mean DASH score was 29 points (0–71). Five patients (18.5%) showed clinical signs of an impingement, which was related to malpositioning of the plate in 3 cases. Screw cutout was seen in 22.2% (6 patients). Avascular necrosis of the head or the tubercula was found in 8 patients (29.6%). The revision rate was 29.6%. However, the patients considered the functional status of their shoulder as “good” or “satisfactory.” The functional and patient-orientated results of the locking plate fixation of complex displaced proximal humerus fractures in the elderly are comparable to those of primary arthroplasty and minimally invasive treatment. Proper surgical technique (screw length, plate position) is mandatory for reducing the revision rate.

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