Session 15: Poster med foredrag B

Onsdag 21. oktober
11:00 – 12:00
Lokale: Stockholm / Copenhagen
Chairmen: Søren Overgaard / Casper Foldager

151. No effect on tissue oxygenation at the ankle level after sciatic and saphenous nerve block
Ane Linde, Thomas Fichtner Bendtsen, Niels Christian Jensen, Kristian Kibak Nielsen, Frank Linde
Foot and ankle section, department of orthopaedics, Aarhus University Hospital; Department of Anaestesiology, Aarhus University Hospital

Background: Wound healing complications is a significant problem after major foot and ankle surgery. A frequency of more than 30% wound healing complications is reported after total ankle replacement. The frequency has apparently not changed over the years despite strict selection of patients and interventions in order to reduce wound healing complications. Therefore other components of clinical practice are examined for possible negative effect on wound healing. A possible contributory factor to reduction of oxygen tension and thereby negative effect on wound healing frequency could be peripheral nerve blocks.
Purpose / Aim of Study: The purpose was to detect any influence of sciatic and saphenous nerve block on tissue oxygenation at the ankle level.
Materials and Methods: 20 patients scheduled for major foot surgery had a sciatic and saphenous nerve block prior to surgery. Transcutaneous oxygen tension (tcpO2) was measured before and after the nerve block and after surgery. TcpO2 was measured at the ankle level and at the thigh of both legs. The TCM400 Transcutaneous pO2 Monitoring System (Radiometer, Copenhagen) was used for all measurements.
Findings / Results: The median tcpO2 at the ankle level was 63 mmHg (IQR 53-66 mmHg) before and 60 mmHg (IQR 54-66 mmHg) after the nerve block (p>0,05, Wilcoxon sign test). No significant changes occurred in the ipsilateral thigh or the contralateral leg. Generally, a small increase of TcpO2 was observed both in the operated leg and the non-operated leg the first few postoperative hours. However, one patient had a marked reduction at the ankle level in tcpO2 from 66 mmHg to 45 mmHg after the nerve block has been applied.
Conclusions: Sciatic and saphenous nerve blocks have generally no influence on the tissue oxygenation at the ankle level measured by transcutaneous oxygen tension.

152. Can MRI predict the tissue quality of a meniscus tear?
Ahmad Siar Barat, Trine Torfing, Uffe Christiansen Jørgensen
Orthopedicsurgery and traumatology, Odense University Hospital; Radiology, Odense University Hospital

Background: Studies suggest that arthroscopic treatment of degenerative meniscus tears in middle-aged and elderly patients have a small effect, but not more than supervised physical exercise. The question is however, can MRI predict if a meniscus tear is degenerative or not?
Purpose / Aim of Study: The objective of this study was to investigate the correlation between meniscus tissue quality (degenerative/non-degenerative) assessed on MRI and during arthroscopy, in order to predict degenerative meniscus tears by MRI.
Materials and Methods: 51 menisci from 50 patients (31 males, 19 females, mean age 41.2 years), who underwent arthroscopic meniscus surgery due to clinical signs of meniscus tear, were included in order to describe the meniscus tissue quality (degenerative/non- degenerative/combination of both/undetermined) arthroscopically and on MRI. All surgeries were performed or supervised by a senior surgeon in knee arthroscopy. The tissue quality of the torn meniscus was classified as hard or soft at resection. MRI was analyzed by a senior musculoskeletal radiologist according to a validated MRI score.
Findings / Results: 15 menisci were rated non-degenerative and 17 menisci were rated degenerative both arthroscopic and on MRI. (p=0.003, Fisher’s exact test). This suggests a statistically significant relationship between meniscus tissue quality rated arthroscopic and meniscus tissue quality rated on MRI. Cramer’s V was calculated to V=0.38 indicating a medium to large effect size.
Conclusions: Our results suggest a statistically significant relationship between meniscus tissue quality rated arthroscopically and on MRI in patients with a meniscus tear. Degenerative and non-degenerative tears could not be predicted in all cases by MRI. The predictive effect was medium to large.

153. Preoperative Oral Anticoagulants in Fast-track Hip and Knee Arthroplasty, Practice and Outcomes
Christoffer C Jørgensen, Kehlet Henrik
Section for Surgical Pathophysiology & The Lundbeck Foundation Centre for Fast-Track Hip and Knee Re, Rigshospitalet

Background: Perioperative management of oral anticoagulants(OAC) is an increasing challenge in major joint arthroplasty. Current guidelines are complex and the benefit of preoperative bridging in patients with preoperative OAC treatment vs. potential increased risk of bleeding is uncertain.
Purpose / Aim of Study: Investigation of management of OAC and adherence to local and Danish Society of Thrombosis and Hemostasis guidelines, postoperative symptomatic thromboembolic (TE), venous thromboembolic (VTE) and major bleeding events.
Materials and Methods: Descriptive cohort study in THA and TKA, prospective data on comorbidity and dispensed prescriptions on OAC 6 months prior to surgery. Information on perioperative management of OAC, cause of length of hospital stay (LOS) >4 days, and 30-days readmissions from the Danish National Patient Registry and medical records.
Findings / Results: Of 13775 procedures, 717(5.2%) had OAC (649 Vitamin-K (Vit-K) antagonists/ 68 new oral anticoagulants (NOAC)) of which 78% were due to atrial flutter. Of Vit-K, 66% received pre and postoperative heparinbridging while 33% paused preoperatively and were bridged postoperatively. Local and national guidelines were followed in 75% and 50% of OAC-patients respectively. There were 5 (0.8%) TE in Vit-K (p<0.05) vs 22 (0.2%) in non-OAC patients. No TE occurred in NOAC patients. We found no difference in VTE between OAC and non-OAC-patients (0.4 vs 0.5%). There were 11 (1.5%) vs. 76 (0.5%) major bleedings in OAC vs non-OAC patients (p<0.05), 7 (1.6%) were in bridged Vit-K and 3 (4%) in NOAC (p<0.05 vs non- OAC).
Conclusions: National guidelines for OAC management are not routinely used in clinical practice. There was no difference in VTE, but increased risk of TE and major bleeding with OAC, especially in bridged Vit-K and NOAC patients.

154. The influence of infecting microorganisms on outcome after infectious revision knee arthroplasty. A two year nationwide study
Martin Lindberg-Larsen, Frederik Taylor Pitter, Marianne Voldstedlund, Henrik Schrøder, Jens Bagger
Department of Orthopaedic Surgery, Bispebjerg Hospital; Section of Surgical Pathophysiology, Rigshospitalet; Department of Infectious Disease Epidemiology , Statens Serum Institut; Department of Othopaedic Surgery, Næstved Hospital

Background: The initial surgical treatment of the infected knee arthroplasty is in most cases a partial revision (surgical debridement and exchange of tibial insert) or a revision to spacer procedure. Impact of the ethiological agent on outcome is unknown.
Purpose / Aim of Study: To describe the distribution of microorganisms causing primary infection and influence on outcome after revision surgery, measured as re-infection or death.
Materials and Methods: 105 partial revisions and 218 revision- to-spacer procedures were registered in the Danish Knee Arthroplasty Register (DKR) from July 1 2011 to June 30 2013. Re- infections causing re-revision (follow- up=396 days) and 90 days mortality were obtained from the Danish National Patient Register and DKR. Microbiology data was obtained from the Danish Microbiology Database. 7 cases without microbiology data were excluded.
Findings / Results: In 66(20.4%) cases cultures were negative and in 12(3.3%) cases 1/5 intraoperative biopsies were culture positive and thus considered contaminated. S.aureus infections were most common (n= 67;28%) and associated with 13.4% re-infections, 6.0% mortality and 2(0.8%) cases of methicillin resistance (MRSA). S.epidermidis was found in 46 (19.2%) cases with 8.7% re- infections and no deaths. Gram- negative species caused infection in 16(6.7%) cases with 23.5% re- infections and 12.5% mortality. In 63 (26.4%) cases a mixed genera caused infection with 17.5% re- infections and 1.6% mortality. S.epidermidis infections were more common in revision-to-spacer procedures (23.1%) than in partial revisions(11.4%). The distribution of the remaining species did not differ between surgical subgroups.
Conclusions: The most frequent ethiological agent was s. aureus, but with a low rate of MRSA. The highest re-infection rates after revision surgery were found in polymicrobial or gram-negative infected knees.

155. Safety of Metal-on-Metal Articulation
Kim Pagh Sperling
Orthopedic Clinic, Aleris-Hamlet Copenhagen

Background: Results after MoM THAs are generally good. Reports have emerged of abnormal soft-tissue reactions to MoM THAs and Total Hip Resurfacing (THR)
Purpose / Aim of Study: To assess the prevalence of pseudotumours in patients, who have received a large diameter MoM prosthesis. To assess the revision rate of large diameter MoM prosthesis. To correlate these findings to the type of prosthesis (THA versus THR).
Materials and Methods: 182 hips (160 patients), 103 THR (Recap Biomet) (93 patients) and 78 MoM THA (uncemented Bi-Metric, Biomet and Magnum head, Biomet) (67 patients) were included in the study designed as an observational cross-sectional study. The follow-up included a clinical hip examination, standardized AP pelvic and lateral hip radiographs, blood serum samples for metal ion level of chrome and cobolt. Patients with elevated metal ion levels (119nmol/L for cobalt and 134,5 nmol/L chromium) or patients with groin pain lasting at least one month considers CT imaging indicated in these patients.
Findings / Results: Mean observation 3,5 year (1-7). X-ray showed two acetabular components with retroversion (1 THA / 1 THR) (elevated ion levels) underwent revision. In total 14 patients (7 THA/7 THR) had elevated ion levels. These and six patients with reaction pain from the hip underwent CT scan (9 THA/ 11 THR). The CT scan showed one pseudotumor (1227 nmol/L Cobalt and 1589 nmol/L Chromium) underwent revision and one minor cyst without clinical symptoms (123 nmol/L Cobalt and 107 nmol/L Chromium) is still under observation. One patient (THR) with groin pain is additional revised.
Conclusions: The main subject was to find the prevalence of cyst formation and correlate to the types of MoM prostheses (THA/THR). There was one in the THA group and NS to the THR group. Revision rate was 2,2 % (2 THA / 2 THR) NS and comparable to traditional hip arthroplasty.

156. Mononucleated Bone Marrow Cells do not Survive During Long-Term in vitro Culture
Kris Chadwick Hede, Helle Lysdahl, Bjørn Borsøe Christensen, Martin Lind, Casper Bindzus Foldager
Orthopedic Research Lab, Aarhus University Hospital; Department of Sports Traumatology, Aarhus University Hospital

Background: The use of mononucleated cells in bone marrow aspirate concentrate (BMAC) for cartilage repair has shown promising early clinical results. The mode of action of the BMAC used with biodegradable scaffolds is unknown.
Purpose / Aim of Study: The purpose of this study was to investigate the chondrogenic differentiation of bone marrow mononucleated cells (BM-MNCs) in vitro. We hypothesized that the chondrogenic response of BM-MNCs was comparable to differentiated chondrocytes following long-term culture.
Materials and Methods: BM-MNCs from 7 healthy donors were isolated using Ficoll-Hypaque solution and centrifugation. Chondrocytes were obtained from 3 donors undergoing anterior cruciate ligament reconstruction. BM-MNCs or chondrocytes were seeded on Chondro- Gide© scaffolds and cultured in HG DMEM with 100 nM Dexamethasone, 50 μg/mL L- Ascorbic Acid 2-Phosphate, 40 μg/mL L- Proline, 1 mM Sodium Pyruvate, 1x ITS, and 10 ng/mL TGFβ3 or DMEM-F12 with 10% FCS, respectively. Cellular distribution in scaffolds was investigated by Hoechst staining on day 7, 14, 21, 28, 42 and 56.
Findings / Results: A very limited number of BM-MNCs was present in the scaffolds after 7 days and after 28 days no viable cells were found. In contrast, chondrocytes remained viable in scaffolds cultured for 56 days. No RNA could be extracted after 28 days from the scaffolds on which the BM-MNCs had been seeded; therefore the chondrogenic response on mRNA level was not investigated.
Conclusions: BM-MNCs cultured in chondrogenic medium on Chondro-Gide© scaffolds do not remain viable over the course of 28 days, and thus do not undergo chondrogenic differentiation. This suggests that the clinical benefits of using BMAC in a one-step procedure with scaffolds may exclusively be due to short- term, humoral effects on native cells, and not long-term proliferation and differentiation of BM-MNCs.

157. Recurrent patellar dislocation in 37 adolescent knees treated with a modified Roux-Goldthwait procedure; a follow-up study with inferior results.
Lars Lykke Hermansen, Knud Gade Freund
Ortopædkirurgisk Afd., SVS Esbjerg

Background: Patients with recurring patellar dislocations are often treated with stabilising surgery to prevent additional events. In immature patients with open growth zones, only soft tissue operations are used in order not to interfere with further growth. One of these procedures is the Roux-Goldthwait operation. Although the published literature regarding this technique and immature patients are sparse, it has shown very good results through the last 115 years. Nevertheless, it has been abandoned in favour of various MPFL reconstruction techniques.
Purpose / Aim of Study: The purpose of this study is to evaluate the outcome after the Roux-Goldthwait procedure in adolescent patients with open growth plates.
Materials and Methods: Between 2000-2009, 37 adolescent knees (30 patients) underwent surgery with the Roux-Goldthwait technique due to recurrent patella dislocation. Mean age 14,3 years (11,3–17,9 years). The same surgeon performed all operations. Follow- up was completed after a mean time of 6,6 years (2,6–11,8 years), with specific interest in subsequent dislocation of the patella. The patients were also evaluated by a KOOS questionnaire.
Findings / Results: 28 patients answered (35 knees), whether they have experienced patella dislocations after surgery or not, and 26 patients (30 knees) returned the KOOS questionnaire. 2 patients (2 knees) were lost during follow-up. 23 out of 35 knees had experienced one/several patella dislocation(s) during the follow-up period. The average KOOS scores were; Pain = 81; Symptoms = 76; ADL = 85; Sport/Rec = 54; QOL = 54.
Conclusions: The present study supports the discarding of the Roux-Goldthwait procedure in immature patients. The majority of patients experienced dislocations after their operation. The study contradicts the already published literature, properly due to publication bias.

158. Success rates and failures after infectious revision knee arthroplasty in Denmark. A two year nationwide study.
Martin Lindberg-Larsen, Christoffer Calov Jørgensen, Jens Bagger, Henrik Schrøder, Henrik Kehlet
Department of Orthopaedic Surgery, Bispebjerg Hospital; Section of Surgical Pathophysiology, Rigshospitalet

Background: The surgical treatment of peiprosthetic knee infection is generally either a partial revision procedure (open debridement and exchange of tibial insert) or a two- stage exchange arthroplasty procedure.
Purpose / Aim of Study: To describe success rates and failures of these procedures.
Materials and Methods: 573 knee arthroplasties revised due to infection from 1st July 2011 to 30th June 2013 were identified from the Danish Knee Arthroplasty Register. Revisions from spacer to spacer, one-stage total exchange procedures, arthrodesis and femoral amputations were excluded. 105 partial revisions, 218 revisions to spacer and 212 spacer to revision- TKA procedures were included in the final analysis. Data on hospitalizations and mortality were obtained from the Danish National Patient Register. Failure was defined as surgically related death ¡Ü90 days postoperatively or re-revision due to re-infection (follow-up 396 days).
Findings / Results: Re-revision rate (due to re-infection) was 24.8% and mortality rate was 2.8% resulting in a success rate of 72.4% after partial revisions. The median time from partial revision to previous arthroplasty procedure was 34 days, without differences in re- revision rates between cases revised within 28 days or later. Re-revision rate was 9.2% and mortality was 4.6% after revision to spacer procedures, whereas re-revision rate was 12.7% and mortality 0.9% after spacer to revision-TKA procedures. Only 75.6% of the revision to spacer procedures (first stage) performed within our study period were later successfully revised from spacer to revision-TKA (second stage).
Conclusions: The success rate of 72.4% after the partial revision procedure may be acceptable taking the relative limited surgical trauma in consideration, whereas the success rate of 75.6% of the resource-intensive two-stage revisions may call for reconsideration.

159. Chemical neutralization of carry-over contaminants in the evaluation of topical antimicrobial effectiveness
Nikolaj Milandt, Tine Nymark, Søren Overgaard, Hans Jørn Kolmos
The Orthopaedic Research Unit, Department of Orthopaedic Surgery and Traumatology, Odense University Hospital; Department of Clinical Microbiology, Odense University Hospital

Background: Valid measurement of bacterial quantities on human skin following disinfection often requires the use an appropriate neutralization system to prevent carry-over contamination from topical antimicrobials. Failure to neutralize such contamination may result in overestimation of disinfection efficacy. Some active components are known, but there is no consensus on an effective formulation for neutralization of chlorhexidine gluconate and iodophor.
Purpose / Aim of Study: The aim of this study was to validate the formulation of a chemical neutralization system for use when sampling human skin prepared with chlorhexidine gluconate or iodophor, using the cylinder-sampling method.
Materials and Methods: The system was tested in accordance with ASTM standard 1054-08. We performed the test using an antiseptic challenge solution collected from human skin with the cylinder-sampling method. The skin had been disinfected with chlorhexidine gluconate in ethanol with and without subsequent covering with an iodophor impregnated incise drape prior to sampling. A test organism (staph epidermidis) was exposed to the antiseptic challenger for 1 and 30 minutes, with and without added neutralizer, and compared to a control. The organism was also added to the neutralizer alone, observing for toxic properties.
Findings / Results: We observed complete neutralization of carry-over chlorhexidine gluconate and iodophor. Not adding the neutralizer resulted in significant loss in viability of the test organism. No organism loss was observed during an exposure time of 30 minutes to the neutralizer alone.
Conclusions: The neutralizer formulation was an effective chemical neutralizer of carry-over contamination from chlorhexidine gluconate in topical skin disinfection products and iodophor from iodine impregnated incise drapes in samples collected using the cylinder sampling method.

160. Changes in Bone Mineral Density of the Proximal Tibia After Uncemented Total Knee Arthroplasty. A Prospective Randomized Study Comparing a Novel Porous Titanium Construct (Regenerex) surface to a Well-Proven Porous- Coated Implant surface
Winther Nikolaj , Claus L Jensen, Thomas lind, Morten Boye Petersen, Henrik Schrøder, Michael Mørk Petersen
Orthopeadic, Rigshospitalet

Background: Regenerex is a novel porous titanium construct with a 3-dimensional porous structure and biomechanical characteristics 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 adaptive bone remodeling of the proximal tibia after uncemented total knee arthroplasty (TKA) using a tibial tray with this novel coating compared to a well- proven standard porous coated (PPS) tibial tray.
Materials and Methods: Sixty patients scheduled for TKA were randomized to receive either a Regenerex or a PPS tibial component. Changes in bone mineral density (BMD) of the proximal tibia were measured at 3, 6, 12 and 24 months by dual-energy x-ray absorptiometry (DEXA).
Findings / Results: In the lateral region (ROI 3), a significant increase in BMD was seen in both groups at 3, 6, and 12 months after surgery. The relative increase at 12 months was 8.1% (P =0.007) for the PPS group and 6.5% (P= 0.002) for the Regenerex group. Positive values were retained at 24 months in both groups. At 24 months BMD in the distal region below the central stem (ROI 1), had decreased in the PPS group by 3.4% (P= 0.005) and in the Regenerex group by 2.4% (P=0.17). In the medial region (ROI 2) BMD remained unchanged at all follow-up evaluations in both groups. There were no significant differences between the 2 groups (P = 0.45).
Conclusions: The significant increase in BMD of the lateral proximal tibia plateau with very limited changes medially and distally seen in both implants suggests that the novel porous titanium construct and the PPS implant have a pronounced beneficial effect with regard to maintaining periprostetic BMD in all regions of interest investigated.

161. Rising incidence of Bacteremia in a Danish Orthopedic Department
René Gren Hansen Voldby, Rolf Magnus Arpi, Jonas Bredtoft Boel
Department of Plastic- ,Breast- and Burnsurgery, Rigshospitalet; Department of Clinical Microbiology, Herlev Hospital

Background: Infections play an important role for the prognosis of orthopedic patients with a high impact on length of stay in the hospital, final mobility outcome and quality of life. Bacteremia is the most severe and life-threatening infection. The incidence of bacteremia in orthopedic patients is poorly elucidated.
Purpose / Aim of Study: To describe the incidence of bacteremia in the Orthopedic Department at Herlev Hospital in the 15-year period 2000-2014.
Materials and Methods: Data about positive blood cultures was extracted from the laboratory database at the Department of Clinical Microbiology, Herlev Hospital. In patients with more than one episode of bacteremia only the first episode was included. Incidence of bacteremia was calculated for the three 5-year periods 2000- 2004, 2005-2009 and 2010-2014 and reported as number of bacteremic episodes per 1.000 occupied bed days.
Findings / Results: The incidence of bacteremia was 0.59, 1.13 and 1.74 per 1.000 occupied bed days in the periods 2000-2004, 2005-2009 and 2010-2014, respectively. This almost 3-fold increase of the incidence of bacteremia was highly significant (p<0.001).
Conclusions: The rising incidence of bacteremia in orthopedic patients is worrying and deserves further investigation with focus on predisposing factors, microbial etiology and resistance patterns.