The accuracy of intramedullary femoral alignment in total knee replacement in the prescence of ipsilateral hip replacement

Objectives: During total knee replacement (TKR) surgery, the most commonly used method for aligning the distal femur appropriately is via an intramedullary (IM) distal femoral alignment rod. The alignment of the rod itself is reliant on the isthmus which is used to most accurately place the rod in the correct anatomical axis. In the instance of something preventing the rod from entering the isthmus correctly, such as a hip replacement, then the degree of accuracy could be assumed to be even less. Mechanical-anatomical malalignment has been shown to decrease the implant (TKR) survival and so methods of increasing accuracy of alignment relative to the mechanical axis have been developed. At present the most accurate method intraoperatively is computer navigation and several studies have demonstrated improved alignment. An increasing number of patients year on year are having both knee and hip replacements and as the population ages the likelihood of having both a knee and hip replacement will also increase. We propose that the presence of a hip replacement within the isthmus of the femur may further decrease the accuracy of the IM alignment of the femur leading to incorrect implant positioning. Methods: The study was conducted on 10 cadaveric specimens (20 femurs). Computational navigation instrumentation was attached in turn to each femur and the ideal alignment data recorded in a standard fashion by a single operator (principal investigator). A standard entry port was then be made in the femur for the introduction of the IM rod. An IM rod was then inserted with the distal femoral cutting block in the accepted position recorded blindly on the computer navigation (both in terms of varus/valgus alignment to the mechanical axis and the degree of flexion). The process was then repeated at 3 levels to represent primary and revision hip lengths from the greater trochanter (replicating the changes that would occur in the presence of a hip replacement) The process was recorded three times at each level. Results: The resection angles between the cutting surface and the mechanical axis were measured and collected by means of computer navigation system. The results show that the IM alignment had mean Valgus of 0 degrees +/- 0.8 but with a hip replacement in situ this increased to 0.46 degrees +/- 1.49 (range 2.5 varus to 4.5 valgus), with a revision stem 0.825 +/- 1.68 (range 2.5 varus to 4.5 valgus)and long stemmed revision 1.325 +/- 2.09 (range 5 varus to 6.5 valgus). In terms of Flexion IM alignment had a mean flexion of 0.92 +/- 1.7 (range 3 extension to 4 flexion) but with a hip replacement in situ this increased to 1.88 degrees +/- 2.03 (range 2.5 extension to 8.5 flexion), with a revision stem 2.35 +/- 2.2 (range 2.5 extension to 8 flexion) and long stemmed revision 2.75 +/- 2.16(range 3.5 extension to 7 flexion). Conclusion: This Study concludes that the prescence of a hip replacement, in particular long stemmed prosthesis, further reduces the accuracy of IM alignment in the Femur for Total Knee Replacement. Consideration of an alternative method, such as navigation, should be considered insuch situations

Humidity a potential risk factor for prosthetic joint infection in a tropical Australian hospital

Background: Many pathogens of importance, including the staphylococcal species of concern in orthopaedics, demonstrate seasonal variations influenced by environmental factors. The aim of this study was to investigate the role of humidity as a risk factor for deep prosthetic joint infection following total knee arthroplasty (TKA) in a tropical Australian hospital. Methods: A retrospective cohort study of all TKAs performed over a 13-year period was conducted at the author's institution. Univariate analysis was used to individually assess for a range of risk factors including humidity >60% and apparent temperature >30°C (86°F). Odds ratios (ORs) were reported. P-value

Spinal clearance practices at a regional Australian hospital:A window to major trauma management performance outside metropolitan trauma centres

Background: Prevention of secondary spinal injury via spinal protection measures is a standard component of trauma management, and a high-quality spinal clearance process is imperative in achieving this aim. To evaluate the current practice with a view to achieving best practice, we sought to examine the spinal clearance process and outcomes at a regional Australian referral hospital, which services a large geographical catchment area. Methods: A retrospective review of medical records of all patients with major trauma who presented to an Australian regional hospital during 2014 was conducted. The primary outcome measure was missed or delayed diagnosis of spinal injury. Secondary outcome measures included compliance with internationally accepted spinal clearance process measures, timing and choice of appropriate imaging modalities, rates of spinal injury and documentation of spinal clearance. Results: Of the 112 patients with major trauma who met the study eligibility criteria and were discharged from hospital during the study period from 1 January to 31 December 2014, 11 spinal injuries were missed or delayed in diagnosis. The injuries occurred in 3.6% of patients and all were thoracolumbar spine (TLS) injuries. The predominant reasons for missed or delayed diagnosis were reduced sensitivity of plain X-ray compared with computed tomography for spinal injury screening and incomplete full spinal imaging to detect non-contiguous fractures. Conclusion: Evidence-based clinical decision rules are imperative in ascertaining the need for imaging in the TLS and would be enhanced by an internationally recognised definition of clinical significance based on injury morphology rather than clinician management decision alone. In addition, regional hospitals may have limited capacity to achieve spinal clearance, and other trauma quality assurance standards commensurate with national and international benchmarks without the valuable performance feedback provided by state trauma registries, as is currently the case in Queensland