Aims

This study aimed to investigate the estimated change in primary and revision arthroplasty rate in the Netherlands and Denmark for hips, knees, and shoulders during the COVID-19 pandemic in 2020 (COVID-period). Additional points of focus included the comparison of patient characteristics and hospital type (2019 vs COVID-period), and the estimated loss of quality-adjusted life years (QALYs) and impact on waiting lists.

There is an apparent need for easily accessible research data on Periprosthetic hip joint infections (PJI)(1). Administrative discharge registers could be a valuable single-sources for this purpose, and studies originating from such registers have been published(2–4). However, the quality of routinely collected data for administrative purposes may be questionable for use in epidemiological research. The aim of this study was to estimate the positive predictive value of the International Classification of Disease 10th revision (ICD-10) periprosthetic hip joint infection diagnose code T84.5.

The study was performed as a cross-sectional study on data extracted from the Danish National Patient Register. Patients with a registration of performed surgical treatment for hip PJI were identified via the ICD-10 code T84.5 (Infection and inflammatory reaction due to internal joint prosthesis) in association with hip-joint associated surgical procedure codes. Medical records of the identified patients (n=283) were verified for the existence of a periprosthetic hip joint infection. Positive predictive values with 95% confidence intervals (95% CI) were calculated.

A T84.5 diagnosis code irrespective of the associated surgical procedure code had a positive predictive value of 85 % (95% CI: 80–89). Stratified to T84.5 in combination with an infection-specific surgical procedure code the positive predictive value increased to 86% (95% CI: 80–91), and in combination with a noninfection-specific surgical procedure code decreased to 82% (95% CI: 72–89).

This study is the first to evaluate the only discharge diagnose code of prosthesis-related infection in an administrative discharge register. It is apparent, that codes in administrative discharge registers are prone to misclassification on an administrative level, either by wrongful coding by the physician or administrative personal in the registration process. Misclassification must be expected and taken into consideration when using single-source administrative discharge registers for epidemiological research on periprosthetic hip joint infection. We believe that the periprosthetic hip joint infection diagnose code can be of use in single-source register based studies, but preferably should be used in combination with alternate data sources to ensure higher validity(5)

This study is funded in part by the Lundbeck foundation Centre for Fast-track Hip and Knee Surgery, Denmark.

The Danish Hip Arthroplasty Register (DHR) is a national database on total hip arthroplasties (THAs) with a high completeness and validity of registration for primary procedures. The aim was to validate the registration in DHR for revisions due to Prosthetic Joint Infection (PJI).

We identified a cohort of patients in the DHR who underwent primary THA from January 1, 2005 to December 31, 2012 and we followed these patients until first-time revision, death, emigration or December 31, 2012. The PJI diagnosis registered was tested against a gold standard encompassing information from microbiology, prescription, and clinical biochemistry registries in combination with clinical findings retrieved from medical records. We estimated the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) with 95% confidence interval (CI) for PJI in DHR alone and in DHR combined with microbiology registries.

Out of 37,828 primary THAs, 1,382 were registered with any revision, 232 of which were due to PJI. For PJI revisions in DHR, the sensitivity was 67.0% (CI: 61.0 – 72.6), specificity 95.2% (CI: 93.8 – 96.4), PPV 77.2% (CI: 71.2 – 82.4), and NPV 92.3% (CI 90.7 – 93.8).

Combining DHR with microbiology registries led to a notable increased in the sensitivity for PJI revision to 90.3% (CI: 86.1 – 93.5) and likewise for specificity 99.6% (CI: 99.1 – 99.9), PPV 98.4% (CI: 95.9 – 99.6) and NPV 98.5% (CI: 97.6 – 99.1).

Only two thirds of PJI revisions were captured in DHR and the PPV was moderate. However, combining DHR with microbiology registries improved the accuracy remarkably.

The study was supported by Region of Southern Denmark and Lillebaelt Hospitals.

Introduction: As a consequence of the rising prevalence of diabetes worldwide, an increasing proportion of diabetic THR patients may be expected in coming years. Diabetes research on postoperative complications among arthroplasty patients is limited. We evaluated the extent to which diabetes affect the revision rate due to aseptic loosening, deep infection and dislocation following total hip arthroplasty (THA).

Material and Methods: We used the Danish Hip Arthroplasty Registry (DHR) to identify all primary THR patients operated on during the period from 1 January 1996 to 31 December 2005. The presence of diabetes among THA patients was identified by using The Danish National Registry of Patients and The Danish National Drug Prescription Database. We used Poisson regression analyses, to estimate relative risk (RR) and 95% Confidence Interval (CI) for patients with diabetes compared to patients without diabetes, both crude and adjusted for potentially confounding factors.

Results: We identified 57 575 first primary THR patients in DHR, of which 3 278 (5.7%) were with diabetes and 54 297 (94.3%) without diabetes. An adjusted RR for revision due to deep infection of 1.45 (CI: 1.00–2.09) was found for THA diabetic patients compared to patients without diabetes. The RR was particularly high for THA patients with diabetes less than five years (RR was 1.71 (CI: 1.24–32.34), with the presence of diabetes related comorbidites prior THA (RR was 2.35 (CI: 1.39–3.98) and diabetes related complications (RR was 1.88 (CI: 1.17–3.03).

Conclusion. The patient and the surgeon should be aware of the relative increased risk of revision due to deep infection following THA as compared with the risk in THA patients without diabetes.

Introduction: There is an increasing interest in surface replacement arthroplasty (SRA) as an alternative to conventional THA (cTHA) in young and active patients. However, there has been considerable variability in reported outcomes. National joint registry reports have shown increased revision rates compared to cTHA. We analysed outcome measured as non-septic revision rate within two years for SRA in the NARA data base (Nordic Arthroplasty Register Association).

Materials and Methods: 1638 SRA and 163802 cTHA with age up to 73 years and a non-fracture diagnosis, operated from 1995 to 2007, were compared using Cox multiple regression including age, gender, diagnosis, nation and prosthesis type with cTHA divided into cemented, uncemented, hybrid and reversed hybrid fixation. Men below 50 years of age (460 SRA and 7185 cTHA) were analysed as a subset. The SRA cohort with a mean follow-up 1,8 years was also analysed with the same method including age, gender, diagnosis, number of performed SRA per hospital and the four most commonly used prosthesis designs. In an additional analysis femoral head diameter was added, reducing the number of cases to 1552. results are presented as relative risk (RR) with 95 % confidence interval(CI).

Results: SRA had a more than twofold increased revision risk compared to cTHA, RR=2,50 (1,67–3,70), which increased to 3,63 (2,42–5,44) when compared with all cemented THA. In the subpopulation of men below 50 years of age, there was no difference between SRA and any of the cTHA cathegories. Within the SRA group RR was reduced by male gender, RR=0,46 (0,25–0,86), in hospital performing > 70 SRA (RR=0,26, 0,11–0,60) and with use of BHR (Birmingham Hip Resurfacing) compared to all other designs (RR=0,27, 0,12–0,61). The size of the femoral head diameter had no significant influence on the early revision rate.

Discussion and Conclusion: Surface replacement arthroplasty has an increased risk of early revision compared to conventional and cemented THA except for men below 50 years of age. There is a learning curve on the hospital level. Cases with secondary osteoarthritis were comparatively few and were mainly caused by pediatric hip disease. SRA might become an alternative for young men, but our follow up is too short to determine if this indication remains in the longer perspective.

Introduction: Up to now comparisons and pooling of data between the Scandinavian arthroplasty registers have been restrained by use of separate and incompatible data systems.

Purpose: To create a common Scandinavian database for hip arthroplasties and to compare demographics and results between the Scandinavian countries.

Materials and methods: For this study we selected primary total hip prostheses (THR) from 1995–2006. A common code set was made, and after de-identification of the patients’ identity, including deletion of the national civil registration numbers, Denmark, Sweden, and Norway delivered data. Kaplan-Meier and Cox multiple regression, with adjustment for diagnosis, age, and gender, were used to calculate prosthesis survival, with any revision as end-point.

Results: 280,201 operations were included (Denmark 69,242, Sweden 140,821, Norway 70,138). Female patients constituted 60% in Denmark and Sweden and 70% in Norway. In Denmark, Sweden, and Norway childhood disease constituted 3.1%, 1.8%, and 8.7% respectively. The posterior approach was used in 91% of cases in Denmark, 60% in Sweden, and 24% in Norway. Cemented THRs were applied in 46% of patients in Denmark, 89% in Sweden, and in 79% in Norway. Resurfacing hips constituted 0.5% or less in all countries.

9,596 of the 280,201 primary THRs, had been revised. Ten-years survival was 91.9% (95% CI: 91.5 – 92.3) in Denmark, 93.9% (95% CI: 93.6–94.1) in Sweden, and 92.6% (95% CI: 92.3–93.0) in Norway.

In Sweden and Norway 23% of revisions were due to dislocation, compared to 34% in Denmark. Replacement of only cup or liner constituted 29% of the revisions in Sweden, 33% in Norway, and 44% in Denmark.

Conclusion: This unique database is now functioning, and has showed differences among the countries concerning demographics, prosthesis fixation, prosthesis survival, and reasons for revisions. The large number of THRs in this database significantly enhances our perspectives for future research, especially in diagnostic- and treatment groups with too small numbers in each separate

Background: A general increase in total number of primary total hip arthroplasty (THA) has been observed in Denmark from 3.828 in 1995 to 7.645 in 2006. During the same period the number of pa-tients treated at private clinics has also increased. To our knowledge no studies, comparing patient characteristics and treatment quality between public and private hospitals, have been published.

We compared patients’ characteristics and outcome following THA in private and public hos-pitals.

Materials and Methods: We used data from the Danish Hip Arthroplasty Registry to identify 69 249 primary THA’ies performed between 1 January 1995 to 31 December 2006.

To detect eventual difference in patient characteristics- age, gender, diagnosis leading to THA, Carlson’s comorbidity score and Charnley category were evaluated.

We matched 3 658 cases operated in private with 3 658 controllers operated in public hospitals on propensity score. Scoring parameters were age, gender, diagnosis leading to THA, Carlson’s comorbidity score, Charnley category, operating time, type of anesthesia and type of prosthesis.

We used multivariate logistic regression on propensity score matched data to assess association between type of hospital and outcome by computing relative risks and 95% Confidence Interval (CI). Outcomes were perioperative complications, readmission within 3 months, re-operation within 2 years, implant failure after 5 years, and mortality within 3 months of surgery.

Results: Private hospitals operated on older females, patients with primary osteoarthritis and low comorbidity and Charnley category 1.

Patients in private and propensity matched controls from public hospitals showed no differences in age, gender, diagnosis leading to THA, Carlson’s comorbidity score, Charnley category, operating time, type of anesthesia and type of prosthesis (p-value < 0,0001).

Based on matched data, private hospitals had lower relative risk for perioperative complications (0.39, 0.26–0.60), reoperations (0.59, 0.41–0.83) and readmissions (0.57, 0.42–0.77) compared with public. There was no difference in mortality or implant failure.

Discussion and Conclusions: We had no data on surgeon, general health and socioeconomic status of the patients. In addition, reported data from private clinics have not been validated in contrast to public hospitals

We found significant difference between patient characteristics operated at public versus private hospitals. No difference was evident regarding mortality and implant failure but for complications, reoperations and readmissions between private and public hospitals.

Introduction: We examined the risk of blood transfusion in patients undergoing THA at 21 different orthopaedic departments in Denmark.

Material and Methods: Patients with primary THA (n=21,773) registered in the Danish Hip Arthroplasty Registry between 1999 and 2006 were identified. Data on use of blood transfusion was collected from the Danish Transfusion Data Base (DTDB). The outcome was defined as red blood cell transfusion (yes/no) within 7 days after surgery. Modified Poisson regression analyses were used to estimate the risk of red blood cells transfusion (RR) and a 95% confidence interval (CI) adjusting for possible confounding factors including patient related factors (age, gender, comorbidity and diagnosis for primary THA) and surgery related factors (type of anestesia, type of osiffication prophylaxis type of operation, duration of surgery, and duration of admission. The risk of blood transfusion for each department was compared with the general risk of blood transfusion for all departments.

Results: Overall, red blood cells transfusion was given to 8,162 of 21,773 patients (37%) (range between 16% and 64%, depending on department). After adjusting for different patient–and surgery-related factors, the adjusted RRs differed from 1.24 (95% CI, 2.07–3.43) to 0.52 (95% CI, 0.4–0.69) using all departments as reference. Coefficient of variation was 23%.

Conclusions: Substantial differences in the risk of red blood cells transfusion among THA patients were found when comparing a sample of Danish orthopaedic departments. The differences in use of transfusions appeared not to be explained by a range of patient – and surgery – related factors and may thus reflect true differences in transfusion practice.

Background: Intraoperative femoral fracture is a well-known complication to primary total hip arthroplasty (THA). Experimental studies have suggested that intraoperative fractures may affect implant survival. How-ever, available clinical data are sparse.

Methods: We used data from the Danish Hip Arthroplasty Registry to identify patients treated with a primary THA due to primary osteoarthritis in Denmark between 1995 and 2005 (n=39478). Data was linked to two national Danish databases to conduct time dependent implant survival analyses. Implant survival and relative risk estimates were calculated for patients treated conservatively and patients treated with osteosynthesis after sustaining intraoperative femoral fractures during THA surgery. The reference group was THA’s performed without sustaining intraoperative femoral fracture. Furthermore we assessed the relative risk for reoperations and readmission to an orthopaedic department 3 months postoperatively.

Results: 282 patients (0.7%) were treated conservatively due to intraoperative femoral fracture and 237 patients (0.6%) were treated with osteosynthesis. The Kaplan– Meier survival plots revealed a significant poorer THA survival after osteosynthesis of intraoperative femoral fractures. In the 0–6 months postoperative period the adjusted relative risk (RR) for revision was 1.5 (95% CI: 1.1–1.7) for patients treated conservatively. In the same period the adjusted RR for revision was 5.7 (3.3–10.0) for patients treated with osteosynthesis. In the period 6 months to 11 years postoperatively we did not find any significant differences in the RR for revision among the groups.

Interpretation: Intraoperative fractures increase the relative risk for revision the first 6 postoperative months. Therefore, patients should be informed about the risk for revision when sustaining an intraoperative femoral fracture. Further, initiatives aimed at reducing the risk of revision in the first 6 months following THA should be considered in patients with intraoperative fractures including immediate revision of the stem to a larger stem with distal fixation and restricted weight bearing.

Introduction: We studied the survival of primary total hip arthroplasty (THA) in patients undergoing surgery because of rheumatoid arthritis (RA) and compared our results to the survival of primary THA in patients undergoing surgery because of osteoarthritis (OA). Furthermore, we evaluated the effect of primary THA-survival in RA-patients concerning multiple confounders such as age, gender, comorbidity, and cemented/uncemented prosthesis.

Material and Methods: Using the Danish Hip Arthroplasty Register we gathered info concerning 1.302 primary THA’s in 1.106 RA-patients and 41.848 primary THA’s in 35.729 OA-patients. These patients underwent surgery from 1995 to 2004. Using the Cox regression model we estimated the relative risk (RR) for revision due to aseptic loosening, other reasons, and all reasons and adjusted for above mentioned confounders.

Results: The adjusted RR’s for cup-revision of primary THA’s in patients with RA (compared to OA) were 1.22 (aseptic loosening − 95% Confidence Interval (CI) 0.75–1.99), 0.90 (other causes for revision − 95% CI 0.61–1.32), and 1.00 (all revisions − 95% CI 0.74–1.35). For the stem the RR’s were 0.50 (aseptic loosening − 95% CI 0.25–0.99), 0.58 (other causes for revision − 95% CI 0.35–0.95), and 0.54 (all revisions − 95% CI 0.36–0.80). RR for all revisions (both cup and stem) was 0.83 (95% CI 0.64–1.09). The RAsubanalysis showed an increased RR (all revisions) for men compared to women (RR 2.60; 95% CI 1.19–5.66). No significant result concerning all revisions for age, comorbidity, and cemented/ uncemented prosthesis was found. The mean follow-up was 5,4 years for RA and 4,8 years for OA.

Conclusion: The survival of primary THA’s in RA could not be associated with any clearly overall increased risk of revision when compared to OA. However, male gender seems to be a risk factor for undergoing revision-THA in the RA-subgroup.

Aim: We determined 90 days mortality following primary total hip replacement (THR) and examined the impact of age and level of comorbidity.

Methods: We used data from the nationwide population based Danish Hip Arthroplasty Registry between 1 January 1995 and 31 December 2004. Each THR patient was matched according to gender and age on the time of surgery with 3 persons from the general population randomly sampled using the Danish Civil Registration system, resulting in a total of 44 818 THA patients and 120 883 controls. We used a Cox regression analyses to computed age and comorbidity specific mortality rates (MR) and mortality rate ratio (MRR) with 95% Confidence Intervals (CI) for THR patients compared with the general population, as well as Number Needed to Harm (NNH).

Results: The MRs for THR patients relative to those for the general population were highest in the patients younger than 60 years, corresponding to an adjusted MRR of 3.6 (95% CI: 2.2–5.5). Similar, an adjusted MRR was 1.2 (95% CI: 1.0–1.4) in patients aged 80 years and over. The THR patients younger than 60 years had more comorbidity than the controls, whereas distribution of comorbidity was equal in all other age groups. MRRs increase with comorbidity level for both THR patients and controls in all age groups. MRR for THR patients vs. controls within high comorbidity level aged below 60 years and aged 80 years and over was 3.5 (1.3–9.8) and 0.7 (0.5–0.9), respectively. However, hospitalisation with particularly cardio–og cerebrovasculaar disease before surgery increase mortality risk for both age groups, whereas hospitalisation with cancer increase mortality risk for patients younger than 60 years and decrease it for patients aged 80 years and over.

Conclusions: Overall mortality of THR patients relative to those in the general population was higher 90 days after surgery. Our findings apply particularly for THR patients aged 10 to 59 and 80 years and over. Although THR patients aged 80 years and over with high comorbidity level had lower mortality than corresponding persons from the general population, some particular groups of medical condition prior to surgery is associated with increased mortality risk whereas other medical conditions are associated with decreased mortality risk. We should be careful in making clinical decisions based on the Charslon comorbidity index; subgroups analyses may be necessary.

Further, we will present data on 90 days cause of death following primary THR and predictors for death, including age, gender and comorbidity (analyses are not finished yet).