The prevalence of pseudotumours in patients with large-head metal-on-metal (MOM) THA has been the subject of implant recalls and warnings from various regulatory agencies. To date, there is no consensus on whether ultrasound or MRI is superior for the detection and following the progression of pseudotumours. Ultrasound is relatively cheap but can be operator dependent. MARS MRI has the advantage of excellent visibility of the soft tissue. However, MRI comes at a marked increase cost and takes about twice as long to perform. At our institution, we prospectively compared ultrasound to MRI for pseudotumour detection in an asymptomatic cohort of patients with MOM THAs. We enrolled 40 patients with large-head MOM THAs in the study. The mean age was 54 years (range, 34–76 years). The mean time from surgery was 54 months (range, 40–81 months). There were 28 men and 12 women. All patients underwent ultrasound and MRI using slice encoding for metal artifact correction. The gold standard was defined as follows: if both ultrasound and MRI agreed, this was interpreted as concordant and the result was considered accurate. Ultrasound and MRI agreed in 37 of 40 patients (93%). The prevalence of pseudotumours was 31% (12 of 39) in our cohort. Twenty-three of 39 patients (59%) had completely normal tests and four (10%) had simple fluid collections. Ultrasound had a sensitivity of 100% and specificity of 96% while MRI had a sensitivity of 92% and specificity of 100%. Conclusions: A negative ultrasound rules out pseudotumour in asymptomatic patients as this test is 100% sensitive. Given its lower cost, we recommend ultrasound as the initial screening tool for pseudotumours. More recently, Kwon et al have compared ultrasound to MARS MRI for following the progression of pseudotumours. They found a strong agreement between the 2 modalities for assessing change in size and consistency of pseudotumours.
Two-stage exchange has been the gold standard in North America for the treatment of infected knee replacements. The choice of static versus articulated spacers has been debated for a number of years. At our institution our choice of spacer for 2-stage exchanges is an articulated spacer. This allows motion between stages which facilitates recovery, and makes the second stage technically easier. In a study from our institution we followed 115 infected TKAs treated with the PROSTALAC articulated spacer for 5–9 years. Success for eradication of infection was 88%. With a repeat two-stage, overall infection control was 98%. In addition, we compared functional outcomes to a group of aseptic knee revisions and found no difference in functional outcomes with standard quality of life outcome scores. While the articulated spacers were our treatment of choice in 2-stage exchange, around 2012 the company that manufactured the PROSTALAC knee components ceased to manufacture them, based on the work of 2 previous studies (Hofmann, Lee). At our institution, we continued to use articulated spacers. However, this was now the so-called Hofmann technique with a new standard femoral component with an all-polyethylene tibia. The only difference from a standard knee revision was no stems and the utilization of high dose antibiotics. Around the same time as we instituted the change in articulated spacers, results out of Europe were showing promising results with one-stage exchange. In September 2015, our technique was modified to now include an all-polyethylene tibia with a keel. To date we have no results but it is our hope that a high percent of these will achieve stable fixation and will then have a one-stage exchange.
The goals of revision total hip on the femoral side are to achieve long term stable fixation, improve quality of life and minimise complications such as intra-operative fracture or dislocation. Ideally these stems will preserve or restore bone stock. Modular titanium stems were first introduced in North America around 2000. They gained popularity as an option for treating Paprosky 3B and 4 defects. Several studies at our institution have compared the modular titanium stems with monoblock cobalt chromium stems. The main outcomes of interest were quality of life. We also looked at complications such as intra-operative fracture and post-operative dislocation. We also compared these 2 stems with respect to restoration or preservation of bone stock. In two studies we showed that modular titanium stems gave superior functional outcomes as well as decreased complications compared to a matched cohort of monoblock cobalt chromium stems. As mentioned one of the initial reasons for introduction of these stems was to address larger femoral defects where failure rates with monoblock cobalt chromium stems were unacceptably high. We followed a group of 65 patients at 5–10 years post-revision with a modular fluted titanium stem. Excellent fixation was obtained with no cases of aseptic loosening. However, there were 5 cases of fracture of the modular junction. Due to concerns of fracture of the modular junction more recently, at our institution we have switched to almost 100% monoblock fluted titanium stems. We recently reviewed our first 100 cases of femoral revision with monoblock stem. Excellent fixation was achieved with no cases of aseptic loosening. Quality of life outcomes were similar to our previous reported series on modular tapered titanium stems. Both monoblock and modular fluted titanium stems can give excellent fixation and excellent functional outcomes. This leaves a choice for the surgeon. For the low volume revision surgeon modular tapered stems are probably the right choice. Higher volume surgeons or surgeons very comfortable with performing femoral revision may want to consider monoblock stems. If one is making the switch it would be easiest to start with a simple case. Such a case would be one that can be done through an endofemoral approach. In this the greater trochanter is available as the key landmark for reaming. After the surgeon is comfortable with this system more complex cases can easily be handled with the monoblock stem. In summary, both modular and monoblock titanium stems are excellent options for femoral revision. As one becomes more familiar with the monoblock stem it can easily become your workhorse for femoral revision. At our institution, we introduced a monoblock titanium stem in 2011. It started out at 50% of cases and now it is virtually used in almost 100% of revision cases
The anterior pelvic plane (APP) is used as a reference in various pelvic surgeries in orthopaedics. Current methods for identifying the APP are limited in accuracy and efficiency. A quick and accurate method for registering the pelvis orientation can be very useful. Previously, we have introduced a Tracked C-arm (TC-arm) system for use with any C-arm fluoroscopy for producing spatially calibrated imaging views. This system has been tried for estimating the APP. Early results, however, has shown limited repeatability in identifying the anterior superior iliac spine (ASIS) landmarks. This study improves the previous algorithms for a robust registration of the APP. A Sawbone pelvis was used, and its APP was marked by radio-dense ball-bearings. In the new addition, the TC-arm allowed segmenting the ASIS in an interactive user-interface by taking guidance from a reference line tangential to the ipsilateral pubic tubercle for marking the most anterior point on the iliac-crest. The imaging and analysis was repeated 10 times. The results were compared to reconstruction of the fiducial markers placed on the true APP. Accuracy of 1.4° and 4.4° were found for registering the pelvic tilt and rotation, correspondingly. The overall accuracy and precision of registration of the APP were 4.7° and 0.82°, correspondingly. The new method showed 7.5 times improvement in repeatability of measuring the pelvic tilt (SD<0.4°) compared to the previous fluoroscopic methods. This technique addresses an important challenge in estimation of the pelvic bone which is crucial for reliable device placement and producing standard radiographic views in surgery.
The prevalence of pseudotumours in patients with large-head metal-on-metal (MOM) THA has been the subject of implant recalls and warnings from various regulatory agencies. To date, there is no consensus on whether ultrasound or MRI is superior for the detection of pseudotumours. Ultrasound is relatively cheap but can be operator dependent. MARS MRI has the advantage of excellent visibility of the soft tissue. However MRI comes at a marked increase cost and takes about twice as long to perform. At our institution we prospectively compared ultrasound to MRI for pseudotumour detection in an asymptomatic cohort of patients with MOM THAs. We enrolled 40 patients with large-head MOM THAs in the study. The mean age was 54 years (range, 34–76 years). The mean time from surgery was 54 months (range, 40–81 months). There were 28 men and 12 women. All patients underwent ultrasound and MRI using slice encoding for metal artifact correction. The gold standard was defined as follows: if both ultrasound and MRI agreed, this was interpreted as concordant and the result was considered accurate. Ultrasound and MRI agreed in 37 of 40 patients (93%). The prevalence of pseudotumours was 31% (12 of 39) in our cohort. Twenty-three of 39 patients (59%) had completely normal tests and four (10%) had simple fluid collections. Ultrasound had a sensitivity of 100% and specificity of 96% while MRI had a sensitivity of 92% and specificity of 100%.Methods
Results
Segmental defects of the acetabulum are often encountered in revision surgery. Many times these can be handled with hemispherical cups. However when larger defects are encountered particularly involving the dome and/or posterior wall structural support for the cup is often needed. In the past structural allograft was used but for the last 12 years at our institution trabecular metal augments have been used in the place of structural allograft in all cases. This talk will focus on technique and mid-term results using augments in association with an uncemented revision shell. The technique can be broken down into 6 steps outlined below: 1. Exposure, 2. Reaming, 3. Trialing, 4. Augment Inserted, 5. Cup Insertion/Stabilization, 6. Trial Reduction/Liner Cementation A recent study was undertaken to assess the mid-term results of this technique. We prospectively followed the first 56 patients in whom these augments were utilised in combination with a trabecular metal acetabular component in our unit. Details of this study will be presented. The median follow up of the surviving patients was 110 months (range 88–128 months). Survivorship of the augments at 10 years was 92.2% (95% CI: 97.0–80.5%). In one case the augment was revised for infection and in 3 for loosening. In 1 of the revised cases there was a pre-operative pelvic discontinuity, the other 2 discontinuities in the series were not revised and remain asymptomatic. The results of the acetabular trabecular metal augments continue to be encouraging in the medium to long term with low rates of revision or loosening in this complex group of patients.Conclusions
MRSA/MRSE infections appear to be increasing in prevalence and virulence. Prevalence has increased from 2.4% of all infected TJAs in 1975 to 37% in 2006. In addition work from several centers has shown that cure rates for these infections are far below that of nonresistant organisms. In a recent study from our institution 50 consecutive cases of MRSA/MRSE were treated with two-stage exchange with a Prostalac spacer as the interval operation. Final reinfection rate was 18% which was far worse than the 4% failure reported from our center in MS staph species. This high failure rate is supported by work from other centers. Clearly with the increasing prevalence and virulence of MRSA/MRSE new strategies are needed. The rest of this talk will focus on 2 different strategies: prevention and treatment. Prevention strategies can either target carriers or all patients. In a study by Kim et al. carriers were targeted and they reported a 50% reduction in surgical site infections. At our institution a recent program was implemented where all surgical patients were targeted. Results from this will be presented. While prevention strategies seem quite hopeful new treatment options have to be looked at. Traditionally vancomycin has been the mainstay of local and systemic treatment. Other options currently being explored include such agents as fusidic acid, daptomycin and liniazid. Research is looking at the effectiveness of these agents both locally and systemically. MRSA/MRSE infections are becoming increasingly difficult to treat. New strategies for combatting these will include both new prevention and treatment strategies as outlined in this talk.
Poor acetabular cup orientation in total hip arthroplasty (THA) can cause dislocation and impingement, and lead to osteolysis (Little et al., 2009) and inflammatory soft tissue reactions (Haan et al., 2008). While the intrinsic accuracy of cup positioning in navigation is reported as low as 1° (Parratte et al., 2009), a large anterior pelvic tilt may lead to an offset of the same magnitude in the final cup anteversion (Wolf et al., 2005). The objectives of this study are to demonstrate feasibility of a new, non-invasive radiographic tool for accurate preoperative determination of a patient's specific pelvis angle, and intraoperative and postoperative assessment of the acetabular cup orientation with respect to boney landmarks. The methodology stitches multiple radiographic views around the pelvis using a multi-planar radiography setup (Amiri et al., 2011) and reconstructs the reference boney landmarks and the acetabular cup in three dimensions using previously developed algorithms and software (Amiri et al., 2012). To validate the methodology, a Sawbone model of the pelvis and femur was implanted with a standard cementless metal-on-polyethylene THA, and was tracked and digitized by an Optotrak motion tracking system. Five radiographic views were acquired at the pubic tubercle (PT) and anterior-superior iliac spine (ASIS) levels (Views 1 to 5 in Fig 1). Imaging and analysis were repeated 10 times. Custom software (Joint 3D) was used to reconstruct the right and left PT and ASIS by fitting spheres to the corresponding pairs of images (Fig 1). The three-dimensional pose of the acetabular cup was reconstructed in the software by solving a back-projection equation of the elliptical shadow of the cup opening. Accuracies were measured as mean differences from the digitized references. A sample of the reconstructed graphical output for the anterior pelvic plane (APP) and the cup, in comparison to the digitized reference, is shown in Fig 2. Repeatability was estimated as standard deviation of the measures for the reconstructed locations of the boney landmarks and the APP (known as a standard reference plane for cup placement).INTRODUCTION
METHODS
Achieving durable implant–host bone fixation is the major challenge in uncemented revision hip arthroplasty when significant bone stock deficiencies are encountered. The purpose of this study was to develop an experimental model which would simulate the clinical revision hip scenario and to determine the effects of alendronate coating on porous tantalum on gap filling and bone ingrowth in the experimental model. Thirty-six porous tantalum plugs were implanted into the distal femur, bilaterally of 18 rabbits for four weeks. There were 3 groups of plugs inserted; control groups of porous tantalum plugs (Ta) with no coating, a 2nd control group of porous tantalum plugs with micro-porous calcium phosphate coating, (Ta-CaP) and porous tantalum plugs coated with alendronate (Ta-CaP-ALN). Subcutaneous fluorochrome labelling was used to track new bone formation. Bone formation was analysed by backscattered electron microscopy and fluorescence microscopy on undecalcified histological sections.Introduction
Methods
Despite advances in surgical technique and prosthetics there continues to be a number of patients who are dissatisfied with the results of their knee replacement procedure. The outcome after total knee arthroplasty (TKA) has been reported frequently with use of condition-specific measures, but patient satisfaction has not been well studied. 160 patients who received primary total knee arthroplasty (TKA) were evaluated prospectively to evaluate factors that may be associated with patient satisfaction. At minimum one year follow-up all patients were evaluated and completed validated self-report satisfaction questionnaires. Patient, surgeon, implant and process of care variables were assessed along with WOMAC, Oxford Knee and SF-12 scores. Univariate and multivariate analyses were performed to assess for independent factors associated with post-operative satisfaction.Introduction
Material and methods
to develop an experimental model which would simulate the clinical revision hip scenario and determine the effects of alendronate coating on porous tantalum on gap filling and bone ingrowth in the experimental model.
This single incision, anterolateral intermuscular approach (AL-IM) utilises the interval between gluteus medius and tensor fascia lata. The aims of the study were to compare the quality of life, satisfaction and complications of this approach with two of the most commonly used limited incision transmuscular (TM) approaches, namely the mini-posterior (P-TM) and the mini-direct lateral (L-TM). One hundred and ninety-nine patients receiving MIS THA surgical procedures were evaluated prospectively (63 AL-IM, 68 P-TM and 68 L-TM). The outcome variables were WOMAC function, pain, stiffness, SF-12 (physical &
mental), Oxford-12, satisfaction and radiological outcome. Parametric and non-parametric analyses were performed. There were no significant differences between groups in baseline characteristics including age, sex, BMI, co-morbidity, or pre-op WOMAC, SF-12, Oxford-12 (p>
0.05). However, the AL-IM group was associated with superior outcomes (p<
0.05) in WOMAC function, WOMAC pain, global WOMAC, Oxford-12 and SF-12 physical component. In the short term the AL-IM approach provides significant improvements in quality of life scores over other limited incision approaches. It provides minimal soft tissue disruption and maintains the abductor musculature and posterior soft tissue envelope, with similar complications and radiological outcomes.
Revision surgery is an important outcome of hip and knee arthroplasty among patients with osteoarthritis (OA). The objective of this study was to determine the risk of revision over time in a large, geographically defined population in North America, and to assess the effects of age, sex, and socioeconomic status (SES) on knee and hip revision rates in this population. We used data on admissions to all acute care hospitals in British Columbia (BC), Canada (population of four million people) from 1986 until 2004 (eighteen years of follow-up). Primary knee and hip replacement surgery for OA and revision procedures were identified using diagnostic (ICD-9, ICD-10) codes and surgical procedure codes. We excluded cases admitted due to injury or neoplasm. SES was assigned based on residential address linked to census data at the level of enumeration area (ecological variable), and analyzed according to quintiles or deciles of the distribution. In the analysis, we used Kaplan-Meier survival curves to describe the risk of first revision following first primary replacement surgery over time and parametric (Weibull) survival regression models to analyze the effects of joint (hip vs. knee) age, sex, and SES on revision rates. Death, emigration, and another primary joint replacement were treated as censoring events. Between 1986 and 2004, we observed 24,169 first primary hip replacements and 22,875 first primary knee replacements. In these patients, there were 1,313 hip revisions and 914 knee revisions following a primary replacement. The risk of revision at five, ten and fifteen years after primary replacement according to joint and sex were identified The overall risks were 10.1% for the hip and 8.7% for the knee at ten years, and 15.5% and 14.7%, respectively, at fifteen years. Risk of revision (%) following first primary joint replacement surgery Hip Knee Years Men Women Men Women 5 5.0 3.9 4.6 3.8 10 11.0 9.4 9.7 8.0 15 17.8 14.1 18.5 12.4 In a multivariate survival regression model including joint, age, sex, and SES, only age and sex were significantly associated with revisions. The hazard ratio was 1.2 for men compared with women (p<
0.0001). Revision rates were higher in younger persons, with hazard ratios increasing from 1.7 for age 70–79 (p<
0.0001) to 3.9 for age <
49 (p<
0.0001) compared with age 80+. After adjusting for age and sex, SES was not significantly associated with revision risk following primary hip or knee replacement surgery in this population (p=0.75). This is one of the largest and longest cohort studies in North America to look at the epidemiology of revision procedures following hip and knee replacement for OA. Higher rates in men and in younger persons are consistent with previous reports. The lack of association between revision risk and SES in BC is an important finding given current concerns about socioeconomic disparities in access to and outcomes of treatment for OA.
We report the outcomes ten to fifteen years after two stage revision for hip infection in one hundred and three patients. All patients or their next of kin were contacted to determine their current functional status and whether they had required repeat surgery or had recurrent infection. The Oxford-12, SF-12, and WOMAC questionnaires were administered. A comprehensive chart review was undertaken to review the infective organisms, surgery, approach, complications, and need for further revision surgery. Ten patients had re-infection, six of whom responded to repeat surgery with no further sequelae. Two patients required resection arthroplasty, one patient underwent hip disarticulation after eventual failure of treatment and bone loss, and one immunocompromised patient developed osteomyelitis and was subsequently lost to follow-up. Long-term success rate for two stage- revision is thus 90.3%, or 96.1% with additional surgery. Since then, three patients required revisions for aseptic loosening, one for recurrent dislocation. We were able to follow up forty-one patients, 85 % of whom provided health-related quality of life outcome scores. Thirty-nine patients were deceased, with their outcome confirmed via their last follow-up or with family members, for a total follow-up rate of 78 %. Twenty-three patients were lost to follow-up, but did not undergo further surgery or have reinfections treated at our centre. Two-stage revision for hip infection, which includes an interim prosthesis of antibiotic loaded cement, offers a predictable and lasting solution for patients with this difficult problem.