Therapeutic ultrasound has been studied for over seven decades for different medical applications. The versatility of ultrasound applications are highly dependent on the frequency, intensity, duration, duty cycle, power, wavelength, and form. In this review article, we will focus on low-intensity continuous ultrasound (LICUS). LICUS has been well-studied for numerous clinical disorders, including tissue regeneration, pain management, neuromodulation, thrombosis, and cancer treatment. PubMed and Google Scholar databases were used to conduct a comprehensive review of all research studying the application of LICUS in pre-clinical and clinical studies. The review includes articles that specify intensity and duty cycle (continuous). Any studies that did not identify these parameters or used high-intensity and pulsed ultrasound were not included in the review. The literature review shows the vast implication of LICUS in many medical fields at the pre-clinical and clinical levels. Its applications depend on variables such as frequency, intensity, duration, and type of medical disorder. Overall, these studies show that LICUS has significant promise, but conflicting data remain regarding the parameters used, and further studies are required to fully realize the potential benefits of LICUS.

Background: The incidence of revision TKA is escalating. The safety and efficacy of performing revision TKA in an outpatient setting is important given this increased demand. Questions/purposes: (1) Are patients who undergo revision TKA in an outpatient setting more likely to undergo a repeat revision within 1 year compared with patients undergoing revision TKA in an inpatient setting? (2) Are patients who undergo outpatient revision TKA more likely to have increased hospital readmissions, manipulation under anesthesia (MUA), and medical complications compared with patients undergoing revision TKA in an inpatient setting? Methods: Patients who underwent single-component revision TKA in either an outpatient or inpatient setting were identified in the PearlDiver Mariner database using Current Procedural Terminology codes or ICD-9 and ICD-10 diagnosis codes. The PearlDiver database is a for-fee insurance patient records database that contains > 165 million individual patient records from 2010 to 2022 and allows patients to be tracked over time. Groups were propensity score–matched to minimize the risk of selection bias that patients with greater comorbidities would be treated in an inpatient setting. Propensity matching was performed using a 1:4 ratio by age, gender, and Elixhauser Comorbidity Index (ECI). After propensity matching, a total of 30,924 patients who underwent single-component revision TKA were included in the inpatient group and 7731 patients were included in the outpatient group. Outcome measures included rates of repeat revision at 1 year, hospital readmission at 90 days, and complications including deep vein thrombosis, pulmonary embolus, blood transfusion, wound complications, periprosthetic joint infection, and MUA at 90 days. Chi-square analyses were used to compare categorical variables, and independent samples t-tests were used to compare continuous variables. Because any observed differences favoring outpatient revision TKA were likely due to selection bias with no biologically plausible explanation for outpatient surgery resulting in fewer medical or surgical complications, the findings were interpreted as a noninferiority analysis, indicating that outpatient revision TKA is not inferior to inpatient revision TKA even if the data indicated a potential advantage for outpatient revision TKA over inpatient revision TKA. Results: The 1-year incidence of repeat revision was no higher in the outpatient group than the inpatient group (5% [359 of 7731] versus 5% [1606 of 30,924]; p = 0.05). The incidence of 90-day hospital readmission was no higher in the outpatient revision TKA group compared with the inpatient revision TKA group (8% [643 of 7731] versus 15% [4561 of 30,924]; p < 0.001). The incidence of all medical and surgical complications investigated was no higher in the outpatient revision TKA group compared with the inpatient revision TKA group. Conclusion: In this study, outpatient revision TKA did not have a higher incidence of repeat revision, hospital readmission, and medical or surgical complications compared with performing revision TKA in an inpatient setting. However, we do not suggest that revision TKA in the outpatient setting is appropriate for all patients or that it is safer than in the inpatient setting, as there was some unmeasured confounding despite propensity matching in this large data set. Our findings suggest that with careful patient selection, complication and revision rates can be comparable to those seen with inpatient revision surgery while also freeing up inpatient resources for patients who would benefit from them. When determining the appropriate setting for revision TKA, it is crucial to consider the patient’s overall health and medical comorbidities. Future studies should explore patient selection criteria and outcomes including patient satisfaction, pain scores, and cost savings of outpatient versus inpatient revision TKA to refine best practices and guide clinical decision-making. Level of Evidence: Level III, therapeutic study.