Gravitational wave emission from dynamical stellar interactions

We are witnessing the dawn of gravitational wave (GW) astronomy. With currently available detectors, observations are restricted to GW frequencies in the range between ${\sim} 10\,\mathrm{Hz}$ and $10\,\mathrm{kHz}$, which covers the signals from mergers of compact objects. The launch of the space observatory LISA will open up a new frequency band for the detection of stellar interactions at lower frequencies. In this work, we predict the shape and strength of the GW signals associated with common-envelope interaction and merger events in binary stars, and we discuss their detectability. Previous studies estimated these characteristics based on semi-analytical models. In contrast, we used detailed three-dimensional magnetohydrodynamic simulations to compute the GW signals. We show that for the studied models, the dynamical phase of common-envelope events and mergers between main-sequence stars lies outside of the detectability band of the LISA mission. We find, however, that the final stages of common-envelope interactions leading to mergers of the stellar cores fall into the frequency band in which the sensitivity of LISA peaks, making them promising candidates for detection. These detections can constrain the enigmatic common-envelope dynamics. Furthermore, future decihertz observatories such as DECIGO or BBO would also be able to observe this final stage and the post-merger signal, through which we might be able to detect the formation of Thorne-\.Zytkow objects.Comment: Accepted for publication in A&A, 12 pages, 8 figure

Postoperative spinal infection mimicking systemic vasculitis with titanium-spinal implants

<p>Abstract</p> <p>Background</p> <p>Secondary systemic vasculitis after posterior spinal fusion surgery is rare. It is usually related to over-reaction of immune-system, to genetic factors, toxicity, infection or metal allergies.</p> <p>Case Description</p> <p>A 14 year-old girl with a history of extended posterior spinal fusion due to idiopathic scoliosis presented to our department with diffuse erythema and nephritis (macroscopic hemuresis and proteinuria) 5 months post surgery. The surgical trauma had no signs of inflammation or infection. The blood markers ESR and CRP were increased. Skin tests were positive for nickel allergy, which is a content of titanium alloy. The patient received corticosteroids systematically (hydrocortisone 10 mg) for 6 months, leading to total recess of skin and systemic reaction. However, a palpable mass close to the surgical wound raised the suspicion of a late infection. The patient had a second surgery consisting of surgical debridement and one stage revision of posterior spinal instrumentation. Intraoperative cultures were positive to Staphylococcus aureus. Intravenous antibiotics were administered. The patient is now free of symptoms 24 months post revision surgery without any signs of recurrence of either vasculitis or infection.</p> <p>Literature Review</p> <p>Systemic vasculitis after spinal surgery is exceptionally rare. Causative factors are broad and sometimes controversial. In general, it is associated with allergy to metal ions. This is usually addressed with metal on metal total hip bearings. In spinal surgery, titanium implants are considered to be inert and only few reports have presented cases with systemic vasculitides. Therefore, other etiologies of immune over-reaction should always be considered, such as drug toxicity, infection, or genetic predisposition.</p> <p>Purposes and Clinical Relevance</p> <p>Our purpose was to highlight the difficulties during the diagnostic work-up for systemic vasculitis and management in cases of posterior spinal surgery.</p

Rare causes of scoliosis and spine deformity: experience and particular features

<p>Abstract</p> <p>Background</p> <p>Spine deformity can be idiopathic (more than 80% of cases), neuromuscular, congenital or neurofibromatosis-related. However, there are many disorders that may also be involved. We present our experience treating patients with scoliosis or other spine deformities related to rare clinical entities.</p> <p>Methods</p> <p>A retrospective study of the records of a school-screening study in North-West Greece was performed, covering a 10-year period (1992–2002). The records were searched for patients with deformities related to rare disorders. These patients were reviewed as regards to characteristics of underlying disorder and spine deformity, treatment and results, complications, intraoperative and anaesthesiologic difficulties particular to each case.</p> <p>Results</p> <p>In 13 cases, the spine deformity presented in relation to rare disorders. The underlying disorder was rare neurological disease in 2 cases (Rett syndrome, progressive hemidystonia), muscular disorders (facioscapulohumeral muscular dystrophy, arthrogryposis) in 2 patients, osteogenesis imperfecta in 2 cases, Marfan syndrome, osteopetrosis tarda, spondyloepiphyseal dysplasia congenita, cleidocranial dysplasia and Noonan syndrome in 1 case each. In 2 cases scoliosis was related to other congenital anomalies (phocomelia, blindness). Nine of these patients were surgically treated. Surgery was avoided in 3 patients.</p> <p>Conclusion</p> <p>This study illustrates the fact that different disorders are related with curves with different characteristics, different accompanying problems and possible complications. Investigation and understanding of the underlying pathology is an essential part of the clinical evaluation and preoperative work-up, as clinical experience at any specific center is limited.</p

Vascular anatomy and microcirculation of skeletal zones vulnerable to osteonecrosis: vascularization of the femoral head

Bone, regardless of its type or location, is a highly vascular structure with unique features in its internal blood flow. Changes that occur in blood flow through bone have important implications in disease, and several attempts have been made to correlate vascular patterns with the clinical incidence of osteonecrosis. Examination of the arterial anatomy of bones that undergo osteonecrosis in other regions of the body has allowed identification of types of vascular interruptions that place particular bones at risk. Although the role of an impaired blood supply of the femoral head in the pathogenesis of osteonecrosis has not been clarified, several studies have found abnormal blood supply in patients with osteonecrosis

Late infection in patients with scoliosis treated with spinal instrumentation

Sixty patients were treated using a multilevel spinal instrumentation system. Spine arthrodesis was done posteriorly in all patients using a combination of two rods, hooks, screws, and cross-link plates. The Galveston technique was used in three patients. Five patients presented with late deep wound infections 1 to 5 years postoperatively. Two patients presented with a local subcutaneous abscess, whereas the remaining patients had a local drainage. Exploration revealed pus lining the instrumentation surface, at least one loose cross-link nut, and local hardware corrosion and metal infiltration of the surrounding tissues. All patients had a satisfactory bony arthrodesis, so instrumentation was removed. Intraoperative cultures revealed three coagulase-negative Staphylococci, one Acinetobacter baumani, and one Peptostreptococcus. A continuous irrigation system with antibiotics was placed for 5 days in all patients in combination with intravenous antibiotics and oral antibiotics. All patients responded to the treatment, with no recurrence of the infection after removal of the instrumentation. Although the exact nature of these infections requires additional investigation, the findings suggest a correlation between instrumentation failure and loosening and late infection. Bone involvement was not observed and removal of instrumentation was a reliable means of treatment

Rib hump deformity assessment using the rib index in adolescent idiopathic scoliotics treated with full screw or hybrid constructs: Aetiological implications

Background: Review of literature reveals that in Idiopathic Scoliosis (IS) children, the post-operative rib hump (RH) correction using full transpedicular screw construct has never been compared to hybrid constructs, applying the Rib-Index (RI) method. Therefore the aim of this report is to study which of the above two constructs offers better postoperative Rib Hump Deformity (RHD) correction. Methods: Twenty five patients with Adolescent Idiopathic Scoliosis (AIS) were operated using full pedicle screw construct or hybrid construct. Sixteen underwent full screw instrumentation (group A) and nine an hybrid one (group B). The median age for group A was 15 years and for group B 17.2 years. The RHD was assessed on the lateral spinal radiographs using the RI. The RI was calculated by the ratio of spine distances d1/d2, where d1 is the distance between the most extended point of the most extending rib contour and the posterior margin of the corresponding vertebra on the lateral scoliosis films and d2 is the distance from the least projected rib contour and the posterior margin of the same vertebra. Moreover the amount of RI correction was calculated by subtracting the post-operative RI from the pre-operative RI. Results: Although within group A the RI correction was statistical significant (the pre-op RI was 1.93 and the post-op 1.37; p&lt;0.001) and similarly in group B (the mean pre-op RI was 2.06 while the mean post-op 1.51; p=0.008), between group A and B the post-operative RI correction mean values were found to be no statistically significant, (p=0.803). Conclusion: Although the pre- and post-operative RI correction was statistically significant within each group, this did not happen post-operatively between the two groups. It appears that the RHD correction is not different, no matter what the spinal construct type was used. Provided that the full screw construct is powerful, the post-operative derotation and RHD correction was expected to be better than when an hybrid construct is applied, which is not the case in this study. It is therefore implied that the RHD results more likely from the asymmetric rib growth rather than from vertebral rotation, as it has been widely believed up to now. In 2013 Lykissas et al, reported that costoplasty combined with pedicle screws and vertebral derotation significantly improved RH deformity as opposed to pedicle screws and vertebral derotation alone. Another interesting implication is that the spinal deformity is the result of the thoracic asymmetry, implication in line with the late Prof. John Sevastikoglou&apos;s (Sevastik&apos;s) thoracospinal concept. © 2015 Soultanis et al; licensee BioMed Central Ltd

Tuberculous spondylitis of the craniovertebral junction

Craniovertebral junction tuberculosis is rare, accounting for 0.3 to 1% of all tuberculous spondylitis cases. MR imaging is the modality of choice to detect bone involvement, abscess formation and subligamentous spreading of the pus, to differentiate from other lesions affecting the craniovertebral junction, and to determine the efficacy of treatment. Given the fact that surgical treatment of patients with craniovertebral junction tuberculosis has been associated with a high mortality rate ranging up to 10% and recurrence rate ranging up to 20%, conservative is the standard of treatment for most patients. This article presents a patient with craniovertebral junction Mycobacterium tuberculosis infection diagnosed with CT-guided biopsy. A halo vest was applied and antituberculous treatment with rifampicin, isoniazid and ethambutol was initiated. At 6-month follow-up, the patient was asymptomatic; CT of the cervical spine showed healing of the bony lesions. The halo vest was removed and physical therapy was recommended. Antituberculous treatment was continued for a total of 18 months, without any evidence of infection recurrence. © 2016 Panayiotis D. Megaloikonomos et al

Postoperative spinal infection mimicking systemic vasculitis with titanium-spinal implants

Background: Secondary systemic vasculitis after posterior spinal fusion surgery is rare. It is usually related to over-reaction of immune-system, to genetic factors, toxicity, infection or metal allergies.Case Description: A 14 year-old girl with a history of extended posterior spinal fusion due to idiopathic scoliosis presented to our department with diffuse erythema and nephritis (macroscopic hemuresis and proteinuria) 5 months post surgery. The surgical trauma had no signs of inflammation or infection. The blood markers ESR and CRP were increased. Skin tests were positive for nickel allergy, which is a content of titanium alloy. The patient received corticosteroids systematically (hydrocortisone 10 mg) for 6 months, leading to total recess of skin and systemic reaction. However, a palpable mass close to the surgical wound raised the suspicion of a late infection. The patient had a second surgery consisting of surgical debridement and one stage revision of posterior spinal instrumentation. Intraoperative cultures were positive to Staphylococcus aureus. Intravenous antibiotics were administered. The patient is now free of symptoms 24 months post revision surgery without any signs of recurrence of either vasculitis or infection.Literature Review: Systemic vasculitis after spinal surgery is exceptionally rare. Causative factors are broad and sometimes controversial. In general, it is associated with allergy to metal ions. This is usually addressed with metal on metal total hip bearings. In spinal surgery, titanium implants are considered to be inert and only few reports have presented cases with systemic vasculitides. Therefore, other etiologies of immune over-reaction should always be considered, such as drug toxicity, infection, or genetic predisposition.Purposes and Clinical Relevance: Our purpose was to highlight the difficulties during the diagnostic work-up for systemic vasculitis and management in cases of posterior spinal surgery. © 2011 Sakellariou et al; licensee BioMed Central Ltd