Session 2: Hip 1

Onsdag den 23. oktober
09:00 – 10:30
lokale: Helsinki/Oslo
Chairmen: Stig Storgaard Jakobsen / Per Kjærsgaard-Andersen

9. Microbiologic diagnosis based on implant sonication in hip and knee arthroplasty revision surgery
Christen Ravn, Michael Kemp, Per Kjærsgaard-Andersen, Søren Overgaard
Department of Orthopaedic Surgery and Traumatology, Clinical Institute, Odense University Hospital, University of Southern Denmark; Department of Clinical Microbiology, Odense University Hospital; Department of Orthopaedic Surgery, Vejle Sygehus

Background: In order to determine prosthetic joint infection (PJI) the microbiological diagnosis in hip and knee arthroplasty revision is traditionally found by culture of joint aspirate and periprosthetic tissue (PPT). Poor sensitivity of these modalities has been explained by lack of access to the dormant biofilm bacteria on the implant surface.
Purpose / Aim of Study: To compare cultivation of joint aspirate and PPT with culture of sonication fluid from removed hip and knee prostheses.
Materials and Methods: In a prospective study at Odense University Hospital and Vejle Hospital we analyzed all prosthetic materials removed in revision surgery of any indication. The prostheses were individually sonicated due to a well- established protocol (Trampuz et al. N Engl. J Med., 2007). Aliquots of sonication fluid (SF) were cultured under aerobic and anaerobic conditions for up to 14 days, and considered positive with >10 colonies/ml. Conventional fluid and tissue sampling was performed systematically in each revision and cultured due to best practice for 5 days. PJI was defined by finding of the same bacterial specie in at least two out of five PPT samples, or in both joint fluid and PPT. Positive culture of one tissue sample or joint fluid alone was defined as contamination.
Findings / Results: In 160 consecutive revisions of total hip (94) and knee (66) arthroplasties conventional culture methods diagnosed 38 cases (24%) of PJI, whereas positive culture of sonication fluid was found in 52 cases (33%). Most common bacteria found in conventional / SF were S. aureus (9/10), S. epidermidis (13/13). P. acnes in large numbers were found only in SF (0/ 4). Contamination was found in 10 resp. 1 case.
Conclusions: Culture of SF revealed 14 more positive cultures than by conventional methods and fewer cases with contamination.

10. A Randomized controlled Radiostereometric study comparing a novel porous titanium construct to a porous coated surface in cementless total knee arthroplasty
Nikolaj Sebastian Winther, Claus Lindkær Jensen, Thomas Lind, Claus Munk Jensen, Henrik Schrøder, Michael Mørk Petersen
Department of Orthopedics, Rigshospitalet, Copenhagen

Background: Aseptic loosening of the tibial component in total knee arthroplasty (TKA) remains a leading cause of revision surgery, and newer techniques are currently developed to meet the patients´ demands for increased durability of the implants.Regenerex is a novel porous titanium construct and a micro- casting of normal trabecular bone. It has a porous structure and biomechanical characteristics very close to that of normal trabecular bone. It is believed that these characteristics will facilitate bone ingrowth and secure a better fixation to the host bone, thus increasing the implant survival.
Purpose / Aim of Study: The aim of this study was to evaluate the migration of the tibial component in a clinical randomized trial comparing the use of a novel titanium construct Regenerex, versus a well proven porous plasma spray (PPS) component.
Materials and Methods: 60 patients scheduled for a TKA were randomized to receive a modular tibial component coated with a new porous titanium construct (Regenerex®Biomet) or a porous coated component (Vanguard® Biomet). X-rays for Radiosteriometric analysis of tibial component migration were performed postoperatively and at 3, 6, and 12 months of follow-up. Patients were clinical evaluated by KSS score and the WOMAC score.
Findings / Results: Knee and function scores as well as the WOMAC score improved significantly from preoperatively to 1 year follow-up.the majority of migration appeared during the first 3 months. The dominant mode of migration of the Regenerex implant was subsidence, external rotation and posterior tilt. No statistically significant differences between MTPM or segment motion between the two groups were found.
Conclusions: The novel titanium construct had maximum total point motion comparable with other uncemented implants. Both groups showed stable migration pattern and good clinical results.

11. The revision risk of 28480 primary total hip replacements (THR) in patients younger than 55 years of age. Results from the Nordic Arthroplasty Register Association (NARA)
Alma B. Pedersen, Frank Mehnert, Ove Furnes, Leif Havelin, Johan Kärrholm, Søren Overgaard
Department of Clinical Epidemiology, Aarhus University Hospital, Denmark; The Norwegian Arthroplasty Register, Department of Orthopaedic Surgery and Department of Clinical Me, Haukeland University Hospital, Bergen and University of Bergen, Norway; The Swedish Hip Arthroplasty Register, Department of Orthopaedics, Institute of Surgical Sciences, Sahlgrenska University Hospital, University of Gothenburg, Mölndal, Sweden; 6 Department of Orthopaedic Surgery, Traumatology and Clinical Institute, Odense University Hospital, Odense, Denmark

Background: During the last decades there has been a trend towards use of cementless implants in younger patients without clear evidence.
Purpose / Aim of Study: To evaluate the association between prosthetic concepts and risk of revision, particularly time trend of any association, among younger THR patients using NARA dataset.
Materials and Methods: We identified all primary THR due to osteoarthritis aged less than 55 years performed in four Nordic countries from 1995-2011(n=28480). Using Cox regression we calculated relative risk (RR) for any revision and aseptic loosening with 95% confidence interval (CI). Cemented implants were reference group
Findings / Results: In the period 1995-2011, no difference between cementless and cemented implants due to risk of any revision was observed. Hybrid implants had higher risk for any revision (RR=1.28, CI: 1.13-1.45), but time trend analyses revealed, that this only applies to hybrid implants inserted in 1995-1999 and 2004-2007. During 1995-2011, cementless implant had reduced risk for revision due to aseptic loosening (RR=0.52, CI:0.45- 0.59), but this was only evident for cementless implant inserted in 1995- 2003. No difference between hybrid and cemented implants in relation to risk of revision due to aseptic loosening. Within 2 years of THR, no difference between prosthetic concepts was observed in 1995-2007, but in 2008-2011 the cementless implants had elevated risk of any revision within 2 years with RR=1.11, CI:1.02-1.20 versus cemented implants.
Conclusions: Our large population-based study in younger patients provides evidence that, in general hybrid implant had higher risk for any revision and cementless implant had lower risk of revision due to aseptic loosening compared with cemented, but for any revision cause. The risks were clearly dependent on calendar year of primary THR and follow-up period.

12. What do patients perceive as important preoperative information in total hip- and knee arthroplasty?
Jonas Vestergård Iversen , Henrik Husted, Mira Jørgensen, Anders Troelsen
Ortopædkirurgisk Afdeling, Hvidovre Hospital

Background: Preoperative information may influence the preoperative level of patient anxiety and expectations to the outcome of surgery. However, there is little knowledge concerning patient perception of what important information is and exactly what information patients should receive preoperatively
Purpose / Aim of Study: To investigate 1) what patients perceive as important preoperative information, 2) their preoperative anxiety level, and 3) their preoperative expectations to the outcome of surgery
Materials and Methods: A structured questionnaire concerning anxiety, expectations and the importance of different aspects of preoperative information was returned by 45 unselected total hip and knee arthroplasty patients after surgery was decided and prior to the patient education classes. Answers were given on VAS (0-10) or likert-style scales. Mean age of patients was 68.6 years (range: 29-81)
Findings / Results: Patients had very high expectations to reduced level of pain (median VAS 0), other symptoms (median VAS 0), and quality of life (median VAS 9) 1 year postoperatively. Patients experienced moderate anxiety concerning all aspects of the upcoming operation. The answers to questions concerning the preoperative importance of information on different aspects of admission, surgery, hospitalization, and the postoperative course were median VAS 8 to 10 (very or extremely important) in 43 of 45 questions
Conclusions: Patients have very high expectations to the surgery outcome and experience moderate preoperative anxiety levels. It seems patients are unable to differentiate the importance of different aspects of preoperative information indicating a need for information on all aspects perioperatively. Patient education classes should be multidisciplinary, include information on all aspects perioperatively, and aimed specifically to address patient expectations

13. Fall-related readmissions after fast-track total hip and knee arthroplasty, cause of concern or consequence of success?
Christoffer Jørgensen, Henrik Kehlet, The Lundbeck Foundation Centre for Fast-
Section for Surgical Pathophysiology 4074, Rigshospitalet; ,

Background: Falls are common in the elderly with potential severe consequences including fractures and other injuries. Few studies have investigated falls after discharge resulting in contact with hospital after fast-track elective total hip and knee arthroplasty, despite a potential increased risk of falling after these procedures.
Purpose / Aim of Study: A detailed analysis on falls with contact to hospital ¡Ü90 days. Outcomes: Time after index surgery, circumstances leading to falling and fall related injuries.
Materials and Methods: A prospective descriptive cohort study in 5145 procedures performed in 6 centres between Feb 1st 2010 and Dec 1st 2011, with 90 days follow-up through the Danish National Patient Registry and patient¡¯s medical charts. Falls were sorted according to injury (none, minor, moderate, major) and circumstances (high activity, extrinsic factors and surgery-related).
Findings / Results: Of 83 fall-related hospital-contacts (1.6%), 43 (51.8%) were treated in the emergency room only. Mean age was 70.8 (range 39-96) in fallers vs. 67.3 yrs. (18-97) in non-fallers (p= 0.004) with a median length of stay (LOS) following index surgery of 3 (Interquartile range: 2-3) vs. 2 (2-3) days (p= 0.022). 24.1% of falls were during the first week and 26.5% of all falls were due to high activity and extrinsic factors. 39.8% of falls resulted in no or minor injury, 9.6% in moderate and 50.6% in major injury. Multivariate analysis found age (OR:1.05 [95%CI:1.0- 1.08]; p-value:0.001), living alone (2.09 [1.20-3.62];0.009) and psychiatric disease (2.80[1.42-5.50];0.001), but not the use of walking aids (1.20[0.67- 2.16];0.544) or LOS ¡Ü4days (0.63[0.30- 1.33];0.223) to be associated with surgery-related falls.
Conclusions: Falls after fast-track THA/TKA are not related to short LOS, but rather to inherent patient characteristics and external factors.

14. Factors Influencing Health-related Quality of Life after Total Hip Replacement - a comparison of data from the Swedish and the Danish Hip Arthroplasty Registers
Max Gordon, Aksel Paulsen, Søren Overgaard, Göran Garellick, Alma B Pedersen, Ola Rolfson
Swedish Hip Arthroplasty Register, Division of Orthopaedics, Department of Clinical Sciences at Danderyd Hospital, Karolinska Institute; Danish Hip Arthroplasty Register, Department of Orthopaedic Surgery and Traumatology, Odense University Hospital, University of Southe; Department of Clinical Epidemiology, Aarhus University Hospital, Denmark

Background: There is an increasing focus on measuring patient-reported outcomes (PROs) as part of routine medical practice, particularly in fields like joint replacement surgery where pain relief and improvement in health-related quality of life (HRQoL) are primary outcomes. Between-country comparisons of PROs may present difficulties due to differences in the provision of health-care and cultural differences. However, in order to understand how these differences affect PROs, common predictors for poor and good outcomes need to be investigated.
Purpose / Aim of Study: This cross-sectional study aim at investigating factors influencing health- related quality of life (HRQoL) one year after total hip replacement (THR) surgery in Sweden and in Denmark.
Materials and Methods: Data was retrieved from the Swedish (n=14 956 patients) and the Danish (n=1 210 patients) Hip Arthroplasty Registers according to preset selection criteria. Using linear regression models, we examined how sex, age, comorbidity and country of surgery are associated with different aspects of HRQoL measured by the EQ-5D index and EQ VAS.
Findings / Results: Danish patients had overall higher EQ- 5D index and EQ VAS than Swedish patients (p<0.001). After regression analysis, the estimated coefficients for sex, age, or the Charlson score did not differ between the countries for either the EQ-5D index (p=0.55) or EQ VAS (p=0.08) one year after THR.
Conclusions: We conclude that there are clear similarities in how basic predictors influence patient-reported outcomes (PROs) in patients with THR in Sweden and Denmark and these known predictors of good or poor HRQoL outcomes are not specific for each country.

15. Patient compliance and findings of hip pain, elevated metal ion levels and revision surgery during a centrally mandated recall of patients with Metal-on-Metal articulations.
Malchau Erik, Peter Gebuhr, Kristian Otte, Tommy Korsgaard Larsen, Anders Troelsen
Orthopaedics, Hvidovre Hospital; Orthopeadics, Hvidovre Hospital

Background: In March 2012 a total stop in the use of Metal-on-metal (MoM) large head articulations (MoM) was mandated. This included a mandatory contact to all patients and prospective follow-up. The objective was to identify all patients with a potentially harmful condition related to the MoM articulation. However, it is unknown what the patient compliance is during a nationwide centrally mandated patient recall.
Purpose / Aim of Study: To investigate patient-compliance following a centrally mandated recall of patients with MoM implants and to investigate what rate of patients had hip pain, elevated metal ion levels and revision surgery.
Materials and Methods: Between 2004 and 2012 589 patients (64.7 % males) received MoM implants at our institution. At patient recall they received a questionnaire regarding hip pain and were summoned to a series of follow-ups. At follow-up serum levels of chrome (S-Cr) and cobalt (S-Co) were recorded. Patients with revision surgery were tracked and the cause noted. 30 patients were excluded from analysis due to death or emigration prior to patient recall.
Findings / Results: Of 361 males, 16% reported hip pain, 67% had no pain and 17% did not respond to the questionnaire (DNRQ). Of 198 females 18% reported hip pain, 56% no pain and 25% DNRQ. 90% of the males and 94% of the females with hip pain had metal ion levels measured. Of 241 males with ion metal measurements, 10 had S-Co and/or S-Cr > 7 ppm, with 2 reporting pain. Of 134 females with ion metal measurements, 24 had S-Co and/or S-Cr > 7 ppm, with 8 reporting pain. 4 patients had revision surgery due to ALVAL.
Conclusions: Patient compliance during the centrally mandated recall was high. One in six patients reported hip pain and for females a significant proportion had elevated metal ion levels. Following recall < 1 % had revision surgery attributable to the MoM articulation.

16. Treatment of a displaced femoral neck fracture – cemented vs uncemented femoral stem in total hip arthroplasty
Michelle Fog Andersen, Thomas Jakobsen, Anne Soon Bensen, Niels Krarup
Department of Orthopedic Surgery, The Regional Hospital of Viborg

Background: Total hip arthroplasty (THA) is a treatment of displaced femoral neck fractures in elderly patients and in Denmark, more cemented than uncemented stems are implanted. Debate remains concerning the choice of optimal implant fixation in THA with or without cement.
Purpose / Aim of Study: The aim of this study is to retrospective compare rates of implant survival and operative complications following THA treatment of displaced femoral neck fractures with either a cemented or uncemented femoral stem.
Materials and Methods: The population of this study consists of 2 consecutive groups of patients (n=262) who were treated for a displaced femoral neck fracture with either a cemented (Exeter, 33,6%) or uncemented (Corail/Ancafit, 66,4%) THA stem at the Regional Hospital of Viborg in the periode 01.01.2007 – 31.12.2012. In all cases, the THA was made with a Saturne dual mobility cup and patients were followed up to 3 months postoperatively. Data regarding rates of implant survival and operative complications were obtained by retrospective review of medical records.
Findings / Results: We found a statistical significant difference regarding rates of reoperation with 1,1% (95%CI 0,00003-0,061) for cemented and 2,1% (95%CI 0,045-0,13) for uncemented stem (p=0,03). The main cause of reoperation was fracture. There was no difference regarding dislocation or operative complications. Rates of dislocation were 3,4% (95%CI 0,007-0,096) for cemented and 4,6% (95%CI 0,020-0,089) for uncemented stem (p=0,65). Rates of operative complications were 5,7% (95%CI 0,019-0,13) for cemented and 8,6% (95%CI 0,049-0,14) for uncemented stem (p=0,03).
Conclusions: Our results indicate that cemented femoral stem are superior to cementless when rates of reoperation are compared. However further RCT´s are necessary to determine the optimal treatment for displaced femoral neck fractures.

17. Neck narrowing and BMC after resurfacing, 2 year result from a randomised study
Minh That Pham , Jeannette Penny
Dept. of orthopeadics, Koege Hospital

Background: Resurfacing arthroplasty maintains bone mineral density in the femoral neck (FN) and prox. femur, important for later conversion to THA. Neck narrowing (NN) below the prosthesis has been described and may be a result of changes in strain patterns, but concerns are that continued NN could indicate aseptic loosening or vascular insult. NN could mean that bone is lost despite high BMD. Bone mineral content (BMC) is a more accurate measure of total bone stock
Purpose / Aim of Study: To measure the change in BMC at the prox. medial femur (G7) and FN following resurfacing and to establish if NN measured from X-rays can substitute BMC measurements. The zero hypothesis is, that there would be no change in BMC and secondary that no NN occurs and that NN and BMC are independent
Materials and Methods: 19 pts with primary OA from a RCT operated with an ASR, had DXA and X- ray images obtained within 3 days of surgery, at 8 w, 1 and 2 years. Following inter/intra rate reliability test, neck width was measured by the same observer on the 30 degree lateral view stereo x-rays images as headrim/neck ratio. BMC in G7 and FN were measured by DXA. ANOVA analyzed changes in BMC and head/neck ratio over time as well as the relationships between NN and BMC at FN and G7
Findings / Results: The intra-rate ICC (95 CI) was 0.97 (0.94- 0.99)BMC rose by 13% at FN and 3% at G7 (p < 0.01), but no changes were found in the mean head/neck ratio. We found the head/neck ratio to affect BMC at the neck (p =0.04), but no statistical relationship was seen at G7 (p = 0.19)
Conclusions: In this cohort, BMC in the proximal femur and neck is increased within the first 2 years. Our results are limited by small numbers without major NN, but suggest that narrowing on X-rays are indicative of bone loss in the neck. As NN does not change BMC at G7 it should not influence a later conversion to THA

18. No association between serum metal-ions and implant fixation in large-head metal-metal THA. A 5 year RSA study.
Mette Holm Hjorth, Kjeld Søballe, Stig Storgaard Jakobsen, Nina D Lorenzen, Inger Mechlenburg, Maiken Stilling
Orthopædkirurigsk, Aarhus Universitetshospital

Background: The failure mechanism of metal-metal(MoM) total hip arthroplasty(THA) has been related to metal wear-debris and pseudotumor, but it is unknown if implant fixation is affected by metal wear-debris.
Purpose / Aim of Study: Study if the fixation of large-head (LH) MoM THA is affected by the metal wear-debris
Materials and Methods: 41 patients (31 male) at a mean age of 47 (23-63) years with a total of 49 MoM THA were followed with radiostereometric analysis post-operative and at 1, 2 and 5 years for analysis of implant migration. They also participated in a 5-7 year follow-up with measurement of serum metal-ions, questionnaires (Oxford Hip Score(OHS) and Harris Hip Score(HHS), measurement of cup and stem position and periprosthetic BMD
Findings / Results: Between 1-2 years Total Translation (TT) was mean 0.04 mm (95% CI: -0.07-0.14) (p=0.49) for the stems and between 2-5 years TT was mean 0.13 mm (95% CI: -0.25; -0.01) which was significant (p=0.03) but within the precision limit of the method. Between 1-2 and 2-5 years there was no significant TT or total rotation for the cups. We found a dichotomized migration pattern of TT between 2-5 years, where 6 cups and 6 stems had migrations above the precision limit of the method (2 pt. had both cup and stem migrations above precision limits).A positive association between total OHS <40 (n=4) and cup migration (p=0.04) was found, but no significant associations between cup or stem migration and female gender, stem and cup position, T scores <-1 or metal-ion levels>7ug/l.
Conclusions: Between 2-5 years, 6 cups and 6 stems had migrated above the precision limits of the method, but patients were asymptomatic and serum ion levels were <7ug/l. The remaining cups and stems were well-fixed between 1- 5 years. Seemingly, metal wear-debris does not influence fixation of hip components in LH MoM THA at midterm follow-up.

19. Can the need for Arthroscopy be predicted in Patients undergoing Periacetabular Osteotomy?
Charlotte Hartig-Andreasen, Anders Troelsen, Theis Muncholm Thillemann, John Gelineck, Kjeld Søballe
Orthopedic Research Unit, Aarhus University Hospital; Dept. of Orthopedic Surgery, Copenhagen University Hospital, Hvidovre,; Dept. of Radiology, Aarhus University Hospital; Dept, of Orthopedic Surgery, Aarhus University Hospital

Background: No consensus exists regarding the treatment of co-existing hip dysplasia and tearing of the acetabular labrum. Identification of such factors can aid in tailoring PAO to each patient.
Purpose / Aim of Study: The aim of this study were to identify risk factors predicting clinical failure in terms of the need for a hip arthroscopy (HA) after PAO, and to assess the results after PAO in patients with MRA diagnosed labral pathology.
Materials and Methods: Eighty-seven hips that underwent PAO from Jan 2010 to May 2011 were evaluated preoperatively and at 2-year follow-up. Mean age at surgery was 34.2 years (range 14.5 – 59 years). MRA was performed prior to PAO. At follow-up patients were divided into a non-HA and HA group. The two groups were compared clinically, radiologically and with patient reported outcome measures. Risk factors for predicting failure in terms of a HA after PAO were calculated.
Findings / Results: Twenty-four out of 87 hips (27.6%) had an HA within 2 years after PAO. Risk factors for failure were preoperative borderline dysplasia, a postoperative. AI-angle <0o, and preoperative acetabular retroversion and labral detachment. A high á-angle (>55o) combined with borderline dysplasia increased the risk of failure. Patients not requiring arthroscopic treatment had a statistically significant better outcome evaluated by patients reported outcome measures.
Conclusions: PAO resulted in great improvements at 2-year follow-up. As expected patients requiring a HA had less improvements indicating negative effects of intra- articular disease in dysplastic hips. We identified risk factors indicating that femoroacetabular impingement and labral disease is a concern in after PAO. In hips at risk simultaneous PAO and HA may be warranted.