Osteoarthrosis of the hip in women and its relation to physical load at work and in the home

Incidence of knee and hip joint replacement associated with cumulative exposure to physical factors at work

BACKGROUND

Knee osteoarthritis (OA) has been quite consistently associated with high physical workload and specific physical factors at work, while for hip OA, fewer studies are available, which still indicate possible associations with heavy lifting and physical workload. The objective of the study was to assess the association between exposure to workplace physical factors and incidence of knee and hip arthroplasty, as markers of severe OA in these joints.

METHODS

The study population was composed of employees 25-60 years who participated in the Turin 2011 census. For each job held since 1995, exposure to physical factors was assigned to individuals in the cohort through a Job-Exposure Matrix constructed from the Italian O*NET database. Using Poisson regression models, the incidence of knee and hip arthroplasty for OA, identified through hospitalizations from 2012 to 2018, was examined in relation to cumulative exposure to 7 different physical hazards and a composite indicator of physical workload constructed from 17 physical factors (Ergo-Index).

RESULTS

The risk of knee OA was significantly increased in the highest cumulative exposure quartile of physical workload (incidence rate ratio = 1.98, 95% confidence interval: 1.24-3.16) and of all single hazards examined, compared to the lowest quartile, with significant trends in risk with increasing exposure. In contrast, no association was found with hip OA, whose relative risks were close to or below one in all higher-exposure quartiles of physical workload and of each single hazard.

CONCLUSIONS

Our results indicate that exposure to physical hazards at work increases the likelihood of developing knee OA, but not hip OA.

Hip osteoarthritis and occupational mechanical exposures: a systematic review and meta-analysis

OBJECTIVES

The aim was to conduct a systematic review and meta-analysis investigating the association between occupational mechanical exposures and hip osteoarthritis.

METHODS

The study was registered in PROSPERO. A systematic literature search was conducted in six databases to identify relevant articles. Two authors independently excluded articles, extracted data, assessed the risk of bias of each included article, and graded the level of evidence. We conducted a meta-analysis using random-effects model and performed a sensitivity analysis stratifying articles based on the risk of bias assessment, study design, and the outcome measurement.

RESULTS

Twenty-four articles were eligible for inclusion. The highest pooled odds ratio (OR) was found for combined mechanical exposures [OR 1.7, 95% confidence interval (CI) 1.4-2.0], non-neutral postures (OR 1.7, 95% CI 1.4-2.1), lifting/carrying loads (OR 1.6, 95% CI 1.3-1.9), and climbing stairs (OR 1.6, 95% CI 1.1-2.2). The range of pooled OR for the remaining mechanical exposures (eg, standing, walking, kneeling, squatting, and sitting) was 0.6-1.6. Grading the quality of evidence, a moderate level of evidence was found for the combined mechanical exposures and for lifting/carrying loads. The remaining exposure categories were graded as having either low or very low levels of evidence.

CONCLUSIONS

Considerable heterogeneity was observed across the included studies, and high-quality literature using objective exposure measurements is warranted. Despite various limitations affecting the comparability, occupational mechanical exposures seem to influence the likelihood of developing hip osteoarthritis.

Osteoarthritis Risks and Sports: An Evidence-based Systematic Review

PURPOSE

Regular sports activities are associated with multiple physical and psychological health benefits. However, sports also may lead to injuries and the development of osteoarthritis (OA). This systematic review investigated the association between sports activity, sports type, and the risk of developing OA.

METHODS

A systematic review was performed by assessing studies that have investigated the risk of OA development in sports. Data extracted included general information, study design, number of participants, related body mass index, sports type, and assessment of OA. The methodological quality of the studies was assessed using the Newcastle-Ottawa Scale.

RESULTS

A total of 63 studies were included in this systematic review. The overall Newcastle-Ottawa Scale score was 6.46±1.44 demonstrating a good methodological quality of the articles included in the present study. A total of 628,036 participants were included, with a mean follow-up of 8.0±8.4 years. The mean age of the included athletes was 45.6±15.8, with a mean body mass index of 24.9±2.3 kg/m 2 .

CONCLUSION

Football and soccer players seem to be at higher risk for the development of OA, although the injury status of the joint should be considered when assessing the risk of OA. High equipment weight and increased injury risk also put military personnel at a higher risk of OA, although elite dancing leads to more hip labral tears. Femoroacetabular impingement was also often diagnosed in ice-hockey players and ballet dancers.

Immune and stem cell compartments of acetabular and femoral bone marrow in hip osteoarthritis patients

OBJECTIVE

Hip osteoarthritis (OA) affects all components of the osteochondral unit, leading to bone marrow (BM) lesions, and unknown consequences on BM cell functionality. We analyzed the cellular composition in OA-affected acetabula compared to proximal femur shafts obtained of hip OA patients to reveal yet not explored immune and stem cell compartments.

DESIGN

Combining flow cytometry, cellular assays and transcription analyses, we performed extensive ex vivo phenotyping of acetabular BM cells from 18 hip OA patients, comparing them with their counterparts from patient-matched femoral shaft BM samples. Findings were related to differences in skeletal sites and age.

RESULTS

Acetabular BM had a greater frequency of T-lymphocytes, non-hematopoietic cells and colony-forming units fibroblastic potential than femoral BM. The incidence of acetabular CD45⁺CD3⁺ T-lymphocytes increased (95% CI: 0.1770 to 0.0.8416), while clonogenic hematopoietic progenitors declined (95% CI: -0.9023 to -0.2399) with age of patients. On the other side, in femoral BM, we observed higher B-lymphocyte, myeloid and erythroid cell frequencies. Acetabular mesenchymal stromal cells (MSCs) showed a senescent profile associated with the expression of survival and inflammation-related genes. Efficient osteogenic and chondrogenic differentiation was detected in acetabular MSCs, while adipogenesis was more pronounced in their femoral counterparts.

CONCLUSION

Our results suggest that distinctions in BM cellular compartments and MSCs may be due to the influence of the OA-stressed microenvironment, but also acetabular vs femoral shaft-specific peculiarities cannot be excluded. These results bring new knowledge on acetabular BM cell populations and may be addressed as novel pathogenic mechanisms and therapeutic targets in OA.

Intensive Physical Activity Increases the Risk of Knee and Hip Arthroplasty: A Systematic Review

PURPOSE

The present study investigated the type of sport and activity level of athletes before they underwent knee and/or hip arthroplasty for osteoarthritis (OA), and compared them with a control group of subjects who did not undergo knee and hip arthroplasty. We hypothesed athletes exposed to high physical loads during sports had the highest risk of developing OA requiring arthroplasty.

MATERIALS AND METHODS

This systematic review was conducted according to the PRISMA guidelines. All the comparative clinical trials to August 2021 investigating the sport activity level between subjects who underwent arthroplasty versus those who did not undergo arthroplasty for OA were considered.

RESULTS

Data from 5 studies and 3638 patients were collected. The mean age for both groups was 47.61±15.5 years, and the mean body mass index was 24.6±2.1 kg/m2 17.6% were women. The Newcastle-Ottawa scale attested good quality of the methodology of the investigations included in the present study.

CONCLUSION

Intense physical exercise, implying a high cumulative number of hours of exercise which can lead to excessive joint overload, in both sexes is associated with greater likelihood of early knee and hip OA which may lead to prosthetic surgery. Moderate and recreational exposure to sport has minor degenerative effects, and is not associated with early onset OA requiring arthroplasty.

Men and Women's Occupational Activities and the Risk of Developing Osteoarthritis of the Knee, Hip, or Hands: A Systematic Review and Recommendations for Future Research

Objective

To systematically review the evidence for an increased risk of osteoarthritis in the hip, knee, hand, wrist, finger, ankle, foot, shoulder, neck, and spine related to diverse occupational activities of men and women and to examine dose‐response information related to the frequency, intensity, and duration of work exposures and the risk of osteoarthritis (OA).

Methods

Established guidelines for systematic reviews in occupational health and safety studies were followed. MEDLINE, Embase, CINAHL, and Cochrane Library were searched from inception to December 2017. Studies were reviewed for relevance, quality was appraised, and data were extracted and synthesized.

Results

Sixty‐nine studies from 23 countries yielded strong and moderate evidence for lifting, cumulative physical loads, full‐body vibration, and kneeling/squatting/bending as increasing the risks of developing OA in men and women. Strong and moderate evidence existed for no increased risk of OA related to sitting, standing, and walking (hip and knee OA), lifting and carrying (knee OA), climbing ladders (knee OA), driving (knee OA), and highly repetitive tasks (hand OA). Variability in dose‐response data resulted in an inability to synthesize these data.

Conclusion

Evidence points to the potential for OA occupational recommendations and practice considerations to be developed for women and men. However, research attention is needed to overcome deficits in the measurement and recall of specific work activities so that recommendations and practice considerations can provide the specificity needed to be adopted in workplaces.

Exposure-Response Relationship and Doubling Risk Doses-A Systematic Review of Occupational Workload and Osteoarthritis of the Hip

In this review, we critically evaluated the evidence of exposure–response relationships between occupational workload and the risk of hip osteoarthritis. The existing evidence was evaluated in order for us to extrapolate possible doubling risk doses for hip osteoarthritis. Comprehensive searches for epidemiological studies of hip osteoarthritis and occupational workload were performed in literature databases (PubMed, EMBASE, Cochrane Work and Google Scholar) and recent reviews up to February 2019. In total, 85 papers met the preliminary inclusion criteria, and 10 studies indicating an exposure-response relationship between occupational workload and hip osteoarthritis were identified. All studies were assessed on the basis of their study design, defined quality scores and relevant confounders considered. An exposure–response relationship between heavy lifting and the risk of hip osteoarthritis is consistently observed among the male populations but not among the female populations. We quantified the doubling risk doses in two studies in which both an exposure–response relationship and cumulative exposure doses were stated. These two studies provided the highest quality level of all studies published to date. The estimated doubling risk doses in these two studies lie between 14,761 and 18,550 tons (daily lifting 2.2–2.8 tons, 220 days/year for 30 years). These results can be used for workplace interventions to prevent hip osteoarthritis.

Hip Osteoarthritis and Physical Workload: Influence of Study Quality on Risk Estimations-A Meta-Analysis of Epidemiological Findings

In this paper, we critically evaluate the quality of epidemiological evidence on hip osteoarthritis and workload published so far. The influence of study quality on risk estimations was analyzed in sensitivity meta-analyses and meta-regression analyses. Comprehensive searches for epidemiological studies of hip osteoarthritis and occupational workload were performed in literature databases and current reviews. All studies were assessed on the basis of study design, defined quality scores, and relevant confounders considered. In total, 34 suitable studies were identified for critical evaluation. Of these, 20 are prevalence studies and 14 incidence studies. Strong heterogeneity is observed in study design, quality level, and estimated exposure parameters. A consistent positive association between heavy physical workload and hip osteoarthritis was observed only among the male populations, not among the female populations. In general, cohort studies provided lower effect estimates than cross-sectional and population-based case-control studies. Studies with high quality scores also produced lower effect estimates than studies with low quality scores. Consideration of BMI as a confounder in published studies also yielded lower effect estimates than studies without consideration of BMI as a confounder. Our analyses indicate that high-quality studies of the association between occupational workload and hip osteoarthritis provide lower effect estimates than studies of lower quality.

Occupational Strain as a Risk for Hip Osteoarthritis

BACKGROUND

Multiple epidemiological studies have revealed an association between occupational physical strain and the risk of developing hip osteoarthritis.

METHODS

To determine the association between the lifting and carrying of heavy loads or other physically demanding work and the risk of hip osteoarthritis (HOA) or total hip replacement (THR), we systematically searched the literature for primary studies on the effects of exposure to physical strain and meta-analytically reviewed the results that were amenable to comparisons across studies. We separately assessed studies that had hip pain as an endpoint.

RESULTS

5 cohort studies and 18 case-control studies were found suitable for inclusion. The lifting of heavy loads increases the risk of HOA or THR: exposure doubles the risk in men (relative risk [RR] 2.09, 95% confidence interval [1.4; 3.1]) and increases it by roughly 40% in women (RR 1.41 [1.0; 1.9]). Physically demanding work consisting of a combination of activities of various kinds (dealing with heavy loads, heavy manual work, or prolonged walking and standing) increases the risk by roughly 150% in men (RR 2.46 [1.3; 4.8]) and 40% in women (RR 1.38 [0.9; 2.2]). Hip pain was also reported more commonly in the exposed groups.

CONCLUSION

The studies are moderately to highly heterogeneous. An association exists between years of lifting heavy loads or other kinds of physical strain on the job and the risk of developing osteoarthritis of the hip. The greater the exposure, the greater the risk. The evidence base for risk assessment in women is currently inadequate.

Dose-response relationship between cumulative physical workload and osteoarthritis of the hip - a meta-analysis applying an external reference population for exposure assignment

Background

There is consistent evidence from observational studies of an association between occupational lifting and carrying of heavy loads and the diagnosis of hip osteoarthritis. However, due to the heterogeneity of exposure estimates considered in single studies, a dose-response relationship between cumulative physical workload and hip osteoarthritis could not be determined so far.

Methods

This study aimed to analyze the dose-response relationship between cumulative physical workload and hip osteoarthritis by replacing the exposure categories of the included studies with cumulative exposure values of an external reference population. Our meta-regression analysis was based on a recently conducted systematic review (Bergmann A, Bolm-Audorff U, Krone D, Seidler A, Liebers F, Haerting J, Freiberg A, Unverzagt S, Dtsch Arztebl Int 114:581–8, 2017). The main analysis of our meta-regression comprised six case-control studies for men and five for women. The population control subjects of a German multicentre case-control study (Seidler A, Bergmann A, Jäger M, Ellegast R, Ditchen D, Elsner G, Grifka J, Haerting J, Hofmann F, Linhardt O, Luttmann A, Michaelis M, Petereit-Haack G, Schumann B, Bolm-Audorff U, BMC Musculoskelet Disord 10:48, 2009) served as the reference population. Based on the sex-specific cumulative exposure percentiles of the reference population, we assigned exposure values to each category of the included studies using three different cumulative exposure parameters. To estimate the doubling dose (the amount of physical workload to double the risk of hip osteoarthritis) on the basis of all available case-control-studies, meta-regression analyses were conducted based on the linear association between exposure values of the reference population and the logarithm of reported odds ratios (ORs) from the included studies.

Results

In men, the risk to develop hip osteoarthritis was increased by an OR of 1.98 (95% CI 1.20–3.29) per 10,000 tons of weights ≥20 kg handled, 2.08 (95% CI 1.22–3.53) per 10,000 tons handled > 10 times per day and 8.64 (95% CI 1.87–39.91) per 10⁶ operations. These estimations result in doubling dosages of 10,100 tons of weights ≥20 kg handled, 9500 tons ≥20 kg handled > 10 times per day and 321,400 operations of weights ≥20 kg. There was no linear association between manual handling of weights at work and risk to develop hip osteoarthritis in women.

Conclusions

Under specific conditions, the application of an external reference population allows for the derivation of a dose-response relationship despite high exposure heterogeneities in the pooled studies.

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2085-8) contains supplementary material, which is available to authorized users.

Occupation, Physical Workload Factors, and Disability Retirement as a Result of Hip Osteoarthritis in Finland, 2005–2013

Objective.

To identify occupations with a high risk of disability retirement as a result of hip osteoarthritis (OA), and to examine the effect of physical workload factors on the occupational differences in disability retirement.

Methods.

A total of 1,135,654 (49.4% women) Finns aged 30–60 years in gainful employment were followed from 2005 to 2013 for full disability retirement as a result of hip OA. Information on pensions, occupation, and education were obtained from national registers. Physical workload was assessed by a sex-specific job exposure matrix. We calculated age-adjusted incidence rates and examined the associations of occupation, education, and physical workload factors with disability retirement using a competing risk regression model.

Results.

Age-adjusted incidence rate was 25 and 22 per 100,000 person-years in men and women, respectively. Both men and women working in lower-level nonmanual and manual occupations had an elevated age-adjusted risk of disability retirement as a result of hip OA. A very high risk of disability retirement was found among male construction workers, electricians, and plumbers (HR 12.7, 95% CI 8.4–19.7), and female professional drivers (HR 15.2, 95% CI 7.5–30.8) as compared with professionals. After adjustment for age and education, the observed occupational differences in disability retirement were largely explained by physical workload factors among men and to a smaller extent, among women.

Conclusion.

Our results suggest that education and physical workload factors appear to be the major reasons for excess disability retirement as a result of hip OA in manual occupations, particularly among men.

Understanding Occupation, Sick Leave, and Disability Pension Due to Knee and Hip Osteoarthritis From a Sex Perspective

OBJECTIVE

To investigate the association between occupation and risk for sick leave or disability pension due to knee or hip osteoarthritis (OA) from a sex perspective.

METHODS

We conducted a population-based study including residents ages 40-70 years in the Skåne region, Sweden (2007) and working in the included job sectors (n = 165,179). We retrieved data on cause-specific sick leave and disability pension (2007-2012) and linked to individual information on occupation and education (2007). Occupations were classified into job sectors. We calculated sex-specific, age-adjusted odds ratios (ORs) of sick leave and disability pension due to OA in traditionally female-dominated job sectors (health care, child care, and cleaning) and traditionally male-dominated job sectors (construction, farming, metal work, or transportation) compared to business and administration.

RESULTS

Of all eligible subjects, 2,445 had sick leave or disability pension due to knee or hip OA. Adjusted for age, the risk of sick leave due to knee OA was increased for women working in health care, with an OR of 3.3 (95% confidence interval [95% CI] 2.6-4.2), child care OR 2.9 (95% CI 2.2-3.8), and cleaning OR 3.0 (95% CI 2.2-4.1), as was the risk for disability pension. The risk was increased also for persons working in occupations with higher educational requirements. The risk was similarly increased in male-dominated sectors. In female-dominated job sectors the risk of sick leave and disability pension due to knee OA, but not hip OA, was higher than that for other musculoskeletal diseases.

CONCLUSION

Traditionally female-dominated occupational sectors are associated with an increased risk of sick leave and disability pension due to knee OA.

Physical workload is associated with increased risk of rheumatoid arthritis: results from a Swedish population-based case-control study

Objectives

This study investigated: (1) the association of physical workload (PW) and risk of rheumatoid arthritis (RA); (2) the potential interactions between PW and the genes in the human leucocyte antigen (HLA) region.

Methods

A population-based case–control study involving incident cases of RA (3150 cases and 5130 controls) was performed using data from the Swedish Epidemiological Investigation of Rheumatoid Arthritis. Information on 7 types of self-reported PW exposure and HLA-DRB1 genotypes of cases and controls were gathered. Anticitrullinated protein antibody (ACPA) status of cases was identified. For each PW exposures, exposed participants were compared with unexposed participants. ORs with 95% CIs of RA (overall), ACPA-positive RA and ACPA-negative RA associated with different PWs were estimated using logistic regression. HLA-PW interactions were estimated using the principle of departure from additivity of effects by calculating attributable proportion (AP) due to interaction.

Results

ORs of developing RA associated with 6 various PW exposures ranging from 1.3 (95% CI 1.1 to 1.4) to 1.8 (95% CI 1.6 to 2.0) were observed. Exposure to more types of PW was associated with increasing risk for RA (p<0.0001). No major difference in the ORs between ACPA-positive and ACPA-negative RA was found. For some exposures, we found evidence of interactions between PW and the HLA-DRB1 shared epitope genes, regarding risk of ACPA-positive RA (AP: from 0.3 (95% CI 0.1 to 0.5) to 0.4 (95% CI 0.2 to 0.6)).

Conclusions

PW is associated with the risk of ACPA-positive and ACPA-negative RA. Interactions between PW and the HLA-DRB1 shared epitope were found in ACPA-positive RA.

Laboratory Stresses and Tractional Forces on the TMJ Disc Surface

The etiology of degenerative disease of the TMJ may involve fatigue produced by surface tractional forces and compressive stresses. This study tested the time-dependent effects of compressive loading and stress-field translation on TMJ disc-surface tractional forces and stresses. In laboratory experiments with 50 porcine discs, an acrylic indenter imposed 10 N static loads for 10 and 60 sec, followed by translation of the loaded indenter along the mediolateral axis of the disc. Maximum tractional forces were found to occur following 60 sec of static loading (p < 0.001), and increased with translation velocity (R2 = 0.73); whereas maximum compressive stresses occurred after 10 sec of static loading (p < 0.001). Overall, the results were consistent with current mechanical theories of the time-dependent effects of compressive loading of cartilage.

Associations of radiographic degeneration and pain with daily cumulative hip loading in patients with secondary hip osteoarthritis

The purpose of this study was to investigate the associations of radiographic and clinical variables of hip osteoarthritis (OA) with alterations in gait and joint loading in patients with secondary hip OA. Fifty females with secondary hip OA were participated. The minimum joint space width (mJSW) of the hip as a degenerative sign and Sharp and center edge (CE) angles as morphological variables were measured radiographically. Hip joint pain was assessed using a visual analog scale. As gait variables, walking speed, range of hip motion, hip moment peak, and hip moment impulse were calculated. Daily cumulative hip loading was calculated as the hip moment impulse multiplied by the mean number of steps per day. After bivariate correlation analyses between dependent (mJSW and pain) and independent variables (age, body mass index, sharp/CE angles, steps per day, and gait variables), separate forward-backward stepwise multiple regression analyses were performed for each dependent variable. Daily cumulative hip loading in the sagittal plane (β = 0.30, p = 0.021) and age (β = -0.36, p = 0.007) were significantly associated with the mJSW. Walking speed (β = -0.36, p = 0.008) and age (β = 0.29, p = 0.031) were significantly associated with hip joint pain. Decrease in daily cumulative hip loading in the sagittal plane was associated with mJSW independently of age. Although the causal relationship was not clear, patients with hip OA reduced total exposure to hip joint loading adaptively rather than lowering the hip moment peak concerning worsening of hip degeneration. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1977-1983, 2016.

HIP osteoarthritis and work

Epidemiological evidence points strongly to a hazard of hip osteoarthritis from heavy manual work. Harmful exposures may be reduced by the elimination or redesign of processes and the use of mechanical aids. Reducing obesity might help to protect workers whose need to perform heavy lifting cannot be eliminated. Particularly high relative risks have been reported in farmers, and hip osteoarthritis is a prescribed occupational disease in the UK for long-term employees in agriculture. Even where it is not attributable to employment, hip osteoarthritis impacts importantly on the capacity to work. Factors that may influence work participation include the severity of disease, the physical demands of the job, age and the size of the employer. Published research does not provide a strong guide to the timing of return to work following hip arthroplasty for osteoarthritis, and it is unclear whether patients should avoid heavy manual tasks in their future employment.

Total hip replacement due to primary osteoarthritis in relation to cumulative occupational exposures and lifestyle factors: a nationwide nested case-control study

OBJECTIVE

To investigate the risk of total hip replacement (THR) due to primary osteoarthritis in relation to cumulative occupational mechanical exposures and lifestyle factors.

METHODS

Using register information, we identified first-time THR cases within the Danish working population in 2005-2006. For each case, 2 age- and sex-matched controls were drawn. Persons within 2,500 randomly selected case-control sets received a questionnaire about job history, weight at age 25 years, present weight and height, smoking, and sports activities at age 25 years. The job history was combined with a job exposure matrix. Cumulative exposure estimates were expressed according to the pack-year concept of smoking (e.g., cumulative lifting was expressed as ton-years). We used conditional logistic regression for statistical analyses.

RESULTS

In total, 1,776 case-control sets (71%) were available for analysis. The adjusted odds ratio (OR) for exposure to ≥20 ton-years was 1.35 (95% confidence interval [95% CI] 1.05-1.74) for men and 1.00 (95% CI 0.73-1.41) for women. Standing/walking and whole body vibration showed no associations. The adjusted OR for body mass index (BMI) ≥30 kg/m(2) at age 25 years was 2.44 (95% CI 1.38-4.32) for men and 5.12 (95% CI 2.30-11.39) for women. The corresponding adjusted ORs for an increase in BMI of ≥10 kg/m(2) since age 25 years were 2.16 (95% CI 1.25-3.70) and 2.46 (95% CI 1.47-4.13). Sports participation showed weak positive associations, while pack-years of smoking showed no associations.

CONCLUSION

The results indicated a modest increase in risk of THR in relation to cumulative lifting among men and an increased risk in relation to a high BMI at age 25 years and to a gain in BMI in both sexes.

Occupational risk factors for hip osteoarthritis are associated with early hip structural abnormalities: a 3.0 T magnetic resonance imaging study of community-based adults

Introduction

Occupational exposure to heavy lifting and stair climbing are associated with radiographic hip osteoarthritis (OA). This study examined whether these activities are associated with early structural hip joint changes in a community-based population.

Methods

In total, 198 community-based people with no history of hip disease, including OA, had 3.0 T-magnetic resonance imaging (MRI) to assess hip cartilage volume, defects and bone marrow lesions (BMLs). Recall of occupational exposure to heavy lifting and stair climbing aged 18 to 30 years and in the previous 10 years were collected. A persistence score was defined as exposure at neither time point (0), at one time point (1) or at both time points (2).

Results

Exposure to heavy lifting when aged 18 to 30 years was associated with BMLs of the central superolateral femoroacetabular region (odds ratio (OR) 3.9, 95% confidence interval (CI) 1.6 to 9.8, P <0.01), with persistence score associated with cartilage defects in the central superolateral region of the femoral head (OR 1.6, 95% CI 1.0 to 2.5, P = 0.04). Exposure to stair climbing aged 18 to 30 years and persistence score were associated with an increased risk of cartilage defects in the central superolateral femoral head and BMLs in the central superolateral and posterior femoroacetabular regions (OR range 2.1 to 3.2, all P ≤0.03).

Conclusions

Occupational exposure to heavy lifting and stair climbing are associated with hip structural abnormalities. If confirmed by longitudinal data, such associations may explain how occupational activities affect the hip joint and may identify new targets for the prevention of hip OA.

Current status of temporomandibular joint disorders and the therapeutic system derived from a series of biomechanical, histological, and biochemical studies

This article was designed to report the current status of temporomandibular joint disorders (TMDs) and the therapeutic system on the basis of a series of clinical, biomechanical, histological and biochemical studies in our research groups. In particular, we have focused on the association of degenerative changes of articular cartilage in the mandibular condyle and the resultant progressive condylar resorption with mechanical stimuli acting on the condyle during the stomatognathic function. In a clinical aspect, the nature and prevalence of TMDs, association of malocclusion with TMDs, association of condylar position with TMDs, association of craniofacial morphology with TMDs, and influences of TMDs, TMJ-osteoarthritis (TMJ-OA) in particular, were examined. In a biomechanical aspect, the nature of stress distribution in the TMJ from maximum clenching was analyzed with finite element method. In addition, the pattern of stress distribution was examined in association with varying vertical discrepancies of the craniofacial skeleton and friction between the articular disk and condyle. The results demonstrated an induction of large compressive stresses in the anterior and lateral areas on the condyle by the maximum clenching and the subsequent prominent increases in the same areas of the mandibular condyle as the vertical skeletal discrepancy became more prominent. Increase of friction at the articular surface was also indicated as a cause of larger stresses and the relevant disk displacement, which further induced an increase in stresses in the tissues posterior to the disks, indicating an important role of TMJ disks as a stress absorber. In a histological or biological aspect, increase in TMJ loading simulated by vertical skeletal discrepancy, which has already been revealed by the preceding finite element analysis or represented by excessive mouth opening, produced a decrease in the thickness of cartilage layers, an increase in the numbers of chondroblasts and osteoclasts and the subsequent degenerative changes in the condylar cartilage associated with the expression of bone resorption-related factors. In a biochemical or molecular and cellular aspect, excessive mechanical stimuli, irrespective of compressive or tensile stress, induced HA fragmentation, expression of proinflammatory cytokines, an imbalance between matrix metalloproteinases and the tissue inhibitors, all of which are assumed to induce lower resistance to external stimuli and degenerative changes leading to bone and cartilage resorption. Excessive mechanical stimuli also reduced the synthesis of superficial zone protein in chondrocytes, which exerts an important role in the protection of cartilage and bone layers from the degenerative changes. It is also revealed that various cytoskeletal changes induced by mechanical stimuli are transmitted through a stretch-activated or Ca2+channel. Finally, on the basis of the results from a series of studies, it is demonstrated that optimal intra-articular environment can be achieved by splint therapy, if indicated, followed by occlusal reconstruction with orthodontic approach in patients with myalgia of the masticatory muscles, and TMJ internal derangement or anterior disk displacement with or without reduction. It is thus shown that orthodontic treatment is available for the treatment of TMDs and the long-term stability after treatment.

Epidemiological evidence for work load as a risk factor for osteoarthritis of the hip: a systematic review

Objective

Osteoarthritis of the hip (OA) is a common degenerative disorder of the joint cartilage that presents a major public health problem worldwide. While intrinsic risk factors (e.g, body mass and morphology) have been identified, external risk factors are not well understood. In this systematic review, the evidence for workload as a risk factor for hip OA is summarized and used to derive recommendations for prevention and further research.

Methods

Epidemiological studies on workload or occupation and osteoarthritis of the hip were identified through database and bibliography searches. Using pre-defined quality criteria, 30 studies were selected for critical evaluation; six of these provided quantitative exposure data.

Results

Study results were too heterogeneous to develop pooled risk estimates by specific work activities. The weight of evidence favors a graded association between long-term exposure to heavy lifting and risk of hip OA. Long-term exposure to standing at work might also increase the risk of hip OA.

Conclusions

It is not possible to estimate a quantitative dose-response relationship between workload and hip OA using existing data, but there is enough evidence available to identify job-related heavy lifting and standing as hazards, and thus to begin developing recommendations for preventing hip OA by limiting the amount and duration of these activities. Future research to identify specific risk factors for work-related hip OA should focus on implementing rigorous study methods with quantitative exposure measures and objective diagnostic criteria.

Association between occupation and knee and hip replacement due to osteoarthritis: a case-control study

Introduction

The objective of this study was to examine the association between occupation and osteoarthritis (OA) leading to total knee (TKR) or hip (THR) joint replacement.

Methods

The following is the case-control study design. All patients still living in Iceland who had had a TKR or THR due to OA as of the end of 2002 were invited to participate. First degree relatives of participating patients served as controls. N = 1,408 cases (832 women) and n = 1,082 controls (592 women), 60 years or older and who had adequately answered a questionnaire were analyzed. Occupations were classified according to international standards. Inheritance of occupations was calculated by using the Icelandic Genealogy Database.

Results

The age adjusted odds ratio (OR) for male farmers getting a TKR due to OA was 5.1 (95% confidence interval (CI) 2.1 to 12.4) and for a male farmer getting a THR due to OA the OR was 3.6 (95% CI 2.1 to 6.2). The OR for a fisherman getting a TKR was 3.3 (95% CI 1.3 to 8.4). No other occupations showed increased risk for men. For women there was no increased risk for any occupation. Farming and fishing were also the occupations that showed the greatest degree of inheritance.

Conclusions

These results support an association in males between occupations with heavy physical load and both TKR and THR for OA.

Temporomandibular joint loads in subjects with and without disc displacement

The likelihood of development of degenerative joint disease (DJD) of the temporomandibular joint (TMJ) is related to the integrity of the TMJ disc. Predilection for mechanical failure of the TMJ disc may reflect inter-individual differences in TMJ loads. Nine females and eight males in each of normal TMJ disc position and bilateral disc displacement diagnostic groups consented to participate in our study. Disc position was determined by bilateral magnetic resonance images of the joints. Three-dimensional (3D) anatomical geometry of each subject was used in a validated computer-assisted numerical model to calculate ipsilateral and contralateral TMJ loads for a range of biting positions (incisor, canine, molar) and angles (1-13). Each TMJ load was a resultant vector at the anterosuperi or-most mediolateral midpoint the condyle and characterized in terms of magnitude and 3D orientation. Analysis of variance (ANOVA) was used to test for effects of biting position and angle on TMJ loads. Mean TMJ loads in subjects with disc displacement were 9.5-69% higher than in subjects with normal disc position. During canine biting, TMJ loads in subjects with disc displacement were 43% (ipsilateral condyle, p=0.029) and 49% (contralateral condyle, p=0.015) higher on average than in subjects with normal disc position. Biting angle effects showed that laterally directed forces on the dentition produced ipsilateral joint loads, which on average were 69% higher (p=0.002) compared to individuals with normal TMJ disc position. The data reported here describe large differences in TMJ loads between individuals with disc displacement and normal disc position. The results support future investigations of inter-individual differences in joint mechanics as a variable in the development of DJD of the TMJ.

Static and dynamic mechanics of the temporomandibular joint: plowing forces, joint load and tissue stress

OBJECTIVES - To determine the combined effects 1) of stress-field aspect ratio and velocity and compressive strain and 2) joint load, on temporomandibular joint (TMJ) disc mechanics. SETTING AND SAMPLE POPULATION - Fifty-two subjects (30 female; 22 male) participated in the TMJ load experiments. MATERIAL AND METHODS - In the absence of human tissue, pig TMJ discs were used to determine the effects of variables 1) on surface plowing forces, and to build a biphasic finite element model (bFEM) to test the effect of human joint loads and 2) on tissue stresses. In the laboratory, discs received a 7.6 N static load via an acrylic indenter before cyclic movement. Data were recorded and analysed using anova. To determine human joint loads, Research Diagnostic Criteria calibrated investigators classified subjects based on signs of disc displacement (DD) and pain (+DD/+pain, n = 18; +DD/-pain, n = 17; -DD/-pain, n = 17). Three-dimensional geometries were produced for each subject and used in a computer model to calculate joint loads. RESULTS - The combined effects of compressive strain, and aspect ratio and velocity of stress-field translation correlated with plowing forces (R(2) = 0.85). +DD/-pain subjects produced 60% higher joint loads (ANOVA, p < 0.05), which increased bFEM-calculated compressive strain and peak total normal stress. CONCLUSIONS - Static and dynamic variables of the stress-field and subject-dependent joint load significantly affect disc mechanics.

Tractional Forces on Porcine Temporomandibular Joint Discs

Tractional forces on the temporomandibular joint (TMJ) disc predispose tissue fatigue. This study tested the hypotheses that tractional forces: (1) increased with stress-field velocity ( V) and aspect ratio ( AR, contact area diameter/cartilage thickness), and compressive strain (ε); and (2) varied depending on cartilage thickness. Porcine TMJ discs (n = 187) received a 10-N vertical static load via an acrylic indenter for 1, 5, 10, 30, or 60 sec, followed by movement. Physical data were recorded and analyzed by quadratic regression relations and a likelihood ratio test. Results showed non-linear increases in tractional forces that were positively correlated with increased V, AR, and ε when the stress-field moved onto relatively thicker (R2 = 0.83) and thinner cartilage (R2 = 0.86). When V was > 27 mm/sec and AR·ε3, was > 0.09, tractional forces were significantly higher (≤ 12% of peak) when the stress-field moved onto thicker cartilage. Stress-field dynamic mechanics and cartilage thickness significantly affected TMJ disc tractional forces.

Tractional Forces, Work and Energy Densities in the Human TMJ

The role of mechanics in degenerative joint disease of the temporomandibular joint (TMJ) is largely unknown. Objectives were to: 1) develop an empirical model to relate variables of cartilage mechanics and tractional forces; and 2) use the empirical model to estimate tractional forces for calculations of work done (mJ) and energy densities (mJ/mm³) in living human TMJs. Sixty-four porcine discs were statically, then dynamically loaded. Aspect ratios and velocities of stress-fields, compressive strains, and tractional forces were recorded and fit to a quadratic equation to derive the empirical model. Aspect ratios and velocities of stress-fields and cartilage thicknesses then were measured via dynamic stereometry in 15 humans with healthy TMJs and 11 with TMJ disc displacement. These data were used in the empirical model to estimate tractional forces for each TMJ, and then mechanical work done and energy densities were calculated. Mechanical work (mJ) was on average 20 times greater in TMJs with disc displacement than in healthy TMJs (P<0.02). TMJs with disc displacement showed 350% more mechanical work (mJ) and 180% higher energy densities in women compared to men (P<0.02). A power analysis (α=0.05, β=0.90) indicated that 40 women and 40 men would be required to detect a 50% difference in TMJ energy densities between genders. Mechanical work was significantly higher (P≤0.05) in TMJs with disc displacement compared to healthy TMJs, and mechanical work done and energy densities were significantly higher (P≤0.05) in TMJs with disc displacement in women compare to men.

Static and dynamic loading effects on temporomandibular joint disc tractional forces

Mechanical fatigue-related degeneration of the temporomandibular joint (TMJ) disc may be promoted by tractional forces. This study tested the hypotheses that tractional forces following static loading of the TMJ disc: (1) increase with compressive strain at the start of movement, and (2) are velocity-dependent during movement. Sixty-four porcine discs received a 10-N static load via an acrylic indenter for 1 or 30 sec before cyclic movement. Physical data were recorded and analyzed by ANOVA. The results showed that compressive strain and tractional forces were largest for the start of movement following 30 sec of static loading (p <or= 0.0001) and were correlated (R(2) = 0.84). Peak tractional forces were linearly and positively related to velocity of movement (R(2) = 0.85), and were highest during Cycle 1 after 30 sec of loading (p <or= 0.0067). The results demonstrated that tractional forces were strain-related at the start of movement and velocity-dependent during movement.

ABBREVIATIONS

ANOVA = analysis of variance, PBS = phosphate-buffered physiological saline solution, TMJ = temporomandibular joint, mu(T) =tractional coefficient, mu(s) = static coefficient of friction.

Factors affecting the prevalence of osteoarthritis in healthy middle-aged women: data from the longitudinal Melbourne Women's Midlife Health Project

The prevalence of osteoarthritis (OA) is greater in women then men. Weight, a factor strongly associated with osteoarthritis, is significantly increased over the menopausal transition. Despite the high prevalence of osteoarthritis, a disabling disease with limited treatment options, there is a paucity of studies in women. The longitudinal phase of the Melbourne Women's Midlife Health Project, is a population-based prospective study of 438 Australian born women who have been followed annually over 11 years. 257 (59%) of these women remained in longitudinal assessment at 11th year of follow-up and 224 of these women agreed to undergo X-rays of their knees and hands. In this study, X-rays were scored for evidence of osteoarthritis using a validated scale, by two investigators who were blinded to questionnaire results. Information on hormone therapy use, physical activity, smoking, BMI and age were obtained by both self-administered and face-to-face questionnaires. Results showed that one hundred and twenty-eight women (56%) had evidence of radiological OA. Forty-nine (21.6%) had evidence of radiological knee OA. One hundred and one (44.5%) had evidence of radiological hand OA. Compared to baseline, at 11th year of follow-up participants had put on weight (4 kg range -14 to 25 kg) and a larger proportion (25% vs. 40%) reported exercising frequently (P = 0.005). Physical activity and BMI were associated with higher prevalence of osteoarthritis in the final year of follow-up. Smoking was associated with a lower prevalence of radiological knee OA. The prevalence was 61% among never smokers compared to only 39% among those who smoked (P < 0.05). Total OA was associated with never having used hormone therapy (odds ratio 2.7; CI 1.1-6.9). There was a trend for increasing level of physical activity at ages 20-29 to be associated with an increased risk of knee OA (P value 0.03 for trend). In conclusion increasing age, BMI and history of more frequent physical activity in younger years were risk factors for radiological knee OA. In contrast, smoking appeared to be associated with less knee OA. Never having used hormone therapy was a risk factor for radiological hand and knee OA. Further work will be needed to determine whether modification of these factors can prevent the development of OA.

Osteoarthritis of the knee and hip and activity: a systematic international review and synthesis (OASIS)

The goal of this study was to determine which activities in four domains, daily life, exercises, sports and occupational activities, should be recommended, in favor or against, for the patient suffering from knee or hip OA.

METHODS

Scientific literature was searched in Medline, Embase and Cochrane databases for articles in French or English, reporting original data. The articles were evaluated with standardized epidemiological criteria. Seventy-two articles were retained. Recommendations were graded according to the level of scientific evidence (A high, B moderate, C clinical consensus) and were formulated for primary care.

CONCLUSIONS AND RECOMMENDATIONS

For activity of daily life (ADL), the OASIS group states with a moderate level of scientific evidence, that ADL are a risk factor for knee OA and that risk increases with intensity and duration of activity. The group concludes that healthy subjects as well as OA patients in general can pursue a high level of physical activity, provided the activity is not painful and does not predispose to trauma (grade B). Radiographic or clinical OA is not a contraindication to promoting activity in patients who have a sedentary lifestyle (grade C). For exercises and other structured activities pursued with a goal of health improvement, the group states with a high level of scientific evidence that they have a favourable effect on pain and function in the sedentary knee OA patient. The OASIS group recommends the practice of exercises and other structured activities for the sedentary patient with knee OA (grade A). Static exercises are not favored over dynamic exercises, availability, preference and tolerance being the criteria for the choice of an exercise (grade A). As results deteriorate when exercises are stopped, they should be performed at a frequency of between one and three times per week (grade B). Professional assistance can be useful in improving initial compliance and perseverance (grade B). There is no scientific argument to support halting exercise in case of an OA flare-up (grade C). For sports and recreational activity, the group states with a high degree of scientific evidence, that these activities are a risk factor for knee and hip OA and that the risk correlates with intensity and duration of exposure. The group also states, with a high degree of scientific evidence, that the risk of OA associated with sport is lesser than that associated with a history of trauma and overweight. No firm conclusion could be drawn about the possible protective role of sports such as cycling, swimming or golf. The OASIS group recommends that athletes should be informed that joint trauma is a greater risk factor than the practice of sport (Grade A). The high level athlete should be informed that the risk of OA is associated with the duration and intensity of exposure (Grade B). The OA patient can continue to engage regularly in recreational sports as long as the activity does not cause pain (Grade C). The OA patient who practices a sport at risk for joint trauma should be encouraged to change sport (Grade C). For occupational activity, the OASIS group states with a high level of scientific evidence that there is a relationship between occupational activity and OA of the knee and hip. The precise nature of biomechanical stresses leading to OA remains unclear but factors such as high loads on the joint, unnatural body position, heavy lifting, climbing and jumping may contribute to knee and hip OA. The group recommends that taking an occupational history should always be part of managing the OA patient (Grade B). In the knee or hip OA patient, work-related activity that produces or maintains pain should be avoided (Grade B). Physicians should be alerted by the early knee and hip signs and symptoms in workers exposed to stresses that are known or supposed to favour knee or hip OA (Grade C).

Modeling of Temporomandibular Joint Function Using MRI and Jaw-Tracking Technologies – Mechanics

The study of mechanics of the temporomandibular joint (TMJ) is important because its dysfunction and breakdown could be, at least partially, of mechanical origin. The incongruity of the articular surfaces of the TMJ is compensated by a fibrocartilaginous articular disc. Its dislocation and failure seem to be closely related to the development of osteoarthritis of the TMJ. The analysis of mandibular kinematics permits the detection and assessment of irregularities of TMJ function due to internal obstacles such as a displaced articular disc. Furthermore, the measurement of the dynamic relationship between the articular surfaces of the TMJ is useful to determine the strains undergone by the disc that if too high might compromise its integrity. The development of our research in TMJ mechanics has evolved from the acquisition of the traces of single mandibular points to an accurate and compact description of mandibular motion, in which the mechanical advantage of jaw muscles, and forces and torques acting on the jaw are considered as well. The combination of three-dimensional software models of TMJ anatomies obtained from MRI and jaw tracking with six degrees of freedom permits a subject-specific dynamic analysis of the intra-articular space, providing insight into individual disc deformation during function and TMJ loading. Studies performed with this system indicate that both TMJs are loaded during chewing, the balancing more so than the working joint. In fact, during chewing, the intra-articular distance is smaller for hard than for soft food, on closing than on opening, on the balancing than on the working side. This last finding is confirmed by static biting experiments, in which the condyle-fossa distance decreases more on the side contralateral to the bite force, depending on its magnitude. Also studies on the dynamics of compression areas indicate that plowing can occur through the disc during function, especially mediolaterally, due to stress field translation. This effect might contribute to cartilage wear and fatigue also because the disc is weaker mediolaterally. Further data indicate that the lateral area of the disc is mostly exposed to a higher mechanical energy density. This will be more intensively investigated using finite element method.

Osteoarthritis and the postmenopausal woman: Epidemiological, magnetic resonance imaging, and radiological findings

BACKGROUND

There is some observational evidence to suggest an effect of hormones on osteoarthritis (OA), especially in perimenopausal women.

OBJECTIVES

To review the epidemiological evidence for an effect of estrogen replacement therapy (ERT) on the incidence and prevalence of OA, especially radiological OA, and the effect of ERT on articular cartilage in women.

METHODS

The literature relating to these questions was reviewed using OVID Medline (1966 to March 2003).

RESULTS

Some studies which have suggested a protective effect of ERT on the incidence and prevalence of OA. However, many of the confidence intervals include unity. Although a protective effect also was seen on articular knee cartilage in long-term users of ERT compared with never users, no difference in change in cartilage was seen over 2 years.

CONCLUSIONS

There is weak epidemiological evidence suggesting a role for estrogen therapy in joint health in postmenopausal women. The data are more suggestive of an effect on large joint OA than small joint OA.

Osteoarthritis in Other Joints (Hip, Elbow, Foot, Ankle, Toes, Wrist) after Sports Injuries

Osteoarthritis of nonknee joints, although less common than knee osteoarthritis, remains a significant and disabling condition for many present and former athletes. These injuries can be caused by repeated loads or following a specific traumatic event. The resulting pain and loss of motion can limit function and ability. Arthroscopic techniques in many cases enable surgeons to symptomatically treat limitations of range of motion and pain, prolonging active careers. Joint replacement remains the ultimate solution for hip osteoarthritis, and may be a viable option in ankle osteoarthritis.

High contact hip stress is related to the development of hip pathology with increasing age

BACKGROUND

High contact hip stress is believed to be one of the key biomechanical factors involved in the hip cartilage degeneration and osteoarthritis. Accordingly, with increasing age high contact hip stress is expected to cause elimination of subjects from the population of healthy hips, but its predictive value has not been evaluated so far. The objective of the paper is to investigate whether the exposure of healthy hips to estimated high contact hip stress is related to the development of hip pathology with increasing age.

METHODS

A cross-sectional age- and gender-matched analysis of the peak contact hip stress calculated from pelvic geometry was made in 103 adult subjects with healthy hips. The peak contact hip stress was calculated from anterior-posterior pelvic radiographs of healthy hips by using a mathematical model of the human hip in the static one-legged stance.

FINDINGS

In both female and male population, the average values of the peak contact hip stress normalized to the body weight are significantly higher and the values are also more dispersed in younger subjects when compared to older subjects.

INTERPRETATION

The hip joints which remain healthy in the old age have lower average estimated peak contact hip stress. These results are consistent with the explanation that subjects with high estimated peak contact hip stress are more likely to develop hip disease in the course of life.

Primary osteoarthritis and occupation in the Quebec national health and social survey

BACKGROUND

The scientific evidence available is consistent in linking osteoarthritis (OA) and occupation but is lacking information regarding preventable risks in the workplace.

AIMS

To explore the effect of different dimensions of physical demand in the relation between self reported OA and occupation.

METHODS

Nationwide population survey of employed and self employed adults aged 25-64.

RESULTS

Of the 11,44 workers surveyed, 3.1% (two females for one male) reported a problem with OA (any site). They reported some degree of limitations in their daily activities in a proportion that was six times higher (26.8%) than the rest of the population of the same age without OA and twice as high for absence from work in the previous year (23.8%). Of the different dimensions of risks used in the survey and controlling for age, body mass index, and smoking, "use of force with tools or machines" showed a statistically significant association with OA in males and females. In occupations significant risks of OA were identified in male unskilled labourers and skilled labourers, and in female technicians, and workers in the services sector.

CONCLUSIONS

Results of the present survey indicated that occupational stresses associated with OA may differ substantially between male and female workers and that specific risks may affect the younger workforce (25-44 years old) in some occupations, including housekeeping and other ill defined skilled and unskilled labour.

Osteoarthritis in the hip and whole-body vibration in heavy vehicles

BACKGROUND

Farmers have an increased risk of osteoarthritis in the hip, but the mechanism is not known. It has been suggested that the driving of tractors and jumping up and down from the tractor cabin is of importance. In this study, we test the hypothesis that driving vehicles with high levels of whole-body vibration (WBV) is associated with an increased risk of osteoarthritis in the hip.

METHODS

This is a cohort study of male operators of heavy vehicles working in the construction industry. They participated in a national health control program. The incidence rate for joint replacement in the hip was found in the Swedish Hospital Discharge Register for 1987 to 1998 and compared with the incidence in reference groups. Their exposure to WBV was estimated from their job titles. The rates were adjusted to body mass index (BMI) and smoking habits and compared to referents participating in the same health control program.

RESULTS

Drivers exposed to WBV had not an increased risk of joint replacement due to osteoarthritis in the hip (RR = 0.82; 95% CI 0.51-1.24).

CONCLUSIONS

This study does not support the hypothesis that exposure to WBV during operating a vehicle cause an increased risk of osteoarthritis in the hip.

Weight change and the risk of total hip replacement

BACKGROUND

We examined the effect of adult weight change on risk for total hip replacement resulting from primary osteoarthritis, using a prospective study design.

METHODS

We linked data on body mass index and body weight from 3 screening surveys in 3 Norwegian counties (mean ages at screenings 34, 43, and 47 y; n = 38,868) with follow-up data on total hip replacement (n = 572). Mean age at the start of follow up was 55 years, and mean duration of follow up was 9 years. For each participant we calculated a rate of weight change (weight slope) by linear regression of body weight versus time from the first through the third screening.

RESULTS

Among men, mean weight change from first to last screening was +9.8 kg in the highest quartile and -3.7 kg in the lowest quartile. In women, the corresponding figures were +9.5 kg in the highest quartile and -5.2 kg in the lowest quartile. There was no association of weight slope, absolute weight change, or relative weight change between screenings with later total hip replacement resulting from primary osteoarthritis. We saw no change in the association between body mass index and later hip arthroplasty as the participants' age increased from 34 to 47 years at the 3 screenings.

CONCLUSION

The risk for later total hip replacement resulting from primary osteoarthritis was unaffected by weight change during the fourth and fifth decades of life. The dose-response association between adult body mass index and later total hip replacement was similar across these age groups.

Total hip replacement due to osteoarthritis: the importance of age, obesity, and other modifiable risk factors

We studied whether several modifiable factors were associated with the risk of total hip replacement due to hip osteoarthritis among women.We identified 568 women from the Nurses' Health Study who reported total hip replacement due to primary hip osteoarthritis on questionnaires from 1990 to 1996, using a validated algorithm. The relation of potential risk factors, such as age, body mass index, physical activity, smoking, alcohol intake, and hormone use, to hip replacement was assessed using pooled logistic regression models. Higher body mass index was associated with an increased risk of hip replacement due to osteoarthritis (P for trend = 0.0001). Compared with women in the lowest category of body mass index (<22 kg/m(2)), those in the highest category of body mass index (> or =35 kg/m(2)) had a twofold increased risk (95% confidence interval [CI]: 1.4 to 2.8), whereas those in the highest category of body mass index at age 18 years had more than a fivefold increased risk (95% CI: 2.5 to 10.7). Age also had a positive association; women aged > or =70 years were nine times more likely to have hip replacement than those aged <55 years (95% CI: 5.4 to 13.9). Recreational physical activity, smoking, alcohol use, and postmenopausal hormone use were not associated with an increased risk of hip replacement. In the Nurses' Health Study, higher body mass index and older age significantly increased the risk of total hip replacement due to osteoarthritis. Part of this risk appeared to be established early in life.

An update on the relationship between occupational factors and osteoarthritis of the hip and knee

This study reviews articles published in 2000 and 2001 about occupational physical activities as risk factors for osteoarthritis (OA) of the knee and hip. Six studies were identified in MEDLINE and EMBASE; five case-control studies and one cross-sectional study. Criteria for OA were: (on the waiting list for) joint replacement or (symptomatic) radiologic OA. Exposure was assessed by structured interviews or self-administered questionnaires. Job titles or details on specific physical activities were used as determinants. The authors determine that information bias and nondifferential misclassification, with respect to occupational risk factors, cannot be excluded. Relevant confounding factors were adequately taken into account. Even though response rates were high, nonresponse bias may still have an influence, although its impact cannot be assessed accurately. Within these constraints the studies gave further evidence to support the role of jobs and occupational physical activities on the occurrence of OA.

Risk factors for total hip replacement due to primary osteoarthritis: a cohort study in 50,034 persons

OBJECTIVE

To identify prospectively the possible risk factors for total hip replacement (THR) due to primary osteoarthritis in a large cohort.

METHODS

Data from a cardiovascular screening were matched with 9 years of national data on THR. Mean age at the start of followup was 54.9 years, and the 50,034 participants were followed up for an average of 9 years. During followup, 672 persons had a first THR due to primary osteoarthritis.

RESULTS

We found dose-response associations between body mass index (BMI), body weight, and the level of physical activity at work and THR for primary osteoarthritis. The highest versus the lowest quarter of BMI had a relative risk of 2.0 (95% confidence interval [95% CI] 1.4-2.9) among men and 3.0 (95% CI 2.1-4.1) among women. The highest versus the lowest quarter of body weight had a relative risk of 2.1 (95% CI 1.4-3.2) among men and 3.4 (95% CI 2.4-4.9) among women. Intensive versus sedentary physical activity at work had a relative risk of 2.1 (95% CI 1.5-3.0) among men and 2.1 (95% CI 1.3-3.3) among women. No association was found between physical activity in leisure and THR for primary osteoarthritis.

CONCLUSION

Intensive physical activity at work and a high BMI each contribute significantly to the overall risk of undergoing THR due to primary osteoarthritis. Lowering the exposure to these risk factors may substantially reduce the need for hip replacement.

Clinical, radiologic, demographic, and occupational aspects of hand osteoarthritis in the elderly

OBJECTIVE

Osteoarthritis (OA) of the hand is common in elderly patients. The aim of this study was to characterize OA frequency, severity, and distribution and to trace interrelationships between these findings and the demographic, occupational, and medical data from elderly Jewish nonrheumatologic patients.

METHODS

Study participants were 253 consecutive patients admitted to a geriatric center for a variety of nonrheumatic medical conditions. Excluded patients were those with rheumatoid arthritis; neurologic, orthopedic, or other conditions that would interfere with symmetric hand function; and mental or medical states that would interfere with history taking and radiographic studies. Patient occupations were graded as workload degree (on a scale of 1 to 3) and as the total occupational score (workload degree multiplied by the duration of each job). Clinical findings of Heberden nodes, Bouchard nodes, and malignment, graded on a scale of 0 to 3, were summed as the clinical OA score. Hand radiographs were independently read (modified Altman method), grading 5 parameters in each joint on a scale of 0 to 3, summed as a radiologic OA score. Statistical analyses included the Student t test, chi(2) test, ANOVA, Pearson correlation, and partial correlation coefficients.

RESULTS

Among 253 elderly patients (171 women, 82 men; mean age, 79 years) OA was frequent (occurring in about 80% of patients), involving most severely the second and third distal interphalangeal, right first interphalangeal, and both first carpometacarpal joints. The prevalence of OA was similar in women and men, with higher scores in women, and reached significance only in the distal interphalangeal joints. Metacarpophalangeal joints were more involved in men. Age had a clear influence on OA scores. Ethnicity affected OA severity, with Ashkenazi Jews having significantly higher scores than Sepharadi Jews. Dominant hands had significantly higher global OA scores as well as isolated joint scores (except for the first carpometacarpal joint). Occupational load, housekeeping tasks, and the number of children did not influence the total or specific joint OA scores. Associated conditions such as obesity, diabetes, hypothyroidism, and chondro calcinosis were not associated with more pronounced OA.

CONCLUSIONS

Hand OA was prevalent in our elderly cohort, and its severity was influenced by inherent traits such as age, female gender, ethnicity, and handedness. In contrast, acquired factors such as workload, number of children, and associated diseases did not appear to influence OA expression.

The effect of disc thickness and trauma on disc surface friction in the porcine temporomandibular joint

The pathomechanics of osteoarthritis in the human temporomandibular joint (TMJ) are unknown. Compromised lubrication is a potential factor, but, lubrication within even the normal TMJ is not understood completely. Weeping lubrication is a concept that may be applicable to the TMJ. A characteristic of weeping lubrication is a slow increase in friction during static loading. The rate of increase in friction is related to the rate of lateral movement of synovial fluid away from the loading area. The TMJ disc is expected to be the main source of TMJ lubrication. This study tested two variables, disc thickness and magnitude of trauma to the disc, as factors that can affect the rate of flow of synovial fluid and thus alter lubrication of the disc surfaces. To test these variables, TMJ disc surface friction was measured before and after an impulse load. Before the impulse load, all discs demonstrated a gradual increase in friction during light static loading. The rate of increase in friction was inversely related to the disc thickness (R(2)=0.75). After an impulse load of known magnitude and peak force, disc surface friction was higher. The magnitude of this surface friction was correlated with the magnitude of the impulsive blow (R(2)=0.89) and the area of surface damage (R(2)=0.85). Disc thickness was a significant factor in determining the minimal impulse needed to produce higher surface friction (R(2)=0.99). These results confirm that disc thickness and trauma to the disc affect surface friction in the TMJ, and therefore may be important factors in compromised lubrication and the development of osteoarthritis.