The causal role of smoking on the risk of hip or knee replacement due to primary osteoarthritis: a Mendelian randomisation analysis of the HUNT study.

OBJECTIVE: Smoking has been associated with a reduced risk of hip and knee osteoarthritis (OA) and subsequent joint replacement. The aim of the present study was to assess whether the observed association is likely to be causal. METHOD: 55,745 participants of a population-based cohort were genotyped for the rs1051730 C > T single-nucleotide polymorphism (SNP), a proxy for smoking quantity among smokers. A Mendelian randomization analysis was performed using rs1051730 as an instrument to evaluate the causal role of smoking on the risk of hip or knee replacement (combined as total joint replacement (TJR)). Association between rs1051730 T alleles and TJR was estimated by hazard ratios (HRs) and 95% confidence intervals (CIs). All analyses were adjusted for age and sex. RESULTS: Smoking quantity (no. of cigarettes) was inversely associated with TJR (HR 0.97, 95% CI 0.97-0.98). In the Mendelian randomization analysis, rs1051730 T alleles were associated with reduced risk of TJR among current smokers (HR 0.84, 95% CI 0.76-0.98, per T allele), however we found no evidence of association among former (HR 0.97, 95% CI 0.88-1.07) and never smokers (HR 0.97, 95% CI 0.89-1.06). Neither adjusting for body mass index (BMI), cardiovascular disease (CVD) nor accounting for the competing risk of mortality substantially changed the results. CONCLUSION: This study suggests that smoking may be causally associated with the reduced risk of TJR. Our findings add support to the inverse association found in previous observational studies. More research is needed to further elucidate the underlying mechanisms of this causal association.

Weight gain and the risk of knee replacement due to primary osteoarthritis: a population based, prospective cohort study of 225,908 individuals.

OBJECTIVE: To study the association between weight gain and the risk of knee replacement (KR) due to primary osteoarthritis (OA), and to evaluate whether the association differs by age. DESIGN: 225,908 individuals from national health screenings with repeated measurements of height and weight were followed prospectively with respect to KR identified by linkage to the Norwegian Arthroplasty Register. Cox proportional hazard regression was used to calculate sex-specific relative risks (RR) of KR according to change in Body Mass Index (BMI) and weight, corresponding analyses were done for age categories at first screening. RESULTS: During 12 years of follow up, 1591 participants received a KR due to primary OA. Men in the highest quarter of yearly change in BMI had a RR of 1.5 (95% confidence interval (CI) 1.1-1.9) of having a KR compared to those in the lowest quarter. For women the corresponding RR was 2.4 (95% CI 2.1-2.7). Men under the age of 20 at the first screening had a 26% increased risk for KR per 5 kg weight gain, for women the corresponding increase was 43%. At older age the association became weaker, and in the oldest it was lost. CONCLUSIONS: Weight gain increases the risk for later KR both in men and women. The impact of weight gain is strongest in the young, at older age the association is weak or absent. Our study suggests that future OA may be prevented by weight control and that preventive measures should start at an early age.

Weight gain and the risk of total hip replacement a population-based prospective cohort study of 265,725 individuals.

OBJECTIVE: To study the association between change in the body mass index (BMI) at different ages and the risk of a later total hip replacement (THR) due to primary osteoarthritis (OA). DESIGN: A total of 265,725 individuals who had two repeated measurements of weight and height were included from national health screenings. These individuals were followed prospectively. The data were matched with the Norwegian Arthroplasty Register and 4,442 of these individuals were identified as having received a THR for primary OA. Cox proportional hazard regression was used to calculate sex-specific relative risks for having a THR according to age at screening and BMI change. RESULTS: Men and women aged 20 years or younger at the first screening in the quartile with the greatest BMI change per year had more than twice the risk of later having a THR compared with those in the quartile with the smallest BMI change per year. For men older than 30 years at the first screening, there was no relationship between BMI gain, or weight gain, and later risk of THR. For older women, BMI gain was associated with risk of THR, but to a lesser degree than in younger women. CONCLUSION: There was a clear relationship between change in BMI and the risk of later THR in young men and women, whereas the association was absent in older men and weaker in older women. It is important to focus on weight control to prevent future OA, and the preventive strategy should be focused on the young population.

Plate fixation versus intramedullary nailing of completely displaced midshaft fractures of the clavicle: a prospective randomised controlled trial.

AIMS: This is a prospective randomised controlled trial comparing the functional outcomes of plate fixation and elastic stable intramedullary nailing (ESIN) of completely displaced mid-shaft fractures of the clavicle in the active adult population. PATIENTS AND METHODS: We prospectively recruited 123 patients and randomised them to either plate fixation or ESIN. Patients completed the Quick Disabilities of the Arm, Shoulder and Hand (DASH) score at one to six weeks post-operatively. They were followed up at six weeks, three and six months and one year with radiographs, and their clinical outcome was assessed using both the DASH and the Constant Score. RESULTS: Plate fixation provided a faster functional recovery during the first six months compared with ESIN, but there was no difference after one year. The duration of surgery was shorter for ESIN (mean 53.4 minutes, 22 to 120) than for plate fixation (mean 69.7 minutes, 35 to 106, p < 0.001). The recovery after ESIN was slower with increasing fracture comminution and with open reduction (p < 0.05). CONCLUSION: Both methods return the patients to their pre-injury functional levels, but plate fixation has a faster recovery period in comminuted fractures than ESIN. ESIN has a shorter operative time and lower infection and implant rates of failure when using 2.5 mm nails or wider, suggesting that this is the preferred method in mid-shaft fractures with no comminution, whereas plate fixation is the superior method in comminuted fractures. Cite this article: Bone Joint J 2017;99-B:1095-1101.

Cemented femoral impaction bone grafting for severe osteolysis in revision hip arthroplasty. Good results at 4-year follow-up of 10 patients.

Ten hips underwent impaction bone grafting with cement as revision of the femoral stem for severe osteolysis. At clinical follow-up of a median of 4 years (range 3.0-4.6 years) there were no failures. The median Harris hip score increased from 53 to 80, and pain score from 25 to 40. Radiographically, there was no resorption of the impacted grafts. All of the 9 patients with radiographical follow-up of more than 1 year showed trabecular remodelling, 7 of whom had signs of cortical repair. Subsidence was a median of 2 mm, with the maximum subsidence being 5 mm. The results appeared clinically stable after 4 years with radiographic reconstitution of the bone stock.