Norwegian Arthroplasty Register Research Articles

Promoting cemented fixation of the femoral stem in elderly female hip arthroplasty patients and elderly hip fracture patients: a retrospective cohort study from the Norwegian Arthroplasty Register and the Norwegian Hip Fracture Register.

Uncemented stems increase the risk of revision in elderly patients. In 2018, we initiated a national quality improvement project aiming to increase the proportion of cemented stems in elderly female total hip arthroplasty (THA) and hip fracture hemiarthroplasty (HA) patients. We aimed to evaluate the association of this project on the frequency of cemented stems and the risk of secondary procedures in the targeted population. 10,815 THAs in female patients ≥ 75 years in the Norwegian Arthroplasty Register and 19,017 HAs in hip fracture patients ≥ 70 years in the Norwegian Hip Fracture Register performed in 2015-2017 and 2019-2021 at all Norwegian hospitals were included in this retrospective cohort study. The quality improvement project was implemented at 19 hospitals (8,443 patients). 1-year revision risk (THAs) and reoperation risk (HAs) were calculated for uncemented and cemented stems by Kaplan-Meier and Cox adjusted hazard rate ratios (aHRRs) with all-cause revision/reoperation as main endpoint. The use of cemented stem fixation in the targeted population increased from 26% to 80% for THAs and from 27% to 91% for HAs. For THAs, the 1-year revision rate decreased from 3.7% in 2015-2017 to 2.1% in 2019-2021 (aHRR 0.7, 95% confidence interval [CI] 0.5-0.9) at the intervention hospitals. For HAs, the reoperation rate decreased from 5.9% in 2015-2017 to 3.3% in 2019-2021 (aHRR 0.6, CI 0.4-0.8) at the intervention hospitals. The quality improvement project resulted in a significant increase in the proportion of cemented stems and reduced risk of secondary procedures for both THAs and HAs.

Previous cartilage surgery is associated with inferior patient-reported outcomes after knee arthroplasty.

The hypothesis of the present study assumed that a history of focal cartilage lesions would not affect Knee Injury and Osteoarthritis Outcome scores (KOOSs) following knee arthroplasty compared to a matched national cohort of knee arthroplasty patients. Fifty-eight knee arthroplasty patients with previous surgery for focal cartilage lesions (cartilage cohort) were compared to a matched cohort of 116 knee arthroplasty patients from the Norwegian Arthroplasty Register (control group). Age, sex, primary or revision arthroplasty, type of arthroplasty (total, unicondylar or patellofemoral), year of arthroplasty surgery and arthroplasty brand were used as matching criteria. Demographic data and KOOS were obtained through questionnaires. Regression models were employed to adjust for confounding factors. Mean follow-up post knee arthroplasty surgery was 7.6 years (range 1.2-20.3) in the cartilage cohort and 8.1 (range 1.0-20.9) in the control group. The responding patients were at the time of surgery 54.3 versus 59.0 years in the cartilage and control group, respectively. At follow-up the control group demonstrated higher adjusted Knee Injury and Osteoarthritis Outcome subscores than the previous focal cartilage patients with a mean adjusted difference (95% confidence interval in parentheses): Symptoms 8.4 (0.3, 16.4), Pain 11.8 (2.2, 21.4), Activities of daily living (ADL) 9.3 (-1.2, 18.6), Sport and recreation 8.9 (-1.6, 19.4) and Quality of Life (QoL) 10.6 (0.2, 21.1). The control group also demonstrated higher odds of reaching the patient-acceptable symptom state threshold for the Knee Injury and Osteoarthritis Outcome subscores with odds ratio: Symptoms 2.7 (1.2, 6.4), Pain 3.0 (1.3, 7.0), ADL 2.1 (0.9, 4.6) and QoL 2.4 (1.0, 5.5). Previous cartilage surgery was associated with inferior patient-reported outcomes after knee arthroplasty. These patients also exhibited significantly lower odds of reaching the patient-acceptable symptom state threshold for the Knee Injury and Osteoarthritis Outcome subscores. Level III.

How good are surgeons at disclosing periprosthetic joint infection at the time of revision, based on pre- and intra-operative assessment? A study on 16,922 primary total hip arthroplasties reported to the Norwegian Arthroplasty Register.

Revision due to infection, as reported to the Norwegian Arthroplasty Register (NAR), is a surrogate endpoint to periprosthetic joint infection (PJI). We aimed to find the accuracy of the reported causes of revision after primary total hip arthroplasty (THA) compared with PJI to see how good surgeons were at disclosing infection, based on pre- and intraoperative assessment. We investigated the reasons for revision potentially caused by PJI following primary THA: infection, aseptic loosening, prolonged wound drainage, and pain only, reported to the NAR from surgeons in the region of Western Norway during the period 2010-2020. The electronic patient charts were investigated for information on clinical assessment, treatment, biochemistry, and microbiological findings. PJI was defined in accordance with the Musculoskeletal Infection Society (MSIS) definition. Sensitivity, specificity, and accuracy were calculated. 363 revisions in the NAR were eligible for analyses. Causes of revision were (reported/validated): infection (153/177), aseptic loosening (139/133), prolonged wound drainage (37/13), and pain only (34/40). The sensitivity for reported revision due to infection compared with PJI was 80%, specificity was 94%, and accuracy-the surgeons' ability to disclose PJI or non-septic revision at time of revision-was 87%. The accuracy for the specific revision causes was highest for revision due to aseptic loosening (95%) and pain only (95%), and lowest for revision due to prolonged wound drainage (86%). The accuracy of surgeon-reported revisions due to infection as representing PJI was 87% in the NAR. Our study shows the importance of systematic correction of the reported cause of revision in arthroplasty registers, after results from adequately taken bacterial samples.

The Delta III and Delta Xtend reverse shoulder arthroplasty—risk of revision and failure mechanisms: a report on 3650 cases from the Norwegian Arthroplasty Register 1994-2021

The Delta reverse shoulder arthroplasty (RSA) is commonly used worldwide and is the most frequently used RSA in Norway. The aim of this registry-based study was to report 10- and 20-year implant survival, risk of revision, and reasons for revision in 2 consecutive time periods for Delta III (1994-2010) and Delta Xtend (2007-2021) prostheses. We included 3650 primary RSAs reported to the Norwegian Arthroplasty Register: 315 Delta III (42% cemented stems) and 3335 Delta Xtend (88% cemented stems). We used Kaplan-Meier analyses to investigate implant survival. The reasons for revision were compared for the 2 designs and fixation technique. Factors that could influence the risk of revision, such as implant design, fixation technique, and patient factors, were investigated using Cox regression analyses with adjustments for age, sex, and diagnosis. Patients operated with Delta III were more likely to be diagnosed with inflammatory disease or fracture sequela, whereas acute fracture, osteoarthritis, and cuff arthropathy were the most frequent indications for Delta Xtend. Ten-year survival was 93.0% (95% confidence interval [CI]: 87.0-99.0) (cemented stem) and 81.6% (95% CI: 75.3-87.9) (uncemented stem) for Delta III and 94.7% (95% CI: 93.3-96.1) (cemented stem) and 95.7% (95% CI: 88.3-100) (uncemented stem) for Delta Xtend. Twenty-year survival for Delta III (uncemented stem) was 68.2% (95% CI: 58.8-77.6). Compared with DeltaXtend (cemented stem) at 10-year follow-up, we found a higher risk of revision for Delta III (uncemented stem) (hazard ratio [HR]: 2.9, 95% CI: 1.7-5.0), whereas no significant difference was found for Delta III (cemented stem) and Delta Xtend (uncemented stem). The most common reason for revision of Delta III (uncemented stem) was glenoid loosening followed by deep infection and instability. Instability was the most frequent revision cause for Delta Xtend (both cemented and uncemented stem). Men had an overall higher revision risk than women (HR: 2.8 [95% CI: 2.0-3.9]), and patients with fracture sequela had increased risk for revision (HR: 2.8, 95% CI: 1.7-4.7) compared with patients with osteoarthritis. We found that Delta III (uncemented stem) had a higher risk of revision compared with Delta Xtend (cemented stem). The risk of revision for glenoid component loosening was lower for Delta Xtend, but revisions due to instability/dislocation are still a concern. This register study cannot determine whether the differences found were caused by differences in implant design or other factors that changed during the study period. Risk of revision may have been affected by the indication for primary operation.

Long-term follow-up and survival of delayed total hip arthroplasty following acetabular fracture: a matched cohort study of 552 cases from the Norwegian Arthroplasty Register.

Operative treatment of acetabular fractures generally yields good results, but several authors report up to 15-20% of patients developing post-traumatic osteoarthritis (OA). Previous studies have shown that total hip arthroplasty (THA) following post-traumatic OA have inferior results compared to THA for primary OA. The aim of this study was to report on long-term outcome of THA following acetabular fracture, compared to primary OA. We performed a matched cohort study with data from the Norwegian Arthroplasty Register (NAR). All patients receiving THA following an acetabular fracture between 1987 and 2018 were identified. A 3:1 matched cohort consisting of patients treated for primary OA with THA was selected using propensity scores and matched for age, gender and year of surgery. Survival analysis was performed with revision of any cause as endpoint. Cox regression was used to identify factors associated with risk of revision surgery. 552 cases were identified, 397 men and 155 women. Mean age was 58.8 (11-91) years. 224 had previously been operated for the acetabular fracture, 328 had been treated non-operatively. Mean follow up time was 8.7 (1-29) years. Implant survival at 10 years was 79.7% (75.6-83.3) and at 20 years 62.4% (55.5-69.3). The hazard ratio for revision was 1.38 (1.07-1.77, p < 0.001) compared to the OA cohort, regardless of operative or non-operative treatment of the index acetabular fracture. Uncemented acetabular components had an increased risk of revision with hazard ratio for revision 1.61 (p = 0.012). THA following an acetabular fracture can be performed with acceptable results regarding implant survival, however, we report an increased risk for revision when compared to primary OA. Our results indicate that previous operative fracture treatment does not increase the risk for THA revision compared to cases treated non-operatively.

No difference in risk of revision due to infection between clindamycin and cephalosporins as antibiotic prophylaxis in cemented primary total knee replacements: a report from the Norwegian Arthroplasty Register 2005-2020.

Systemic antibiotic prophylaxis with clindamycin, which is often used in penicillin- or cephalosporin-allergic patients', has been associated with a higher risk of surgical revision for deep prosthetic joint infection (PJI) than cloxacillin in primary total knee replacement (TKR). We aimed to investigate whether clindamycin increases the risk of surgical revisions due to PJI compared with cephalosporins in primary cemented TKR. Data from 59,081 TKRs in the Norwegian Arthroplasty Register (NAR) 2005-2020 was included. 2,655 (5%) received clindamycin and 56,426 (95%) received cephalosporins. Cox regression analyses were performed with adjustment for sex, age groups, diagnosis, and ASA score. Survival times were calculated using Kaplan-Meier estimates and compared using Cox regression with revision for PJI as endpoint. The cephalosporins cefalotin and cefazolin were also compared. Of the TKRs included, 1.3% (n = 743) were revised for PJI. 96% (n = 713) had received cephalosporins and 4% (n = 30) clindamycin for perioperative prophylaxis. Comparing cephalosporins (reference) and clindamycin, at 3-month follow-up the adjusted hazard ratio rate (HRR) for PJI was 0.7 (95% confidence interval [CI] 0.4-1.4), at 1 year 0.9 (CI 0.6-1.5), and at 5 years 0.9 (CI 0.6-1.4). Analysis using propensity score matching showed similar results. Furthermore, comparing cefalotin (reference) and cefazolin, HRR was 1.0 (CI 0.8-1.4) at 3 months and 1.0 (CI 0.7-1.3) at 1-year follow-up. We found no difference in risk of revision for PJI when using clindamycin compared with cephalosporins in primary cemented TKRs. It appears safe to continue the use of clindamycin in penicillin- or cephalosporin-allergic patients.

Poor survivorship of total ankle replacements. 1368 cases from the period 1994–2021 in the Norwegian arthroplasty register

Background and purposeThe aim of the study was to present the performance of total ankle replacements (TAR) in a national register. MethodsAll surgeons in the country report to the Norwegian Arthroplasty Register. The completeness of primary TARs in NAR was 79–90% in the years 2017–2020. Cox regression analyses and the Kaplan-Meier method were used to study implant survival and revision risk. Results1368 primary TAR´s were implanted in 1266 patients during the period 1994–2021. The last few years saw a marked decrease in the incidence of TARs. The overall survival at 5 years was 81.1% (80.9–81.3) and 69.3% (66.4–72.2) at 10 years. Higher age was strongly associated with better survival. Current prosthesis designs had a better survival than earlier designs ((HRR 0.7, 95% CI 0.6–0.9) ConclusionRevision rates were high in our registry, but current implants had better survival. Younger age increased the risk of revision. Level of evidenceLevel II: prospective cohort study

THIRTY YEARS’ FOLLOW-UP OF THREE COMMONLY USED FEMORAL STEMS IN THE NORWEGIAN ARTHROPLASTY REGISTER: 1987–2021

The Norwegian Arthroplasty Register (NAR) started collecting data on total hip arthroplasty (THA) in 1987. Very long-term results of implants for THA are scarce. We aimed to show long-term results for the three most used femoral stems, operated from 1987.We included the uncemented Corail femoral stem (n=66,309) and the cemented Exeter stem (n=35,050) both of which are currently in frequent use. In addition, we included the Charnley stem (n=32,578, in use until 2014). To ensure comparable conditions, stems fixated with low viscosity cement and stems revised due to infections were excluded. Differences in risk of revision (all reasons and stem revisions) were assessed with Kaplan-Meier and Cox regression analyses with adjustment for possible confounding from age, sex and diagnosis (OA, other). Stem revision was defined as a revision caused by loosening of the stem, dislocation, osteolysis in the femur, or periprosthetic femur fracture, and in which the femoral component was removed or exchanged.The median and max follow-up for Corail, Exeter and Charnley were 6.3 (33.1), 8.0 (34.2) and 13.1 (34.3) respectively. Thirty years survival estimates for Corail, Exeter and Charnley stems were 88.6% (CI:85.8–90.9%), 86.7% (83.7–89.2%) and 87.1% (85.4–88.5%) respectively with stem revision as endpoint, and 56.1% (CI:53.1–59.1%), 73.3% (70.5–76.1%) and 80.2% (78.4–82.0%) with all THA revisions as endpoint. Compared to the Corail, the Exeter (HRR=1.3, CI:1.2–1.4) and the Charnley (HRR=1.9, CI:1.7–2.1) had a significant higher risk of stem revision. Women 75 years and older had better results with the cemented stems. Analyses accounting for competing risk from other causes of revision did not alter the findings.The uncemented Corail stem performed well in terms of stem revisions for stem-related revision causes compared to two frequently used cemented stems with very long follow-up. The differences between the three stems were small.

Postvaccination immune responses and risk of primary total hip arthroplasty—A population-based cohort study

To investigate the relationship between individual postvaccination immune responses and subsequent risk of total hip arthroplasty (THA) due to idiopathic osteoarthritis (OA) or rheumatoid arthritis (RA). Results of tuberculin skin tests (TSTs) following the Bacille Calmette-Guerin (BCG) vaccination were used as a marker of individual immune responses. TST results from the mandatory mass tuberculosis screening program 1948-1975 (n=236 770) were linked with information on subsequent THA during 1987-2020 from the Norwegian Arthroplasty Register. The multivariable Cox proportional hazardregression was performed. A total of 10 698 individuals received a THA during follow-up. In men, there was no association between TST and risk of THA due to OA (Hazard ratio [HR] 1.01, 95% confidence interval [CI] 0.92-1.12 for positive versus negative TST and HR 1.06, 95% CI 0.95-1.18 for strong positive vs negative TST), while the risk estimates increased with increasingly restrictive sensitivity analyses. In women, there was no association with THA due to OA for positive versus negative TST (HR 0.98, 95% CI 0.92-1.05), while a strong positive TST was associated with reduced risk of THA (HR 0.90, 95% CI 0.84-0.97). No significant associations were observed in the sensitivity analysis for women or for THA due to RA. Our results suggestthat an increased postvaccination immune response is associated with a nonsignificant trend of increased risk of THA among men and a decreased risk among women, although risk estimates were small.

CORR Insights®: Did a New Design of the Oxford Unicompartmental Knee Prosthesis Result in Improved Survival? A Study From the Norwegian Arthroplasty Register 2012-2021.

1Clinical Assistant Professor, Department of Orthopaedic Surgery, University of Michigan Health System, Ann Arbor, MI, USA B. R. Hallstrom, University of Michigan Health System, Department of Orthopaedic Surgery, 2912 Taubman Center, Box 5328, 1500 East Medical Center Drive, Ann Arbor, MI 48109-5328, USA, Email: [email protected] This CORR Insights® is a commentary on the article “Did a New Design of the Oxford Unicompartmental Knee Prosthesis Result in Improved Survival? A Study From the Norwegian Arthroplasty Register 2012-2021” by Skåden and colleagues available at: DOI: 10.1097/CORR.0000000000002671. The author certifies that there are no funding or commercial associations (consultancies, stock ownership, equity interest, patent/licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article related to the author or any immediate family members. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writer, and do not reflect the opinion or policy of CORR® or The Association of Bone and Joint Surgeons®.

The Long-Term Risk of Knee Arthroplasty in Patients with Arthroscopically Verified Focal Cartilage Lesions: A Linkage Study with the Norwegian Arthroplasty Register, 1999 to 2020.

Focal cartilage lesions are common in the knee. The risk of later ipsilateral knee arthroplasty remains unknown. The purposes of the present study were to evaluate the long-term cumulative risk of knee arthroplasty after arthroscopic identification of focal cartilage lesions in the knee, to investigate the risk factors for subsequent knee arthroplasty, and to estimate the subsequent cumulative risk of knee arthroplasty compared with that in the general population. Patients who had undergone surgical treatment of focal cartilage lesions at 6 major Norwegian hospitals between 1999 and 2012 were identified. The inclusion criteria were an arthroscopically classified focal cartilage lesion in the knee, an age of ≥18 years at the time of surgery, and available preoperative patient-reported outcomes (PROMs). The exclusion criteria were osteoarthritis or "kissing lesions" at the time of surgery. Demographic data, later knee surgery, and PROMs were collected with use of a questionnaire. A Cox regression model was used to adjust for and investigate the impact of risk factors, and Kaplan-Meier analysis was performed to estimate cumulative risk. The risk of knee arthroplasty in the present cohort was compared with that in the age-matched general Norwegian population. Of the 516 patients who were eligible, 322 patients (328 knees) consented to participate. The mean age at the time of the index procedure was 36.8 years, and the mean duration of follow-up was 19.8 years. The 20-year cumulative risk of knee arthroplasty in the cartilage cohort was 19.1% (95% CI, 14.6% to 23.6%). Variables that had an impact on the risk of knee arthroplasty included an ICRS grade of 3 to 4 (hazard ratio [HR], 3.1; 95% CI, 1.1 to 8.7), an age of ≥40 years at time of cartilage surgery (HR, 3.7; 95% CI, 1.8 to 7.7), a BMI of 25 to 29 kg/m2 (HR, 3.9; 95% CI, 1.7 to 9.0), a BMI of ≥30 kg/m2 (HR, 5.9; 95% CI, 2.4 to 14.3) at the time of follow-up, autologous chondrocyte implantation (ACI) at the time of the index procedure (HR, 3.4; 95% CI, 1.0 to 11.4), >1 focal cartilage lesion (HR, 2.1; 95% CI, 1.1 to 3.7), and a high preoperative visual analog scale (VAS) score for pain at the time of the index procedure (HR, 1.1; 95% CI, 1.0 to 1.1). The risk ratio of later knee arthroplasty in the cartilage cohort as compared with the age-matched general Norwegian population was 415.7 (95% CI, 168.8 to 1,023.5) in the 30 to 39-year age group. In the present study, we found that the 20-year cumulative risk of knee arthroplasty after a focal cartilage lesion in the knee was 19%. Deep lesions, higher age at the time of cartilage surgery, high BMI at the time of follow-up, ACI, and >1 cartilage lesion were associated with a higher risk of knee arthroplasty. Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Risk of total hip arthroplasty after elite sport: linking 3304 former world-class athletes with the Norwegian Arthroplasty Register

ObjectivesAt present, there is no cure for osteoarthritis (OA), but severe hip joint degeneration can require total hip arthroplasty (THA). The literature on OA after elite sport is limited. We...

Predicting total knee arthroplasty from ultrasonography using machine learning

ObjectiveTo investigate the value of ultrasonographic data in predicting total knee replacement (TKR). DesignData from the Musculoskeletal Pain in Ullensaker study (MUST) was linked to the Norwegian Arthroplasty Register to form a 5–7 year prospective cohort study of 630 persons (69% women, mean (SD) age 64 (8.7) years). We examined the predictive power of ultrasound (US) features, i.e. osteophytes, meniscal extrusion, synovitis in the suprapatellar recess, femoral cartilage thickness, and quality for future knee osteoarthritis (OA) surgery. We investigated 4 main settings for multivariate predictive modeling: 1) clinical predictors (age, sex, body mass index, knee injury, familial OA and workload), 2) radiographic data (assessed by the Kellgren Lawrence grade, KL) with clinical predictors, 3) US features and clinical predictors. Finally, we also considered an ensemble of models 2) and 3) and used it as our fifth model. All models were compared using the Average Precision (AP) and the Area Under Receiver Operating Characteristic Curve (AUC) metrics. ResultsClinical predictors yielded AP of 0.11 (95% confidence interval [CI] 0.05–0.23) and AUC of 0.69 (0.58–0.79). Clinical predictors with KL grade yielded AP of 0.20 (0.12–0.33) and AUC of 0.81 (0.67–0.90). The clinical variables with ultrasound yielded AP of 0.17 (0.08–0.30) and AUC of 0.79 (0.69–0.86). ConclusionUltrasonographic examination of the knee may provide added value to basic clinical and demographic descriptors when predicting TKR. While it does not achieve the same predictive performance as radiography, it can provide additional value to the radiographic examination.

Long-term survival of 2997 finger metacarpophalanageal joint arthroplasties from the Norwegian Arthroplasty Register.

We present the long-time survival of 2997 primary metacarpophalangeal (MCP) joint implants from the Norwegian Arthroplasty Register from 1994 to 2019. Six different implants were compared in terms of survival and risk of revision. The majority of implants were inserted in patients diagnosed with inflammatory diseases and in women. The overall survival was found to be 94%, 89%, 85% and 84% after 5, 10, 15 and 20 years. The most prevalent reason for revision was a fractured prosthetic component, and the second was pain. Implants inserted in the right hand and in younger patients had a higher risk for revision. Sex, type of implant, finger treated, one- or two-component prosthesis, and inflammatory or non-inflammatory conditions did not influence the survival. The frequency of MCP joint implantations decreased during the observation period. Our data show satisfactory long-term survival of the MCP implants, with no difference found between implant types or concepts.Level of evidence: II.

Risk factors for revision surgery due to dislocation within 1 year after 111,711 primary total hip arthroplasties from 2005 to 2019: a study from the Norwegian Arthroplasty Register.

Background and purposeDislocation of a hip prosthesis is the 3rd most frequent cause (after loosening and infection) for hip revision in Norway. Recently there has been a shift in surgical practice including preferred head size, surgical approach, articulation, and fixation. We explored factors associated with the risk of revision due to dislocation within 1 year and analyzed the impact of changes in surgical practice.Patients and methods111,711 cases of primary total hip arthroplasty (THA) from the Norwegian Arthroplasty Register were included (2005–2019) after primary THA with either 28 mm, 32 mm, or 36 mm femoral heads, or dual-mobility articulations. A flexible parametric survival model was used to calculate hazard ratios for risk factors. Kaplan–Meier survival rates were calculated.ResultsThere was an increased risk of revision due to dislocation with 28 mm femoral heads (HR 2.6, 95% CI 2.0–3.3) compared with 32 mm heads. Furthermore, there was a reduced risk of cemented fixation (HR 0.6, CI 0.5–0.8) and reverse hybrid (HR 0.6, CI 0.5–0.8) compared with uncemented. Also, both anterolateral (HR 0.5, CI 0.4–0.7) and lateral (HR 0.6, CI 0.5–0.7) approaches were associated with a reduced risk compared with the posterior approach. The time-period 2010–2014 had the lowest risk of revision due to dislocation. The trend during the study period was towards using larger head sizes, a posterior approach, and uncemented fixation for primary THA.InterpretationPatients with 28 mm head size, a posterior approach, or uncemented fixation had an increased risk of revision due to dislocation within 1 year after primary THA. The shift from lateral to posterior approach and more uncemented fixation was a plausible explanation for the increased risk of revision due to dislocation observed in the most recent time-period. The increased risk of revision due to dislocation was not fully compensated for by increasing femoral head size from 28 to 32 mm.

Incidence and risk factors of intraoperative periprosthetic femoral fractures during primary total hip arthroplasty: 218,423 cases reported to the Norwegian Arthroplasty Register between 1987 and 2020.

Background and purposeIntraoperative periprosthetic femoral fractures (IPFFs) can occur during primary total hip arthroplasty (THA). We describe the incidence of IPFFs during THA in Norway and estimate potential risk factors that could be associated with IPFFPatients and methodsData from the Norwegian Arthoplasty Register (1987–2020) was used: 2,268 IPFFs from 218,423 primary THAs in 172,598 patients. The following factors were analyzed: sex, age, diagnosis, previous operation on the same hip, surgical approach, and stem fixation technique. Association of these factors with IPFF risk was assessed using multivariable Poisson regression.ResultsIPFF occurred during 2,268 operations with an incidence of 1.0% among all primary THAs. The risk of IPFF was associated with female sex (relative risk 1.8; 99% CI 1.5–2.1), age 80–90 years and age over 90 years (compared with age 60–70 years: 1.3; CI 1.0–1.6 and 2.6; CI 1.6–4.3, respectively), non-osteoarthritis diagnoses (2.2; CI 1.9–2.6), previous surgery to the same hip (1.8; CI 1.5–2.2), lateral approach (compared with the posterior approach: 1.5; CI 1.1–2.0), and cementless stem fixation (2.7; CI 2.0–3.6).InterpretationSurgeons should be aware of the factors associated with an increased risk of IPFF: female sex, age above 80 years, non-osteoarthritis diagnoses, and previous surgery to the same hip. Cemented stem fixation and posterior approach should be favored in high-risk patients, such as elderly women.

ACL Reconstruction Patients Have Increased Risk of Knee Arthroplasty at 15 Years of Follow-up: Data from the Norwegian Knee Ligament Register and the Norwegian Arthroplasty Register from 2004 to 2020.

Background:Anterior cruciate ligament (ACL) injury is considered a risk factor for osteoarthritis. The primary aim of the present study was to investigate the cumulative risk of, and risk factors associated with, a subsequent knee arthroplasty after an ACL reconstruction at up to 15 years of follow-up. The secondary aim was to compare the relative risk of knee arthroplasty after ACL reconstruction compared with that in the general population.Methods:Data were analyzed by combining data from 2 national registries, the Norwegian Knee Ligament Register and the Norwegian Arthroplasty Register. The cumulative risk of knee arthroplasty after undergoing ACL reconstruction was calculated as 1 minus the corresponding Kaplan-Meier estimate, and possible risk factors for knee arthroplasty after ACL reconstruction were assessed in a Cox regression model with hazard ratios (HRs) as estimated effect measurements. The relative risk of knee arthroplasty for patients managed with ACL reconstruction as compared with that in the general population was calculated in stratified age groups.Results:From the study population of 27,122 knees, 115 knees underwent knee arthroplasty. We found a 1.1% (95% confidence interval [CI], 0.9 to 1.4) cumulative risk of knee arthroplasty 15 years after ACL reconstruction. Deep cartilage injury, ICRS (International Cartilage Repair Society) grade 3 to 4 (HR, 4.8; 95% CI, 3.1 to 7.6), revision of the ACL (HR, 3.9; 95% CI, 2.2 to 7.1), and a 2-year postoperative KOOS Sport/Recreation subscore of <44 (HR, 3.1; 95% CI, 1.5 to 6.2) were important risk factors for knee arthroplasty. We found a higher risk of knee arthroplasty at the age of 30 to 39 years after a previous ACL reconstruction as compared with the general population (relative risk, 3.3; 95% CI, 1.6 to 6.7).Conclusions:Fifteen years after an ACL reconstruction, the overall cumulative risk of knee arthroplasty was 1.1%. Cartilage injury at the time of ACL reconstruction, revision ACL reconstruction, and a KOOS Sport/Recreation subscore of <44 (at 2 years postoperatively) were major risk factors for subsequent knee arthroplasty. We found a 3.3-times higher risk of knee arthroplasty at the age of 30 to 39 years after a previous ACL reconstruction as compared with that in the general population.Level of Evidence:Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Kaplan-Meier and Cox Regression Are Preferable for the Analysis of Time to Revision of Joint Arthroplasty: Thirty-One Years of Follow-up for Cemented and Uncemented THAs Inserted From 1987 to 2000 in the Norwegian Arthroplasty Register.

Background:Previous studies have suggested that the probability function of 1 minus the Kaplan-Meier survivorship overestimates revision rates of implants and that patient death should be included in estimates as a competing risk factor. The present study aims to demonstrate that this line of thinking is incorrect and is a misunderstanding of both the Kaplan-Meier method and competing risks.Methods:This study demonstrated the differences, misunderstandings, and interpretations of classical, competing-risk, and illness-death models with use of data from the Norwegian Arthroplasty Register for 15,734 cemented and 7,867 uncemented total hip arthroplasties (THAs) performed from 1987 to 2000, with fixation as the exposure variable.Results:The mean age was higher for patients who underwent cemented (72 years) versus uncemented THA (53 years); as such, a greater proportion of patients who underwent cemented THA had died during the time of the study (47% compared with 29%). The risk of revision at 20 years was 18% for cemented and 42% for uncemented THAs. The cumulative incidence function at 20 years was 11% for cemented and 36% for uncemented THAs. The prevalence of revision at 20 years was 6% for cemented and 31% for uncemented THAs.Conclusions:Adding death as a competing risk will always attenuate the probability of revision and does not correct for dependency between patient death and THA revision. Adjustment for age and sex almost eliminated differences in risk estimates between the different regression models. In the analysis of time until revision of joint replacements, classical survival analyses are appropriate and should be advocated.Level of Evidence:Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

How Does Implant Survivorship Vary with Different Corail Femoral Stem Variants? Results of 51,212 Cases with Up to 30 Years Of Follow-up from the Norwegian Arthroplasty Register.

BackgroundThe Corail® cementless stem (DePuy Synthes) has been used in Norway since 1987 and is one of the most frequently used stems in THA worldwide. Although the published survival results of the standard Corail stem have been good, little is known about the long-term (more than 20 years) survival of other stem design variants. Further, some changes were made to the extramedullary part of the stem in 2003, and the effect of these changes on survival is unknown.Questions/purposes(1) What is the survival up to 30 years of the standard collarless Corail femoral stem, and were extramedullary changes (slimmer, polished and rectangular neck, shorter taper) associated with differences in survivorship? (2) How does the 10-year survival and the risk of revision of other Corail stem variants, including the standard collared stem, coxa vara collared stem, and high offset collarless stem, compare with those of the standard collarless stem? (3) Which factors are associated with an increased risk of revision of the Corail stem, and are there any differences in those factors among the four stem variants?MethodsData for this study were drawn from the Norwegian Arthroplasty Register. Since 1987, THAs have been registered in the Norwegian Arthroplasty Register with completeness of data greater than 97% for primary THAs and 93% for revisions. To study survivorship with up to 30 years of follow-up (1987 to 2018; median 7.7-year follow-up), and to compare the original stem with stems with extramedullary modifications, we included 28,928 standard collarless Corail stems in 24,893 patients (mean age at time of implantation 62 years; 66% [16,525 of 24,893] were women). To compare the newer stem variants with the standard collarless stem (2008 to 2018), we included 20,871 standard collarless, 10,335 standard collared, 6760 coxa vara collared, and 4801 high offset collarless stems. Survival probabilities were estimated using the Kaplan-Meier method with endpoints of stem revision, revision due to aseptic stem loosening, and periprosthetic fracture. The endpoint of all noninfectious causes of THA revision (including cup revision) was additionally analyzed for the long-term comparison. The proportion of patients who died was limited, and there was no difference in death rate between the groups compared. Therefore, we believe that competing events were not likely to influence survivorship estimates to a large degree. To compare different stem variants and evaluate factors that could be associated with the risk of revision, we calculated hazard ratios using Cox regression analyses with adjustments for gender, age group, surgical approach, diagnosis, and stem size.ResultsThe 30-year Kaplan-Meier survival of the standard collarless stem was 88.4% (95% confidence interval 85.4% to 91.4%), 93.3% (95% CI 91.1% to 95.5%), and 94.4% (95% CI 92.0% to 96.8%) using stem revision for any noninfectious cause, aseptic loosening, and periprosthetic fracture of the femur as endpoints, respectively. There was no difference in survival between the original stem and the modified stem. The 10-year Kaplan-Meier survivorship free of stem revision (all causes including infection) was 97.6% (95% CI 97.2% to 98.0%) for the standard collarless stem, 99.0% (95% CI 98.8% to 99.2%) for the standard collared stem, 97.3% (95% CI 96.3% to 98.3%) for the coxa vara collared stem, and 95.0% (95% CI 93.6% to 96.4%) for the high offset collarless stem. Compared with the standard collarless stem, the standard collared stem performed better (HR 0.4 [95% CI 0.3 to 0.6]; p < 0.001) and the high offset collarless stem performed more poorly (HR 1.4 [95% CI 1.1 to 1.7]; p = 0.006) with any stem revision as the endpoint, and similar results were found with revision for aseptic stem loosening and periprosthetic fracture as endpoints. Controlling for the noted confounders, the standard collared stem had a lower revision risk. The high offset collarless stem had an increased stem revision risk for any reason (HR 1.4 [95% CI 1.1 to 1.7]; p = 0.006) and aseptic loosening (HR 1.6 [95% CI 1.1 to 2.3]; p = 0.022). Other factors associated with an increased risk of stem revision for all stem variants were being a man (HR 1.7 [95% CI 1.4 to 2.0]; p < 0.001), age 70 to 79 years and 80 years and older compared with the age group of 50 to 59 years (HR 1.6 [95% CI 1.2 to 2.0]; p < 0.001 and HR 1.9 [95% CI 1.4 to 2.6]; p < 0.001, respectively), the anterior approaches (direct anterior Smith-Petersen and anterolateral Watson-Jones combined) compared with the posterior approach (HR 1.4 [95% CI 1.1 to 1.7]; p = 0.005), as well as a preoperative nonosteoarthritis diagnosis (HR 1.3 [95% CI 1.0 to 1.6]; p = 0.02) and small stem sizes (sizes 8-11) compared with the medium sizes (sizes 12-15) (HR 1.4 [95% CI 1.1 to 1.6]; p = 0.001). The very small sizes (8 and 9) were associated with a 2.0 times higher risk of revision (95%. CI 1.4 to 2.6; p < 0.01) compared with all other sizes combined.ConclusionWhen using the uncemented Corail stem, surgeons can expect good results with up to 30 years of follow-up. Our results should be generalizable to the typical surgeon at the average hospital in a comparable setting. From our results, using a collared variant would be preferable to a collarless one. Due to an increased risk of periprosthetic fracture, caution with the use of the uncemented Corail stem in patients older than 70 years, especially in women, is warranted. Poorer stem survival should also be expected with the use of small stem sizes. The risk of periprosthetic fractures for the Corail uncemented stem versus cemented stems in different age categories has not been extensively examined, nor has the use of a collar for different age groups and genders, and both should be subjects for further investigation.Level of EvidenceLevel III, therapeutic study.

Thromboprophylaxis in primary shoulder arthroplasty does not seem to prevent death: a report from the Norwegian Arthroplasty Register 2005–2018

Background and purpose — There is still no consensus on whether to use thromboprophylaxis as a standard treatment in shoulder replacement surgery. We investigated the use of thromboprophylaxis reported to the Norwegian Arthroplasty Register (NAR). The primary endpoint was early mortality after primary shoulder arthroplasty with and without thromboprophylaxis. Secondary endpoints included revisions within 1 year and intraoperative complications. Patients and methods — This observational study included 6,123 primary shoulder arthroplasties in 5,624 patients reported to the NAR from 2005 to 2018. Cox regression analyses including robust variance analysis were performed with adjustments for age, sex, ASA score, diagnosis, type of implant, fixation, duration of surgery, and year of primary surgery. An instrumental variable Cox regression was performed to estimate the causal effect of thromboprophylaxis. Results — Thromboprophylaxis was used in 4,089 out of 6,123 shoulder arthroplasties. 90-day mortality was similar between the thromboprophylaxis and no thromboprophylaxis groups (hazard ratio (HR) = 1.1, 95% CI 0.6–2.4). High age (> 75), high ASA class (≥ 3), and fracture diagnosis increased postoperative mortality. No statistically significant difference in the risk of revision within 1 year could be found (HR = 0.6, CI 0.3–1.2). The proportion of intraoperative bleeding was similar in the 2 groups (0.2%, 0.3%). Interpretation — We had no information on cause of death and relation to thromboembolic events. However, no association of reduced mortality with use of thromboprophylaxis was found. Based on our findings routine use of thromboprophylaxis in shoulder arthroplasty can be questioned.