The high number of perforations, filled with intact trabeculae, indicates an adequate fixation; bridging trabeculae between adjacent endplates and tricortical iliac struts in all vertebrae indicates that the anchorage is adequate to promote fusion in this animal model, even in the osteoporotic sheep.

There is no clinically relevant substantial advantage in using either SS or Ti pins on reducing pin loosening or pin track irritation/infection.

Objective: This study was designed to assess the benefits of a new Anodic Plasma Chemical calcium-phosphate (APC-CaP) surface treatment on reducing pin track infection and pin loosening in comparison to anodized titanium (Ti) during external fracture fixation.Methods: A tibial midshaft, transverse, 6-mm gap osteotomy was created in 17 adult female Swiss alpine sheep. The tibia was stabilized with an external fixator and 4 Schanz screws of Ti or APC-CaP-treated Ti. The sheep were examined during a 12-week observation period. Infection was assessed with weekly clinical pin track grading and microbiologic assessment at sacrifice. Pin loosening was assessed by grading for radiolucency on biweekly radiographs and by measuring extraction torque on pin removal. In vivo bending stiffness measurements were performed to determine gap healing. A qualitative histologic assessment of the tissue adjacent to pin sites was also performed.Results: A trend (P = 0.056) for less infection around APC-CaP pins was found at 6 weeks, but the strength of this difference diminished with time. Significantly more radiolucency was found around Ti pins after 8 (P = 0.011) and 12 (P , 0.001) weeks. At all pin sites, the extraction torque for APC-CaP pins was higher than for Ti pins (P = 0.007). No difference in the progression of gap healing was found. Histology showed bone growth at the implant surface in the form of distance osteogenesis for Ti and contact osteogenesis for APC-CaP. Conclusions:This study has shown that the APC-CaP surface improves the clinical performance of Ti pins with respect to pin loosening and pin track infection. P in track infection and bone resorption are common problems associated with external fixation. 1,2 A recent clinical study showed that 40% of patients treated with an external fixator and titanium (Ti) pins experienced pin loosening. Twelve percent of the pins became infected and 13% of the pins had to be removed due to infection and/or loosening. 3 Although many causes of pin loosening and infection have been identified 1,4 and strategies have been used to diminish them, 5,6 they are still a common problem, which needs to be addressed. 7 The integrity of the bone-implant interface contributes to the success of the implant. 8 Osseointegration is the direct contact at the light microscope level (mm) between living bone and implant (at steady state) 9,10 and is essential for stable implant anchorage. 8 Hydroxyapatite (HA) and calcium-phosphate (CaP) coatings have been used to improve osseointegration around stainless steel and Ti implants because of their similar chemical structure to mineralized bone. These coatings have been shown to promote osseointegration by encouraging direct bone growth onto the coating surface. 11,12 Plasma sprayed-HA-coated external fixation pins have previously been tested in a long-term, loaded, ovine model. 13 This study showed a reduction in the incidence of pin loosening by the improved osseointegration of the HA coated pins compared with uncoated pins. These findings were corrob...