Aneurysmal bone cysts (ABCs) are benign bone lesions arising predominantly in the pediatric population that can cause local pain, swelling, and pathologic fracture. Primary lesions, which constitute roughly two thirds of all ABCs, are thought to be neoplastic in nature, with one third of ABCs arising secondary to other tumors. Diagnosis is made with various imaging modalities, which exhibit characteristic features such as Bfluid-fluid levels,^although biopsy is critical, as telangiectatic osteosarcoma cannot be excluded based on imaging alone. Currently, the standard of care and most widely employed treatment is intralesional curettage. However, tumor recurrence with curettage alone is common and has driven some to propose a multitude of adjuvants with varying efficacy and risk profiles. Historically, therapies such as en bloc resection or radiation therapy were utilized as an alternative to decrease the recurrence rate, but these therapies imposed high morbidity. As a result, modern techniques now seek to simultaneously reduce morbidity and recurrence, the pursuit of which has produced preliminary study into minimally invasive percutaneous treatments and medical management.

Oxatriquinanes are fused, tricyclic oxonium ions that are known to have exceptional stability compared to simple alkyl oxonium salts. C-O bonds in ethers are generally ∼1.43 Å in length, but oxatriquinane has been found to have C-O bond lengths of 1.54 Å. A search of the Cambridge Structural Database turned up no bona fide C-O bond length exceeding this value. Computational modelling of oxatriquinane alongside other alkyl oxonium ions indicated that the electronic consequences of molecular strain were primarily responsible for the observed bond elongation. We also show that substitution of the oxatriquinane ring system with alkyl groups of increasing steric demand pushes the C-O bond to unheard of distances, culminating in a tert-butyl derivative at a predicted 1.60 Å. Chemical synthesis and an X-ray crystallographic study of these compounds validated the results of the modelling work and, finally, an extraordinary 1.622 Å C-O bond was observed in 1,4,7-tri-tert-butyloxatriquinane.

Objective The purpose of this study was to investigate the degree of standardized evaluation and reporting of cartilage lesion characteristics in high-impact clinical studies for symptomatic lesions of the knee. We hypothesized that there are significant inconsistencies in reporting these metrics across orthopedic literature. Design A total of 113 clinical studies on articular cartilage restoration of the knee were identified from 6 high-impact orthopedic journals between 2011 and 2016. Full-text review was used to evaluate sources for details on study methodology and reporting on the following variables: primary procedure, location, size, grade, and morphology of cartilage lesions. Results All studies reported on the type of primary cartilage procedure and precise lesion location(s). Approximately 99.1% reported lesion morphology (chondral, osteochondral, mixed). For lesion size, 32.7% of articles did not report how size was measured and 11.5% did not report units. The lesion sizing method was variable, as 27.4% used preoperative magnetic resonance imaging to measure/report lesion size, 31.0% used arthroscopy, and 8.8% used both. The majority of studies (83.2%) used area to report size, and 5.3% used diameter. Formal grading was not reported in 17.7% of studies. Only 54.8% of studies reported depth when sizing osteochondral defects. Conclusions Recent literature on cartilage restoration provides adequate information on surgical technique, lesion location, and morphology. However, there is wide variation and incomplete reporting on lesion size, depth, and grading. Future clinical studies should include these important data in a consistent manner to facilitate comparison among surgical techniques.

KPF report that they are employees of PerkinElmer, a manufacturer of optical and PET imaging equipment. LSM reports that he has received grant support from MedImmune, Pfizer, Moderna Therapeutics, Regeneron Pharmaceuticals, and Boehringer Ingelheim and consulting fees from Integrated BioTherapeutics, related to Staphylococcus aureus vaccines and therapeutics. JMVD reports that he has filed a patent application (WO2015/088346) on the use of 1D9, which is owned by his employer University Medical Center Groningen. NMB reports that he has received consulting fees from Zimmer Biomet, Bonesupport, Daiichi Sankyo, and Onkos and that he is a board or committee member of the Musculoskeletal Tumor Society and Orthopaedic Research and Education Foundation.

Extremity reconstruction surgery is increasingly performed rather than amputation for patients with large-segment pathologic bone loss. Debate persists as to the optimal void filler for this “limb salvage” surgery, whether metal or allograft bone. Clinicians focus on optimizing important functional gains for patients, and the risk of devastating implant infection has been thought to be similar regardless of implant material. Recent insights into infection pathophysiology are challenging this equipoise, however, with both basic science data suggesting a novel mechanism of infection of Staphylococcus aureus (the most common infecting agent) into the host lacunar–canaliculi network, and also clinical data revealing a higher rate of infection of allograft over metal. The current translational study was therefore developed to bridge the gap between these insights in a longitudinal murine model of infection of allograft bone and metal. Real-time Staphylococci infection characteristics were quantified in cortical bone vs metal, and both microarchitecture of host implant and presence of host immune response were assessed. An orders-of-magnitude higher bacterial burden was established in cortical allograft bone over both metal and cancellous bone. The establishment of immune-evading microabscesses was confirmed in both cortical allograft haversian canal and the submicron canaliculi network in an additional model of mouse femur bone infection. These study results reveal a mechanism by which Staphylococci evasion of host immunity is possible, contributing to elevated risks of infection in cortical bone. The presence of this local infection reservoir imparts massive clinical implications that may alter the current paradigm of osteomyelitis and bulk allograft infection treatment.