Chondrolysis of the Hip following Septic Arthritis: A Rare Complication of Magnetic Resonance Arthrography

Magnetic resonance arthrography (MRA) is commonly used to detect labral tears of the hip. Complications of MRA are unusual and include minor reactions such as chemical synovitis and urticaria. This paper presents a rapidly progressive chondrolysis of the hip in a young patient after arthrography. The patient had suffered from acute septic arthritis and was treated by emergent arthroscopic surgery followed by appropriate antibiotics. At 18 months of followup, there were no signs of active infection but evidence of joint chondrolysis. Magnetic resonance arthrography (MRA) of the hip is an invasive procedure and should therefore be recommended judiciously. Post-MRA pain is common but often mild and temporary, while post-MRA joint infection is rare; nevertheless, severe joint pain and limitation should raise suspicion for septic hip

Measurement of Two-Dimensional Binding Constants between Cell-Bound Major Histocompatibility Complex and Immobilized Antibodies with an Acoustic Biosensor

Gaining insights into the dynamic processes of molecular interactions that mediate cell-substrate and cell-cell adhesion is of great significance in the understanding of numerous physiological processes driven by intercellular communication. Here, an acoustic-wave biosensor is used to study and characterize specific interactions between cell-bound membrane proteins and surface-immobilized ligands, using as a model system the binding of major histocompatibility complex class I HLA-A2 proteins to anti-HLA-A2 monoclonal antibodies. The energy of the acoustic signal, measured as amplitude change, was found to depend directly on the number of HLA-A2/antibody complexes formed on the device surface. Real-time acoustic data were used to monitor the surface binding of cell suspensions at a range of 6.0 × 104 to 6.0 × 105 cells mL−1. Membrane interactions are governed by two-dimensional chemistry because of the molecules' confinement to the lipid bilayer. The two-dimensional kinetics and affinity constant of the HLA-A2/antibody interaction were calculated (ka = 1.15 × 10−5 μm2 s−1 per molecule, kd = 2.07 × 10−5 s−1, and KA = 0.556 μm2 per molecule, at 25°C), based on a detailed acoustic data analysis. Results indicate that acoustic biosensors can emerge as a significant tool for probing and characterizing cell-membrane interactions in the immune system, and for fast and label-free screening of membrane molecules using whole cells

Fractures of the distal humerus in elderly patients treated with a ring fixator

The aim of distal humerus fracture treatment is articular surface reduction and stable fixation for early mobilisation and rehabilitation. This is usually performed by open reduction and internal fixation with plates. In the elderly osteoporotic patient this treatment is difficult to achieve due to fixation failure in fragile bone. We present our experience with treatment by closed reduction and external fixation with a non-bridging ring fixator in distal humerus fractures in elderly patients. There were ten females, aged 70–89 (average 78.4). Fracture types (AO/ASIF) included three supracondylar fractures (type A) and seven intercondylar fractures (type C). All patients were treated by closed reduction and external fixation with a non-bridging ring fixator of the distal humerus and immediate postoperative mobilisation of the elbow. External fixation was removed on an average of 72 days (range 62–90). All fractures united. Average time to union was 56 days. Average range of movement at six months was 22° extension lag (range 15°–30°) and 115° flexion (range 110°–120°). Complications included one patient with transient radial palsy and one patient with a superficial decubitus ulcer on the chest wall from the hardware. Minimally invasive treatment by closed reduction and external fixation with a ring fixator is effective for treatment of fractures of the distal humerus in elderly patients with osteoporotic bone. This treatment enables immediate mobilisation of the elbow, and allows return to function. It should be considered an alternative to open reduction and internal fixation or total elbow replacement

Exorotated radiographic views have additional diagnostic value in detecting an osseous impediment in patients with posterior ankle impingement

Objectives A standard lateral radiograph is the first step in the diagnostic workup in patients with posterior ankle pain. Because of overprojection by other structures at suboptimal radiographic projection angle, often an os trigonum is not discovered or erroneously be mistaken for a hypertrophic posterior talar process. The aim of this study was to identify the projection angles at which a radiograph is optimal for detecting bony impediments in patients suffering from posterior ankle impingement. Methods Using ankle CT scans of patients with posterior ankle impingement, digitally reconstructed radiographs (DRRs) simulating 13 different radiographic projection angles were generated. The ankle CT scans served as a reference for the detection of an os trigonum and hypertrophic posterior talar process. Members of the Ankleplatform Study Group were invited to assess the DRRs, for presence or absence of an os trigonum or hypertrophic posterior talar process. Diagnostic accuracy and interobserver reliability were estimated for each projection angle. In addition, the diagnostic accuracy of the standard lateral view in combination with the rotated views was calculated. Results High sensitivity for detecting an os trigonum was found for +15° (90.3%), +20° (81.7%) and +25° (89.7%) degrees of exorotation. Specificity in this range of projection angles was between 89.6% and 97.8%. Regarding the presence of a hypertrophic posterior talar process, increased sensitivity was found for +15° (65.7%), +20° (61.0%), +25° (60.7%), +30° (56.3%) and +35° (54.5%). Specificity ranged from 78.0% to 94.7%. The combination of the standard lateral view in combination with exorotated views showed higher sensitivity. For detecting an os trigonum, a negative predictive value of 94.6% (+15°), 94.1% (+20°) and 96.1% (+25°) was found. Conclusion This study underlines the additional diagnostic value of exorotated views instead of, or in addition to the standard lateral view in detecting an osseous impediment. We recommend to use the 25° exorotated view in combination with the routine standard lateral ankle view in the workup of patients with posterior ankle pain. Level of evidence Level III

The calcium-sensing receptor

Cell surface sensors for extracellular Ca2+ and Mg2+51 provide an important mechanism for the regulation of diverse physiological processes by extracellular divalent mineral ions.53, 190 and 402 These ion sensors function as “calciostats” for Ca2+ and/or Mg2+ that not only regulate divalent mineral metabolism at the level of the whole organism but also control a variety of other cellular processes (e.g., salt and water handing in various epithelia and cell proliferation-differentiation) in terrestrial and aquatic animals, as well as in plants. This chapter will focus on the role of the extracellular calcium-sensing receptor (CaSR) in the mammalian parathyroid, kidney, and other tissues participating in divalent mineral ion homeostasis. The unique properties of the mammalian CaSR include: (1) Having extracellular Ca2+ and Mg2+ as its primary physiological ligands, establishing that ions can function as first messengers. (2) Responding with a millimolar EC50, close to the normal plasma ionized Ca2+ concentration, but several orders of magnitude higher than that for ligands of other G protein–coupled receptors. (3) Possessing a remarkable ability to detect small deviations from the normal ionized calcium concentration of 1.1–1.3 mM, making it an ideal sensor for Ca2+, functioning as a “calciostat.” The identification of inherited disorders due to activating or inactivating mutations of the CaSR, basic research in CaSR biology, the development of CaSR-active compounds (calcimimetics), and the results from clinical trials of calcimimetics have established the biological roles of this receptor in mineral ion homeostasis and have suggested roles of the CaSR in several non-Ca2+ homeostatic processes. The reader is referred to Chapter 65 and other chapters in the section, “Regulation and Disorders of Calcium Homeostasis,” for additional information and background