Bone formation in a long bone defect model using a platelet-rich plasma-loaded collagen scaffold.

Platelet-rich plasma (PRP), a platelet concentrate made of autogenous blood, has been used in recent years to improve bone defect healing particularly in maxillofacial reconstructions. The aim of the present study was to assess the effect of PRP on new bone formation in a critical diaphyseal long bone defect. A critical size defect (2.5 cm) in the tibial diaphysis of 16 sheep was supplied either with autogenous PRP in a collagen carrier or with collagen alone (controls). Platelets were enriched about 3.5 fold compared to normal blood in the PRP. After 12 weeks, the explanted bone specimens were quantitatively assessed by X-ray, computed tomography (CT), biomechanical testing and histological evaluation. Bone volume, mineral density, mechanical rigidity and histology of the newly formed bone in the defect did not differ significantly between the PRP treated and the control group, and no effect of PRP upon bone formation was observed. It was suggested that PRP does not enhance new bone formation in a critical size defect with a low regenerative potential. Such bone defects might require more potent stimuli, e.g. combinations of functional biomaterials or autografts, precursor cells or osteoinductive growth factors.

A scanning electron microscopy study of human osteoblast morphology on five orthopedic metals.

Despite the long-standing use of metals as orthopedic implants there still are unsolved problems with these materials and open questions about their behavior in a biological environment. Cell-culture studies provide a useful tool for investigations. In addition to the determination of biochemical or molecular biological parameters, the morphology of adhering cells reflects their interaction with the substrata. This article describes an investigation of the morphology of human osteoblasts on stainless steel, cobalt chromium alloy, commercially pure titanium, Ti-6Al-4V, and Ti-6Al-7Nb with surface designs similar to those used as clinical implants. A cell culture plastic surface was used as a control material. The materials were examined by scanning electron microscopy at different points of time. The cells spread, proliferated, and formed nodules on all test substrates in a time-dependent manner, without signs of a disturbing influence from any of the materials. On the smooth surfaces the cells showed a flattened fibroblast-like morphology and only slight differences could be detected. Therefore, the cellular morphology seems not to be markedly affected by the different chemical material compositions. In contrast, the titanium alloy with a rough, sandblasted surface induced a three-dimensional growth. This three-dimensional cellular network could be the basis for the known earlier differentiation of osteoblasts on rough surfaces in vitro and a better osseointegration in vivo.