Session 1: Hip

Onsdag den 22. oktober
09:00 – 10:30
Lokale: Reykjavik
Chairmen: Nanna Sillesen Hylleholt / Mogens Berg Laursen

1. Prosthetic Joint Infection (PJI): Bacterial Identification with Heat Flow Detection in Sonication Fluid of Removed Total hip or knee Arthroplasty (THA/TKA)
Christen Ravn, Michael Kemp, Per Kjærsgaard-Andersen, Søren Overgaard
Orthopaedic Research Unit, University of Southern Denmark; Department of Clinical Microbiology, Odense University Hospital; Department of Orthopaedic Surgery, Vejle Hospital; Department of Orthopaedic Surgery and Traumatology, Odense University Hospital

Background: In PJI a delay of 5-10 days after surgery is frequent before bacterial diagnosis by conventional culture methods. Introduction of sonication for biofilm dislodgement of removed implants have increased the sensitivity of PJI- diagnostics as compared to culture of biopsies (Trampuz et al. NEJM, 2007). Microcalorimetry can demonstrate microbial growth in small fluid samples as measured by heat flow (µW), and may even give a more rapid diagnosis than simple culture.
Purpose / Aim of Study: To compare microcalorimetry with culture of sonication fluid for bacterial detection, and to evaluate the time to detection (TTD) of bacterial presence by microcalorimetry.
Materials and Methods: We analyzed prosthetic components removed during joint revision for deep infection (Dinf) or aseptic loosening (Asl) of THA and TKA. The prostheses were individually sonicated before aerobic and anaerobic culture, and checked for positive growth (>20 colonies/ml) twice daily. Furthermore sonication fluid (SF) was analyzed with microcalorimetry (TA Instruments) for 48 hours. TTD (hours) was defined as time to reach a detection limit of 10 µW.
Findings / Results: In 111 revisions of THA (70) and TKA (41) indications were resp. Dinf (49) and Asl (62). Sonication fluid was found culture positive in 50 cases, whereas microcalorimetry was positive in only 35 (sensitivity 0.70 / specificity 0.93) with a mean TTD of 9.4 hours (range 1.5-29.4). Bacterial findings of microcalorimetry appears as species (no./mean TTD): S.aureus (9/6.4), E.faecalis (7/8.2), streptococcus sp. (4/12.3), E.coli (1/12.7), and coagulase neg. staph. (13/14.3). Bacteria not found incl. CNS (3), P.acnes (2) and streptococc sp. (2).
Conclusions: Microcalorimetry of sonication fluid demonstrated good specificity, but rather low sensitivity. A bacterial diagnosis was rapidly found (mean 9.4 hr) by heat flow detection.

2. Revision risk of cementless metal-on-metal total hip arthroplasty is influenced by component brand
Claus Varnum, Alma B. Pedersen, Mäkelä Keijo, Leif Ivar Havelin, Johan Kärrholm, Søren Overgaard
Orthopaedic department, Vejle Hospital; Department of clinical epidemiology, Aarhus University Hospital; Department of Orthopaedics and Traumatology, Turku University Hospital, Finland; The Norwegian Arthroplasty Register, Department of Orthopedic Surgery, Haukeland University Hospital, Bergen, Norway; Institute of Clinical Sciences, Department of Orthopaedics, Sahlgrenska University Hospital, Gothenburg, Sweden; Department of Orthopaedic Surgery and Traumatology, Odense University Hospital

Background: There are several concerns for the use of metal-on-metal (MoM) bearings in total hip arthroplasty (THA) especially for certain brands of MoM components due to increased revision rates.
Purpose / Aim of Study: We aimed to investigate the 6-year revision risk of cementless stemmed MoM THAs in a population-based follow-up study from the Nordic Arthroplasty Registry Association (NARA).
Materials and Methods: In the NARA database, we identified 85,371 cementless stemmed primary THAs operated from 2002 to 2010. Metal-on- polyethylene (MoP) THA was used as reference, and only patients operated with MoM or MoP bearings were included. In total, 32,678 patients were included. At 6 years follow-up, the adjusted relative risk (aRR) for any revision with 95% confidence intervals (CI) was assessed by the use of regression with the pseudo-value approach and modelled with death as competing risk.
Findings / Results: 11,567 patients (35%) had MoM and 21,111 (65%) had MoP THAs. The aRR of any revision for MoM was 1.49 (CI: 1.30-1.71). For different brands of acetabular cups in MoM THA, higher RR of any revision was found for the ASR cup (n=759; aRR 6.38, CI: 4.99-8.15), the Conserve Plus cup (n=478; aRR 1.70, CI: 1.14-2.54), and ”other” cups (n=351; aRR 2.38, CI: 1.45-3.92). No difference in RR of any revision was found for the Recap, M2a, Pinnacle, Birmingham, and Durom cups compared to MoP THA. After exclusion of the 759 patients having the ASR acetabular component, the aRR of any revision was 1.12 (CI: 0.97-1.30) for MoM compared to MoP THA.
Conclusions: The aRR of any revision at 6 years follow- up was 49% higher for MoM compared to MoP THA. After exclusion of the ASR cup, the aRR of any revision was 12% higher for MoM THA – although this was not significant. Based on recent reports, we may expect increasing revision rates of MoM THAs with longer follow-up.

3. Regional differences between US and Europe in radiological osteoarthritis and self assessed quality of life in patients undergoing Total Hip Replacement (THR) surgery
Kirill Gromov, Meridith Greene, Nanna Sillesen, Peter Gebuhr, Anders Troelsen, Henrik Malchau
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre; Harris Orthopaedic Laboratory, Massachusetts General Hospital

Background: Precise indications for THR remain unclear and regional differences might exist in selecting patients for surgery.
Purpose / Aim of Study: In this study we investigate radiological grade of OA and self-reported quality of life in patients undergoing THR in US and Europe
Materials and Methods: There are 909 patients from 16 centers in the USA and Europe enrolled into a prospective 10year outcome study. All patients were operated using an uncemented RingLoc® or Regenerex® cup and a Biomet® stem of surgeons’ choice. Recorded patient demographics included age, gender, BMI and Charnley score. Preoperative grade of OA was recorded using Tönnis classification as well as JSW. Self reported survey data included pain visual analogue scale (VAS), EQ-5D, SF36, Harris Hip, and UCLA scores that were recorded preoperatively and at 1 year follow up.
Findings / Results: Patients in US were significantly younger (61.4vs 64.2; p<0.001) and had a higher BMI (29.9vs 27.4; p<0.001). More patients with mild Tonnis OA grade underwent surgery in US compared to Europe (5.3% vs 2.2%, p=0.046). Patients in the US had significantly higher pain VAS (6 vs 5; p=0.004) and significantly lower SF-36 Physical Function (29.7 vs 33.9; p=0.003), while having significantly higher EQ VAS scores (78 vs 66; p<0.001) preoperatively.
Conclusions: Patient demographics and disease severity according to radiological OA grade and self- reported survey scores vary between United States and Europe. This knowledge can be used in the interpretation of US and European based studies on outcome following THR.

4. The “true” incidence of prosthetic joint infection after 32,896 primary total hip arthroplasties: A prospective cohort study
Per Hviid Gundtoft, Søren Overgaard, Henrik Carl Schønheyder, Jens Kjølseth Møller, Per Kjærsgaard-Andersen, Alma Becic Pedersen
Orthopedic, Kolding Hospital and Odense University Hospital; Orthopaedic Surgery and Traumatology, Odense University Hospital; Clinical Microbiology, Aalborg University Hospital; Clinical Epidemiology, Aarhus University Hospital

Background: The risk of prosthetic joint infection in patients with total hip arthroplasty (THA) is often underestimated when based on registry data.
Purpose / Aim of Study: The purpose of this study was to estimate the “true” incidence of prosthetic joint infection in THA using multiple data sources.
Materials and Methods: The Danish Hip Arthroplasty Register (DHR) was searched for primary THAs performed between January 1, 2005 and December 31, 2011 in the Danish provinces Jutland and Funen. The DHR and the Danish National Register of Patients (NRP) were searched to identify first revisions following a primary THA. The revisions were classified as due to prosthetic joint infection or to causes other than infection using an algorithm incorporating intraoperative cultures, aspirations of joint fluid, plasma C- reactive protein, prior use of antibiotics, and clinical findings described in the medical record. We calculated the cumulative incidences.
Findings / Results: A total of 32,896 primary THAs were identified. Of these, first time revisions were reported to the DHR and/or NRP for 1,546. The 1-year cumulative incidences of prosthetic joint infection were 0.51 % [CI 0.44; 0.59] and 0.48 % [0.41; 0.56] for the DHR and NRP, respectively; while, the 5-year cumulative incidences were 0.64 % [0.51; 0.79] and 0.57 % [0.45; 0.71], respectively. The corresponding 1- and 5-year cumulative incidences estimated by the algorithm were 0.86 % [0.77; 0.97] and 1.03 % [0.87; 1.22], respectively. Thus, the “true” incidence of prosthetic joint infection in primary THA was approximately 40 % higher compared with the national registers when using additional data.
Conclusions: The “true” incidence of prosthetic joint infection in primary THA is significantly higher than reported by the Danish national registers and can be estimated using multiple clinical and paraclinical data.

5. Comparison of outcomes and complications of hip arthroscopy for mixed hip disorders in adolescents versus adults: a prospective cohort study
Manoj Ramachandran, Pramod Achan , Martin Gottliebsen , Bjarne Møller-Madsen
Department of Paediatric Orthopaedics, Barts and The London Children’s Hospital, Whitechapel Road, Whitechapel, London, England ; Department of Children’s Orthopaedics, Aarhus University Hospital

Background: The current literature indicates that hip arthroscopy is safe in both adolescents and adults with good early outcomes. There are no available studies however that directly compare the outcomes of this procedure for mixed indications between these two groups.
Purpose / Aim of Study: This was a prospective cohort study of 102 consecutive supine hip arthroscopies in 96 patients (48 adolescent (<18) hips, mean age 13.9 years and 54 adult (>18 hips), mean age 33.8 years) at a tertiary referral paediatric and adult university hospital followed-up for a minimum of two years.
Materials and Methods: At two-year follow-up, the Modified Harris Hip Score improved from a mean of 55.3 to 87.5 (p<0.05) in the adolescent group and from 58.7 to 86.9 (p<0.05) in the adult group while the Non-Arthritic Hip Score improved from 57.1 to 86.7 (p<0.05) in the adolescent group and from 61.4 to 87.4 (p<0.05) in the adult group. There was no statistical significance difference in outcome between the two groups at 2 years. With respect to complications, there were 3 transient pudendal nerve palsies that resolved spontaneously in the adolescent group by 4 weeks. No cases of proximal femoral physeal growth disturbance or osteonecrosis were seen at final follow-up.
Findings / Results: This study confirms that hip arthroscopy for mixed indications leads to good early outcomes with low complication rates in adolescent and adult patients. The incidence of pudendal nerve palsy in the adolescent group is however noted and is of concern. Advances in hip arthroscopy for adolescent hip disorders should focus on reducing or eliminating the side effects of traction.
Conclusions: Hip arthroscopy, although effective in adolescents and adults in the short-term for mixed indications, has a higher incidence of pudendal nerve palsy in adolescents.

6. Higher UHMWPE wear rate in cementless compared with cemented cups with the Saturne® Dual-Mobility system.
Steffan Tabori Jensen, Morten Homilius, Christina Frølich, Torben Bæk Hansen, Maiken Stilling
Ortopædkirurgisk, Hospitalsenheden Vest

Background: Displaced medial femoral neck fracture (FNF) may be treated with primary arthroplasty. Dual-mobility articulations have advantages on stability and range of motion, however polyethylene (PE) wear on two articulating sides might lead to excessive wear.
Purpose / Aim of Study: To investigate PE wear rate of primary DM cups in patients with acute FNF
Materials and Methods: From 2005-2011, 414 consecutive patients were operated with Saturne DM cups, 28mm femoral metal heads, UHMWPE. Cementless cups were coated with hydroxyapatite (HA). 239 cups were cemented and 175 were press-fit by choice of the surgeon. In 2012, at minimum 1-year follow-up, 155 patients were dead and the remaining 259 were invited for clinical follow-up. 80 patients were evaluated with standard radiographs for analysis of cup placement, 2D wear and wear rate (PolyWare software 3D Pro). Mean age at time of surgery was 80 (range 30-98) years.
Findings / Results: At a mean follow-up of 3.5 (1.4 – 7.7) years the mean 2D wear was 0.82 (sd 0.38, 0.3-2.2) mm and 2D wear rate was 0.29 (sd 0.21, 0.1-1.2). Wear rate of 0.35 (sd 0.22) in cementless cups were higher (p=0.045) than 0.16 (sd 0.07) in cemented cups. Patients with cementless cups were younger (78 vs. 81 years, p=0.005). Mean cup inclination was 44 (26-65) degrees and mean cup anteversion 17 (-12-47). There was no correlation between cup inclination and wear (p>0.34) and no difference in wear between gender (p>0.33). There was no correlation between age at time of surgery and wear (p>0.06). Cup inclination was similar (p=0.13) for cemented and cementless cups.
Conclusions: At short term follow-up, we found a higher wear rate in cementless HA coated cups compared with cemented cups. In general mean 2D wear and wear rate in these old and low demand patients was high and above the osteolysis threshold (0.1mm).

7. Early morbidity after aseptic revision hip arthroplasty in Denmark. A 2 year nationwide study.
Martin Lindberg-Larsen, Christoffer Calov Jørgensen , Torben Bæk Hansen, Søren Solgaard, Henrik Kehlet
Section of Surgical Pathophysiology and The Lundbeck Centre for Fast-track Hip and Knee Arthroplasty, Rigshospitalet, Copenhagen University, Denmark; Department of Orthopaedic Surgery and The Lundbeck Centre for Fast-track Hip and Knee Arthroplasty, Holstebro Regional Hospital, Holstebro, Denmark

Background: Limited data exist on early morbidity after revision total hip arthroplasty (RTHA).
Purpose / Aim of Study: To describe early morbidity after aseptic RTHA and relate the morbidity to the extent of the revision procedure.
Materials and Methods: All aseptic RTHA procedures from 2009 to 2011 were analysed using the Danish National Patient Registry with additional information from the Danish Hip Arthroplasty Registry. The procedures were divided into total revisions, acetabular cup revisions, femoral stem revisions and partial revisions. All readmissions and in- hospital complications were analyzed based upon detailed evaluation of patient records and causes were divided into “surgical” and “medical” complications.
Findings / Results: 1553 procedures were performed in 40 centres. The mean age was 70.4 years (range: 25-98) and median length of hospital stay (LOS) 5 days (interquartile range, IQR: 3-7). Within 90 days postoperatively the readmission rate was 18.3% and mortality rate 1.4%. The 90-day reoperation rate was 6.1%, dislocation rate 7.0% and infection rate 3.0%. Of all readmissions, 63.9% were due to “surgical” complications vs. 36.1% “medical” complications. The duration of surgery, bone loss, intraoperative complications and LOS indicated that the total revisions and femoral stem revisions represented the most complex surgery, but there were no differences in early morbidity across the surgical subgroups.
Conclusions: Aseptic RTHA was performed with LOS of 5 days and without differences in early morbidity across revision subgroups despite major differences surgical extent. All types of RTHA were associated with increased early morbidity compared to primary hip arthroplasty. The results from this study suggest that future focus should be held on the surgical technique as well as the perioperative set-up according to the “fast-track” methodology.

8. Promising migration Pattern at 1 year follow-up of the short Primoris Femoral Stem
Mogens Berg Laursen, Janus Duus Christiansen, Gordon Blunn, Poul Torben Nielsen
Northern Ortopaedic Division, Aalborg University Hospital; University College London, RNOHT, Stanmore, United Kingdom

Background: In order to save proximal bone stock in primary total hip arthroplasty (THA), short femoral stems are introduced.
Purpose / Aim of Study: Designed for perfect fit within the femoral neck, the Primoris® femoral stem has been released for clinical studies in coherence with the stepwise introduction of new implants. This is the preliminary report of the Radio Stereometric Analysis (RSA) results after 1 year follow-up (FU).
Materials and Methods: We carried out a prospective cohort study of 52 patients scheduled for surgery with the femoral neck-preserving Primoris® stem. Migration was analyzed by RSA, and the Harris hip score, UCLA activity score, WOMAC, EQ5D health questionnaire and Oxford Hip scores were recorded.
Findings / Results: 2 patients were excluded intra-operatively and 1 patient was revised due to aseptic loosening after 3 months, leaving 47 patients for analysis. Further 2 patients were excluded from the RSA analysis due to technical problems. RSA showed minor micromotion of the stem: Mean subsidence was 0.35 mm (precision: 0.10 ) and mean rotation around the longitudinal axis was 0.10º (precision: 0.64) after 1 year.
Conclusions: The stems showed very small migration—as it is characteristic for stable uncemented implants. If they stay stable until the 2 year FU, we will go on with a multi center study.

9. Fast-track pathway for reduction of dislocated Hip Arthroplasty reduces surgical delay and length of stay
Kirill Gromov, Fatin Willendrup , Henrik Palm, Anders Troelsen, Henrik Husted
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre

Background: Dislocation is one of the most common complications following hip arthroplasty. Delay until reduction leads to pain and discomfort for the patient and can potentially increase risk for complications.
Purpose / Aim of Study: In this study we investigated the safety aspect of a fast-track pathway for dislocated hip arthroplasties and evaluated its effect on surgical delay and Length of Stay (LOS)
Materials and Methods: 402 consecutive and unselected dislocations (253 patients) were admitted at our institution between 05-10-2010 and 09- 31-2013. Fast track pathway for early reduction was introduced on 01.01.2012. Fast track patients with clinically suspected dislocation (no radiographic verification) were moved directly to post anesthesia care unit (PACU) and then straight to the OR (operating room). Dislocation was confirmed under fluoroscopy and reduced under general anesthesia. Surgical delay (hours), LOS (hours), perioperative complications and complications during hospital stay were recorded. Dislocation status for fast-track patients (confirmed vs unconfirmed by fluoroscopy) was recorded as well
Findings / Results: Both surgical delay (2.5 vs 4.1; p<0.001) and LOS (26.0 vs 30.5; p<0.05) were significantly reduced in patients admitted through fast-track pathway compared to regular pathway. Perioperative complications (1.6% vs 3.7%) and complications during stay (11.2% vs 15.4%) were also reduced, however insignificantly. Only 1 case admitted through fast-track pathway had a fracture instead of a dislocation; no fast-track patients with suspected dislocation had no dislocations
Conclusions: Fast-track pathway for reduction of dislocated hip arthroplasty results in decreased surgical delay as well as LOS, without increasing perioperative complications or complications during hospital stay

10. Re-revision rates following revision of cemented and cementless primary hip arthroplasty
Kirill Gromov, Alma Pedersen, Søren Overgaard, Peter Gebuhr, Henrik Malchau, Anders Troelsen
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre; Department of Clinical Epidemiology, Aarhus University Hospital; 3Department of Orthopaedic Surgery, Traumatology and Clinical Institute, Odense University Hospital; Orthopaedic Department, Massachusetts General Hospital

Background: Increased use of cementless technique for primary THA in most parts of the world can lead to changes in reoperation patterns, ie indications for revision, and potentially influence the survival of revision arthroplasty.
Purpose / Aim of Study: In this registry-based study we wanted to investigate the role, primary femoral fixation plays in survival of revision arthroplasty.
Materials and Methods: Primary THA’s with cemented (n=1889) and uncemented (n=805) femoral component that subsequently sustained 1st revision of femoral component were identified from the Danish Hip Registry. Survival of 1st revision THA, with 2nd revision of the femur as outcome, was evaluated using cox regression analyses to calculate adjusted hazard ratios (HR). Patient demographics, time until revision, indications for revision and femoral bone defects at the time of 1st revision were also recorded.
Findings / Results: Adjusted HR for 2nd revision due to any reason of cementless compared with cemented primary THA with 1st revision was 1.36; 95%CI (1.02 -1.83). 71.6% of cemented primary THAs were revised due to aseptic loosening; while 46.1% of cementless primary THAs were revised due to femoral fracture. 3.6% of revisions on cemented primary THAs were performed <1 year after index surgery, compared to 37.1% of revisions on cementless THA’s when only looking at revisions performed due to aseptic loosening.
Conclusions: We found significantly increased risk of 2nd revision after 1st revision performed on primary cementless THA compared to cemented THA considering all causes for revision. Different indications for 1st revision could potentially explain inferior survival of revision performed on cementless THA. Our data suggest that increased use of cementless fixation in primary THA might lead to inferior survivorship of 1st revision THA.

11. Can hip surgeons code periprosthetic joint infection? A cross-sectional study of data validity in the Danish National Patient Registry.
Jeppe Lange, Alma B. Pedersen, Anders Troelsen, Kjeld Søballe
Lundbeckfoundation Centre for Fast-track Hip and Knee Surgery, Tage-Hansens Gade 2, 8000 Aarhus, Den, Department of Orthopaedic Surgery, Aarhus University Hospital, Tage-Hansens Gade 2, 8000 Aarhus, Den; Department of Clinical Epidemiology, Aarhus University Hospital, Olof Palmes Allé 43-45, 8200 Aarhus, Denmark; Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Kettegaard Allé 30, 2650 Hvidovre Denmark

Background: The Danish National Patient Registry (DNPR) collects data for all patients in Denmark. The DNPR is a potential high quality research database, however, validity of data on prosthetic joint infection (PJI) is unknown.
Purpose / Aim of Study: To evaluate the positive predictive value (PPV) of diagnosis and procedure codes associated with hip PJI.
Materials and Methods: We identified patients in the DNPR from 2003-2008 in Aarhus, Aalborg, Silkeborg, Viborg, Hvidovre, Vejle, Gentofte, Hørsholm, Hillerød, Helsingør, and Frederikssund with a primary and secondary ICD10 discharge diagnosis of T84.5. As we aim to validate only hip joint affections, we combined T84.5 with a hip joint noninfectious-specific (NIS) or infectious-specific (IS) procedure code. Medical records of all identified patients (n= 236) were reviewed by one of the authors.
Findings / Results: 190 of the 236 patients were confirmed as having a hip PJI according to a priori defined criteria, corresponding to an overall PPV of 81%. This means that the T84.5 diagnosis code truly correlates with hip PJI in 81% of the patients coded with the investigated combination in the DNRP. The PPV of the T84.5 diagnosis code in combination alone with a hip NIS procedure code was 69%, while T84.5 in combination alone with a hip IS procedure codes was 87%.
Conclusions: T84.5 is the sole discharge diagnosis regarding PJI. The PPV of T84.5 in the DNRP is currently not satisfactory. Data on PJI obtained from administrative registries are a valuable source of information, but should be used with caution in medical research. We urge hip surgeons to be meticulous in their onward coding practice, to increase the PPV of the T84.5 code to enable valid research in a field where absolute number of PJI is low, making clinical epidemiologic research on register data a valuable source of future knowledge.

12. No association between pseudotumors, high serum metal-ion levels and metal hypersensitivity in large-head metal-on-metal total hip arthroplasty at 5-7-year follow-up
Mette Holm Hjorth, Maiken Stilling, Kjeld Søballe, Lars Hans Bolvig, Inger Mechlenburg, Stig Storgaard Jakobsen
Department of Orthopaedics, Aarhus University Hospital; Department of Radiology , Aarhus University Hospital

Background: The relationship between metal wear debris, pseudotumor formation and metal hypersensitivity is complex and not completely understood.
Purpose / Aim of Study: The purpose of this study was to assess the prevalence of pseudotumor formation in a consecutive series of metal-on-metal (MoM) total hip arthroplasty (THA) and to investigate its relationship to serum metal-ion levels and hypersensitivity to metal.
Materials and Methods: Forty-one patients (31 males), mean age 52 (28-68) years, with a total of 49 large-head MoM THA participated in a 5-7-year follow-up study. Patients underwent ultrasonography (US), serum metal-ion concentrations were measured, metal allergy (patch test) and atopic dermatitis were evaluated, and the patients completed the questionnaires of the Oxford Hip Score (OHS), Harris Hip Score (HHS) and the Short-Form Health Survey (SF- 36).
Findings / Results: Pseudotumors were found in eight patients, but they were asymptomatic and their serum metal-ion levels were similar to those observed in patients with no pseudotumors (p>0.36). The capsule- stem distance of mean 8.6 mm (SD 3.82, 95% CI: 5.40-11.79) was wider (p=0.02) in patients with pseudotumours than in patients without pseudotumors of mean 5.6 mm (SD 2.89, 95% CI: 4.68-6.58). Positive patch test reactions were seen in three patients (two to nickel and one to iron). Higher serum metal-ion levels of chromium and cobalt were significantly correlated with steeper cup inclination and smaller femoral head sizes, and were associated with female gender (p<0.04).
Conclusions: We found no association between pseudotumor formation, serum metal-ion levels, metal patch test reactivity, and atopic dermatitis. However, clinicians should be aware of asymptomatic pseudotumors, and we advise further exploration into the mechanisms involved in the pathogenesis of pseudotumors.