Healing pattern of reamed bone following bone harvesting by a RIA device.

Intramedullary nailing has been used for decades to treat fractures of the long bones. However, complications related to the increase in medullary pressure culminated in the development of the Reamer Irrigator Aspirator (RIA). Since its first clinical use, the RIA has moved from a reaming device to a cell and autologous bone-harvesting tool. This increase in use brings with it further clinical questions; namely, does the endosteal bone regenerate sufficiently to allow subsequent reaming procedures. In the current study, endosteal bone regeneration post reaming was assessed in an ovine model. The study included six animals that had one tibia reamed, while the contralateral tibia acted as an intact control. Animals were administered fluorochrome labels in vivo, and bone regeneration was assessed using radiographical analysis. The endpoint of the study was 12 weeks post-surgery, at which time ex vivo analysis consisted of computed tomography and histological assessments. In vivo radiographs indicated limited healing of the reamed bone. However, ex vivo computer tomographical analysis indicated no significant differences in terms of bone volume between the reamed bone and the intact bone. Histological assessment of these regions indicated new bone formation. Fluorescent labelling indicates strong bone formation from 9 weeks post-surgery and as such, the bone formed at 12 weeks was immature in nature and was actively undergoing remodelling. These results indicate that bone regeneration post-reaming was continuing at three months. Therefore, given more time it may have sufficiently healed to allow a surgeon to use the intramedullary canal for a re-reaming procedure.

Development of a novel method for surgical implant design optimization through noninvasive assessment of local bone properties.

A method was developed to improve the design of locking implants by finding the optimal paths for the anchoring elements, based on a high resolution pQCT assessment of local bone mineral density (BMD) distribution and bone micro-architecture (BMA). The method consists of three steps: (1) partial fixation of the implant to the bone and creation of a reference system, (2) implant removal and pQCT scan of the bone, and (3) determination of BMD and BMA of all implant-anchoring locations along the actual and alternative directions. Using a PHILOS plate, the method uncertainty was tested on an artificial humerus bone model. A cadaveric humerus was used to quantify how the uncertainty of the method affects the assessment of bone parameters. BMD and BMA were determined along four possible alternative screw paths as possible criteria for implant optimization. The method is biased by a 0.87 ± 0.12 mm systematic uncertainty and by a 0.44 ± 0.09 mm random uncertainty in locating the virtual screw position. This study shows that this method can be used to find alternative directions for the anchoring elements, which may possess better bone properties. This modification will thus produce an optimized implant design.