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Purpose There is no consensus on intraoperative references for the posterior tibial slope (PTS) in medial unicompartmental knee arthroplasty (UKA). An arthroscopic hook probe placed on the medial second quarter of the medial tibial plateau (MTP) in an anteroposterior direction may be used as a direct anatomical reference for the PTS. The purpose of this study is to investigate availability and accuracy of this method. Methods Marginal osteophyte formation and subchondral depression of the MTP, and angles between the bony MTP and the cartilage MTP were retrospectively evaluated using preoperative sagittal MRI of 73 knees undergoing medial UKA. In another 36 knees, intraoperative lateral knee radiographs with the probe placed on the MTP were prospectively taken in addition to the preoperative MRI. Then, angles between the bony MTP and the probe axis and angles between the preoperative bony MTP and the postoperative implant MTP were measured. Results Among 73 knees, one knee with Grade 4 osteoarthritis had a posterior osteophyte higher than the most prominent point of the cartilage MTP. No subchondral depression affected the direct reference of the MTP. Mean angle between the bony MTP and the cartilage MTP was − 0.8°±0.7° (-2.6°-1.0°, n = 72), excluding the one knee with “high” osteophyte. Mean angle between the bony MTP and the probe axis on the intraoperative radiograph was − 0.6°±0.4° (-1.7-0.0, n = 36). Mean angle between the pre- and the postoperative MTP was − 0.5°±1.5° (-2.9°-1.8°). Root mean square (RMS) error of these two PTS angles was 1.6° with this method. Conclusion Cartilage remnants, osteophyte formation and subchondral bone depression does not affect the direct referencing method in almost all knees for which medial UKA is indicated. When the posterior “high” osteophyte of the MTP is noted on preoperative radiograph, preoperative MRI or CT scan is recommended to confirm no “high” osteophyte on the medial second quarter. Accuracy of this method seems equal to that of the robotic-assisted surgery (the RMS error in previous reports, 1.6°-1.9°).

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Objective: To examine the clinical features and outcomes of adolescent and young adult sarcoma patients who underwent surgical management and clarify important factors associated with prognosis. We reviewed 18 young adult sarcoma patients sarcoma patients treated surgically in our hospital. The tumor site, histology, grade, stage, and American Society of Anesthesiologists-Physical Status before surgery, operation time, intraoperative blood loss, complications, surgical margin, local recurrence, metastasis, and outcomes were investigated. The 3-year survival rate was also calculated. We compared survival based on age, grade, and surveyed features of poor outcome cases.Results: The 3-year survival rate was 61.3%. There was no significant difference in survival based on age, grade, operation time, or intraoperative blood loss. Three of five patients who died of the disease had stage ≥ IV at diagnosis. All patients with R1 surgical margins developed recurrence and all those with an American Society of Anesthesiologists-Physical Status ≥ 2 died. Patients with late-stage sarcomas, R1 tumor margin, or high American Society of Anesthesiologists-Physical Status score had poor prognoses. To achieve a favorable outcome in adolescent and young adult sarcoma patients, early detection and obtaining R0≥ surgical margin are essential.

To introduce wrapping vancomycin-containing cement around a mega-prosthesis (MP) as a novel method to prevent prosthetic joint infection after reconstruction surgery for malignant bone and soft tissue tumors. Five patients with malignant bone and soft tissue tumors treated at our hospital from April 2009 to December 2019 were included. The average age was 71.4 years. Four males and one female were included. Three patients had a bone tumor, and two had a soft tissue tumor. Three right thighs and two left femurs were affected. These tumors were identified histologically as undifferentiated pleomorphic sarcoma, spindle cell sarcoma, diffuse large cell B-cell lymphoma, metastasis of renal cancer, and metastasis of lung cancer. All patients underwent tumor resection and reconstruction with a MP. In all cases, vancomycin-containing cement (2 g/40 g) was wrapped around the implant at the extension. The average follow-up period was 30.4 months. We surveyed whether infection occurred after surgical treatment. We also investigated the Musculoskeletal Tumor Society score and clinical outcome. We observed no postoperative infection. One case of local recurrence was observed, and a hip dissection was performed. The Musculoskeletal Tumor Society score was 79.26 ± 1.26 (mean ± standard deviation) (range: 76‐80.3). Three patients remained disease-free, one survived but with disease, and one died of disease. Wrapping vancomycin-containing cement around the MP may be a useful method of preventing postoperative joint infections.