Constructing a clinical radiographic knee osteoarthritis database using artificial intelligence tools with limited human labor: A proof of principle.

OBJECTIVE: To create a scalable and feasible retrospective consecutive knee osteoarthritis (OA) radiographic database with limited human labor using commercial and custom-built artificial intelligence (AI) tools. METHODS: We applied four AI tools, two commercially available and two custom-built tools, to analyze 6 years of clinical consecutive knee radiographs from patients aged 35-79 at the University of Copenhagen Hospital, Bispebjerg-Frederiksberg Hospital, Denmark. The tools provided Kellgren-Lawrence (KL) grades, joint space widths, patella osteophyte detection, radiographic view detection, knee joint implant detection, and radiographic marker detection. RESULTS: In total, 25,778 knee radiographs from 8575 patients were included in the database after excluding inapplicable radiographs, and 92.5% of the knees had a complete OA dataset. Using the four AI tools, we saved about 800 hours of radiologist reading time and only manually reviewed 16.0% of the images in the database. CONCLUSIONS: This study shows that clinical knee OA databases can be built using AI with limited human reading time for uniform grading and measurements. The concept is scalable temporally and across geographic regions and could help diversify further OA research by efficiently including radiographic knee OA data from different populations globally. We can prevent data dredging and overfitting OA theories on existing trite cohorts by including various gene pools and continuous expansion of new clinical cohorts. Furthermore, the suggested tools and applied approaches provide an ability to retest previous hypotheses and test new hypotheses on real-life clinical data with current disease prevalence and trends.

Spinal anaesthesia versus general anaesthesia (SAGA) on recovery after hip and knee arthroplasty: A study protocol for three randomized, single-blinded, multi-centre, clinical trials.

Mobilisation difficulties, due to muscle weakness, and urinary retention are common reasons for prolonged admission following hip and knee arthroplasty procedures. Whether spinal anaesthesia is detrimental to early mobilisation is controversial. Previous studies have reported differences in post-operative recovery between spinal anaesthesia and general anaesthesia; however, up-to-date comparisons in fast-track setups are needed. Our randomized, single-blinded, multi-centre, clinical trials aim to compare the post-operative recovery after total hip (THA), total knee (TKA), and unicompartmental knee arthroplasties (UKA) respectively when using either spinal anaesthesia (SA) or general anaesthesia (GA) in a fast-track setup. Included patients (74 THA, 74 TKA, and 74 UKA patients) are randomized (1:1) to receive either SA (2 mL 0.5% Bupivacaine) or GA (Induction: Propofol 1.0-2.0 mg/kg iv with Remifentanil 3-5 mcg/kg iv. Infusion: Propofol 3-5 mg/kg/h and Remifentanil 0.5 mcg/kg/min iv). Patients undergo standard primary unilateral hip and knee arthroplasty procedures in an optimized fast-track setup with intraoperative local infiltrative analgesia in TKA and UKA, post-operative multimodal opioid sparing analgesia, immediate mobilisation with full weightbearing, no drains and in-hospital only thromboprophylaxis. Data will be collected on the day of surgery and until patients are discharged. The primary outcome is the ability to be safely mobilised during a 5-m walking test within 6 h of surgery. Secondary outcomes include fulfilment of discharge criteria, post-operative pain, dizziness, and nausea as well as patient reported recovery and opioid related side effects. Data will also be gathered on all hospital contacts within 30-days of surgery. This study will offer insights into advantages and disadvantages of anaesthetic methods used in fast-track arthroplasty surgery.

Perioperative association between c-reactive protein, pain catastrophizing and acute pain after total knee arthroplasty: A secondary analysis of two randomised trials.

BACKGROUND: Total knee arthroplasty is associated with an inflammatory response and high levels of pain in a subset of patients. Pain catastrophizing has been associated with acute postoperative pain. The association between these variables has not been investigated in an optimised fast-track setup including preoperative glucocorticoids. The aim of this study was, first, to investigate the correlation between the increase in postoperative c-reactive protein (CRP) and acute postoperative pain after total knee arthroplasty, and second, to investigate the correlation between the increase in CRP and preoperative pain catastrophizing. METHODS: This study is a secondary analysis of data from 119 patients participating in two randomised controlled trials. Correlation analyses were performed for preoperative CRP and CRP increase at 24 and 48 h and pain during a well-defined mobilisation at 24 and 48 h after total knee arthroplasty. Additionally, correlation analyses were performed between CRP increase and pain catastrophizing using the pain catastrophizing scale. RESULTS: There was no correlation between preoperative CRP or postoperative CRP increase and pain at both 24 and 48 h. Analyses were similar when separated into high and low pain catastrophizers. There was no correlation between preoperative CRP or postoperative CRP increase and pain catastrophizing. CONCLUSION: There was no association between the postoperative CRP response and postoperative acute pain or pain catastrophizing in patients undergoing total knee arthroplasty in a well-defined multimodal fast-track regime including preoperative glucocorticoids. These results suggest that acute pain after knee arthroplasty is not reflected by CRP when applying preoperative glucocorticoids.

Starting up a Lateral Unicompartmental Knee Arthroplasty Practice - Is Outcome Affected?

BACKGROUND: In the past, the utilization of lateral unicompartmental knee arthroplasty (UKA) has been limited at national levels, despite the fact that an estimated 10% of patients who have an indication for arthroplasty, present with isolated lateral compartment osteoarthritis (OA). Units dedicated to UKA have reported good outcomes. Identifying patients for the procedure has been less clear, and the procedure has been perceived to be technically more demanding than medial UKA. This may result in a reluctance to start a lateral UKA practice and challenge the early phase. Therefore, this paper aimed to present the outcomes and learning curve when starting up a lateral UKA practice, as this theme remains unelucidated. METHODS: There were 85 primary fixed-bearing lateral UKAs, with a minimum of 1-year follow-up, performed between 2016 and 2022 by 2 arthroplasty surgeons with existing UKA practices. The indications were primary (n = 79) or post-traumatic (n = 6) OA. Patient-reported outcome measures (PROMs) were assessed at 3, 12, and 24 months. A cumulative sum (CUSUM) analysis was used to evaluate surgical duration and the 12-month Oxford Knee Score (OKS). RESULTS: Median (interquartile range) 12-month OKS, activity and participation questionnaire, and Forgotten Joint Score (FJS) were 43 (37.5 to 46), 78 (42.5 to 98.5), and 72 (55 to 90), respectively. The OKS outcomes did not reveal adverse effects from the learning curve. A performance shift in surgical duration was observed around case 33. Kaplan-Meier implant survival reached 95.4% at 7 years for the endpoint "implant revision" and 93.5% for "implant revision or implant addition." CONCLUSIONS: Starting up a lateral UKA practice is safe and efficient for surgeons who have prior medial UKA experience, provided strict adherence to indications. While surgical duration indicated a learning curve over approximately 33 cases, PROMs remained stable, suggesting proficient outcomes irrespective of the learning curve.

The Use of Large Metal Heads in Thin Vitamin E-Doped Cross-Linked Polyethylene Inserts Does Not Increase Polyethylene Wear in Total Hip Arthroplasty: 5-Year Results From a Randomized Controlled Trial.

BACKGROUND: Vitamin E-doped cross-linked polyethylene (VEPE) has encouraged the use of larger heads in thinner liners in total hip arthroplasty (THA). However, there are concerns about wear and mechanical failure of the thin liner, especially when metal heads are used. The aim of this randomized controlled trial was to investigate if the use of a large metal head in thin VEPE liner would increase polyethylene wear compared with a standard 32-mm metal head and to compare periacetabular radiolucencies and patient-reported outcomes in THA. METHODS: There were 96 candidates for uncemented THA who were randomly allocated to either the largest possible metal head (36 to 44 mm) that could be fitted in the thinnest available VEPE liner (intervention group) or a standard 32-mm metal head (control group). The primary outcome was proximal head penetration, measured with a model-based radiostereometric analysis. Secondary outcomes were periacetabular radiolucencies and patient-reported outcomes. The midterm results of the trial at 5 years are presented. RESULTS: The median total proximal head penetration (interquartile range) was -0.04 mm (-0.12 to 0.02) in the intervention group and -0.03 mm (-0.14 to 0.05) in the control group (P = .691). The rates of periacetabular radiolucencies were 1 of 44 and 4 of 42 (P = .197), respectively. Patient-reported hip function and health-related quality of life did not differ between the groups, but participants in the intervention group reported a higher level of activity (median University of California Level of Activity score 7 versus 6, P = .020). There were 5 revisions caused by dislocations (2), periprosthetic fracture (1), stem subsidence (1), or iliopsoas impingement (1). CONCLUSIONS: Large metal heads in thin VEPE liners did not increase liner wear and were not associated with liner failure 5 years after THA.

One-Year Postoperative Patient-Reported Outcome Measures Are Associated With Three-Year to Five-Year Postoperative Satisfaction in Total Knee Arthroplasty.

BACKGROUND: Over the past couple of decades, the definition of success after total knee arthroplasty (TKA) has shifted away from clinician-rated metrics and toward the patient's subjective experience. Therefore, understanding the aspects of patient recovery that drive 3-year to 5-year satisfaction after TKA is crucial. The aims of this study were to (1) determine the 1-year postoperative factors, specifically patient-reported outcome measures (PROMs) that were associated with 3-year and 5-year postoperative satisfaction and (2) understand the factors that drive those who are not satisfied at 1 year postoperatively to become satisfied later in the postoperative course. METHODS: This was a retrospective study of 402 TKA patients who were gathered prospectively and presented for their 1-year follow-up. Demographics were collected preoperatively and patient-reported outcomes were collected at 1, 3, and 5 years postoperatively. Logistic regressions were used to identify the factors at 1 year that were associated with 3-year and 5-year satisfaction. RESULTS: Associations between 1-year PROMs with 3-year satisfaction were observed. Longer term satisfaction at 5 years was more closely associated with EuroQol 5 Dimension Mobility, Activity Score, and Numerical Rating Scale Satisfaction. Of those who were not satisfied at 1 year, EuroQol 5 Dimension Mobility, Knee Disability Osteoarthritis Outcome Score Function in Sport and Recreation, and Satisfaction were associated with becoming satisfied at 3 years. CONCLUSION: The 1-year PROMs were found to be associated with satisfaction at 3 to 5 years after TKA. Importantly, many of the PROMs that were associated with 3-year to 5-year satisfaction, especially in those who were not originally satisfied at 1 year, were focused on mobility and activity level.

Anteromedial knee osteoarthritis (AMOA) evaluated with magnetic resonance imaging (MRI): a cohort study of 100 patients.

INTRODUCTION: Magnetic resonance imaging (MRI) scans are increasingly used for knee osteoarthritis evaluation and preoperative planning before unicompartmental knee arthroplasty (UKA), and often patients already have MRI scans before their initial surgeon consultation. This highlights the need for surgeons to understand anteromedial osteoarthritis (AMOA) patterns on MRI. Hence, we aim to describe MRI findings in patients with AMOA meeting current indications for medial UKA. MATERIALS AND METHODS: We analysed MRI scans from 100 knees evaluated for UKA between 2006 and 2013. Inclusion criteria comprised full-thickness medial compartment loss and intact lateral compartment joint space on preoperative radiographs. Assessment included cartilage lesions, osteophytes, meniscal damage, and anterior-cruciate ligament (ACL) status on tibial and femoral surfaces. Final decision to proceed with UKA relied on intraoperative findings, independent of MRI. RESULTS: Complete anteromedial tibial and femoral cartilage loss preserved posterior cartilage rims was evident in all cases. Cartilage thinning occurred in the lateral compartment in 34% of cases. While 62% displayed lateral osteophytes, only 6 exhibited small areas of full-thickness cartilage loss. ACL abnormalities varied: 27% normal, 3% ruptured, and 70% had intrasubstance high signal. Larger osteophytes in the medial (p = 0.012) and lateral (p = 0.002) intercondylar notch correlated significantly with ACL damage. All underwent medial UKA, with no evidence of areas with full lateral compartment cartilage loss intraoperatively. CONCLUSIONS: The MRI findings confirmed the radiographic diagnosis of bone-on-bone medial disease but highlights a range of findings in the ACL, lateral compartment, and patellofemoral joint compartment for patients who met the current x-ray and intraoperative indication for UKA. Further research is required to understand if these MRI changes will affect long-term outcomes.

Half of all hip and knee arthroplasty patients may be potential day-case candidates: a nationwide register study of 166,730 procedures.

BACKGROUND AND PURPOSE: The overall potential pool of day-case candidates on a national level in hip and knee arthroplasty is unknown. We aimed to estimate the proportion of hip and knee arthroplasty patients eligible for day-case surgery based on contemporary widely used criteria and determine whether there has been a change in the proportion of eligible patients over time and, secondarily, to investigate the proportion of eligible patients discharged on the day of surgery. METHODS: Based on data from the Danish National Patient Register, we identified all patients undergoing primary unilateral hip or knee arthroplasty from January 2010 to March 2020. Using a modification of day-case eligibility criteria proposed by a national multicenter collaboration, we sorted patients into either day-case eligible or ineligible. A day-case procedure was defined as discharge on the day of surgery. RESULTS: We included patients comprising a total of 166,730 primary total hip (THA), total knee (TKA), and unicompartmental knee arthroplasty (UKA). 48% (95% confidence interval [CI] 48-49) were eligible for day-case surgery, with a decline from 50% (CI 49-51) in 2010 to 46% (CI 46-47) eligible in 2019. More UKA patients were day-case eligible (55%, CI 54-56) than THA (47%, CI 47-48) and TKA patients (49%, CI 48-49). A maximum of 8.0% (CI 7.4-8.5) of eligible patients were discharged on the day of surgery in 2019. CONCLUSION: 48% of the Danish hip and knee arthroplasty patients were potential day-case candidates, with a small decline in eligibility from 50% in 2010 to 46% in 2019. Day of surgery discharge among day-case eligible patients peaked at 8% in 2019. Thus, the potential for more day-case surgery seems large.

Enhancing the data capture of periprosthetic joint infections in the Danish Knee Arthroplasty Registry: validity assessment and incidence estimation.

BACKGROUND AND PURPOSE: Revisions due to periprosthetic joint infection (PJI) are underestimated in national arthroplasty registries. Our primary objective was to assess the validity in the Danish Knee Arthroplasty Register (DKR) of revisions performed due to PJI against the Healthcare-Associated Infections Database (HAIBA). The secondary aim was to describe the cumulative incidences of revision due to PJI within 1 year of primary total knee arthroplasty (TKA) according to the DKR, HAIBA, and DKR/HAIBA combined. METHODS: This longitudinal observational cohort study included 56,305 primary TKAs (2010-2018), reported in both the DKR and HAIBA. In the DKR, revision performed due to PJI was based on pre- and intraoperative assessment disclosed by the surgeon immediately after surgery. In HAIBA, PJI was identified from knee-related revision procedures coinciding with 2 biopsies with identical microbiological pathogens. We calculated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of revision due to PJI in the DKR (vs. HAIBA, within 1 year of TKA) with 95% confidence intervals (CI). Cumulative incidences were calculated using the Kaplan-Meier method. RESULTS: The DKR's sensitivity for PJI revision was 58% (CI 53-62) and varied by TKA year (41%-68%) and prosthetic type (31% for monoblock; 63% for modular). The specificity was 99.8% (CI 99.7-99.8), PPV 64% (CI 62-72), and NPV 99.6% (CI 99.6-99.7). 80% of PJI cases not captured by the DKR were caused by non-reporting rather than misclassification. 33% of PJI cases in the DKR or HAIBA were culture-negative. Considering potential misclassifications, the best-case sensitivity was 64%. The cumulative incidences of PJI were 0.8% in the DKR, 0.9% in HAIBA, and 1.1% when combining data. CONCLUSION: The sensitivity of revision due to PJI in the DKR was 58%. The cumulative incidence of PJI within 1 year after TKA was highest (1.1%) when combining the DKR and HAIBA, showing that incorporating microbiology data into arthroplasty registries can enhance PJI validity.

Genome-wide association meta-analysis of knee and hip osteoarthritis uncovers genetic differences between patients treated with joint replacement and patients without joint replacement.

OBJECTIVES: Osteoarthritis is a common and severe, multifactorial disease with a well-established genetic component. However, little is known about how genetics affect disease progression, and thereby the need for joint placement. Therefore, we aimed to investigate whether the genetic associations of knee and hip osteoarthritis differ between patients treated with joint replacement and patients without joint replacement. METHODS: We included knee and hip osteoarthritis cases along with healthy controls, altogether counting >700 000 individuals. The cases were divided into two groups based on joint replacement status (surgical vs non-surgical) and included in four genome-wide association meta-analyses: surgical knee osteoarthritis (N = 22 525), non-surgical knee osteoarthritis (N = 38 626), surgical hip osteoarthritis (N = 20 221) and non-surgical hip osteoarthritis (N = 17 847). In addition, we tested for genetic correlation between the osteoarthritis groups and the pain phenotypes intervertebral disc disorder, dorsalgia, fibromyalgia, migraine and joint pain. RESULTS: We identified 52 sequence variants associated with knee osteoarthritis (surgical: 17, non-surgical: 3) or hip osteoarthritis (surgical: 34, non-surgical: 1). For the surgical phenotypes, we identified 10 novel variants, including genes involved in autophagy (rs2447606 in ATG7) and mechanotransduction (rs202127176 in PIEZO1). One variant, rs13107325 in SLC39A8, associated more strongly with non-surgical knee osteoarthritis than surgical knee osteoarthritis. For all other variants, significance and effect sizes were higher for the surgical phenotypes. In contrast, genetic correlations with pain phenotypes tended to be stronger in the non-surgical groups. CONCLUSIONS: Our results indicate differences in genetic associations between knee and hip osteoarthritis depending on joint replacement status.

High-dose dexamethasone in low pain responders undergoing total knee arthroplasty: a randomised double-blind trial.

BACKGROUND: Postoperative pain after total knee arthroplasty (TKA) is a continuing problem despite optimised multimodal analgesia. Previous studies have shown preoperative glucocorticoids to reduce postoperative pain, but knowledge about specific doses and effects in specific patient groups is lacking. METHODS: A two-centre, double-blind, two-arm study comparing preoperative dexamethasone (1 mg kg-1vs 0.3 mg kg-1 i.v.) on postoperative pain in 160 planned TKA subjects with low preoperative pain catastrophising and no opioid use. Subjects received multimodal analgesia with paracetamol, cyclooxygenase-2 inhibitors, local anaesthetic infiltration analgesia, and rescue opioids. The primary outcome was percentage of subjects experiencing moderate to severe pain (visual analogue scale >30 mm) upon ambulation at 24 h. Secondary outcomes included pain scores, postoperative inflammation (C-reactive protein), opioid and antiemetics use, and 'Quality of Recovery-15' and 'Opioid-Related Symptom Distress Scale', length of stay, readmissions, and complications up to Day 90. RESULTS: A total of 157 subjects (80 vs 77) were included. No difference was found between groups in the incidence of subjects experiencing visual analogue scale >30 on ambulation 24 h after surgery (56% vs 53%, relative risk =1.07, confidence interval: 0.8-1.4, P=0.65). No differences in other pain outcomes or use of rescue opioids and antiemetics, in Quality of Recovery-15 and Opioid-Related Symptom Distress Scale, length of stay, readmissions, or complications. C-reactive protein values were comparable at 24 h (13 [6-25] mg L-1vs 16 [9-38] mg L-1, P = 0.07), but lower at 48 h (26 [9-52] mg L-1vs 50 [30-72] mg L-1, P<0.01) in the high-dose group. CONCLUSION: Use of 1 mg kg-1vs 0.3 mg kg-1 i.v. dexamethasone in low pain responders after TKA did not improve early postoperative pain or other outcomes in contrast to benefits in a high pain responder population. CLINICAL TRIAL REGISTRATION: NCT03758170 (first registration 29-11-2018).

Repeat dose steroid in high pain responders after total knee arthroplasty: A study protocol.

Pain after total knee arthroplasty (TKA) is a well-known clinical problem potentially delaying ambulation and recovery. Perioperative glucocorticoids reduce pain and facilitate early recovery, but the optimal timing and dose are still unknown. High pain catastrophizers have an increased risk of poorly controlled postoperative pain, and moderate to severe pain at 24 h is associated with a risk of pain relapse at 48 h. To evaluate the effect of a repeat moderate dose of glucocorticoids after TKA in high pain catastrophizers presenting with moderate to severe pain 24 h postoperatively, having received preoperative high-dose glucocorticoids. High pain catastrophizers (Pain Catastrophizing Scale > 20) undergoing TKA are screened 24 h postoperatively and are included if they experience moderate to severe pain (VAS > 30) during a 5 m walk test. The included patients will receive either oral 24 mg dexamethasone (n = 55) or placebo (n = 55) on the evening of Day 1 (~30-37 h) after surgery. In addition, patients receive a standard multimodal analgesic regimen, including paracetamol, celecoxib, local infiltration analgesia, and preoperative dexamethasone (1 mg/kg). Patients will fill out a pain diary for 7 days after surgery. The primary outcome is moderate to severe pain (VAS > 30) during a 5 m walk test on the morning of Day 2 after surgery. The secondary outcomes include cumulated pain at rest and during ambulation, cumulated use of rescue analgesics, quality of sleep, lethargy, dizziness, nausea, satisfaction with the analgesic regimen, length of stay, morbidity, mortality, and reasons for readmissions. Follow-up is at 8 and 30 days. The data from this study will provide evidence for the effect of a repeated dose of dexamethasone as an analgesic adjuvant in patients undergoing TKA with a high risk of postoperative pain.

High dose dexamethasone in high pain responders undergoing total hip arthroplasty: A randomized controlled trial.

BACKGROUND: Postoperative pain after total hip arthroplasty (THA) may delay postoperative mobilization and discharge. Postoperative pain has been shown to be higher in pain catastrophisers and patients receiving opioids. A single dose of glucocorticoid reduces pain after THA, and an increased dose of glucocorticoids has been found to be effective in patients at high risk of postoperative pain after total knee arthroplasty (TKA), however, the ideal dose in THA remains unknown. OBJECTIVE: To evaluate the effect of a high dose (1 mg kg -1 ) vs. intermediate dose (0.3 mg kg -1 ) of dexamethasone on pain after THA. DESIGN: A randomized double-blind controlled study. SETTING: A two-centre study including two large arthroplasty sites in Denmark was conducted from February 2019 to August 2020. PATIENTS: A total of 160 patients undergoing THA by neuraxial block with multimodal analgesia, having a Pain Catastrophising Scale score >20 and/or preoperative opioid use were included. INTERVENTION: Patients were randomly assigned to receive dexamethasone 1 mg kg -1 or 0.3 mg kg -1 before THA. MAIN OUTCOME MEASURES: Primary outcome was percentage of patients experiencing moderate to severe pain (visual analogue scale, VAS > 30 mm on a 0 to 100 mm scale) on ambulating 24 h after surgery. Secondary outcomes included cumulated pain scores, C-reactive protein (CRP), opioid use, postoperative recovery scores, length of stay, complications, and re-admission within 30 and 90 days. RESULTS: No difference was found in percentage of VAS >30 mm 24 h after surgery in the 5-m walk test (VAS > 30/VAS ≤ 30%); 33/42 (44%) vs. 32/43 (43%), relative risk = 1.04 (95% confidence interval 0.72-1.51; P  = 0.814) in 1 mg kg -1vs. 0.3 mg kg -1 respectively. No differences were found in CRP and opioid use between groups. Also, no intergroup differences were found in recovery scores, re-admissions, or complications. CONCLUSION: 1 mg kg -1vs. 0.3 mg kg -1 dexamethasone improved neither postoperative pain nor recovery in THA in a cohort of predicted high pain responders. TRIAL REGISTRATION: ClinicalTrials.gov ID-number NCT03763760 and EudraCT-number 2018-2636-25.

Patient-reported outcomes and satisfaction after revisions of medial unicompartmental knee arthroplasties for unexplained pain vs aseptic loosening.

PURPOSE: Does patients revised for unexplained pain after mUKA present the same PROM and satisfaction scores 1-3 years after revision as patients revised for aseptic loosening?". METHODS: 104 patients undergoing revision of mUKA's for the indications unexplained pain and aseptic loosening were included in the period January 1, 2018 to December 31, 2020. from the Danish Knee Arthroplasty Register. 52 patients were revised for unexplained pain and 52 for aseptic loosening. Patient demographics did not differ between the two groups. PROMs [Oxford Knee Score (OKS), EQ-5D-5L, Forgotten Joint Score (FJS)] and questions about satisfaction with the surgery were sent to digitally secured mailboxes. Pearson's Chi-square test and Wilcoxon Rank Sum test were used to test for statistical differences between groups. RESULTS: The median OKS 1-3 years after revision was 26 (IQR 22) for unexplained pain vs 34 (IQR 12) for aseptic loosening, p = 0.033. The median EQ-5D-5L Index after revision was 0.7 (IQR 0.6) for unexplained vs 0.8 (IQR 0.1) for aseptic loosening, p = 0.014. The median FJS after revision was 48 (IQR 10) for unexplained pain vs 52 (IQR 14) for aseptic loosening, p = 0.1. The mean satisfaction with the surgery on a 0-100 scale (100 = not satisfied; 0 = very satisfied) was 55 (IQR 60) for unexplained pain vs 50 (IQR 67) for aseptic loosening, p = 0.087, and patients revised for unexplained pain were less likely to find their knee problem importantly improved (p = 0.032). CONCLUSION: Patients undergoing revision of mUKAs for unexplained pain presented poor postoperative PROM scores, and PROM scores were worse compared to those of patients revised for aseptic loosening. Patients revised for unexplained pain were less likely to find their knee problem importantly improved. This study support the evidence against revisions for unexplained pain. LEVEL OF EVIDENCE: Level III.

Patient-Reported Outcomes and Satisfaction 1 to 3 Years After Revisions of Total Knee Arthroplasties for Unexplained Pain Versus Aseptic Loosening.

BACKGROUND: It is unknown if patients are relieved of pain after knee arthroplasty revision for unexplained pain. The aim of this cross-sectional case-control study was to compare patient-reported outcome measures (PROMs) and satisfaction 1 to 3 years after revision of total knee arthroplasties (TKAs) for the indications of unexplained pain versus aseptic loosening. METHODS: We included 384 patients undergoing TKA revision for the indications of unexplained pain and aseptic loosening from January 1, 2018 to December 31, 2020 from the Danish Knee Arthroplasty Register. A total of 81 patients were revised for unexplained pain and 303 for aseptic loosening. Questionnaires including PROMs (Oxford Knee Score, EQ-5D-5L, and Forgotten Joint Score) and satisfaction with the surgery on a 0-100 scale (100 = not satisfied; 0 = very satisfied) were sent to digitally secured mailboxes. Time from revision to data collection was a median 3.1 years (range, 1.4-4.4 years). RESULTS: Median Oxford Knee Score was 25 (interquartile range [IQR] 15) versus 31 (IQR 18) 1-3 years after revisions for unexplained pain versus aseptic loosening, P = .009. Median EQ-5D-5L was 0.6 (IQR 0.4) versus 0.8 (IQR 0.3) for unexplained pain versus aseptic loosening, P = .009. Median Forgotten Joint Score was 50 (IQR 7) versus 50 (IQR 16) for unexplained pain versus aseptic loosening, P = .905. Satisfaction was 75 (IQR 38) for unexplained pain and 50 (IQR 73) for aseptic loosening, P < .001. CONCLUSION: Patients undergoing TKA revision for the indication of unexplained pain had worse results on PROMs than those revised for aseptic loosening. Likewise, patients revised for unexplained pain were less satisfied compared to patients revised for aseptic loosening. This information is valuable to both surgeons and patients when candidates for revision surgery are selected, to obtain the best possible outcomes.

Obese Patients Achieve Good Improvements in Patient-Reported Outcome Measures After Medial Unicompartmental Knee Arthroplasty Despite a Lower Preoperative Score.

BACKGROUND: In this study, we examined the association between obesity and patient-reported outcome measures after medial unicompartmental knee arthroplasty (MUKA), assessed through score changes, Patient Acceptable Symptom State (PASS), and minimal important change (MIC). Second, the association between obesity and early readmissions was examined. METHODS: A total of 450 MUKAs (mean body mass index [BMI] 30.3, range, 19.6-53.1), performed from February 2016 to December 2020, were grouped using BMI: <30, 30-34.9, and >34.9. Oxford Knee Score (OKS), Forgotten Joint Score (FJS), and Activity and Participation Questionnaire (APQ) were assessed preoperatively and at 3, 12, and 24 months, postoperatively. The 12-month PASS and MIC were also assessed, defining PASS as OKS = 30, MIC-OKS as change in OKS = 8, and MIC-FJS as change in FJS = 14. RESULTS: No significant differences in OKS change were found between BMI groups. After 12 months, patients who had a BMI of 30-34.9 had lower change in FJS (estimate -8.1, 95% CI -14.9 to -1.4) and were less likely to reach PASS (odds ratio 0.4, 95% CI 0.2-0.7) as well as MIC-FJS (odds ratio 0.5, 95% CI 0.2-0.9). Both obese groups had lower change in APQ after 12 months. Differences in 90-day readmission rates were nonsignificant between groups. CONCLUSION: Our findings of no differences in OKS improvement between BMI groups and achieving MIC for BMI > 34.9 suggest good improvements in obese patients despite lower preoperative scores, supporting contemporary indications for MUKA. Lower APQ development and achievement of 12-month PASS may be used when addressing expectations of recovery.

Temporal trends in revision rate due to knee periprosthetic joint infection: a study of 115,120 cases from the Danish Knee Arthroplasty Register.

BACKGROUND AND PURPOSE: We aimed to examine the temporal trends in periprosthetic joint infection (PJI) revision incidence after knee arthroplasty (KA) from 1997 through 2019. PATIENTS AND METHODS: 115,120 primary KA cases from the Danish Knee Arthroplasty Register were followed until the first PJI revision. We computed cumulative incidences and adjusted hazard ratios (aHRs) of PJI revision by calendar periods and several patient- and surgical-related risk factors. Results were analyzed from 0-3 months and from 3-12 months after KA. RESULTS: The overall 1-year PJI revision incidence was 0.7%, increasing from 0.5% to 0.7% (1997 through 2019). The incidence of PJI revision within 3 months increased from 0.1% to 0.5% (1997 through 2019). The adjusted hazard ratio (aHR) within 1 year of primary KA was 5.1 comparing 2017-2019 with 2001-2004. The PJI revision incidence from 3-12 months of KA decreased from 0.4% to 0.2%, with an aHR of 0.5 for 2017-2019 vs. 2001-2004. Male sex, age 75-84 (vs. 65-74), and extreme obesity (vs. normal weight) were positively associated with the risk of PJI revision within 3 months, whereas only male sex was associated from 3-12 months. Partial knee arthroplasty (PKA) vs. total KA was associated with a lower risk of PJI revision both within 3 months and 3-12 months of KA. CONCLUSION: We observed an increase in PJI revision within 3 months of KA, and a decrease in PJI revision incidence from 3-12 months from 1997 through 2019. The reasons for this observed time-trend are thought to be multifactorial. PKA was associated with a lower risk of PJI revision.

No difference in short-term readmissions following day-case vs. one overnight stay in patients having hip and knee arthroplasty: a nationwide register study of 51,042 procedures from 2010-2020.

BACKGROUND AND PURPOSE: Day-case hip and knee arthroplasty has gained in popularity, but there are conflicting results regarding readmissions. We aimed to investigate differences in 30- and 90-day readmission rates between day-case patients and patients with a single overnight stay following primary total hip arthroplasty (THA), total knee arthroplasty (TKA), and unicompartmental knee arthroplasty (UKA). PATIENTS AND METHODS: We identified day-case (DC) and overnight (ON) THA, TKA, and UKA patients, operated on between 2010 and 2020, from the Danish National Patient Register. Day-case surgery was defined as discharge on the day of surgery. Overnight readmissions within 30 or 90 days of surgery were considered readmissions. We compared readmission rates between DC and ON patients within arthroplasty types using logistic regression adjusted for patient characteristics and year of surgery. We included 29,486 THAs (1,353 DC and 28,133 ON), 15,116 TKAs (617 DC and 14,499 ON), and 6,440 UKAs (1,528 DC and 4,914 ON). RESULTS: The 30-day readmission rates were: DC-THA 4.4% vs. ON-THA 4.4% (adjusted odds-ratio [aOR] 1.2, 95% confidence interval [CI] 0.91-1.6), DC-TKA 4.7% vs. ON-TKA 4.4% (aOR 1.1, CI 0.69-1.5), and DC-UKA 3.0% vs. ON-UKA 3.0% (aOR 1.1, CI 0.78-1.5). Similarly, no significant differences were present between DC and ON THA, TKA, and UKA regarding 90-day readmissions or time to readmission. CONCLUSION: We found no differences in readmission rates between day-case THA, TKA, and UKA patients and patients with a single overnight stay.

Complications after lateral unicompartmental knee arthroplasty in a fast-track setting: a prospective cohort study of 170 procedures.

BACKGROUND AND PURPOSE: In existing studies on fasttrack unicompartmental knee arthroplasty (UKA), the majority of surgeries are medial. There are substantial differences between lateral and medial UKA, which is why outcomes cannot automatically be compared. To gain information on the feasibility and safety of fast-track protocols in lateral UKAs, we investigated length of stay (LOS) and early complications after lateral UKA, performed using a fast-track protocol in well-established fast-track centers. PATIENTS AND METHODS: We retrospectively evaluated prospectively collected data on patients undergoing lateral UKA in a fast-track setup from 2010 to 2018 at 7 Danish fast-track centers. Data on patient characteristics, LOS, complications, reoperations, and revisions was analyzed using descriptive statistics. Safety and feasibility were defined as complication and reoperation rates within 90 days comparable to non-fast track lateral UKA or fast-track medial UKA. RESULTS: We included 170 of patients with a mean age of 66 (SD 12) years. Median LOS was 1 day (interquartile range 1-1), which was unchanged from 2012-2018. 18% were discharged on the day of surgery. Within 90 days, 7 patients experienced medical complications and 5 patients experienced surgical complications. 3 patients underwent reoperation, 2 were soft tissue revisions and the third was removal of an exostosis due to catching of the patella. 1 patient was revised due to a bearing dislocation. CONCLUSION: Our findings suggest that lateral UKA in a fast-track setting is feasible and safe.

Use of a tourniquet is not associated with increased risk of venous thromboembolism after fast-track total knee arthroplasty: a prospective multicenter cohort study of 16,250 procedures.

BACKGROUND AND PURPOSE: Venous thromboembolism (VTE) is a serious postoperative complication after total knee arthroplasty (TKA). Use of a tourniquet has shown conflicting results for risk of VTE after TKA. We aimed to investigate the associated risk of VTE after TKA using tourniquet in a fast-track set-up as no previous data exists. PATIENTS AND METHODS: We performed an observational cohort study from 9 fast-track centers including unilateral primary TKA from 2010-2017 with prospective collection of preoperative risk-factors and complete 90-day follow-up. Use of a tourniquet was registered in the Danish Knee Arthroplasty Register. Postoperative VTE was identified from health records. We performed risk analyses using a mixed-effects logistic regression model adjusting for previously identified risk factors. RESULTS: Of the 16,250 procedures (39% males, mean age 67.9 [SD 10.0] years, median LOS 2 [interquartile range 2-3]) 12,518 (77%) were performed with a tourniquet. The annual tourniquet usage varied greatly between departments from 0% to 100%, but also within departments from 0% to 99%. There was no significant difference between the 2 groups with 52 (0.42%) VTEs in the tourniquet group vs. 25 (0.67%) in the no-tourniquet group (p = 0.06 for cumulative 90-day incidence of VTE). This association remained statistically insignificant for VTE using tourniquet after adjustment for previously identified risk factors. CONCLUSION: We found no association between the use of a tourniquet and increased risk of 90-day VTE after primary fast-track TKA, irrespective of the length of time for which the tourniquet was applied.