Background: Whether to use unicompartmental knee arthroplasty (UKA) or total knee arthroplasty (TKA) for appropriate osteoarthritis cases is a subject of debate. UKA potentially offers faster recovery and fewer short-term complications. However, reported differences in preoperative comorbidity between TKA and UKA-treated patients could affect outcomes. The aim of this study was to investigate differences in the length of the postoperative hospital stay (LOS) as well as readmissions and complications within 90 days after surgery between matched UKA and TKA cohorts.Methods: Patients undergoing UKA or TKA in a fast-track setup at 9 orthopaedic centers from 2010 to 2017 were included in the study. Propensity score matching with exact matching for surgical year was used to address differences in demographics and comorbidity between the UKA and TKA groups, resulting in a matched cohort of 2,786 patients who underwent UKA and 7,708 who underwent TKA. Univariable linear or logistic regression models, multivariable mixed-effects models, and a chisquare test were used to investigate differences in LOS, readmissions, and complications between the UKA and TKA groups. Results:The UKA group had a shorter median LOS than the TKA group (1 compared with 2 days, p < 0.001). The UKA group was more likely to be discharged on the day of surgery (21.1% compared with 0.5%, odds ratio [OR] = 38.5, 95% confidence interval [CI] = 27.0 to 52.6) and less likely to have an LOS of >2 days (OR = 0.20, 95% CI = 0.17 to 0.24) compared with the TKA group. There was no difference in the 90-day readmission rate (p = 0.611) between the groups. The UKA group had fewer periprosthetic joint infections (OR = 0.50, 95% CI = 0.26 to 0.99) and reoperations (OR = 0.40, 95% CI = 0.20 to 0.81) compared with the TKA group. However, aseptic revisions were more frequent in the UKA group (OR = 2.5, 95% CI = 1.1 to 6.0). Conclusions:The UKA group had shorter hospital stays, a higher rate of discharge on the day of surgery, and fewer periprosthetic joint infections and reoperations compared with the matched TKA group. However, the TKA group had fewer aseptic revisions. Our findings support the use of UKA in a fast-track setup when indicated.

Background and purpose — Previous studies have investigated risk factors related to prolonged length of stay following total knee arthroplasty (TKA), but little is known about specific factors resulting in continued hospitalization within the 1st postoperative days after unicompartmental knee arthroplasty (UKA). We investigated what specific factors prevent patients from being discharged on the day of surgery (DOS) and the first postoperative day (POD-1) following primary UKA in a fast-track setting. Patients and methods — We prospectively collected data on 100 consecutive and unselected medial UKA patients operated from December 2017 to May 2019. All patients were operated in a standardized fast-track setup with functional discharge criteria continuously evaluated from DOS and until discharge. Results — Median length of stay for the entire cohort was 1 day. 22% and 78% of all patients were discharged on DOS and POD-1, respectively. Lack of mobilization and pain separately delayed discharge in respectively 78% and 24% of patients on DOS. The main reasons for lack of mobilization were motor blockade (37%) and logistical factors (26%). For patients placed 1st or 2nd on the operating list, we estimate that the same-day discharge rate would increase to 55% and 40% respectively, assuming that pain and mobilization were successfully managed. Interpretation — One-fifth of unselected UKA patients operated in a standardized fast-track setup were discharged on DOS. Pain and lack of mobilization were the major reasons for continued hospitalization within the initial postoperative 24–48 hours. Strategies aimed at decreasing length of stay after UKA should strive to improve analgesia and postoperative mobilization.

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Background and purpose: No previous studies have investigated the use of day-case arthroplasty in Denmark on a national scale. We investigated the frequency of day-case surgery in total hip (THA), total knee (TKA), and unicompartmental knee arthroplasty (UKA) from 2010 to 2020 in Denmark.Patients and methods: Primary unilateral THAs, TKAs, and UKAs performed for osteoarthritis were identified in the Danish National Patient Register using procedural and diagnosis codes. Day-case surgery was defined as discharge on the day of surgery. 90-day readmissions were defined as any overnight admissions following discharge.Results: From 2010 to 2020 Danish surgical centers performed 86,070 THAs, 70,323 TKAs, and 10,440 UKAs. From 2010 to 2014, less than 0.5% of THAs and TKAs were day-case procedures. They increased to 5.4% (95% confidence interval [CI] 4.9–5.8) of THAs and 2.8% (CI 2.4–3.2) of TKAs in 2019. From 2010 to 2014, 11% of UKAs were day-case procedures, but they increased to 20% (CI 18–22) in 2019. This increase was driven by a few surgical centers (3–7 centers). In 2010, readmission rates within 90 days of surgery were 10% after THAs and 11% after TKAs, and 9.4% for both THAs and TKAs in 2019. Readmission rates after UKA fluctuated between 4% and 7%.Conclusion: From 2010 to 2020 the use of day-case surgery in THA, TKA, and UKA increased in Denmark, driven by only a few centers. During the same period readmissions did not increase.

Background and purpose — The indications for unicompartmental knee arthroplasty (UKA) have become less restrictive and, today, high age and high BMI are not considered contraindications by many surgeons. While the influence of these patient characteristics on total knee arthroplasty is well documented, evidence on UKA is lacking. We investigated the effect of BMI and age on day of surgery (DOS) discharge, prolonged admission, and 90-day readmission following UKA surgery. Patients and methods — This retrospective cohort study included 3,897 UKA patients operated on between 2010 and 2018 in 8 fast-track arthroplasty centers. Patients were divided into 5 BMI groups and 5 age groups. Differences between groups in the occurrence of DOS discharge, prolonged admission > 2 days, and 90-day readmission was investigated using a chi-square test and mixed-effect models adjusted for patient characteristics using surgical center as a random effect. Results — Median LOS was 1 day. DOS discharge was achieved in 26% of patients with no statistically significant differences between BMI groups. DOS discharge was less likely in UKA patients aged > 70 years (age 71–80; odds ratio [OR] 0.7 [95% CI 0.6–0.9]). Prolonged admission was not affected by BMI or age in the adjusted analysis. 90-day readmission was more likely in patients with BMI > 35 (OR 1.9 [CI 1.1–3.1]) and patients aged 71–80 (OR 1.5 [CI 1.1–2.1]). Interpretation — Age > 70 years decreased the likelihood of DOS discharge after UKA. High BMI as well as advanced age increased the likelihood of 90-day readmission. This should be noted by surgeons operating on patients with high BMI and age.

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AimsMedial unicompartmental knee arthroplasty (mUKA) is an advised treatment for anteromedial knee osteoarthritis. While long-term survival after mUKA is well described, reported incidences of short-term surgical complications vary and the effect of surgical usage on complications is less established. We aimed to describe the overall occurrence and treatment of surgical complications within 90 days of mUKA, as well as occurrence in high-usage centres compared to low-usage centres.MethodsmUKAs performed in eight fast-track centres from February 2010 to June 2018 were included from the Lundbeck Foundation Centre for Fast-track Hip and Knee Replacement Database. All readmissions within 90 days of surgery underwent chart review and readmissions related to the surgical wound or the prosthesis were recorded. Centres were categorized as high-usage centres when using mUKA in ≥ 20% of annual knee arthroplasties. The occurrence of complications between high- and low-usage centres were compared using Fisher’s exact test.ResultsWe included 3,757 mUKAs: 2,377 mUKAs from high-usage centres and 1,380 mUKAs from low-usage centres. Surgical complications within 90 days occurred in 69 cases (1.8%), 45 (1.9%) in high-usage centres and 24 (1.7%) in low-usage centres (odds ratio (OR) 1.1 (95% confidence interval (CI) 0.65 to 1.8)). The most frequent complications were periprosthetic joint infections (PJIs) (n = 18; 0.48%), wound-related issues (n = 14; 0.37%), and periprosthetic fractures (n = 13; 0.35%). Bearing dislocations (n = 7; 0.19%) occurred primarily in procedures from high-usage centres. In high-usage centres, seven periprosthetic fractures (0.29%) occurred compared to six (0.43%) in low-usage centres (OR 0.68 (95% CI 0.20 to 2.0)). In high-usage centres, nine PJIs (0.38%) occurred compared to nine (0.65%) in low-usage centres (OR 0.58 (95% CI 0.22 to 1.6)).ConclusionSurgical complications are rare after fast-track mUKA surgery and with no difference in overall occurrence of surgical complications between high- and low-usage centres, although the risk of some specific surgical complications may favour high-usage centres.Cite this article: Bone Jt Open 2023;4(6):457–462.