Many navigation (Image Guided Surgery or IGS) systems are keyed to safely and accurately placing implants into complex anatomy. In spine surgery such as disc arthroplasty and fusion surgery this can be extremely helpful. Likewise, in joint arthroplasty the accurate placement with respect to the operative plan is widely recognized to be of benefit to long term results. However, where realignment of anatomy is desired following implant placement, such as in high tibial osteotomy, spinal fusion with correction of deformity, and spinal disc arthroplasty, navigation systems can tell you where you are, but not where you would like to be. We have developed specific software modification technology, applicable to all current navigation systems that addresses this need for assistance in surgical correction of anatomy to a desired alignment without the requirement for further imaging or irradiation. The benefits of our software allow image free re-referencing of image guided surgery, accommodation of intra-operative changes in anatomy, and intra-operative accountability and adjustment to allow errors of image guidance to be identifiable and correctible, at any stage of image guided surgery. This software allows accurate pre-operative planning, intra-operative verification and assessment of the operative plan, and actual outcomes of the surgery to be assessed as the surgery is performed. It allows the surgeon to subsequently verify if the operative planning has been adequately achieved, and if not can verify if continued surgery has then achieved the planning goals. This verification and image guidance does not require further imaging during surgery, relying upon the original data set and software enhancements.
Image guided surgery (IGS), or “Navigation,” is now widely used in many areas of surgery including arthroplasty. However, the options for establishing, in real time, the veracity of the navigation information are limited. Manufacturers recommend registering with a “prominent anatomical feature” to confirm accurate navigation is being presented. In their fine print, they warrant the accuracy proximate to the navigation array attached to the body. In multi-level spine surgery where it is most sorely needed, this limits the warrants to the vertebra of reference array attachment. In arthroplasty surgery, the accuracy of the system can be erroneous through technical errors and a delay may occur prior to verification of such innacuracy. In response to this situation surgeons have taken to using K-wires, FaxMax screws and a variety of other “Fiducial Markers”, but these were not specifically designed for this purpose and in many ways are inadequate for the task of verification of navigation accuracy. We have developed a fiducial marker that is designed to address these unmet needs. The Precision Screw is clearly visible on imaging modalities and the central registration point is identifiable at any angle of viewing, with accuracy of fractions of a millimeter. It does not interfere with surgery, being low profile and securely fixed to bone. Finally, in use, it is secure in capturing the navigation probe so that the surgeon does not need to focus on keeping the probe located while reviewing the navigation data. We believe these features make this a useful and worthwhile addition to IGS.
The concept and method of repeatedly connecting an extracorporeal blood pump to produce elevated pancycle inflow pressures to ischaemic limbs is presented. The aim of this study was to determine if intermittent increased perfusion would improve the clinical picture in peripheral arterial disease. Animal studies—to determine the safety and efficacy of the pumping and the access device were performed on 12 sheep. Following successful completion of that study, pilot studies of 18 patients were treated using the Peripheral Access Device (PAD) and Hypertensive Extracorporeal Limb Hyperperfusion (HELP). Treatment was offered to patients who had no other alternative than major amputation. Patients were treated for less than 100 hours of total pumping, broken over three or less treatment periods over approximately one week. Improvement was measured by pain scores, clinical examination and digital thermography.Introduction
Methods
It is well established in the literature that the tribological properties of sliding metallic and ultra-high molecular weight polyethylene (UHMWPE) counterfaces are a major contributor to accelerate wear rates that contribute to osteolysis. The majority of the research over the years has been on improving the UHMWPE properties through manufacture and secondary processing of the polymer. Little attention has been directed towards the optimisation of the Chromium Cobalt Molybdenum (CrCoMo) surface finish. The focus of this research has been on the highly polished CrCoMo metallic surface. A new surface finishing technique was applied to CrCoMo femoral knee prosthetic implants. The surface finish of our finished implants was compared to that finished by traditional mechanical polishing techniques. A representative number of polished CrCoMo knee femoral components were compared under the following topics; tribological, topographical and the extent of processing containments present. It was found that traditional mechanically polished parts contained a significant amount of embedded polishing compounds (Al2O3), coarse interdendritic (M7C3) and fine (M23C6) carbide elements. Both the polishing containments and carbide elements stand proud of the articulating surface and thus act as micro cutting tools to accelerate UHMWPE wear. The new polishing technique completely eliminated hard carbide particles and embedded polishing compound media. Consequently, the samples prepared using the new polishing technique produced lower UHMWPE wear debris and improved wear patterns to that of the traditionally polished samples. Additionally, all sub-micron scratching was removed from the surface of the samples. This polishing technique for CrCoMo prosthesis represents a milestone in CrCoMo surface finishing and will significantly reduce the UHMWPE wear debris generated and consequently increasing prosthesis longetivity.
