Postersession I

Onsdag den 23. oktober
11:00 – 12:00
lokale: Reykjavik
Chairmen: Jeannette Østergaard Penny / Ole Ovesen

139. No increased risk of elevated metal ions and pseudotumour formation when using modular neck-stems bilaterally
Peter Revald, Claus Varnum, Poulsen Thomas K., Per Kjærsgaard-Andersen
Department of orthopaedic surgery, Vejle Hospital

Background: Lately, potential corrosion/fretting and metal ion release from the neck-stem taper junction of modular total hip arthroplasty (THA) has been in focus.
Purpose / Aim of Study: The aim of this study was to compare blood levels of metal-ion and abnormal soft tissue reactions in patients having a modular neck- stem in one or both hips.
Materials and Methods: All patients having implanted a cementless THA with modular neck-stem (ABG2 stem and Trident cup) were examined. The patients underwent surgery from May 2009 to November 2011. In total, 39 unilateral and 7 bilateral operated patients were included corresponding to 53 THAs. All had metal- on-HXL polyethylene bearings with a head diameter of 36 mm. At follow-up, plasma chrome and cobalt ion levels were measured, and a MRI of the hip was performed. The Wilcoxon rank-sum test was used to compare metal ions levels between uni- and bilaterally operated patients. Chi-test was used to compare proportions.
Findings / Results: The mean age at surgery was 65.6 years.70% were males. The overall mean follow-up was 2.3 years. In the unilateral group, the median chrome plasma value was 14.7 nmol/l, and the median cobalt level was 51.2 nmol/l. In the bilateral group, the median values were 16.5 nmol/l for chrome and 54.6 nmol/l for cobalt. There was no difference in chrome (p=0.26) or cobalt levels (p=0.60) between the two groups. Five patients (13.5%) in the unilateral group and one (14.3%) in the bilateral group had elevated plasma cobalt values (>119 nmol/l) (p=0.89). There were no elevated chrome values (>134.5 nmol/l) in either group. Four (10.3%) cystic type 2 pseudotumours were found on MRI in the unilateral group, none in the bilateral group (p=0.32).
Conclusions: No increased risk of elevated metal ions or pseudotumour formation could be noticed when operated with modular neck-stems in THA in both hips.

140. Body composition preoperatively has no impact on clinical outcome after hip arthroplasty - A cohort study of 102 patients 1year after surgery
Anette Liljensøe, Jens Ole Laursen, Kjeld Søballe , Inger Mechlenburg
Orthopaedic Research Unit, Aarhus University Hospital; Department of Orthopaedics, Hospital Southern Jutland

Background: Previous studies indicate that knee arthroplasty patients preoperative BMI is a predictor of the clinical effect postoperatively. A high BMI increases the risk of quality of life (QoL) and physical function. However, the association between obesity and outcome after THA is controversial.
Purpose / Aim of Study: To investigate whether there is an association between the preoperative body composition of patients undergoing THA and their QoL and physical function 1 year after surgery.
Materials and Methods: 102 patients scheduled for THA participated in a 1-year follow-up study. Body composition (fat and muscle mass) was measured with Dual Energy X-ray Absorptiometry (DXA) preoperatively and 1-year after surgery. The outcome measures were patient reported questioners: SF-36 and Hip disability and Osteoarthritis Outcome Score (HOOS).
Findings / Results: Mean percentage of fat (%fat) for females were 40(23-53)% and for males 31(15-46)%. Mean percentage of muscle mass for females were 58 (46-74)%, males 66(52-82)%. We found no statistically significant association between body composition and any of the SF-36 and HOOS sub- scales. For %fat and Physical component score (PCS) odds ratio (OR)=0,98 (p=0,4), %fat and Mental component score (MCS) OR=0,99 (p=0,6), muscle mass and PCS OR=1,03 (p=0,4), muscle mass and MCS OR=1,02 (p=0,6).
Conclusions: Our findings indicate that overweight and obesity has no impact on the QoL and the self-assessed physical function for THA patients 1year after surgery.

141. 3 year Follow-up of a Long-term Registry-based Multicenter study on Vitamin E Diffused Polyethylene in Total Hip Replacement
Nanna H. Sillesen, Meridith E. Greene, Audrey K. Nebergall, Anders Troelsen, Peter Gebuhr, Henrik Malchau
Harris Orthopaedic Laboratory, MGH + Department of Orthopedics, Hvidovre Hospital. , Massachusetts General Hospital, Boston, MA, USA. + Copenhagen University Hospital, Hvidovre, Denmark; Harris Orthopaedic Laboratory, MGH, Boston, Massachusetts General Hospital, Boston, MA, USA.; Department of Orthopedics, Hvidovre., Copenhagen University Hospital Hvidovre, Copenhagen, Denmark

Background: Preclinical studies of vitamin E diffused highly cross-linked polyethylene (VEPE) have shown improved material and wear properties due to the antioxidative properties of the vitamin E.
Purpose / Aim of Study: To document both early and long-term clinical outcome of VEPE in order to ensure that there are no detrimental effects of the new developments and to evaluate the materials performances from clinical use.
Materials and Methods: 977 patients from 17 centers in USA and Europe are enrolled into a prospective 10year outcome study. Patients received either Porous Titanium Coated or Porous Plasma Sprayed acetabular shells with either VEPE liners or medium cross-linked (XLPE) liners. At each follow-up, 3 radiographs were obtained, 5 PROMs were completed (Harris hip score, case mix indicator, UCLA, SF-36, EQ-5D). Radiographs were measured for cup and stem position, as well as femoral head penetration into the liner. Postoperative complications and revisions were also collected.
Findings / Results: Mean age at surgery was 62±9 years. At 3year follow-up there were 15 dislocations in 11 patients and 13 revisions (4 periprosthetic fracture, 1 sepsis, 6 instability, and 2 implant mismatch at surgery). Five patients died due to causes unrelated to the operation. Wear analysis of AP pelvis films with Martell method from post-op to 3year showed a penetration rate at 0.01 mm/year for XLPE and a penetration rate of 0.003 mm/year for VEPE with no significant difference between them (p=0.43). Improvement was seen in all PROMs pre-op to 3years postop (p<0.0001).
Conclusions: Early follow-up of VEPE liners provide encouraging results with few intra- and postoperative complications. PROMs indicate improvement after THA in functionality and quality of life across the centers. We have not observed any early adverse effects from diffusing the liners with vitamin E.

142. Effect of early progressive resistance training compared to home based exercise after fast track total hip replacement. -A randomised controlled trial.
Lone Ramer Mikkelsen, Inger Mechlenburg, Kjeld Søballe, Søren Mikkelsen, Thomas Bandholm, Mette Krintel Petersen
Elective Surgery Centre, Silkeborg Regional Hospital ; Department of Orthopaedics, Aarhus University Hospital; (1)Physical Medicine & Rehabilitation Research – Copenhagen (PMR-C), Department of Physiotherapy, (2, Copenhagen University Hospital, Hvidovre; (1)Department of Physiotherapy- and Occupational Therapy, (2)Centre of Research in Rehabilitation (C, (1)Aarhus University Hospital, (2)Institute of Clinical Medicine, Aarhus University

Background: After Total Hip Replacement (THR) deficits in muscle strength and physical function persist. There is lack of evidence concerning which rehabilitation strategy is most effective and the amount of rehabilitation needed after fast track THR.
Purpose / Aim of Study: To investigate the effect of supervised progressive resistance training in the early rehabilitation phase after fast track THR in improving muscle strength and functional performance.
Materials and Methods: 73 THR patients with preoperative self- assessed disability (HOOS ADL score≤67) were randomly assigned to a control group (CG, home based exercise 7 days/week) or intervention group (IG, home based exercise 5 days/week and resistance training of hip and thigh muscles 2 days/week). The IG trained with loads of 10 repetition max from week 1 to 10 after THR . Before surgery and after the intervention, performance was evaluated by; leg extension power (primary outcome), isometric strength (hip abduction + flexion), sit-to-stand test (STS), stair test and 20 meter walking speed.
Findings / Results: 62 patients completed the trial (31 in each group). Leg extension power improved significantly in both groups, with no between group difference: IG (difference baseline to follow up): 0.28 [0.1;0.3] Watt/kg, CG: 0.26 [0.0;0.5] Watt/kg, p=0.91. 20 m walk performance improved more in IG: 2.98 [1.8;4.2] sec than CG: 1.58 [0.8;2.4] sec, p=0.05. No significant differences were found in the other outcomes, yet borderline significance (p=0.06-0.09) was seen in favour of IG in STS and isometric muscle strength.
Conclusions: 7 days/week of home based exercise was equally effective as 5 days/week of home based exercise plus 2 days/week of supervised progressive resistance training in improving leg extension power after THA. For some of the secondary outcomes, trends were in favour of resistance training.

143. 3 months home-training by a standardized program improves walking distance and knee extension strength in old patients 1-7 years after surgery with dual-mobility THA following femoral neck fracture.
Christina Frølich, Inger Mechlenburg, Sara Birch, Lone Lundager, Torben Bæk Hansen, Maiken Stilling
Department of Orthopaedics, Regional Hospital Holstebro; Department of Physiotherapy, Regional Hospital Holstebro

Background: Dual-mobility total hip arthroplasty (THA) has become the treatment choice for displaced femoral neck fracture (FNF) at our institution. However, ambulatory follow-up has revealed poor gait function and leg strength increasing the fall-risk in many of these patients.
Purpose / Aim of Study: To test the effect of a standardized home-based resistance training program.
Materials and Methods: 31 patients (27 women) at mean 82 (60-96) years were included at mean 3 (1-7) years past dual-mobility THA after FNF. Patients trained daily for 3 months, with 1 weekly physiotherapist supervision, and kept a training-diary. Criteria for study participation were: dementia score > 7, STS10 > 30sek, TUG > 12sek, and NMS < 8. Patients were examined at baseline and at 3 months follow-up with spatio-temporal parameters during 3 functional tests: timed-up and go(TUG), 10m walk, sit- to-stand(STS), and block-step test (BST). Also, 6 minute walk test(6WT) and sit-to-stand in 30 seconds(STS30) was performed. Oxford Hip Score (OHS) was collected. Leg muscle mass was measured by DXA, and muscle strength was tested by hand- held dynamometer(HHD). Activity was monitored by a 3-axial accelerometer.
Findings / Results: Between baseline and 3 months follow- up 6WT improved by 19m (p=0.01). TUG, STS30, and OHS was unchanged (p>0.20). Knee extension strength improved in the operated leg (p=0.03) but not in the contralateral leg (p=0.74). Muscle mass did not improve (p>0.06). 92% were satisfied with the training program and wished to continue. Analysis of spatiotemporal parameters and activity are ongoing.
Conclusions: Initial data assessment revealed improved walking distance and knee extension strength after a standardized 3 months home-based resistance training program in old and fragile patients 1-7 years THA after femoral neck fracture.

144. Preoperative planning in cementless total hip arthroplasty - Accuracy of digital templating
Mikkel Krüger Jensen, Søren Solgaard
Ortopædkirurgisk afdeling, Gentofte hospital

Background: Choosing the correct implant size and determining the correct femoral cut is important for the optimal result after THA.
Purpose / Aim of Study: In the present study we investigated the accuracy of pre-operative digital templating in uncemented THA compared to the actual implanted component size (cup and stem) and furthermore we evaluated the discrepancy in leg-length pre- and post-operatively.
Materials and Methods: 150 patients undergoing uncemented THA during the period from 1/1-2011 until 31/12- 2012 were retrospectively reviewed. Four experienced surgeons performed the operations. Component size and difference in leg-length data were registered pre- operative, per-operative and 3 months post- operative. Leg-length was measured radiographically. Data was stratified in relation to gender, age and surgeon.
Findings / Results: Overall the pre-operative templated cup- size was predicted correctly in 59% of the cases. If +/- 1 cup-size was included the precision increased to 95%. The pre- operative templated stem-size was correctly predicted in 61% of the cases. If +/- 1 stem-size was included the precision increased to 97%. The mean pre-operative leg-length difference was -2,1mm(+/- 6,4mm) compared to a mean leg-length difference post-operative of 1,7mm(+/- 6,7mm). 18(12%) out of 150 included patients had a difference in leg-length >10mm pre- operative. 18 out of 150 patients still had a difference in leg-length >10mm post- operative. Only 2 patients had a discrepancy of more than 20 mm.
Conclusions: It can be concluded from the present study that digital preoperative templating is safe and reliable. There was an overall trend towards increased leg-length of the operated leg. Equal leg-length within 10mm was achieved in 88% of the patients.

145. Timing of preoperative prophylactic antibiotics for knee arthroplasties. A quality study after the introduction of the WHO checklist with a standard “time-out” before skin incision.
Arne Svensson, Lars Peter Jorn
Department of Orthopaedic Surgery., Regionshospitalet Viborg

Background: A slight increase in revisions for infected joint arthroplasties has been observed in the Nordic countries since 2000 and the reasons for this are not clear. The most commonly used antibiotics have a short half-life, and it has been documented that administration more than 60 min preoperatively is associated with higher risk of surgical infection. It has been considered optimal to start the infusion 45 – 15 min before inflation of the cuff for the blood less field.
Purpose / Aim of Study: To evaluate our current routine, where antibiotic infusion is scheduled to start when the patient has arrived at the operation theater, and before further anesthetic procedures are initiated.
Materials and Methods: 118 consecutive patients operated during 2011 at our Hospital with primary knee prosthesis had their anesthetic journal evaluated retrospective. Time markings of the start of the antibiotic infusion, of the inflation of the cuff for the blood less field (in-BLF) and the closure of the wound were recorded for each patient.
Findings / Results: All patients did receive preoperative prophylactic antibiotic. Mean time of infusion before in-BLF was 37 min (range 5min – 230min). 82 (70%) of the patients received antibiotics at the optimal time interval. 6 (5%) of the patients received antibiotic more than 60 min before in-BLF, and 26 (22%) patients more than 45 min before in- BLF. 10 (8%) patients received antibiotic later than 15 min before in-BLF. Mean time from in-BLF till wound closure was 80 min (range 50min – 145min), and 44 (37%) patients did receive antibiotics more than 120 min before wound closure.
Conclusions: Our findings are in accordance with reports from a national Swedish survey from 2011, and leave room for improvements. Detailed instructions as to when the antibiotics should be given in relation to the start of the operation might improve timing.

146. No correlations between radiological angles and self-assessed Quality of Life in patients with Hip Dysplasia at 2-13 years of follow up after periacetabular osteotomy
Sara Birch, Anette Liljensøe, Charlotte Hartig-Andreasen, Kjeld Søballe, Inger Mechlenburg
Department of Physiotherapy and Occupational Therapy, Herning Regional Hospital; Department of Orthopedic Surgery, Aarhus University Hospital

Background: Only few studies have described the patients' health-related Quality of Life (QoL) after periacetabular osteotomy (PAO). Thus, there is a lack of data on the self-assessed outcome of patients operated with PAO, and none of the existing studies correlate the results from SF-36 with the radiological parameters.
Purpose / Aim of Study: The aim of this study was to investigate the health-related QoL for patients with hip dysplasia operated with PAO and investigate whether QoL is associated with the acetabular angles or hyper mobility.
Materials and Methods: Out of 388 patients, 228 patients (mean age of 40.5 years, mean follow-up of 7.1 years) returned the SF-36 and Beighton questionnaires. The patients' QoL was compared to reference data from a Danish population. Center-Edge (CE) and Acetabular Index (AI) angles were measured before and after PAO and the association with the patients' QoL was tested with logistic regression.
Findings / Results: For both males and females the SF-36 score was significantly lower than for the reference data for a Danish population, especially for those dimensions concerning physical health. No association was found between the patients' CE- or AI-angles before or after PAO and their subsequent QoL. Significant associations were found between both Physical Component Score (PCS) and Physical Function (PF) and follow-up time after the operation. The adjusted OR for a PCS≥50 was 0.87 (95% CI: 0.76-0.99) and for a PF≥85 0.81 (95% CI: 0.71-0.91). No association between hyper mobility and PCS, PF or Bodily Pain (BP) was found.
Conclusions: The results suggest that physical function after PAO decreases with longer follow-up time. Neither the acetabular angles nor hyper mobility is associated with the physical components of QoL.

151. Collateral Ligament Reconstruction of the Chronic Thumb Injury with Biotenodesis Screw Fixation
Robert Gvozdenovic, Michel Boeckstyns
Department of Orthopaedic Surgery, Hand Surgery Unit, Gentofte Hospital

Background: Numbers of techniques have been introduced for the management of chronic insufficiency of the collateral ligaments of the thumb. Fixation of the tendon graft in order to establish good stability of the reconstruction, avoiding stiffness of the MCP-joint and loss of the pinch strength remains a challenge. The potential advantages of using interference screws for fixation of the tendon graft is its ability to stabilize the reconstruction during the healing, allowing a short immobilization time.
Purpose / Aim of Study: The purpose of this review was to analyse short-term results of a consecutive series of 18 collateral ligament reconstructions of the thumb using the 4 x 10 mm Bio-Tenodesis screw for fixation the tendon graft of Palmaris Longus.
Materials and Methods: Seven men and 11 women with posttraumatic instability, pain and dysfunction of the thumb were treated.The mean follow-up period was 26 months (range 12-43 months). We measured active flexion of the MCP- and IP-joints, abduction of the thumb as well as the grip and pinch strength of the injured and contralateral (control) hand, sick-leave, pain score (VAS) and Quick DASH score. For statistical analysis, t-test for paired data has been used.
Findings / Results: The mean active range of motion in the MCP-joint of the operated thumbs was 90% of the contralateral side. The main active range of motion in the IP- joint was 96% of the contralateral side. There was no reduction of the abduction. Neither was there any difference in grip strength between operated and non-operated sides. Pinch strength (pure or tip pinch) of the operated thumb was the same as of the contralateral side.
Conclusions: Our procedure had short immobilization and rehabilitation time, minimal loss of motion of the MCP- and IP- joints, no loss of hand and pinch strength, permitting early return to work.

154. Erythropoietin elicits a dose-dependent osteogenic effect on human mesenchymal stem cells
Jan Duedal Rölfing, Anette Baatrup, Maik Stiehler, Helle Lysdahl, Cody Bünger
Orthopaedic Research Laboratory, Aarhus University Hospital; Department of Orthopaedics and Centre for Translational Bone, Joint and Soft Tissue Research, University Hospital Carl Gustav Carus at Technische Universität Dresden

Background: Erythropoietin (EPO) is a pleiotropic growth factor. Of interest for orthopaedics, EPO increases bone formation and angiogenesis. However, accommodating safety concerns, physiological dosing of EPO is a perquisite before clinical translation can be considered.
Purpose / Aim of Study: The aim of this study was to establish a dose-response relationship and to determine the lowest effective osteogenic dose of continuous EPO stimulation on human mesenchymal stromal cells (MSCs).
Materials and Methods: MSCs from two donors were cultured at 13500 cells/cm2. A wide range of EPO concentrations (0–100 IU/ml) was continuously applied. The primary outcome measurement was Arsenazo mineralization assay after 14 and 21 days. Secondary outcome measurements were an alkaline phosphatase (ALP) and cell viability assay after 2 and 7 days. The positive control was osteogenic medium and proliferation medium served as negative control. Results were normalized to cell number. Statistics consisted of one-way ANOVA and post hoc testing for linear trend and EPO concentration against positive control with Fisher's LSD.
Findings / Results: The observed proportional dose-response relationship can be adequately described with the slope of a fitted line. The effect size corresponds to this slope, which declined from 0.35 to 0.09 between day 14 and 21 (p<0.001). The lowest effective dose of 20 IU/ml increased mineralization to 146 ±17% after 14 days relative to positive control (p=0.002). EPO also increased cell viability and ALP (p<0.01).
Conclusions: EPO increased osteogenic differentiation of MSCs in a dose-dependent manner. In vivo, the lowest effective dose of 20 IU/ml should be used to prevent adverse effects. Ex vivo, the highest dose of 100 IU/ml could overcome the major limitation of cell-based tissue engineering, namely vascularization and bony ingrowth into 3D scaffolds.

155. The influence of hemostatic agents on bone healing after sternotomy in a porcine model
Rikke Falsig Vestergaard, Annemarie Brüel, Jesper Skovhus THomsen, Ellen Margrethe Hauge, Kjeld Søballe, John Michael Hasenkam
Dept. of Ortopeadic surgery , Hospitals Enheden Horsens; Department of Biomedicine – Anatomy, Aarhus University; Department of Rheumatology, Aarhus University Hospital, Nørrebrogade; Department of Orthopedic Surgery, Aarhus University Hospital, Tage-Hansens Gade; Department of Cardio-Thoracic and Vascular Surgery and Department of Clinical Medicine, Aarhus University Hospital, Skejby

Background: Sternotomy is the preferred access to the mediastinum. During sternotomy trabecular bone is exposed, which often results in bleeding. Mechanical hemostatics are used to diminish this bleeding; however, their influence on the sternal healing process is relatively unexplored.
Purpose / Aim of Study: The aim of the present study was to investigate the influence of two hemostatics, bone wax (BW) and a water-soluble polymer wax, Ostene (WSW), on the mechanical properties and histological characteristics of healing sternal bone.
Materials and Methods: Twenty-four pigs underwent sternotomy and were randomized into three groups: WSW, BW, or no hemostatic treatment (control). The animals were sacrificed 6 weeks after surgery and bone samples were obtained. In all, 42 bone samples underwent mechanical testing and 44 histological sections were evaluated microscopically.
Findings / Results: Fracture strength in the BW group was 32% lower than in the control group (p<0.05), and maximum stiffness was 56% lower in the BW group than in control group (p<0.05). The mechanical properties did not differ between the WSW and BW groups. The fraction of granulomatous tissue was 379% higher in the BW group than in the WSW group (p<0.001) and 582% higher than controls (p<0.001). There was 117% more calcified tissue in controls than in BW pigs (p<0.05).
Conclusions: In a porcine model, BW was found to significantly inhibit sternal healing and was associated with chronic inflammation and reduced mechanical integrity. Animals treated with WSW demonstrated bone healing characteristics similar to those of the control group, and WSW is thus a compelling alternative to BW when a mechanical hemostatic is needed.