Total hip replacement (THR) is a very common procedure performed for the treatment of osteoarthritis of the hip. The aim of THR is to restore function and quality of life of the patients, by restoring femoral offset, leg length, centre of rotation, and achieving stability, to avoid dislocation postoperatively. We aimed to perform preoperative assessment of femoral offset on anteroposterior (AP) radiographs of the hip, and on corresponding CT scans, for patients undergoing primary THR. Patients were positioned according to a standardised protocol prior to obtaining radiographs of the hip and CT scan. Inter- and intra-observer reliability was evaluated between 3 observers of differing levels of seniority – an orthopaedic trainee, a fellow, and a consultant. CT scan measurements of offset were performed by one consultant radiologist. The researchers measuring radiographic offset were blinded to the results of the CT measurements.Introduction
Method
There are conflicting views when assessing the best imaging modality by which to assess long leg alignment pre and post operatively for patients’ receiving primary total hip replacements. It has been a long standing standard that long-leg radiographs are used for measuring and interpreting alignment of the lower limb, but recently it has been suggested that CT imaging may be a better option for this assessment. Patients awaiting total knee replacement surgeries were invited to participate in this clinical trial. 120 participants’ consented and completed both pre and post-operative long-leg radiographs, and lower limb CT scans. Long leg radiographs were analysed and measured by senior orthopaedic surgeons pre and post-operatively, while CT scans were analysed using the perth protocol method by trained radiologists. Mechanical alignment of the lower limb was calculated using both imaging modalities, the CT “scout” scan was used for the measurement of the mechanical alignment. Pre-operatively the patients had their imaging performed between 1 year and 1 week pre-operatively, and following surgery their imaging was standardised to 6 months post-operatively. For long leg radiographs, patients were asked to stand with their feet shoulder width apart and toes forward facing (on occasion deformities would not allow for this stance, and they were asked to adopt this stance to the best of their ability).Introduction
Methods
Alignment and soft tissue balance are two of the most important factors that influence early and long term outcome of total knee arthroplasty. Current clinical practice involves the use of plain radiographs for preoperative planning and conventional instrumentation for intra operative alignment. The aim of this study is to assess the SignatureTM Personalised system using patient specific guides developed from MRI. The SignatureTM system is used with the VanguardRComplete Knee System. This system is compared with conventional instrumentation and computer assisted navigation with the Vanguard system. Patients were randomised into 3 groups of 50 to either Conventional Instumented Knee, Computer Navigation Assisted Knee Arthroplasty or Signature Personalised Knee Arthoplasty. All patients had the Vanguard Total knee Arthroplasty Implanted. All patients underwent Long leg X-rays and CT Scans to measure Alignment at pre-op and 6 months post-op. All patients had clinical review and the Knee Society Score (KSS) at 1 year post surgery was used to measure the outcome. A complete dataset was obtained for 124 patients. There were significant differences in alignment on Long leg films ot of CT scan with perth protocol. Notably the Signature group had the smallest spread of outliers. In conclusion the Signature knee system compares well in comparison with traditional instrumentation and CAS Total Knee Arthroplasty.
Safety and efficacy of novel prostheses relies on the determination of early implant migration and subsequent risk of loosening. Radiostereometric Analysis (RSA) has been used to evaluate the clinical failure risks of femoral stems by reporting distal migration, a measure of stem subsidence, when examining early migration characteristics. The migratory patterns of femoral stems, 24 months postoperatively, have provided a surrogate outcome measure to determine implant stabilisation and predict long-term performance and survivorship. RSA assessed femoral stem migration and provided comparison of the early migration characteristics with published data of a clinically established counterpart. Twenty five patients undergoing primary total hip arthroplasty were implanted with a hydroxyapatite-coated femoral stem. The median age was 65 years (range, 43–75 years). During surgery tantalum markers were attached onto the distal tip and shoulder of the stem. Eight tantalum markers were inserted into the femur, four placed in each of the greater and lesser trochanter. RSA examinations were performed postoperatively at 4 to 5 days, 6, 12 and 24 months. Eleven patients who had complete RSA follow-up as well as the valid data from five patients were analysed to determine the movement of the femoral stem relative to the femur and were compared to the published data of a clinically established counterpart.Background
Methods
The five year results of 8187 primary total knee replacements undertaken for osteoarthritis in patients under the age of 55 years are presented. The casese were submitted to the Australian Orthopaedic Association National Joint Replacement Registry in the period 1st September 1999 to 31st December 2006. This represents 6.3% of the 130,377 primary knee replacements recorded by the registry for this period. The five year cumulative revision rate for patients under the age of 55 years was 8.0% (95% CI: 7.2 to 8.9). We compared the results to outcomes of older patients aged over 70 years at the time of surgery. The younger patients have a significantly higher risk of revision in the first five years (hazard ratio of 2.9; 95% CI= 2.59 to 3.26; p<
0.0001). Gender, mode of fixation, the use of cruciate retention or substitution prostheses or patella resurfacing did not significantly affect the rate of revision in those patients aged 55 years or less. Survival of fixed bearing implants was significantly better than that of mobile bearings. The most common reason for revision in this group was loosening (32.3%). Total knee replacement in patients under the age of 55 years is associated with a much higher risk of revision in the first five years. A decision to proceed with total knee replacement in this age group should be accompanied by a careful explanation of this significantly increased risk compared to knee replacement in older individuals.
Dislocation (44.1%) was the main reason for revision of primary THR in the first 2 weeks after surgery followed by fracture (26.8%) and loosening (16%). The main reason for revision of primary TKR was infection (39%) followed by loosening (18%) and fracture (8.6%). Most revisions of primary THRs in the first 2 weeks were major (66.4%). When only one major component was revised it was mainly the femoral stem (32.9% of all revisions). Almost all of these were cementless (94.7%). When a revision of a primary TKR occurred the majority were minor (69.6%) (p<
0.001). The insert (64.7% of all revisions) was the main component revised. Risk factors associated with primary THR revision include a diagnosis of developmental dysplasia (P=0.030) and cementless procedures had a significantly higher risk of revision than either cemented (P<
0.0001) or hybrid (P<
0.0001) procedures. We did not identify any risk factors associated with primary TKR in the first 2 weeks following surgery.
Computer navigation was introduced in Australia in 2000, initially with the use of pre-operative computer scans and then later with image free systems. In 2003 the AOA – NJRR began collecting data for knee replacement performed with computer navigation. Meta analysis of the literature has shown better coronal and sagittal plane alignment in total knee arthroplasty performed with computer navigation as opposed to standard instrumented knee replacement. At present, however, there is no data on improved outcomes or reduced revision rates. Information was requested from the AOA – NJRR on the use of computer navigation for both uni-compartmental and total knee replacements. This included numbers of navigated knees done per year as well as revision rates and reasons for revisions of knees performed by computer navigation surgery. Since data collection began there has been 2,651 computer assisted total knee replacements performed which is 4.1% of the total number of knee replacements in this time period. There has been a steady increase in the last three years in the use of computer navigation. There has been an increased number of computer navigated knees performed in the private hospital sector as opposed to the public hospitals and there is a state by state variation in the uptake of navigation. The revision rate per 100 observed ‘component’ years at three years is 2.8 for non computer assisted and 2.5 computer assisted surgery. This is not statistically significant. There is no difference in the early complication rate leading to revision. The use of computer navigation could be expected to reduce the long term revision rates of knee arthroplasty due to better alignment and potentially less wear. In the short term there is no significant revision rate between the two methods of performing TKR particularly with regard to infection or fracture
