Background: Unicompartmental knee arthroplasty (UKA) is increasingly used for knee osteoarthritis due to faster recovery, better range of motion, and lower costs compared to total knee arthroplasty (TKA). While TKA may offer longer-lasting results with lower revision rates, this study compares the relative benefits and limitations of UKA and TKA using the National Inpatient Sample (NIS) database. Methods: This retrospective analysis examined outcomes of elective UKA and TKA procedures from 2016 to 2019, identifying 2,606,925 patients via ICD-10 codes. Propensity score matching based on demographics, hospital characteristics, and comorbidities resulted in a balanced cohort of 136,890 patients. The present study compared in-hospital mortality, length of stay, postoperative complications, and hospitalization costs. Results: The results showed that UKA procedures increased significantly over the study period. Patients undergoing UKA were generally younger with fewer comorbidities. After matching, both groups had low in-hospital mortality (0.015%). UKA patients had shorter hospital stays (1.53 vs. 2.47 days) and lower costs (USD 55,976 vs. USD 61,513) compared to TKA patients. UKA patients had slightly higher rates of intraoperative fracture and pulmonary edema, while TKA patients had higher risks of blood transfusion, anemia, coronary artery disease, pulmonary embolism, pneumonia, and acute kidney injury. Conclusions: UKA appears to be a less-invasive, cost-effective option for younger patients with localized knee osteoarthritis.

Knee cysts are a common finding in orthopedic practice, with diagnoses that range from benign fluid collections to more complex lesions requiring intervention. This comprehensive review explores the types of cysts around the knee, including popliteal (Baker's) cysts, meniscal cysts, proximal tibiofibular joint cysts, and ganglion cysts within the cruciate ligaments. The review highlights the mechanisms of formation, clinical presentations, diagnostic methods, differential diagnoses, and treatments for each cyst type. Imaging, particularly MRI, plays a critical role in accurate diagnosis, helping differentiate cysts from other pathologies, such as tumors and vascular lesions. Treatment options vary, from conservative management for asymptomatic cases to surgical interventions, such as arthroscopic cyst removal, for symptomatic cysts or those associated with intra-articular pathologies. Emerging biological treatments, including platelet-rich plasma (PRP) and mesenchymal stem cell (MSC) therapies, show promise for addressing underlying joint degeneration and inflammation associated with certain cysts, particularly those linked to osteoarthritis. This review underscores the importance of tailored, evidence-based approaches in managing knee cysts to optimize patient outcomes. Keywords: Knee Cysts, Popliteal Cyst, Meniscal Cyst, Proximal Tibiofibular Joint Cyst, Joint Pathology

Purpose: The purpose of this study was to predict high‐risk patients who experience significant increases in hospital charges and length of stay (LOS) following specific postoperative complications.Methods: This study analyzed over two million patients from the Nationwide Inpatient Sample database undergoing elective total knee arthroplasty (TKA) for primary osteoarthritis. Baseline demographics, clinical characteristics and incidence of postoperative complications were examined. A neural network model was utilized to predict high‐risk patients who fall into the top 25% for both LOS and total hospital charges after complications such as sepsis or surgical site infection (SSI).Results: The most common complications were blood loss anaemia (14.6%), acute kidney injury (1.6%) and urinary tract infection (0.9%). Patients with complications incurred significantly higher total charges (mean $66,804) and longer LOS (mean 2.9 days) compared to those without complications (mean $58,545 and 2.1 days, respectively). The neural network model demonstrated strong predictive performance, with an area under the curve of 0.83 for the training set and 0.78 for the testing set. Key complications like sepsis and SSIs significantly impacted hospital charges and LOS. For example, a 57‐year‐old patient with diabetes and sepsis had a 100% probability of being in the top 25% for both total charges and LOS.Conclusion: Postoperative complications in TKA patients significantly increase hospital charges and LOS. The neural network model effectively predicted high‐risk patients after specific complications occurred, offering a potential tool for improving patient management and resource allocation.Levels of Evidence: Level III.

Background: Obesity is a major risk factor for osteoarthritis (OA) and negatively impacts both short-term and long-term outcomes following total knee arthroplasty (TKA). Bariatric surgery has been proposed as a strategy to improve surgical outcomes in obese patients; however, its effects on postoperative complications, hospital stay, healthcare costs, and revision rates remain insufficiently explored. This study investigates whether bariatric surgery before TKA is associated with improved outcomes. Methods: This retrospective cohort study utilized data from the Nationwide Inpatient Sample (NIS) from 2016 to 2019, including 2,519,099 TKA patients, of whom 56,291 had a history of bariatric surgery. Propensity score matching was applied to balance baseline characteristics between groups. Statistical analyses compared the length of hospital stay (LOS), total healthcare costs, postoperative complications, and revision rates. Results: Patients with a history of bariatric surgery exhibited significantly lower rates of sepsis, deep vein thrombosis (DVT), pulmonary embolism (PE), acute kidney injury (AKI), and ileus compared to those without. Additionally, these patients had a shorter LOS and slightly lower total hospital charges. However, the bariatric surgery group had higher rates of blood loss anemia, intraoperative fractures, and blood transfusions. Revision surgery rates were also higher in the bariatric surgery group, with mechanical loosening and prosthesis instability being more common etiologies. Conclusions: Bariatric surgery is associated with fewer early postoperative complications and shorter hospital stays in TKA patients, suggesting potential perioperative benefits. However, increased risks of blood loss anemia, intraoperative fractures, and revision surgery highlight the need for further research on long-term outcomes and alternative weight-loss strategies, such as pharmacologic interventions.

Background: Periprosthetic fractures following total hip arthroplasty are serious complications occurring in up to 2.4% of primary cases, contributing to significant morbidity, extended hospital stays, and elevated healthcare costs. Predicting these fractures remains a challenge despite advances in surgical techniques and prosthetic materials. Methods: This study analyzed 1,634,615 cases of primary THA from the NIS database (2016–2019) using propensity score matching to compare outcomes between patients with and without intraoperative periprosthetic fractures. Predictive models, including logistic regression, decision tree, and deep neural network, were evaluated for their ability to predict fracture risk. Results: Patients with periprosthetic fractures exhibited a 14-fold increase in pulmonary embolism risk, a 12-fold increase in infections, and a 5-fold increase in hip dislocations. Fractures extended hospital stays (3.8 vs. 2.5 days) and added approximately USD 32,000 in costs per patient. The predictive models yielded low accuracy (AUC max = 0.605), underscoring the complexity of predicting periprosthetic fractures. Conclusions: Intraoperative periprosthetic fractures in THA significantly elevate complication rates, costs, and length of stay. Despite extensive modeling efforts, accurate prediction remains difficult, highlighting the need to focus on preventive strategies, such as improved surgical techniques and real-time intraoperative monitoring.

Introduction: Unicompartmental knee arthroplasty (UKA) is gaining traction as a treatment for knee osteoarthritis due to faster recovery, better range of motion, and reduced healthcare costs compared to total knee arthroplasty (TKA). UKA preserves healthy parts of the knee, leading to a quicker return to function and less pain. However, TKA offers potentially longer-lasting results with lower revision rates. This study investigates the National Inpatient Sample (NIS) database for UKA and TKA patients to understand their relative benefits and limitations, aiming to inform patient care and resource allocation. Methods: This retrospective analysis examined outcomes following UKA and TKA using the Nationwide Inpatient Sample (NIS) database (2016-2019). Patients undergoing elective UKA or TKA (n=2,606,925) were identified using ICD-10 codes (Appendix). To minimize confounding factors, propensity score matching was performed using patient demographics, hospital characteristics, and comorbidities, resulting in a balanced cohort of 136,890 patients. In-hospital mortality, length of stay, postoperative complications, and hospitalization costs were compared (p < 0.05). This study received exempt IRB approval due to de-identified data. Results: The prevalence of UKA procedures significantly increased over the study period, with primary osteoarthritis being the leading cause for both UKA and TKA. Patients undergoing UKA were younger and had less comorbidities compared to those undergoing TKA. Propensity score matching effectively balanced these baseline characteristics between the two groups. Examining hospitalization outcomes in propensity-matched cohorts revealed low in-hospital mortality for both groups (0.015%). However, UKA demonstrated a clear advantage in terms of shorter length of stay (1.53 days vs. 2.47 days) and lower total hospitalization charges ($55,976 vs. $61,513). While UKA had slightly higher rates of intraoperative fracture and pulmonary edema compared to TKA, TKA was associated with a significantly increased risk of various complications. These included blood transfusion, blood loss anemia, acute coronary artery disease, pulmonary embolism, pneumonia, and acute kidney injury. Conclusion: UKA shows promise as a less-invasive option for younger patients with one-sided knee osteoarthritis, potentially offering shorter hospital stays, lower costs, and potentially fewer complications.