Session 15: Hip Arthroplasty

Rikke Sommer Haaber^1,2, Katrine Glintborg Iversen^1,2, André Sejr Klenø^1,3, Martin Bækgaard Stisen^2,3, Inger Mechlenburg^2,3, Alma Becic Pedersen^1,3
1. Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus N, Denmark 2. Department of Orthopedic Surgery, Aarhus University Hospital, Aarhus N, Denmark 3. Department of Clinical Medicine, Aarhus University, Aarhus, Denmark

Background: Primary total hip arthroplasty (THA) is a common major procedure for treating late-stage hip osteoarthritis (OA). However, revision surgery is a severe complication after THA. Evidence for guiding healthcare professionals on the risks of THA in multimorbid patients is sparse.
Aim: To examine the association between multimorbidity and risk of revision due to any cause and specific causes after primary THA due to OA.
Materials and Methods: We identified 98,647 THA patients and subsequent revisions in The Danish Hip Arthroplasty Register from 1995 to 2018. Data on multimorbidity measured with Charlson Comorbidity Index (CCI) was retrieved from The Danish National Patient Registry. By CCI (low, medium, high), we calculated cumulative incidence of revision due to any cause and aseptic loosening within 0-10- years and infection and dislocation within 0-2 years using the Aalen-Johansen method. Cause specific hazard ratios (HR) adjusted for sex, age, cohabitation, education, and surgery year were calculated using Cox regressions comparing patients with medium and high to those of low CCI. All estimates are presented with 95% confidence intervals.
Results: Overall, the prevalence of CCI was 70% (low), 24% (medium), and 6% (high). The cumulative incidence of revision due to any cause and aseptic loosening within 0-10 years was 6.5% (95%CI: 6.2;6.7) and 2.2% (95%CI: 2.1;2.4) in low CCI and 6.5% (95%CI: 5.8;7.3) and 1.5% (95%CI: 1.2;2.0) in high CCI. Revisions due to infection and dislocation within 0-2 years was 0.6% (95%CI: 0.5;0.6) and 0.8% (95%CI: 0.7;0.8) in low CCI and 0.8% (95%CI: 0.6;1.1) and 1.3% (95%CI: 1.01;1.6) in high CCI. The HR for revision due to any cause was 1.2 (95%CI: 1.2;1.3) for medium CCI and 1.4 (95%CI: 1.2;1.6) for high CCI compared to low CCI. In patients with high CCI compared to low CCI, the HRs for aseptic loosening was 1.3 (95%CI: 1.0;1.6), for infection 1.2 (95%CI: 0.9;1.6), and for dislocation 1.7 (95%CI: 1.3;2.2).
Interpretation / Conclusion: Multimorbidity is associated with increased risk of revision due to any cause, as well as revision due to specific causes up to 10 years after primary THA. These results should guide the shared decision when managing patients with multimorbidity.

Rajzan Joanroy^1,2, Sophie Gubbels³, Jens K Møller^2,4, Søren Overgaard⁵, Claus Varnum^1,2
1.Department of Orthopaedic Surgery, Lillebaelt Hospital - Vejle, Denmark 2.Department of Regional Health Research, University of Southern Denmark, Denmark 3.Division of Infectious Disease Preparedness, Statens Serum Institut, Denmark 4.Department of Clinical Microbiology, Lillebaelt Hospital - Vejle, Denmark 5.Department of Orthopedic Surgery and Traumatology, Copenhagen University Hospital, Bispebjerg, Denmark 6.Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen

Background: Revision due to prosthetic joint infection (PJI) after total hip arthroplasty (THA) is associated with increased risk of second revision and death. However, the knowledge on risk and causes of second revision and mortality is sparse.
Aim: We investigated the risk of 2nd revision due to any cause and PJI and mortality following 1st revision due to PJI.
Materials and Methods: We identified 1,669 1st revisions from the Danish Hip Arthroplasty Register (DHR) during 2010-2019 and divided these into revision due to PJI or aseptic revision. Revision due to PJI was defined as a revision within 1 year after primary THA with any culture-positive biopsy or reported PJI to the DHR. Aseptic revisions within 1 year after primary THA were used as controls. From Danish health registries, we retrieved information on Charlson Comorbidity Index (CCI), death, microbiological data on intraoperative biopsies and cohabitation status. The cumulative incidences at the end of the study were calculated by 1st revision due to PJI or aseptic revision with 95% confidence intervals (CI). We estimated the adjusted relative risk (RR) for 2nd revision and mortality using the pseudo-observation method. For 2nd revision, we treated death as competing risk. We adjusted for age, sex, CCI, cohabitation status and femoral head size. All patients were followed from 1st revision until 2nd revision, death, emigration or end of study.
Results: Among 357 patients having 2nd revision, 215 were due to PJI. For 1st revision due to PJI or aseptic revision, the cumulative incidence of any 2nd revision was 35% (CI 31-40) and 19% (CI 15-22), respectively, and the cumulative incidence of 2nd revision due to PJI were 27% (CI 23-31) and 5.3% (CI 4.0-6.9), respectively. The adjusted RR for any 2nd revision was 2.8 (CI 2.2 – 3.7) and 2nd revision due to PJI 7.8 (CI 5 -12) for 1st revision due to PJI vs. aseptic revision. The adjusted relative mortality risk for 1st revision due to PJI vs. aseptic revision was 1.1 (CI 0.4-3.0).
Interpretation / Conclusion: The risk of any 2nd revision and 2nd revision due to PJI is significantly increased for patients with 1st revision due to PJI versus aseptic revision. The risk of mortality is not increased after 1st revision due to PJI.

Anders Peder Højer Karlsen^1,2, Jens Laigaard^3,4, Casper Pedersen¹, Kasper Højgaard Thybo¹, Kasper Smidt Gasbjerg¹, Anja Geisler^1,4, Troels Haxholdt Lunn^2,4, Daniel Hägi-Pedersen^4,5, Janus Christian Jakobsen^6,7, Ole Mathiesen^1,4
1Centre for Anaesthesiological Research, Dept. of Anaesthesiology, Zealand University Hospital, Lykkebaekvej 1, 4600 Koege, Denmark. 2Department of Anaesthesia, Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark 3Dept. of Orthopaedic Surgery and Traumatology, Bispebjerg Hospital, Copenhagen, Denmark. 4Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark 5Research Centre of Anaesthesiology and Intensive care medicine, Dept. of Anaesthesiology, Næstved-Slagelse-Ringsted Hospitals, Denmark 6Department of Regional Health Research, The Faculty of Health Sciences, University of Southern Denmark, Denmark 7Copenhagen Trial Unit, Centre for Clinical Intervention Research, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark

Background: Reductions in opioid consumption is frequently used to measure efficacy of analgesic interventions for total hip and knee arthroplasty. However, it is unclear what constitutes a minimal important difference for this outcome, i.e., how much less opioid the intervention group should consume to have us consider implementing the intervention into clinical practice.
Aim: We therefore aimed to determine the minimal important difference for morphine consumption, using opioid-related adverse events as anchor.
Materials and Methods: We conducted a post-hoc analysis of three trials (PANSAID [NCT02571361], DEX-2-TKA [NCT03506789] and Pain Map [NCT02340052]) assessing pain management after hip or knee arthroplasty. We examined the relationship between 0-24h iv morphine consumption and opioid-related adverse events: nausea, vomiting, sedation, and dizziness. The primary outcome was the Hodges-Lehmann median difference in morphine consumption between patients with no versus mild opioid-related adverse events. The secondary outcomes included the difference in opioid consumption between patients with mild versus moderate, and moderate versus severe opioid-related adverse events. We used quantile regression to test for interactions between the primary outcome and patient baseline characteristics.
Results: The difference in iv morphine consumption was 6 mg (95% CI 4-8) between patients with no versus mild opioid-related adverse events and 5 mg (95% CI 2-8) between patients with mild versus moderate events. There was no difference in opioid consumption between patients with moderate versus severe opioid-related adverse events (0 mg (95% CI -4 – 4)), possible because patients find it difficult distinguish between moderate and severe adverse events and because patients with severe events accept a higher level of pain and thus stop taking additional opioids.
Interpretation / Conclusion: Based on opioid-related adverse events, we suggest that 5 mg reduction in 0-24h iv morphine represents the minimal important difference for patients undergoing total hip and knee arthroplasty.

Jørgensen Peter Bo ^1,2,3, Jakobsen Stig Storgaard^2,3, Vainorius Dovydas⁴, Homilius Morten⁴, Hansen Torben Bæk^3,4, Stilling Maiken^1,2,3
1 AutoRSA Reseach Group, Aarhus University Hospital, 2 Department of Orthopaedics, Aarhus University Hospital 3 Department of Clinical Medicine, Aarhus University 4 Department of Orthopaedics, Gødstrup Regional Hospital

Background: The Exeter short stem was designed for patients with Dorr Type A femurs and short- term results are promising.
Aim: The aim of this study was to evaluate the minimum five-year stem migration pattern of Exeter short stems in comparison with Exeter standard stems.
Materials and Methods: In a case-control study 25 patients (22 female) at mean age 78 years (range 70-89) received cemented Exeter short stem (cases). Cases were selected based on Dorr Type A femurs and matched first by Dorr Type A and then age to a control cohort of 21 patients (11 female) at mean age 74 years (range 70-89) operated with cemented Exeter standard stems (controls). Preoperatively, all patients had primary hip osteoarthritis, and no osteoporosis as confirmed by DXA scanning. Patients were followed with radiostereometry for evaluation of stem migration (primary end-point), evaluation of cement quality and Oxford Hip Score. Follow-ups were preoperative, 3, 12, 24 and minimum 5 years follow-up.
Results: At three months, subsidence of the short stem -0.87 mm (-1.07 to -0.67) was lower compared to the standard stem -1.59 mm (CI95% -1.82 to -1.36) (p=0.00). Both stems continued a similar pattern of subsidence until 5-year follow-up. At 5-year follow-up, the short stem had subsided mean -1.67 mm (CI95% -1.98 to -1.36) compared to mean 2.67 mm (CI95% -3.03 to -2.32) for the standard stem (p=0.00). Subsidence was not influenced by preoperative bone quality (osteopenia vs. normal) or cement mantle thickness
Interpretation / Conclusion: In conclusion, the standard Exeter stem had more early subsidence compared with the short Exeter stem in patients with Dorr type A femurs, but thereafter a similar migration pattern of subsidence until minimum five years follow-up. • Both the standard and the short Exeter stems subsides. • The standard stem subsides more compared to the short stem in Dorr type A femurs. • Subsidence of the Exeter stems was not affected by cement mantle thickness.

Arash Ghaffari ¹, Regitze Gyldenholm Skal¹, Søren Kold¹, Andreas Kappel¹, Thomas Jakobsen¹, Ole Rahbek¹
1. Interdisciplinary Orthopaedics, Aalborg University Hospital.

Background: Wearable technology has emerged as a promising tool for measuring physical activity (PA) and monitoring post-operative recovery. However, the changes in PA as a biomarker for recovery have not been fully explored, particularly during the early post-operative period when the risk of complications is elevated and changes in PA may not be significant.
Aim: We aimed to explore early changes in the pattern and the level of PA after hip and knee replacement surgeries.
Materials and Methods: This cohort study involved 11 hip replacement patients (four females) and five knee replacement patients (four females) with the ages of 66 [43-78] and 66 [25-74] years, respectively. Data were collected two weeks before until four weeks after surgery using a physical activity tracker, which recorded the patients’ daily PA data, including the time spent on different PA categories, the number of steps, and the activity index (AI).
Results: According to the results, the time spent resting during the four weeks after surgery compared to before surgery decreased from 112% to 106%, while continuous walking time increased from 27% to 77%, and the activity index (AI) increased from 35% to 73%. Furthermore, step counts increased from 18% to 67%, and sit-to-stands increased from 65% to 93%. However, there were no significant changes in sitting, standing, and sporadic walk time, as well as the number of steps taken sporadically. Additionally, during the post-operative period, the step counts, walking time, AI, and the number of sit-to-stands had the least variance between weeks.
Interpretation / Conclusion: In conclusion, wearable sensors are a feasible tool for measuring PA during the peri-operative period in orthopedic surgery patients. Continuous step count, walking time, AI, and sit-to-stands showed relatively obvious changes and stable patterns, which makes them reliable parameters for remote monitoring of patients during the post- operative period.

Hans Christian S. Vistisen¹, Mads J. Rex¹, Thomas Jakobsen¹, Mogens Laursen¹
1. Interdisciplinary Orthopaedics, Aalborg University Hospital, Aalborg, Denmark

Background: The benefits of total hip arthroplasty (THA) in patients with hip osteoarthritis are well established. Literature has reported lower improvements and lower total patient-reported outcome scores (PROMs) among obese patients. In addition, reports show increased risk of early complication in obese patients.
Aim: The aim of this study was to investigate the impact of obesity on PROMs, early complications, and revisions in patients with hip osteoarthritis operated with THA.
Materials and Methods: A retrospective observational study on prospectively collected data from 461 total hip replacements at Farsoe Hospital in the period 2015-2021 distributed in an obese (BMI >35) and a reference group (BMI 20-25). OHS and EQ-5D-3L were assessed preoperatively and one year postoperatively. Medical charts were reviewed for readmissions within 90 days and revision surgery within one year. An RCS comorbidity score was calculated for all patients. Crude and adjusted multiple linear regression models were used to detect statistically significant differences in ?OHS, ?EQ-5D-3L, readmission rate and revision rate between the two groups.
Results: Using adjusted multiple linear regression models, we found a statistically significant difference in ?OHS and ?EQ-5D-3L between the obese group and the reference group (-3.06, [-4.78; -1.35]; -0.06, [-0.09; -0.03]). In addition, obese patients had an odds ratio for reaching clinically significant change of 0.41, which was statically significant (0.41, [0.22;0.76]). The mean ?OHS and ?EQ-5D-3L were great among all patients (20 +/-9.6; 0.3 +/-0.2). Furthermore, found a significant difference in readmission between the two groups using an adjusted Poisson regression with linear link function (0.11, [0.19; 0.04]). There was no statistically significant difference in revisions.
Interpretation / Conclusion: This study found obese patients to have lesser improvement in OHS and EQ-5D-3L compared to a normal weight reference group. Both groups exhibited great increases in both OHS and EQ-5D-3L, however postoperative scores were significantly lower in the obese group. Furthermore, this study found obese patients to have a higher rate of early complications, but no significant difference was found regarding revision rates.

Søren Overgaard ¹, Peter Horstmann², Manuel Bieder³, Haubro Martin⁴, Morten Bøgehøj ⁵, Thomas Jakobsen ⁶
1. Bispebjerg Hospital/ DHR. 2. Gentofte Hospital. 3. Næstved Sygehus. 4. Odense Universiteteshospital. 5. Århus Universitetshospital. 6. Ålborg Universitetshospital.

Background: Total hip arthroplasties in Denmark is performed with either cemented or non-cemented stem fixation. The non-cemented stem has been showed to be associated to a higher risk of early reoperation due to periprosthetic fracture. The cemented stem has, in some studies, shown increased risk of late revision due to aseptic loosening.
Aim: Both cemented and non-cemented stems are used today, thus DSHK has found it relevant to compare these two fixation methods for patients above the age of 60 years, with regard to risk of reoperation, dislocation, risk of thromboembolic complication and patient reported outcome.
Materials and Methods: The following PICO questions were investigated: Does patients above 60 years of age with primary osteoarthritis operated with total hip arthroplasty have better effect of a cemented fixation than non-cemented stem fixation with regard to reoperation, mortality, dislocations within the 1st year, thromboembolic complications and functional outcome.
Results: Reoperation: Overall, there is a lower revision rate for cemented and hybrid A THA especially for patients above 75 years of age. Men tend to have a higher revision rate. Few studies report cause for revision, but periprosthetic fracture seems to be a common early complication for the non-cemented THA, whereas the aseptic loosening is more common for the cemented THA in the late revisions. Mortality: The non-adjusted numbers show a higher mortality for the cemented stem but after adjusting the numbers even out. Some studies find a higher mortality in the first days following surgery for cemented fixation but this evens out quite quick and after one year there is no difference between the two groups. Mortality seems not to be associated to fixation type, more to age, gender and comorbidities. Dislocation within the 1st year One study reported that cemented fixation prevents dislocation (OR 0,71 p=0,001) compared to non-cemented. Thromboembolic complications Thromboembolic complications is a well-known complication after THA. One study showed significant increase in pulmonary embolism with in 30 days when comparing cemented to non-cemented. Another study showed no difference between the two groups. Functional outcome: Only two studies were found and due to the low number of included patients, the conclusion were very unclear.
Interpretation / Conclusion: To consider the use of cemented fixation of the stem in patients above the age of 70 years since the risk of reoperation is reduced in cemented stem fixation. The literature shows lower risk of revision in women down to the age of 60 years, the difference increases with rising age.