This study used model-based radiostereometric analysis (MBRSA) to compare migration of a recently introduced cementless hip stem to an established hip stem of similar design. Novel design features of the newer hip stem included a greater thickness of hydroxyapatite coating and a blended compaction extraction femoral broach.

Fifty-seven patients requiring primary total hip arthroplasty (THA) were enrolled at a single centre. Patients were randomized to receive either an Avenir collarless stem and Trilogy IT cup (ZimmerBiomet) or a Corail collarless stem and Pinnacle cup (DePuy Synthes) via a posterior or lateral approach. Both stems are broach-only femoral bone preparation. RSA beads (Halifax Biomedical) were inserted into the proximal femur during surgery. Patients underwent supine RSA imaging a 6 weeks (baseline), 6, 12, and 24 months following surgery. The primary study outcome was total subsidence of the hip stem from baseline to 24 months as well as progression of subsidence between 12 and 24 months. These values were compared against published migration thresholds for well-performing hip stems (0.5mm). The detection limit, or precision, of MBRSA was calculated based on duplicate examinations taken at baseline. Patient reported outcome measures were collected throughout the study and included the Oxford-12 Hip Score (OHS), EuroQoL EQ-5D-5L, Hip Osteoarthritis Score (HOOS) as well as visual analogue scales (VAS) for thigh pain and satisfaction. Analysis comprised of paired and unpaired t-tests with significance set at p≤0.05.

Forty-eight patients (30 males) were included for analysis; 7 patients received a non-study hip stem intra-operatively, 1 patient suffered a traumatic dislocation within three weeks of surgery, and 1 patient died within 12 months post-surgery. RSA data was obtained for 45 patients as three patients did not receive RSA beads intra-operatively. Our patient cohort had a mean age of 65.9 years (±;7.2) at the time of surgery and body mass index of 30.5 kg/m2 (±;5.2). No statistical difference in total stem migration was found between the Avenir and Corail stems at 12 months (p=0.045, 95%CI: −0.046 to 0.088) and 24 months (p=0.936, 95% CI: −0.098 to 0.090). Progression of subsidence from 12-24 months was 0.011mm and 0.034mm for the Avenir and Corail groups which were not statistically different (p=0.163, 95%CI: −0.100 to 0.008) between groups and significantly less than the 0.5mm threshold (pNo statistically significant differences existed between study groups for any pre-operative function scores (p>0.05). All patients showed significant functional improvement from pre- to post-surgery and no outcome measures were different between study groups with exception of EQ-5D-5L health visual analogue scale at 12 months which showed marginally superior (p=0.036) scores in the Avenir group. This study was not powered to detect differences in clinical outcomes.

This study has demonstrated no statistical difference in subsidence or patient-reported outcomes between the Corail hip stem and the more recently introduced Avenir hip stem. This result is predictable as both stems are of a triple-tapered design, are coated with hydroxyapatite, and utilize a broach-only bone preparation technique. Both stem designs demonstrate migration below 0.5mm suggesting both are low-risk for aseptic loosening in the long-term.

Total hip arthroplasty (THA) is one of the most successful and commonly performed surgical interventions worldwide. Based on registry data, at one-year post THA, implant survivorship is nearly 100% and patient satisfaction is 90%. A novel, porous coated acetabular implant was introduced in Europe and Australia in 2007. Several years after its introduction, warnings were issued for the system when used with metal-on-metal bearings due to adverse local tissue reaction, with one study reporting a 24% failure rate (Dramis et al. 2014). A subsequent 2018 study by Teoh et al. showed that the acetabular system had a survival rate of 98.9% at five years when used with conventional polyethylene or ceramic bearing surfaces. The current study was conducted to determine the safety and effectiveness of the acetabular system using standard highly-crosslinked polyethylene (XLPE) and ceramic liners at five-year follow-up. Our hypothesis was that the acetabular system would exhibit survivorship comparable to other acetabular components on the market at five-year follow-up.

A prospective, non-randomized study was conducted from February 2009 to June 2017 at eight sites in Canada and the USA. One hundred fifty-five hips were enrolled and 148 hips analyzed after THA indicated for degenerative arthritis. At five-year follow-up, 103 subjects remained for final analysis. All patients received a zero, three, or multi-hole R3 acetabular shell with Stiktite porous coating (Smith & Nephew, Inc., Memphis, TN, USA). Standard THA surgical techniques were employed, with surgical approach and either of a XLPE or ceramic bearing surface chosen at the discretion of the surgeon. The primary outcome was revision at five-years post-op with secondary outcomes including the Harris Hip Score (HHS), Hip Disability and Osteoarthritis Outcome Score (HOOS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), radiographic analysis, and post-operative adverse events. Data and outcomes were analyzed using summary statistics with 95% confidence intervals, t-tests, and Wilcoxon Rank tests.

At five-year follow-up the overall success rate was 97.14% (95% CI: 91.88–100). When analyzed by liner type, the success rate was 96.81% (95% CI: 90.96–99.34) for polyethylene (n=94) and 100% (95% CI: 71.51–100) for ceramic (n=11), with no significant difference between either liner type (p=1). There were three revisions during the study (1.9%), two for femoral stem revision post fracture, and one for deep infection. The HHS (51.36 pre-op, 94.50 five-year), all 5 HOOS sub-scales, and WOMAC (40.9 pre-op, 89.13 five-year) scores all significantly improved (p < 0 .001) over baseline scores at all follow-up points. One (0.7%) subject met the criteria for radiographic failure at one-year post-op but did not require revision. Six (1.8%) of the reported adverse events were considered related to the study device, including four cases of squeaking, one bursitis, and one femur fracture.

Results from this five-year, multicenter, prospective study indicate good survivorship for this novel, porous coated acetabular system. The overall survivorship of 97.14% at five-year follow-up is comparable to that reported for similar acetabular components and aligns with previous analyses (Teoh et al. 2018).

Introduction

Total hip arthroplasty (THA) is a highly successful procedure achieving excellent clinical outcomes beyond 10 years post-surgery. With exception of periprosthetic infection, dislocation is the most common cause of failure in THA. A novel reverse total hip (RTH) replacement has been developed to address dislocation through reversal of the typical THA articulation in which a femoral cup and acetabular ball interlock at the extremes of motion to enhance mechanical stability in all planes. The purpose of this study was to assess the safety and efficacy of this novel RTH in a series of 22 patients and to monitor implant fixation using radiostereometric analysis (RSA).

Non-large head Metal-on-metal (MoM) hip replacements were seen as a solution to concerns about implant wear in younger patients. Mid-term loosening of once well-fixed hydroxyapatite (HA) coated femoral stems was recently observed in select MoM patients upon revision surgery. Accordingly, an implant retrieval study was undertaken to examine the incidence of aseptic loosening of in HA-coated femoral stems with MoM, ceramic on ceramic (CoC) and metal on polyethylene (MoP) bearing couples.

A single-centre implant retrieval lab reviewed 44 hydroxyapatite (HA)-coated titanium wedge taper stems of the same design retrieved over a period of 9 years. Ten were MoM articulations, 23 MoP and 11 CoC. Head sizes ranged from 28 to 40 with only four 40mm heads, all of which were MoM. Reason for revision, duration of implantation, femoral head size, patient age and body mass index was recorded for each retrieval. Goldberg corrosion scores were determined for the taper surfaces of each retrieval, with ‘0’ indicating no corrosion and ‘3’ indicating severe corrosion. Logistic regression analysis, Wilcoxan Rank Sum and Fischer's exact test were used for statistical analysis.

Aseptic loosening was the listed reason for revision in 18 of 44 cases. MoM bearing was associated with increased probability of aseptic loosening (Odds ratio 7.1 (95%CI 1.1–47.0) p=0.042). Severity of corrosion was also associated with aseptic loosening (Odds ratio 2.75 (95%CI 1.1–6.6) p=0.02). Head size and patient age had no correlation. Median time to revision of implants for aseptic loosening was 4.5 years (range: 4.2–7.0 years) for MoM versus 1.4 years (range: 0.3–3.0) for other bearing couples (p=0.004). Aseptic loosening was categorised as early (<=2 years) or mid-term (>2 years). No MoM hips were revised for aseptic loosening in the first 2 years while 8 of the 11 mid-term revisions had MoM articulations (p=0.004). Taper corrosion was more severe in mid-term aseptic loosing cases (p=0.049).

MoM HA-coated hip replacements appear to be associated with increased mid-term aseptic loosening compared to other bearing couples. Patients with MoM HA-coated hip replacements should be monitored regularly beyond the initial 1 to 2 years following surgery. Future analyses will examine the presence and progression of femoral radiolucency prior to revision surgery to determine an approximate timeline of stem loosening in this patient cohort. This research highlights the importance of implant retrieval programs to assess post-revision implant characteristics for early identification of possible device issues.

Introduction

The purpose of this study was to compare the clinical outcomes and complications following bilateral simultaneous total knee arthroplasty in high body mass index (BMI) patients(>30kg/m²) to those of patients with a BMI<30 kg/m².

Purpose

The purpose of the study was to determine the rate of conversion from RSA to THR in a number of Canadian centers performing resurfacings

Wear of the polyethylene (PE) insert in total knee replacements can lead to wear-particle and fluid-pressure induced osteolysis. One major factor affecting the wear behaviour of the PE insert in-vivo is the surface characteristics of the articulating femoral components. Contemporary femoral components available in Canada are either made of cast Cobalt Chromium (CoCr) alloy or have an oxidized zirconium surface (Oxinium). The latter type of femoral components have shown to have increased abrasive wear resistance and increased surface wettability, thus leading to reduced PE wear in-vitro compared with conventional cast CoCr components. Although surface damage has been reported on femoral components in general, there have been no reports in the literature as to what extent the recommended operating techniques affect the surface tribology of either type of femoral component.

Twenty-two retrieved total knee replacements were identified with profound surface damage on the posterior aspect of the femoral condyles. The femoral components were of three different knee systems: five retrievals from the NexGen(r) total knee system (Zimmer Inc., Warsaw, IN), twelve retrievals from the Genesis II(r) total knee system (CoCr alloy or Oxinium; Smith & Nephew Inc., Memphis, TN), and five retrievals from the Duracon(r) total knee system (Stryker Inc., Mahwah, NJ). Reasons for revision were all non-wear-related and included aseptic loosening in two cases, painful flexion instability, and chronic infection. All retrieved femoral components showed evidence of surface damage on the condyles, at an average of 99° flexion (range, 43° – 135° flexion). Titanium (Ti) alloy transfer and abrasive surface damage were evident on all retrieved CoCr alloy femoral components that came in contact with Ti alloy tibial trays. Surface damage on the retrieved Oxinium femoral components was gouging, associated with the removal and cracking of the oxide and exposure of the zirconium alloy substrate material. CoCr alloy femoral components that had unintended contact with CoCr alloy tibial trays also showed evidence of gouging and abrasive wear.

All femoral components showed severe surface damage in the posterior aspect of the condyles. The femoral surface was heavily scratched and the oxidized zirconium coating surface appeared removed. The surface analysis suggested that the surface damage most likely occurred during the time of initial implantation. In particular, it appeared that the femoral condyles were resting on the posterior aspect of the tibial tray in flexion, thus scratching the femoral components. Such scratches could potentially lead to accelerated PE insert wear and reduced implant longevity, thus making expensive revisions surgery necessary. The authors strongly suggest a revision of the current operating techniques recommended by the implant manufacturer to prevent this type of surface damage from occurring.

Purpose: The purpose of this study is to measure in vivo linear head penetration of a newer generation highly crosslinked liner (X3, Stryker Orthopedics) using Radiostereometric Analysis (RSA).

Method: The 12 hips (11 patients) included in this study are a subset from a larger randomized controlled trial comparing Exeter stem migration in cement mantles with and without Tobramycin. Criteria for inclusion in this subset were the use of an uncemented Trident acetabular component containing X3 polyethylene in combination with a 32 mm stainless steel femoral head. The average age was 72.7 years (range 65 to 80), and there was an equal gender distribution. RSA examinations were taken with patients lying supine at six weeks, six months, one year, and two years postoperatively. The six week examinations were used as the reference examinations for measuring head penetration. Radiographic measurements and analyses were performed with the UmRSA software suite version 6.0 (RSA Biomedical, Umea, Sweden). Head penetration was determined via edge-detection measurements of the femoral head and acetabular cup.

Results: The mean cumulative femoral head penetration at 6 months was 0.23 mm; this remained statistically unchanged both at 1 year: 0.20mm (p=0.69, 95% UCL of the difference: +0.15mm) and 2 years: 0.25mm (p=0.77, 95% UCL of the difference: +0.10mm).

Conclusion: It is generally recognized that femoral head penetration of more than 0.1 mm per year can result in osteolysis. The purpose of cross linking polyethylene is to reduce wear to below this level. The results of this study show that after an initial bedding in of approximately 0.2 mm, femoral head penetration is not detectable over the subsequent 18 months. Further follow-up is underway to confirm that this promising reduction in wear is maintained.

Purpose: The purpose of this study is to determine if the addition of Tobramycin antibiotic powder to cement for primary hip replacement surgery increases the risk of long term aseptic loosening. This was accomplished by measurement of implant micromotion with Radiostereometric Analysis (RSA).

Method: Exeter femoral stems and Trident acetabular components were implanted into 33 patients. Stems were cemented in a randomized manner with either Simplex P or Simplex T. Tantalum beads were injected into the femur to serve as reference points for RSA measurements. RSA examinations were taken with supine positioning at six weeks, six months, one year, and two years post-operatively. Radiographic measurements and analyses were performed with the UmRSA software suite version 6.0 (RSA Biomedical, Umea, Sweden). Distal migration of the stem centroid was measured at each follow-up period and the mean migration rates for both groups were determined. Non-inferiority testing of stem migration in Simplex T compared to Simplex P was accomplished using a one sided t-test, with the significance level set at 0.05. A clinically inferior additional amount of distal migration was set at 0.4mm/yr.

Results: Eleven patients were excluded from the study: seven patients either dropped out of the study or missed the six week and/or two year follow-up examinations, two patients had radiographic image quality issues, and two patients had loosening of their tantalum markers in subsequent follow-ups. Of the remaining 22 patients, eight were male and 14 were female, with an average age at time of surgery of 71.2 (range, 63–81) years. The mean total distal migrations for the Tobramycin and non-Tobramycin cement groups at two years were 0.891 and 0.732 mm, respectively; the mean stem migration rates were 0.263 and 0.179 mm/yr, respectively. The differences in total distal migration and stem migration rate were not statistically significant (P = 0.06 and UCL = 0.173, respectively).

Conclusion: The addition of Tobramycin to Simplex cement does not appear to impact the distal migration pattern for a polished tapered cemented hip stem at two years. This finding suggests that Tobramycin does not have any clinically relevant deleterious effects on the in vivo mechanical properties of Simplex cement.

Image guided navigation systems for total knee replacement surgery (TKR) are gaining popularity in an effort to improve both alignment and functional outcome. This trial was undertaken to compare one year functional outcome and radiological alignment of TKRs inserted with and without an image guided navigation system.

Patients were randomised to undergo surgery using either an image guided navigation system or traditional instrumentation. Pre and post-operative Knee Society (KSS), WOMAC and SF-36 scores were collected. Postoperatively, limb and implant alignment & rotation were assessed using both full-length films and CT scans.

One hundred and twenty-three patients (one hundred and forty-five knees) were enrolled: eighty-one females, forty-two males, mean age sixty-seven years. Age, gender and pre-operative range of motion, KSS WOMAC and SF-36 scores did not differ between the groups. While there was no statistically significant difference in postoperative KSS, WOMAC and seven of eight SF-36 subscales, the navigated group demonstrated better post-operative SF-36 General Health Scores. Mean postoperative flexion in all patients was 115°, and did not differ between groups. Mean post-operative leg alignment demonstrated more varus in the navigated group (2.1°) versus the non-navigated group (0.9°, p=0.02), however there was a trend towards a smaller standard deviation in the navigated group. Rotational alignment of the femoral component relative to the femur, tibial component relative to the tibia, and tibial component relative to the femoral component were not statistically different between groups; however, there were larger standard deviations of these measures in the non-navigated group. Pre-operative alignment appeared to affect tibial component placement; varus knees had a mean of 3° of tibial component internal rotation while valgus knees had a mean of 12° external rotation.

Imaged guided navigation systems appear to reduce the variability in TKR component placement and limb alignment. However, this may not necessarily translate into better mean limb alignment or early functional outcome.

A retrospective case-control study was performed to examine modifiable medical co-morbidities in patients who develop deep infection after primary total hip or knee replacement. To reduce bias, matching was undertaken using age, gender, and procedure. Co-morbidities were classified by system: cardiovascular, respiratory, gastrointestinal, genitourinary, metabolic, haematological and neurological. Initial analyses demonstrate that patients with infected primary hip or knee replacements are more likely to suffer from medical conditions than patients who did not develop infections. Since many of these co-morbidities are preventable or treatable, early screening and intervention may play a role in reducing prosthetic joint infection.

Deep infection of total hip (THA) and knee replacements (TKA) causes significant patient morbidity and requires considerable health care resources to treat. In order to identify preventable or modifiable medical conditions associated with prosthetic joint infection, a retrospective case-control study was undertaken.

Fifty patients who developed a culture proven deep infection after primary THA or TKA were studied. To reduce bias, a control group of arthroplasty patients was selected using one to one matching based on age, gender, and procedure. Co-morbidities in each group were recorded, and classified by system.

Analysis revealed that patients with joint infections are more likely to suffer from an increased number of co-morbidities than the matched control group. The odds ratios and 95% confidence intervals were determined as: cardiovascular 2.3 (1.0–5.0), respiratory 2.3 (0.8–6.7), gastrointestinal 0.8 (0.4–1.9), genitourinary 3.1 (1.1–8.9), metabolic 1.8 (0.7–4.9), haematological 2.9 (1.1–7.8), neurological 2.9 (0.8–9.9) and diabetes 4.0 (1.2–13.4). The case group had a higher mean BMI than the control group: 33.7 versus 30.9, p=0.00.

Since many of the co-morbidities associated with infection are preventable or readily treatable, early screening and intervention may play a role in reducing the burden of prosthetic joint infection.

A retrospective case-control study was performed to examine modifiable medical co-morbidities in patients who develop deep infection after primary total hip or knee replacement. To reduce bias, matching was undertaken using age, gender, and procedure. Co-morbidities were classified by system: cardiovascular, respiratory, gastrointestinal, genitourinary, metabolic, haematological and neurological. Initial analyses demonstrate that patients with infected primary hip or knee replacements are more likely to suffer from medical conditions than patients who did not develop infections. Since many of these co-morbidities are preventable or treatable, early screening and intervention may play a role in reducing prosthetic joint infection.

Deep infection of total hip (THA) and knee replacements (TKA) causes significant patient morbidity and requires considerable health care resources to treat. In order to identify preventable or modifiable medical conditions associated with prosthetic joint infection, a retrospective case-control study was undertaken.

Fifty patients who developed a culture proven deep infection after primary THA or TKA were studied. To reduce bias, a control group of arthroplasty patients was selected using one to one matching based on age, gender, and procedure. Co-morbidities in each group were recorded, and classified by system.

Analysis revealed that patients with joint infections are more likely to suffer from an increased number of co-morbidities than the matched control group. The odds ratios and 95% confidence intervals were determined as: cardiovascular 2.3 (1.0 – 5.0), respiratory 2.3 (0.8 – 6.7), gastrointestinal 0.8 (0.4–1.9), genitourinary 3.1 (1.1–8.9), metabolic 1.8 (0.7 – 4.9), haematological 2.9 (1.1–7.8), neurological 2.9 (0.8–9.9) and diabetes 4.0 (1.2–13.4). The case group had a higher mean BMI than the control group: 33.7 versus 30.9, p=0.00.

Since many of the co-morbidities associated with infection are preventable or readily treatable, early screening and intervention may play a role in reducing the burden of prosthetic joint infection.