Soft tissue sarcomas arise infrequently and make up less than 1% of all cancers. An undifferentiated pleomorphic sarcoma (UPS), formerly known as a malignant fibrous histiocytoma, is a malignant subtype of soft tissue sarcoma identified by a lack of specific immunohistochemical markers for lineage differentiation. These tumors are aggressive and enlarge rapidly with an increased risk of metastasis, thus prompt diagnosis, treatment, and post-resection surveillance are imperative. This case report demonstrates an incidental finding of a large undifferentiated pleomorphic sarcoma of the posterior thigh in an 86-year-old male initially evaluated with a bedside ultrasound.

Introduction: Patellar and quadriceps tendon ruptures after total knee arthroplasty (TKA) have historically poor outcomes. To date, there is no consensus for optimal treatment. The purpose of this study is to directly compare clinical outcomes and survivorship between allograft versus synthetic mesh for reconstruction of native extensor mechanism (EM) rupture after TKA. Methods: A multicenter, retrospective review identifying consecutive TKA patients operated between December 2009 to November 2019 was conducted. Patients aged $ 45 years old with native EM disruption treated with either allograft or synthetic mesh with minimum 2 year follow-up were included. Demographic information, injury mechanism, range of motion, surgical time, revision surgeries, and postoperative Knee Injury and Osteoarthritis Outcome Scores (KOOS Jr.) were collected. Student t-tests and Fisher exact tests were used to compare the demographic data between groups. The Kaplan-Meier survival curve method was used to determine the survivorship as treatment failure was defined as postoperative EM lag .30°or revision surgery. Survival curves were compared using the log-rank test. Univariate Cox proportional hazard regression identified risk factors associated with treatment failure. Results: Twenty patients underwent EM reconstruction using allograft versus 35 with synthetic mesh. Both groups had similar demographics and an average follow-up time of 3.5 years (P = 0.98). Patients treated with allograft had significantly greater postoperative flexion than patients treated with mesh (99.4 6 9.5 allograft versus 92.6 6 13.6 synthetic mesh, P = 0.04). Otherwise, there was no difference in postoperative outcomes between the two groups in average KOOS Jr. (P = 0.29), extensor lag (P = 0.15), graft failure (P = 0.71), revision surgery rates (P = 0.81), surgical time (P = 0.42), or ambulatory status (P = 0.34) at the most recent follow-up. Survival

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