Early Staphylococcal Periprosthetic Joint Infection (PJI) Treated with Debridement, Antibiotics, and Implant Retention (DAIR): Inferior Outcomes in Patients with Staphylococci Resistant to Rifampicin.

It is unknown how rifampicin resistance in staphylococci causing a periprosthetic joint infection (PJI) affects outcomes after debridement, antibiotics, and implant retention (DAIR). We thus aimed to compare the risk of relapse in DAIR-treated early PJI caused by staphylococci with or without rifampicin resistance. In total, 81 patients affected by early PJI were included, and all patients were treated surgically with DAIR. This was repeated if needed. The endpoint of relapse-free survival was estimated using the Kaplan-Meier method, and Cox regression models were fitted to assess the risk of infection relapse for patients infected with rifampicin-resistant bacteria, adjusted for age, sex, type of joint, and type of index surgery. In patients with rifampicin-resistant staphylococci, relapse was seen in 80% after one DAIR procedure and in 70% after two DAIR procedures. In patients with rifampicin-sensitive bacteria, 51% had an infection relapse after one DAIR procedure and 33% had an infection relapse after two DAIR procedures. Patients with rifampicin-resistant staphylococcal PJI thus had an increased adjusted risk of infection relapse of 1.9 (95% CI: 1.1-3.6, p = 0.04) after one DAIR procedure compared to patients with rifampicin-sensitive bacteria and a 4.1-fold (95% CI: 1.2-14.1, p = 0.03) increase in risk of infection relapse after two DAIR procedures. Staphylococcal resistance to rifampicin is associated with inferior outcomes after DAIR. These findings suggest that DAIR may not be a useful strategy in early PJI caused by rifampicin-resistant staphylococci.

Incidence of Rifampicin Resistance in Periprosthetic Joint Infection: A Single-Centre Cohort Study on 238 Patients.

BACKGROUND: Rifampicin is a pillar in the treatment of periprosthetic joint infection (PJI). However, rifampicin resistance is an increasing threat to PJI treatment. This study explores the incidence of rifampicin-resistant bacteria over time in a Swedish tertiary referral centre and the association of rifampicin resistance with infection-free survival after PJI. METHODS: The study included 238 staphylococcal PJIs treated between 2001 and 2020 for which susceptibility data for rifampicin were available. Data on causative bacteria, rifampicin resistance, treatment, and outcome were obtained. Kaplan-Meier survival analysis and Cox regression modelling estimated the infection-free cumulative survival and adjusted hazard ratios (HRs) for the risk of treatment failure. RESULTS: Rifampicin-resistant causative bacteria were identified in 40 cases (17%). The proportion of rifampicin-resistant agents decreased from 24% in 2010-2015 to 12% in 2016-2020. The 2-year infection-free survival rates were 78.6% (95% CI, 66.4-93.1%) for the rifampicin-resistant group and 90.0% (95% CI, 85.8-94.4%) for the rifampicin-sensitive group. Patients with PJI caused by rifampicin-resistant bacteria had an increased risk of treatment failure (adjusted HR, 4.2; 95% CI, 1.7-10.3). CONCLUSIONS: The incidence of PJI caused by rifampicin-resistant bacteria did not increase over the past 20 years. The risk of treatment failure in PJI caused by rifampicin-resistant bacteria is more than four times that caused by rifampicin-sensitive bacteria, highlighting the importance of limiting the development of rifampicin resistance.

Low accuracy in preoperative tissue biopsies for diagnosing chronic periprosthetic joint infection: an observational retrospective single-centre study.

OBJECTIVE: Diagnosing periprosthetic joint infection (PJI) can be challenging. The ability to distinguish between septic and aseptic failure of a joint prosthesis is crucial for treatment strategy optimisation and prognosis prediction. Preoperative tissue cultures are included in many diagnostic algorithms; however, studies report different degrees of concordance (63%-85%) with intraoperative cultures. This study aimed to investigate the diagnostic performance of tissue biopsies in the preoperative diagnostic process with the 2018 International Consensus Meeting criteria as a reference and to describe the concordance between microbiological findings in pre- and intraoperative biopsies. METHODS: This observational retrospective study included 44 patients requiring revision surgery of a total hip or knee arthroplasty, where the diagnostic workup included biopsies of periprosthetic tissue. The accuracy of preoperative biopsies was calculated, and concordance between microbiological findings in pre- and intraoperative biopsies was described. RESULTS: The accuracy was 59%, with a sensitivity of 50% and specificity of 79%. Full concordance between microbiological findings in pre- and intraoperative biopsies was found in 64% of the cases. CONCLUSION: An open biopsy of periprosthetic tissue cannot reliably confirm or exclude PJI, and, therefore, should not be performed.

Study protocol: The DAICY trial-dual versus single-antibiotic impregnated cement in primary hemiarthroplasty for femoral neck fracture-a register-based cluster-randomized crossover-controlled trial.

BACKGROUND AND PURPOSE: Older patients with a displaced femoral neck fracture (FNF) are often treated with a cemented primary hemiarthroplasty (HA). The DAICY trial investigates whether high-dose dual-impregnated antibioticloaded cement (DIAC) including gentamicin and clindamycin can reduce the risk of periprosthetic joint infection (PJI) in comparison with low-dose single-impregnated gentamicin antibiotic-loaded cement (SIAC), in patients ≥ 60 years treated with a cemented HA for a displaced FNF. STUDY DESIGN: The trial is a national, multicenter, register-based, cluster-randomized, crossover trial. Patients ≥ 60 years with a non-pathological, displaced FNF (Type Garden 3-4/AO 31-B2 or B3) suitable for HA according to local guidelines are eligible for inclusion. Participating orthopedic departments will be randomized to start with either SIAC (control group) or DIAC treatment (intervention group) for 2 years. After 2 years, the study departments will then change to the other treatment arm for the remaining 2 years of the study. Approximately 7,000 patients will be included. The study is pragmatic in that the choice of implant brands, surgical approach and peri- and postoperative protocols follow the local routines of each participating department. All outcome variables will be retrieved after linkage of the study cohort to the following Swedish registers: the Fracture Register, the Arthroplasty Register, the National Patient Register and the Prescribed Drug Registry Outcome: The primary outcome will be periprosthetic joint infection of the index joint within 1 year after surgery. Secondary outcomes will be any reoperation on the index joint, mortality within 90 days and 1 year, resistance patterns of causative bacteria in cases of PJI, and health economics. Potential added value: This trial is designed to support or refute the efficacy of DIAC used in patients with a displaced FNF, potentially reducing PJI and resource allocation. Start of the trial and estimated duration - The DAICY trial started recruiting patients in January 2022 and will continue recruiting for approximately 4 years. Complete follow-up expected in 5 years.

Patient-related factors associated with superficial surgical site infection and progression to a periprosthetic joint infection after elective primary total joint arthroplasty: a single-centre, retrospective study in Sweden.

OBJECTIVES: Superficial surgical site infection (SSSI) may increase the risk of serious complications such as periprosthetic joint infection (PJI). This study aims to identify patient-related risk factors associated with SSSI and investigate their correlation with the progression of PJI. DESIGN: In this retrospective study, 1191 elective hip and knee prostheses were included. Patients were interviewed 3-5 months after surgery to answer questions about the postoperative period. Patient records were reviewed to determine whether there had been any documentation of wound-healing difficulties or whether antibiotics were prescribed to treat an infection related to arthroplasty surgery. SETTING: Uppsala University Hospital, patients treated between November 2008 and December 2012. PARTICIPANTS: The study population comprised 433 knees and 758 hips. OUTCOME MEASURES: We studied patient-related risk factors (joint, age, sex, the American Society of Anesthesiologists (ASA) classification, body mass index (BMI), smoking, diabetes and rheumatic disease) to determine whether they were associated with (1) SSSI and (2) the progress from SSSI to PJI. RESULTS: 84 (7%) patients of the total cohort developed SSSI. This infection progressed to a PJI in 24 (29%) of the patients. Factors with increased adjusted risk ratios (aRRs) for SSSIs were knee surgery (1.7; 95% CI: 1.1 to 2.7), age≥65 years (1.7; 95% CI: 1.1 to 2.8), BMI≥30 (1.9; 95% CI: 1.0 to 3.4) and ASA classification≥3 (1.7; 95% CI: 1.0 to 2.9). ASA classification≥3 was the only factor showing a significant progression from SSSI to PJI (aRR=3.3; 95% CI: 1.0 to 10.3). CONCLUSIONS: The risk of progressing from an SSSI to a PJI is high. Older patients, patients with obesity, and those with a high ASA classification considered for elective total knee arthroplasty seem to have an increased risk of developing SSSI. Patients with a high ASA classification seem to have an increased risk of progressing from SSSI to PJI.

EPOS trial: the effect of air filtration through a plasma chamber on the incidence of surgical site infection in orthopaedic surgery: a study protocol of a randomised, double-blind, placebo-controlled trial.

INTRODUCTION: There is controversy regarding the importance of air-transmitted infections for surgical site infections (SSIs) after orthopaedic surgery. Research has been hindered by both the inability in blinding the exposure, and by the need for recruiting large enough cohorts. The aim of this study is to investigate whether using a new form of air purifier using plasma air purification (PAP) in operating rooms (ORs) lowers the SSI rate or not. METHODS AND ANALYSIS: Multicentre, double-blind, cluster-randomised, placebo-controlled trial conducted at seven hospitals in 2017-2022. All patients that undergo orthopaedic surgery for minimum 30 min are included. Intervention group: patients operated in OR with PAP devices turned on. CONTROL GROUP: patients operated in OR with PAP devices turned off. Randomisation: each OR will be randomised in periods of 4 weeks, 6 weeks or 8 weeks to either have the devices on or off. PRIMARY OUTCOME: any SSI postoperatively defined as a composite endpoint of any of the following: use of isoxazolylpenicillin, clindamycin or rifampicin for 2 days or more, International Classification of Diseases codes or Nordic Medico-Statistical Committee codes indicating postoperative infection. In a second step, we will perform a chart review on those patients with positive indicators of SSI to further validate the outcome. Secondary outcomes are described in the Methods section. Power: we assume an SSI rate of 2%, an SSI reduction rate of 25% and we need approximately 45 000 patients to attain a power of 80% at a significance level of 0.05. ETHICS AND DISSEMINATION: The study is approved by the Swedish Ethical Review Authority. The interim analysis results from the study will be presented only to the researchers involved unless the study thereafter is interrupted for whatever reason. Publication in a medical journal will be presented after inclusion of the last patient. TRIAL REGISTRATION NUMBER: NCT02695368.

Continuous periprosthetic bone loss but preserved stability for a collum femoris-preserving stem: follow-up of a prospective cohort study of 21 patients with dualenergy X-ray absorptiometry and radiostereometric analysis with minimum 8 years of follow-up.

Background and purpose - We previously described a decrease in bone mineral density (BMD) in the calcar region 2 years after insertion of the collum femoris-preserving (CFP) stem, but the implants were stable. Now we have examined the long-term changes in periprosthetic BMD and stability of the CFP stem. Patients and methods - We conducted a minimum 8-year follow-up of 21 patients from our original investigation. We examined periprosthetic BMD by dual-energy X-ray absorptiometry (DEXA) and implant stability by radiostereometric analysis (RSA). Results - Between 2 and 8 years 1 stem was revised due to aseptic loosening. Between 2 and 8 years we found a 14% (95% confidence interval [CI] 9-19) reduction in BMD in Gruen zone 6 and 17% (CI 6-28) in Gruen zone 7. From baseline the reduction in BMD was 30% (CI 23-36) in Gruen zone 6, 39% (CI 31-47) in Gruen zone 7, and 19% (CI 14-23) in Gruen zone 2. Between 2 and 8 years, RSA (n = 17) showed a mean translation along the stem axis of 0.02mm (CI -0.02 to 0.06) and a mean rotation around the stem axis of 0.08° (CI -0.26 to 0.41). From baseline mean subsidence was 0.07 mm (CI -0.16 to 0.03) and mean rotation around the stem axis was 0.23° (CI -0.23 to 0.68) at 8 years. Interpretation - There was continuous loss of proximomedial BMD at 8 years while the CFP stem remained stable. Proximal periprosthetic bone loss cannot be prevented by this stem.

Exchange of Modular Components Improves Success of Debridement, Antibiotics, and Implant Retention: An Observational Study of 575 Patients with Infection After Primary Total Hip Arthroplasty.

Debridement, antibiotics, and implant retention (DAIR) is a surgical treatment for periprosthetic joint infection (PJI). DAIR is a desirable treatment option from an economic and patient perspective, if successful. The aim of this observational study was to compare the rates of success, defined as no additional reoperations due to PJI, between DAIR with exchange of modular components and DAIR without exchange in patients who had first-time PJI after primary total hip arthroplasty (THA). METHODS: Patients with PJI at the site of a primary THA who were treated with DAIR in Sweden between January 1, 2009, and December 31, 2016, were identified in the Swedish Hip Arthroplasty Register. Supplementary questionnaires were sent to orthopaedic departments for additional variables of interest related to PJI. The primary end point was another reoperation due to PJI within 2 years after the first-time DAIR. DAIR with exchange was compared with DAIR without exchange using Kaplan-Meier survival analysis and Cox regression analysis. RESULTS: A total of 575 patients treated with DAIR for a first-time PJI at the site of a primary THA were analyzed; 364 underwent component exchange and 211 did not. The exchange of components was associated with a lower rate of reoperations due to PJI after DAIR (28.0%) compared with non-exchange (44.1%). The Kaplan-Meier implant survival estimate for exchange was 71.4% (95% confidence interval [CI] = 66.9% to 76.3%) compared with 55.5% (95% CI = 49.1% to 62.7%) for non-exchange. With the analysis adjusted for confounders, DAIR with exchange was associated with a significantly decreased risk of another reoperation due to PJI compared with non-exchange (hazard ratio [HR] = 0.51 [95% CI = 0.38 to 0.68]). CONCLUSIONS: In patients with a first-time PJI at the site of a primary THA, DAIR with exchange of modular components was superior to non-exchange DAIR. Surgeons should strive to exchange components when they perform DAIR, but there is a need to further identify how DAIR best should be practiced and which patients benefit from it. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Low-dose CT-based implant motion analysis is a precise tool for early migration measurements of hip cups: a clinical study of 24 patients.

Background and purpose - Early implant migration is known to be a predictive factor of clinical loosening in total hip arthroplasty (THA). Radiostereometric analysis (RSA) is the gold standard used to measure early migration in patients. However, RSA requires costly, specialized imaging equipment and the image process is complex. We determined the precision of an alternative, commercially available, CT method in 3 ongoing clinical THA studies, comprising 3 different cups.Materials and methods - 24 CT double examinations of 24 hip cups were selected consecutively from 3 ongoing prospective studies: 2 primary THA (1 cemented and 1 uncemented) and 1 THA (cemented) revision study. Precision of the CT-based implant motion analysis (CTMA) system was calculated separately for each study, using both the surface anatomy of the pelvis and metal beads placed in the pelvis.Results - For the CTMA analysis using the surface anatomy of the pelvis, the precision ranged between 0.07 and 0.31 mm in translation and 0.20° and 0.39° for rotation, respectively. For the CTMA analysis using beads the precision ranged between 0.08 and 0.20 mm in translation and between 0.20° and 0.43° for rotations. The radiation dose ranged between 0.2 and 2.3 mSv.Interpretation - CTMA achieved a clinically relevant and consistent precision between the 3 different hip cups studied. The use of different hip cup types, different CT scanners, or registration method (beads or surface anatomy) had no discernible effect on precision. Therefore, CTMA without the use of bone markers could potentially be an alternative to RSA to measure early migration.

Linezolid in the treatment of periprosthetic joint infection caused by coagulase-negative staphylococci.

Background: Periprosthetic joint infection (PJI) caused by coagulase-negative staphylococci (CoNS) is increasingly common and is sometimes treated with off-label use of linezolid. Methods: We conducted a retrospective study of patients with PJI caused by CoNS treated with surgical intervention and orally administrated linezolid during the period 1995-2014 (n = 28). Clinical outcomes and adverse events related to linezolid administration were evaluated. Mean time to follow-up was 4.3 years (range: 0.2-12). Results: Twenty-two of 28 patients were infection-free at follow-up. No CoNS strain was resistant to vancomycin, but 16 of 28 were resistant to rifampicin, 23 of 28 to clindamycin and 20 of 27 to quinolones. The mean duration of linezolid treatment was 4.2 weeks (range: 1-12). Eleven of 28 patients had an adverse event related to the antimicrobial treatment, and four had to discontinue linezolid, but all adverse events were reversible within 2 months after discontinuation. Conclusions: Oral linezolid administration combined with adequate surgical treatment may be useful for the treatment of PJIs caused by CoNS.

Does the Alpha-defensin Immunoassay or the Lateral Flow Test Have Better Diagnostic Value for Periprosthetic Joint Infection? A Meta-analysis.

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 I 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.

Hydroxyapatite coating does not improve uncemented stem survival after total hip arthroplasty!

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.

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 0.02º (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.

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.