Effect of a thin optical Kerr medium on a Laguerre-Gaussian beam

Using a generalized Gaussian beam decomposition method we determine the propagation of a Laguerre-Gaussian beam that has passed through a thin nonlinear optical Kerr medium. The orbital angular momentum per photon of the beam is found to be conserved while the component beams change. As an illustration of applications, we propose and demonstrate a z-scan experiment using an $LG_0^1$ beam and a dye-doped polymer film.Comment: 3 pages, 2 figures, corrected typo

The powerful placebo effect in osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis. Pain and its related function and stiffness are currently the major symptoms and primary outcomes for treatment. However, the treatment in the past has been primarily targeting on the peripheral changes in the joint that has led to suboptimal outcomes. Recently, we find that people with OA respond better to treatment which targets on both peripheral and central pain abnormalities. We also find that placebo per se is very effective for OA. On average 75% pain reduction, 71% functional improvement and 83% stiffness improvement in the treatment of OA are attributable to the placebo/contextual effect. The effect varies between treatments, for example for pain, from 47% with intra-articular corticosteroid injection to 91% with joint lavage. This begs a question on how to improve the overall treatment effect of an OA therapy in clinical practice by enhancing the contextual effect, rather than to separate a specific treatment effect from the contextual effect as we normally do in clinical trials. The enhancement may be achieved by improving contextual factors such as patient-physician interaction or quality of care. Further research on the development of a simple contextual enhancement package that may be delivered by all physicians according to individual needs would be very helpful

Chondrocalcinosis is common in the absence of knee involvement

Introduction: We aimed to describe the distribution of radiographic chondrocalcinosis (CC) and to examine whether metacarpophalangeal joint (MCPJ) calcification and CC at other joints occurs in the absence of knee involvement. Methods: This was a cross-sectional study embedded in the Genetics of Osteoarthritis and Lifestyle study (GOAL). All participants (n = 3,170) had radiographs of the knees, hands, and pelvis. These were scored for radiographic changes of osteoarthritis (OA), for CC at knees, hips, symphysis pubis, and wrists, and for MCPJ calcification. The prevalence of MCPJ calcification and CC overall, at each joint, and in the presence or absence of knee involvement, was calculated. Results: The knee was the commonest site of CC, followed by wrists, hips, and symphysis pubis. CC was more likely to be bilateral at knees and wrists but unilateral at hips. MCPJ calcification was usually bilateral, and less common than CC at knees, hips, wrists, and symphysis pubis. Unlike that previously reported, CC commonly occurred without any knee involvement; 44.4% of wrist CC, 45.9% of hip CC, 45.5% of symphysis pubis CC, and 31.3% of MCPJ calcification occurred in patients without knee CC. Those with meniscal or hyaline articular cartilage CC had comparable ages (P = 0.21), and neither preferentially associated with fibrocartilage CC at distant joints. Conclusions: CC visualized on a plain radiograph commonly occurs at other joints in the absence of radiographic knee CC. Therefore, knee radiographs alone are an insufficient screening test for CC. This has significant implications for clinical practice, for epidemiologic and genetic studies of CC, and for the definition of OA patients with coexistent crystal deposition

Mild acetabular dysplasia and risk of osteoarthritis of the hip : a case-control study

Objective To determine whether mild variation in acetabular depth (AD) and shape is a risk factor for osteoarthritis (OA) of the hip. Methods The unaffected contralateral hip of patients with unilateral hip OA was compared with hips of asymptomatic controls without hip OA, derived from the Nottingham Genetics Osteoarthritis and Lifestyle case–control study. Standardised anteroposterior x-rays of the pelvis were used to measure centre edge (CE) angle and AD. Cut-off points for narrow CE angle and shallow AD were calculated from the control group (mean −1.96×SD). The relative risk of hip OA associated with each feature was estimated using OR and 95% CI and adjusted risks were calculated by logistic regression. Results In controls, both the CE angle and the AD were lower in the left hip than in the right hip. The CE angle related to age in both hips, and AD of the right hip was lower in men than in women. The contralateral unaffected hip in patients with unilateral hip OA had a decreased CE angle and AD compared with controls, irrespective of side. The lowest tertile of the CE angle in contralateral hips was associated with an eightfold risk of OA (aOR 8.06, 95% CI 4.87 to 13.35) and the lowest tertile of AD was associated with a 2.5-fold risk of OA (aOR 2.53, 95% CI 1.28 to 5.00). Significant increases in the risk of OA were also found as the CE angle and AD decreased

Comorbidities in Osteoarthritis: a systematic review and meta-analysis of observational studies

ObjectivesOsteoarthritis (OA) is a common chronic condition in older people but its association with other chronic conditions is largely unknown. This study aimed to systematically review the literature on comorbidities in people with OA compared to those without.MethodsWe searched four databases for observational studies on comorbidities in people with OA. Studies of OA only or in comparison with non‐OA controls were included. Risk of bias and study quality was assessed using the Newcastle‐Ottawa Scale (NOS). The prevalence of comorbidities in the OA group and prevalence ratio (PR) and 95% confidence interval (CI) between OA and non‐OA groups were calculated.ResultsForty‐two studies from 16 countries (27 case‐only and 15 comparative studies) met the inclusion criteria. Mean age of participants varied from 51 to 76 years. Pooled prevalence of any comorbidity was 67% (95%CI: 57%‐74%) in people with OA versus 56% (95%CI: 44%‐68%) in people without OA. The pooled PR for any comorbidity was 1.21 (95%CI: 1.02‐1.45). The PR increased from 0.73 (95%CI: 0.43‐1.25) for one comorbidity, to 1.58 (95%CI: 1.03‐2.42) for two, and 1.94 (95%CI 1.45‐ 2.59) for three or more comorbidities. The key comorbidities associated with OA were stroke (PR 2.61; 95%CI: 2.13‐3.21), peptic ulcer (PR 2.36; 95%CI: 1.71‐3.27) and metabolic syndrome (PR 1.94; 95%CI 1.21‐3.12).ConclusionsPeople with OA are more likely to have other chronic conditions. The association is dose‐dependent in terms of the number of comorbidities, suggesting multimorbidities. Further studies on the causality of this association and clinical implications are needed

Genetic contribution to radiographic severity in osteoarthritis of the knee

Objective Knee osteoarthritis (OA) has a significant genetic component. The authors have assessed the role of three variants reported to influence risk of knee OA with p<5×10–8 in determining patellofemoral and tibiofemoral Kellgren Lawrence (K/L) grade in knee OA cases. Methods 3474 knee OA cases with sky-line and weight-bearing antero-posterior x-rays of the knee were selected based on the presentation of K/L grade ≥2 at either the tibiofemoral or patellofemoral compartments for one or both knees. Patients belonging to three UK cohorts, were genotyped for rs143383, rs4730250 and rs11842874 mapping to the GDF5, COG5 and MCF2L genes, respectively. The association between tibiofemoral K/L grade and patellofemoral K/L grade was assessed after adjusting for age, gender and body mass index. Results No significant association was found between the rs4730250 and radiographic severity. The rs11842874 mapping to MCF2L was found to be nominally significantly associated with patellofemoral K/L grade as a quantitative trait (p=0.027) but not as a binary trait. The GDF5 single nucleotide polymorphism rs143383 was associated with tibiofemoral K/L grade (β=0.05 (95% CI 0.02 to 0.08) p=0.0011). Conclusions Our data indicate that within individuals affected by radiographic knee OA, OAGDF5 has a modest but significant effect on radiographic severity after adjustment for the major risk factors

Effect of allopurinol on all-cause mortality in adults with incident gout: propensity score–matched landmark analysis

Objective: To examine the association between allopurinol use and all-cause mortality for patients with incident gout. Methods: We compared all-cause mortality in incident gout patients who received allopurinol for at least 6 months within the exposure window (1 year or 3 years) with those who did not, using the UK Clinical Practice Research Data-link. Landmark analysis was used to account for immortal time bias and propensity score matching was used to control for potential effects of known confounders. Results: Of 23 332 incident gout patients identified, the propensity score–matched cohorts contained 1016 patients exposed to allopurinol on the date 1 year from diagnosis (landmark date) and 1016 allopurinol non-users. Over a median follow-up period of 10 years after the landmark date, there were 437 allopurinol users and 443 allopurinol non-users who died during follow-up. Allopurinol users and non-users had similar risk for all-cause mortality (hazard ratio 0.99; 95% CI 0.87, 1.12). In the 3-year landmark analysis, 3519 allopurinol users (1280 died) were compared with 3519 non-users (1265 died). The hazard ratio for all-cause mortality was 1.01 (95% CI 0.92, 1.09). Conclusion: This propensity score–matched landmark analysis in a population of incident gout patients in the UK primary care setting found a neutral effect on the risk of all-cause mortality. Our study provides reassurance about the prescription of allopurinol for gout patients early in their disease course to prevent untoward consequences of chronic uncontrolled hyperuricaemia. However, whether higher than the commonly used dose of allopurinol could influence mortality remains to be determined