With orbital periods of the order of tens of minutes or less, the AM Canum Venaticorum stars are ultracompact, hydrogen-deficient binaries with the shortest periods of any binary subclass, and are expected to be among the strongest gravitational wave sources in the sky. To date, the only known eclipsing source of this type is the P = 28 min binary SDSS J0926+3624. We present multiband, high time resolution light curves of this system, collected with William Herschel Telescope (WHT)/ULTRACAM in 2006 and 2009. We supplement these data with additional observations made with Liverpool Telescope/Rapid Imager to Search for Exoplanets (LT/RISE), XMM-Newton and the Catalina Real-Time Transient Survey. From light curve models we determine the mass ratio to be q = M 2 /M 1 = 0.041 ± 0.002 and the inclination to be 82. • 6 ± 0. • 3. We calculate the mass of the primary white dwarf to be 0.85 ± 0.04 M and the donor to be 0.035 ± 0.003 M , implying a partially degenerate state for this component. We observe superhump variations that are characteristic of an elliptical, precessing accretion disc. Our determination of the superhump period excess is in agreement with the established relationship between this parameter and the mass ratio, and is the most precise calibration of this relationship at low q. We also observe a quasi-periodic oscillation in the 2006 data, and we examine the outbursting behaviour of the system over a 4.5 year period.

PurposeThe Ligament Augmentation and Reconstruction System (LARS®) is a synthetic ligament consisting of fibres made of polyethylene terephthalate. Despite the LARS being used as an anterior cruciate ligament (ACL) device for nearly 30 years and the well‐documented complications from earlier synthetic ligament designs, there is a paucity of published medium‐ to long‐term results. The aim of this study is to report the clinical and functional outcomes after ACL reconstruction using the LARS at a minimum follow‐up of 6 years. MethodsResults of a single surgeon’s entire cohort of 55 patients who underwent primary LARS ACL surgery were reviewed at a median of 7.8 years (6.0–9.4). Patient‐reported outcome measures including the International Knee Documentation Committee (IKDC) score and 36‐Item Short Form Health Survey (SF‐36) were collected and clinical assessment consisted of range of motion (ROM) and the KT‐1000 arthrometer to assess the side–side difference in the operative and non‐operative knee. Mechanical failures of the graft were confirmed at revision surgery and a survivorship analysis was performed using the Kaplan–Meier method. ResultsThe overall mechanical failure rate was 17/51 (33.3%) with ruptures occurring at a median 3.9 years (0.6–8.8 years) following primary LARS ACL surgery. Secondary operative procedures were performed in 39.2% of patients. For intact grafts, there was no statistically significant difference is side‐to‐side ROM or anterior knee laxity and subjective scores revealed a median IKDC subjective score of 85.1 (26.4–100) and SF‐36 physical component score of 94.1. ConclusionThe rates of LARS ACL construct failure (33.3%) in this cohort are high and based on these results the LARS should not be considered as a graft option for primary ACL reconstruction. Level of evidenceIII, cohort study.

PurposeThe Ligament Augmentation and Reconstruction System (LARS ® ) has been at the forefront of a recent revival in the use of synthetic ligaments for ACL reconstruction. However, despite promising short-to-mid-term results its role has been approached with caution due to a high number of major complications in previous synthetic graft designs including mechanical failures, synovitis and osteoarthritis. This study aims to report on the incidence of synovitis in a series of patients undergoing second-look surgery following LARS ACL reconstruction. Methods A retrospective analysis was performed of a single surgeon's series of 12 patients that underwent second-look arthroscopic surgery following primary LARS ACL surgery for indications including mechanical symptoms (meniscal tears/ cyclops lesions/chondral flaps) and/or symptomatic instability secondary to LARS failure. In all cases an examination under anaesthesia (EUA) was performed, and a qualitative assessment of the synovium was carried out and graded as normal, reactive or inflammatory. A synovial biopsy was performed in all knees with visible evidence of synovitis and in all cases of LARS failure. ResultsThe second-look arthroscopy was performed at a mean of 23 months (7-66) after the index surgery. In 6 (50%) knees the LARS device had failed necessitating removal and revision ACL reconstruction, while in the remaining 6 knees the LARS was still intact. Arthroscopic evaluation of the synovium revealed a normal appearance in 8 knees (67%) and reactive synovitis in 4 knees (23%); of these 4 knees, one had an intact LARS device and 3 had failed LARS. Histological examination from these 4 knees and the 3 knees with graft failures without visible synovitis revealed chronic hypertrophic synovitis (moderate 2, mild 5) in all cases with rare giant cells, consistent with a reaction to foreign body material. Conclusions Foreign body synovitis is a common finding in our series of patients undergoing a repeat arthroscopy following a LARS ACL reconstruction. The histological diagnosis of synovitis was more frequently encountered than an arthroscopic appearance of synovitis. Whilst the results of this case series cannot support a direct causative link between LARS failure and the development of synovitis, this study highlights the need to remain vigilant about the risk of reactive synovitis following LARS ACL reconstruction due to exposure of the knee to foreign body material. Level of evidence Level IV, case series.

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