Stergios Lazarinis

Increased risk of revision of acetabular cups coated with hydroxyapatite: A Swedish Hip Arthroplasty Register study involving 8,043 total hip replacements

Background Hydroxyapatite (HA) is the main inorganic component of bone, and HA coating is widely used on acetabular cups in hip arthroplasty. It has been suggested that this surface finish improves cup survival. Methods All patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2007 with an uncemented acetabular implant that was available either with or without HA coating were identified. 8,043 total hip arthroplasties (THAs) with the most common cup types (Harris-Galante, Romanus, and Trilogy) were investigated. A Cox regression model including type of coating, age, sex, primary diagnosis, cup type, and type of stem fixation was used to calculate adjusted risk ratios (RRs) for the risk of revision. Results HA coating was a risk factor for cup revision due to aseptic loosening (adjusted RR 1.7; 95% CI: 1.3–2). Age at primary arthroplasty of < 50 years, a diagnosis of pediatric hip disease, the use of a cemented stem, and the Romanus and Harris-Galante cup types were also associated with statistically significantly increased risk of cup revision due to aseptic loosening. Interpretation Our findings question the routine use of HA-coated cups in primary total hip arthroplasty. With some designs, this practice may even increase the risk of loosening—resulting in revision surgery.

Effects of hydroxyapatite coating on survival of an uncemented femoral stem: A Swedish Hip Arthroplasty Register study on 4,772 hips

Background and purpose Hydroxyapatite (HA) is widely used as a coating for uncemented total hip arthroplasty components. This has been suggested to improve implant ingrowth and long-term stability. However, the evidence behind the use of HA coating on femoral stems is ambiguous. We investigated survival of an uncemented, tapered titanium femoral stem that was available either with or without HA coating (Bi-Metric). Patients and methods The stem had been used in 4,772 total hip arthroplasties (THAs) in 4,169 patients registered in the Swedish Hip Arthroplasty Register between 1992 and 2009. 59% of the stems investigated were coated with HA and 41% were uncoated. Kaplan-Meier survival analysis and a Cox regression model with adjustment for age, sex, primary diagnosis, and the type of cup fixation were used to calculate survival rates and adjusted risk ratios (RRs) of the risk of revision for various reasons. Results The 10-year survival rates of the HA-coated version and the uncoated version were about equal when we used revision for any reason as the endpoint: 98% (95% CI: 98–99) and 98% (CI: 97–99), respectively. A Cox regression model adjusting for the covariates mentioned above showed that the presence of HA coating did not have any influence on the risk of stem revision for any reason (RR = 1.0, 95% CI: 0.6–1.6) or due to aseptic loosening (RR = 0.5, CI: 0.2–1.5). There was no effect of HA coating on the risk of stem revision due to infection, dislocation, or fracture. Interpretation The uncemented Bi-Metric stem showed excellent 10-year survival. Our findings do not support the use of HA coating on this stem to enhance implant survival.

A prospective cohort study on the short collum femoris preserving (CFP) stem using RSA and DXA : Primary stability but no prevention of proximal bone loss in 27 patients followed for 2 years

Background and purpose Short femoral stems have been introduced in total hip arthroplasty in order to save proximal bone stock. We hypothesized that a short stem preserves periprosthetic bone mineral density (BMD) and provides good primary stability. Methods We carried out a prospective cohort study of 30 patients receiving the collum femoris-preserving (CFP) stem. Preoperative total hip BMD and postoperative periprosthetic BMD in Gruen zones 1–7 were investigated by dual-energy x-ray absorptiometry (DXA), stem migration was analyzed by radiostereometric analysis (RSA), and the Harris hip score (HHS) was determined. Results 2 patients were excluded intraoperatively and 1 patient was revised due to a deep infection, leaving 27 patients for analysis. The mean HHS increased from 49 (24–79) preoperatively to 99 (92–100) after 2 years. DXA after 1 year showed substantial loss of BMD in Gruen zone 7 (–31%), zone 6 (–19%), and zone 2 (–13%, p < 0.001) compared to baseline BMD determined immediately postoperatively. The bone loss in these regions did not recover after 2 years, whereas the more moderate bone loss in Gruen zones 1, 3, and 5 partially recovered. There was a correlation between low preoperative total hip BMD and a higher amount of bone loss in Gruen zones 2, 6 and 7. RSA showed minor micromotion of the stem: mean subsidence was 0.13 (95% CI: –0.28 to 0.01) mm and mean rotation around the longitudinal axis was 0.01º (95% CI: –0.1 to 0.39) after 2 years. Interpretation We conclude that substantial loss in proximal periprosthetic BMD cannot be prevented by the use of a novel type of short, curved stem, and forces appear to be transmitted distally. However, the stems showed very small migration—a characteristic of stable uncemented implants.

Hydroxyapatite coating does not improve uncemented stem survival after total hip arthroplasty!: An analysis of 116,069 THAs in the Nordic Arthroplasty Register Association (NARA) database

Background and purpose — It is still being debated whether HA coating of uncemented stems used in total hip arthroplasty (THA) improves implant survival. We therefore investigated different uncemented stem brands, with and without HA coating, regarding early and long-term survival. Patients and methods — We identified 152,410 THA procedures using uncemented stems that were performed between 1995 and 2011 and registered in the Nordic Arthroplasty Register Association (NARA) database. We excluded 19,446 procedures that used stem brands less than 500 times in each country, procedures performed due to diagnoses other than osteoarthritis or pediatric hip disease, and procedures with missing information on the type of coating. 22 stem brands remained (which were used in 116,069 procedures) for analysis of revision of any component. 79,192 procedures from Denmark, Norway, and Sweden were analyzed for the endpoint stem revision. Unadjusted survival rates were calculated according to Kaplan-Meier, and Cox proportional hazards models were fitted in order to calculate hazard ratios (HRs) for the risk of revision with 95% confidence intervals (CIs). Results — Unadjusted 10-year survival with the endpoint revision of any component for any reason was 92.1% (CI: 91.8–92.4). Unadjusted 10-year survival with the endpoint stem revision due to aseptic loosening varied between the stem brands investigated and ranged from 96.7% (CI: 94.4–99.0) to 99.9% (CI: 99.6–100). Of the stem brands with the best survival, stems with and without HA coating were found. The presence of HA coating was not associated with statistically significant effects on the adjusted risk of stem revision due to aseptic loosening, with an HR of 0.8 (CI: 0.5–1.3; p = 0.4). The adjusted risk of revision due to infection was similar in the groups of THAs using HA-coated and non-HA-coated stems, with an HR of 0.9 (CI: 0.8–1.1; p = 0.6) for the presence of HA coating. The commonly used Bimetric stem (n = 25,329) was available both with and without HA coating, and the adjusted risk of stem revision due to aseptic loosening was similar for the 2 variants, with an HR of 0.9 (CI: 0.5–1.4; p = 0.5) for the HA-coated Bimetric stem. Interpretation — Uncemented HA-coated stems had similar results to those of uncemented stems with porous coating or rough sand-blasted stems. The use of HA coating on stems available both with and without this surface treatment had no clinically relevant effect on their outcome, and we thus question whether HA coating adds any value to well-functioning stem designs.

Avascular necrosis and subsequent femoral neck fracture 3.5 years after hip resurfacing: a highly unusual late complication in the absence of risk factors--a case report.

Avascular necrosis and subsequent femoral neck fracture 3.5 years after hip resurfacing : a highly unusual late complication in the absence of risk factors--a case report

Effects of hydroxyapatite coating of cups used in hip revision arthroplasty.

Background and purpose Coating of acetabular revision implants with hydroxyapatite (HA) has been proposed to improve ingrowth and stability. We investigated whether HA coating of revision cups can reduce the risk of any subsequent re-revision. Methods We studied uncemented cups either with or without HA coating that were used at a primary acetabular revision and registered in the Swedish Hip Arthroplasty Register (SHAR). 2 such cup designs were identified: Harris-Galante and Trilogy, both available either with or without HA coating. These cups had been used as revision components in 1,780 revisions of total hip arthroplasties (THA) between 1986 and 2009. A Cox proportional hazards model including the type of coating, age at index revision, sex, cause of cup revision, cup design, the use of bone graft at the revision procedure, and the type of cup fixation at primary THA were used to calculate adjusted risk ratios (RRs with 95% CI) for re-revision for any reason or due to aseptic loosening. Results 71% of the cups were coated with HA and 29% were uncoated. At a mean follow-up time of 6.9 (0–24) years, 159 (9%) of all 1,780 cups had been re-revised, mostly due to aseptic loosening (5%), dislocation (2%), or deep infection (1%). HA coating had no significant influence on the risk of re-revision of the cup for any reason (RR = 1.4, CI: 0.9–2.0) or due to aseptic loosening (RR = 1.1, 0.6–1.9). In contrast, HA coating was found to be a risk factor for isolated liner re-revision for any reason (RR = 1.8, CI: 1.01–3.3). Age below 60 years at the index cup revision, dislocation as the cause of the index cup revision, uncemented cup fixation at primary THA, and use of the Harris-Galante cup also increased the risk of re-revision of the cup. In separate analyses in which isolated liner revisions were excluded, bone grafting was found to be a risk factor for re-revision of the metal shell due to aseptic loosening (RR = 2.1, CI: 1.05–4.2). Interpretation We found no evidence to support the notion that HA coating improves the performance of the 2 studied cup designs in revision arthroplasty. In contrast, patient-related factors such as younger age and dislocation as the reason for cup revision, and technical factors such as the choice of revision cup were found to influence the risk of subsequent re-revision of the cup. The reason for inferior results after revision of uncemented cups is not known, but it is possible that these hips more often had pronounced bone loss at the index cup revision.

Bone loss around a stable, partly threaded hydroxyapatite-coated cup: a prospective cohort study using RSA and DXA

Study purpose Aseptic loosening of the acetabular component is the most common reason for revision after primary THA, and periprosthetic demineralisation has been described as a potential cause for this process. The trabeculae-oriented pattern (TOP)-cup is a flat, hydroxyapatite (HA)-coated titanium shell with a threaded rim that was developed in order to minimise periprosthetic bone loss. We hypothesised that this cup provides good primary stability and improves preservation of periprosthetic bone mineral density (BMD). Basic procedures A prospective cohort study on 30 patients receiving the TOP cup was carried out. Preoperative total hip BMD and postoperative periprosthetic BMD in five periprosthetic regions of interest were investigated by dual energy radiographic absorptiometry (DXA), cup migration was analysed by radiostereometry (RSA), and the Harris hips score (HHS) was determined. Main findings Mean HHS increased from 49 (24-79) preoperatively to 99 (92-100) after two years. DXA after one year demonstrated substantial BMD loss in the proximal periprosthetic zones 1 (-18%), zone 2 (-16 %) and zone 3 (-9%, all p≤0.001 when compared with baseline BMD determined immediately postoperatively). The bone loss in these regions did not recover after two years. RSA (performed on 16 patients) showed that only very limited micromotion of the implant occurred: Mean cranial migration was 0.01 mm (95% confidence interval (CI): −0.09-0.12) and mean inclination decreased by 0.02° (CI: −0.43-0.39) after two years. conclusion We conclude that the TOP cup provides good primary stability in the short-term. However, substantial BMD loss in proximal periprosthetic areas indicates that the design of this cup cannot prevent periprosthetic bone loss that has also been observed around other uncemented cups.

Erratum to: Does the Alpha-defensin Immunoassay or the Lateral Flow Test Have Better Diagnostic Value for Periprosthetic Joint Infection? A Systematic Review

Background Measuring alpha-defensin concentrations in synovial fluid may help to diagnose periprosthetic joint infection (PJI). There are two commercially available methods for measuring alpha-defensin in synovial fluid: the enzyme-linked immunosorbent assay-based Synovasure® alpha-defensin immunoassay, which gives a numeric readout within 24 hours, and the Synovasure lateral flow test, which gives a binary readout within 20 minutes. There is no compilation of the existing literature to support the use of one of these two tests over the other. Questions/purposes Does the immunoassay or the lateral flow test have better diagnostic value (sensitivity and specificity) in diagnosing PJI? Methods We followed PRISMA guidelines and identified all studies on alpha-defensin concentration in synovial fluid as a PJI diagnostic marker, indexed to April 14, 2017, in PubMed, JSTOR, Google Scholar, and OVID databases. The search retrieved 1578 records. All prospective and retrospective studies on alpha-defensin as a PJI marker (PJI classified according to the criteria of the Musculoskeletal Infection Society) after THA or TKA were included in the analysis. All studies used only one of the two commercially available test methods, but none of them was comparative. After excluding studies with overlapping patient populations, four studies investigating the alpha-defensin immunoassay and three investigating the lateral flow test remained. Alpha-defensin immunoassay studies included 482 joints and lateral flow test studies included 119. The quality of the trials was assessed according to the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The heterogeneity among studies was evaluated by the I2 index, indicating that the heterogeneity of the included studies was low. Pooled sensitivity, specificity, positive and negative likelihood ratios, and receiver operating curves were calculated for each method and compared with each other. Results The alpha-defensin immunoassay had superior overall diagnostic value compared with the lateral flow test (area under the curve, 0.98 versus 0.75) with higher sensitivity (96% [90%-98%] versus 71% [55%-83%], p < 0.001), but no difference in specificity with the numbers available (96% [93%-97%] versus 90% [81%-95%], p = 0.060). Conclusions Measurement of alpha-defensin in synovial fluid is a valuable complement to existing diagnostic criteria, and the immunoassay test detects PJI more accurately than the lateral flow test. The lateral flow test has lower sensitivity, making it difficult to rule out infection, but its relatively high specificity combined with the advantage of a quick response time can make it useful to rule in infection perioperatively. Level of Evidence Level III, diagnostic study.

Algorithm to Diagnose Delayed and Late PJI: Role of Joint Aspiration

Total Joint Arthroplasty (TJA) continues to gain acceptance as the standard of care for the treatment of severe degenerative joint disease, and is considered one of the most successful surgical interventions in the history of medicine. A devastating complication after TJA is infection. Periprosthetic joint infection (PJI), represents one of the major causes of failure and remains a significant challenge facing orthopaedics today. PJI usually requires additional surgery including revision of the implants, fusion or amputations causing tremendous patient suffering but also a heavy health economics burden. PJI is at the origin of around 20-25 % of total knee arthroplasty (Bozic et al. 2010; de Gorter et al. 2015; Sundberg et al. 2015) and 12-15 % of total hip arthroplasty (Bozic et al. 2009; Garellick et al. 2014; de Gorter et al. 2015) failures.

Consensus document on prosthetic joint infections

Since the start of the modern era of prosthetic surgery, prosthetic joint infections (PJIs) have been a predominant and most feared complication. Reduction of PJI has been described as a success story, with the infection rate declining from 10% at the beginning of the 1970s to around 1% a couple of decades later (Lidgren 2001, SHPR 2011, SKAR 2013). Concerns are, however, being raised because the Scandinavian arthroplasty registers are now reporting an increase in revision rates due to infection (Dale et al. 2012, SHPR 2011, SKAR 2013). This has caused the Swedish Orthopaedic Society, in association with the patient insurance organization LOF, to take action in a national program covering all clinics with the aim of cutting down PJI by half (http://www.patientforsakring.se/PRISS.html). Prior to a one-day visit by a well-prepared interdisciplinary team, a unit would answer standard questions about its routines regarding important aspects of prophylactic measures. A report on courses of action to be taken had to be delivered by each unit within 6 months—based on critical comments from the visiting group. The effects of the project are now being evaluated. Globally, there is great variation in how PJIs are prevented and managed. Some of the preventive routines used are supported by good evidence from well-conducted studies, but there is limited information on how well the routines are adhered to in daily practice. In a recent study from the ISOC Group, covering 17 leading hospitals together performing more than 50,000 joint implants a year, there were clear discrepancies between the available evidence on the one hand and what was regarded by the participating hospitals to be important for prevention of PJI on the other (Ricciardi et al. 2013). Under the leadership of Dr Javad Parvizi of the Rothman Institute in Philadelphia and Dr Thorsten Gehrke of the ENDO Clinic in Germany, it was decided to start working groups to collect information on prevention and treatment of PJI, prior to a 2-day international consensus meeting in Philadelphia at the end of July 2013. Fifteen groups covered topics that ranged from comorbidities, skin preparation, perioperative antibiotics, and operative environment to the diagnosis of PJI, antibiotic treatment, one-change vs. two-stage exchange arthroplasty, and prevention of late prosthetic infections. The working groups were composed of 400 experts from 51 countries who—over 10 months—summarized, evaluated, and commented on more than 3,500 relevant publications. After making a synthesis of the literature and of the comments received, a preliminary draft was ready for the more than 300 delegates who attended a face-to-face meeting in Philadelphia. The document was discussed during day 1 and several changes were made. A voting process on every one of the 207 consensus statements was then conducted on day 2, by electronic voting. There was a unanimous vote (100% agreement) for one question (controlling OR traffic), 202 questions received strong consensus (66–99% agreement), two questions had weak consensus (60–65%), and only two questions did not achieve any consensus (less than 60%). After the meeting, the document was again edited and is now available at http://www.msis-na.org/international-consensus/. Of the experts who contributed to the final document more than 150 were from the USA, and 19 came from the Nordic countries and the Netherlands. It is quite clear that there is valuable information on PJI in the extensive document, which will serve as a reference and a source of knowledge for orthopaedic surgeons worldwide. It can be seen as a starting point for a global collaboration and discussion that will hopefully accelerate measures to change the present dangerous situation with an increasing number of PJIs and emerging antibiotic resistance. A general comment on the “consensus” process in Philadelphia was that it did not allow any deeper discussions because of the time limitation. Due to the extensiveness of the final draft and the fact that late changes were made, it was difficult for the delegates to evaluate in detail the evidence behind each of the 207 consensus statements that were voted on. Thus, the consensus statements can only be seen as expert opinion, and it is important to emphasize the fundamental difference between expert opinion and clinical guidelines. The working groups have identified a number of possible topics for future research, such as preoperative decolonization, new methods for culture and microbial identification, new resorbable carriers containing antibiotics for prevention and treatment of prosthetic joint infections, randomized studies to determine the outcome of one-stage versus two-stage procedures, and determining the ultimate timing of re-implantation. Our advice to all orthopedic surgeons working with joint implants is to start reading the over 300-page document that is available at http://www.msis-na.org/international-consensus/.