Association between index-to-ring finger length ratio and risk of severe knee and hip osteoarthritis requiring total joint replacement

Sexual difference in 2nd-to-4th digit ratio among 1.5-year-old Japanese children: A cross-sectional study of Aichi regional adjunct cohort of the Japan Environment and Children's Study (JECS-A)

BACKGROUND

A sex difference in the second-to-fourth digit ratio (2D:4D, males < females) has been described in Japanese fetuses and children, and its possible links to autism spectrum disorders (ASDs) have been discussed. Accordingly, this sexual difference in representative neonates merits examination.

AIMS

This study aimed to examine 2D:4D measurements and sexual differences in Japanese toddlers aged 1.5 years.

STUDY DESIGN AND SUBJECTS

The digit lengths used to calculate 2D:4D were measured using an easy-to-use photography method. A total of 1045 JECS-A (the Aichi regional sub-cohort of the Japan Environment and Children's Study) children (males, 523; females, 522) aged 1.5 years were analyzed.

RESULTS

The mean ages for the males and females were 575.3 ± 13.1 and 575.9 ± 17.1 days, respectively. Histograms of left and right 2D:4D were normally distributed regardless of sex (left male, 0.909 ± 0.048; left female, 0.913 ± 0.049, d = 0.08; right male, 0.938 ± 0.055; right female, 0.937 ± 0.049, d = 0.02). Because of high dispersion in the data, t-tests did not support a significant sex difference in 2D:4D. Post-hoc statistical power was calculated as 0.124 and the effect size for the sex difference in 2D:4D was 0.036.

CONCLUSIONS

This study failed to confirm sexual differences in 2D:4D in 1.5-year-old Japanese children. This may be because digit measurement is difficult in this group, resulting in reduced effect sizes, or because rapid growth attenuates the in utero sexual dimorphism. This evidence is useful for the light it casts on the extreme male brain theory of ASDs.

Finger length ratio in longevity populations

OBJECTIVES

The purpose of this study was to compare the prevalence of finger length ratio between three longevity populations (Abkhazians, Azerbaijanis, and Georgians) and one nonlongevity population (Russians), as well as between a longevity and nonlongevity sample within one ethnic group (Abkhazians).

METHODS

In a cross-sectional observational study, we compared the prevalence of finger length ratio in longevity vs nonlongevity samples.

RESULTS

A negative relationship was observed between longevity index and prevalence of type 1 (feminine type) ratio. In longevity samples, the prevalence of type 1 ratio was lower and the prevalence of type 3 (masculine type) ratio was higher than in the nonlongevity sample of Russians. This difference was statistically significant (P < .001) in both males and females. A similar difference between longevity and nonlongevity samples was exhibited in the Abkhazian samples. In males and females, a significantly higher prevalence of type 1 and lower type 3 finger ratios (P < .001) were shown in the nonlongevity samples.

CONCLUSIONS

Finger length ratio pattern in longevity populations differs from that of nonlongevity populations. In longevity samples, the prevalence of type 1 ratio was lower and the prevalence of type 3 ratio was higher vs the nonlongevity sample. A similar type of difference was seen in the longevity and nonlongevity samples belonging to one ethnic group, the Abkhazians. Previous studies found that the type 1 finger length ratio was related to important morbidities that have a potential for shortening the life span. This can be one of the most plausible explanations for our findings.

Clinical Application of Mathematical Long Bone Ratios to Calculate Appropriate Donor Limb Lengths in Bilateral Upper Limb Transplantation

Background: Limited methods exist to aid in deciding the appropriate donor limb lengths in bilateral upper limb amputees qualifying for vascularized composite allotransplantation. We hypothesized mathematical equations could be created using long bone length ratios, and applied to radiographs, to approximate the patient's limb length prior to amputation. Methods: A data set of 30 skeletons' unilateral upper limb long bones measured using osteometric board and calipers was used. Anatomic segment ratios were calculated based on humerus length after multivariate linear regression analysis. For clinical application testing, 5 cadavers' upper limbs were radiographed. Radiographic bone lengths were then measured along the long axis of each long bone. These measured radiographic lengths were then compared with the predicted bone lengths, generated from the skeleton data set ratios, for each cadaver. Results: The chi-square goodness-of-fit test showed excellent fit (P < .01) between the predicted and radiographically measured lengths for the 5 cadavers, and interobserver measurements showed no statistical difference. Depending on the cadaver, percent error in total limb length predicted to measure ranged from 0.9% to 2.7%. The variables to multiply an individual humerus length to calculate a given anatomic segment thus proved to be effective. Conclusions: If a bilateral upper limb amputee has 1 intact humerus, ratios to the humerus length can be reliably applied to calculate the preamputation limb length based on the patient's radiographic humerus length. These formulas are indicated for finding the appropriate limb lengths, and smaller anatomic segments, for donor-recipient matching in upper limb transplantation.

Heritability estimation of 2D:4D finger ratio in a Chuvashian population-based sample

OBJECTIVES

The purpose of this study was to evaluate the familial correlations and heritability of 2D:4D ratio traits using a large population-based sample of ethnically homogeneous pedigrees from Chuvasha and Bashkortostan Autonomies of the Russian Federation.

METHODS

We calculated the familial correlations and performed a heritability analysis of 2D:4D ratio traits in a sample of 1541 subjects (803 men and 738 women, mean age 47.78 ± 16.89 years, range 18-90 years).

RESULTS

Familial correlations of 2D:4D ratio traits showed no significant correlation for spouses; however, parent-offspring (0.15-0.28, P < .001) and sibling correlations (0.13-0.38, P < .009) were found to be significant. Heritability (H² ) of visual classification of 2D:4D ratio was 0.36 for the left and 0.28 for the right hand; finger ratio was 0.55 and 0.66, respectively; the ray ratio was 0.49 and 0.59, respectively, thus indicating the existence of a clear familial aggregation of 2D:4D ratio variation in the Chuvashian pedigrees, which cannot be explained only by common environmental effects.

DISCUSSION

Results of our study suggest familial aggregations of finger ratio variation (for all traits) in Chuvashian pedigrees. No evidence of assortative mating was found.

2D:4D finger length ratio and radiographic hand osteoarthritis

To evaluate the association between the index and ring finger's (2D:4D) length ratio with the prevalence and severity of radiographic hand osteoarthritis (OA). A population-based sample included 802 males (mean age 46.98 ± 17.10 years) and 738 females (mean age 48.65 ± 16.62 years) who had participated in a Chuvashian skeletal aging study. Age, sex, basic demographics, anthropometric data and X-rays of both hands were acquired. Each hand was visually classified on X-ray as either type 1-index finger longer than the ring finger; type 2-index and ring finger equal in length; or type 3-index finger shorter than the ring finger. Hand OA was defined by the number of affected joints (Kellgren-Lawrence score ≥ 2) in both hands and the sum total of Kellgren-Lawrence scores (total OA score). After comparing the OA variables of individuals with different finger length ratio types (after adjustment for age and BMI) significant differences were found only in females between finger ratio types of the right hand in a number of affected joints (F = 3.153, p = 0.043) and finger ratio types of the left (F = 3.330, p = 0.036) and right (F = 2.397, p = 0.047) hands of the total OA score. Females with type 3 ratios had the highest adjusted values of hand OA parameters. We found that finger length ratios are associated with hand OA parameters. Females with a type 3 finger length pattern showed significantly higher hand OA values than those with types 1 and 2.

Low second to fourth digit ratio in Dupuytren disease

The ratio of the lengths of the second and fourth digits (2D:4D) has been described as reflecting endogenous prenatal androgen exposure. In general, 2D:4D is lower in men than in women and has potential as a biomarker or predictor for various diseases, athletic ability, and academic performance. Dupuytren disease has digital flexion contractures and is known to predominate in men, but the pathogenesis of the disease remains unclear. To clarify the relationships between Dupuytren disease and endogenous androgens, we performed a retrospective analysis of hand radiographs to investigate 2D:4D in Dupuytren disease. The study included male patients with Dupuytren disease (n = 22) and a control group (n = 18) of male patients with carpal tunnel syndrome. Only unaffected hands, without contractures or osteoarthritis, were evaluated for the purpose of radiographic assessment. The lengths of the phalanx and metacarpal bones in the second and fourth digits were measured by 2 independent observers who each performed 2 sets of measurements separated by a minimum 1-week interval. The 2D:4D was calculated separately for the phalanges and metacarpals, and a combined (phalanx + metacarpal) 2D:4D was also calculated. The reliability of the observer measurements was established using the intraclass correlation coefficient, and both the intra- and interobserver reliability showed excellent agreement. We found that compared with control group, the Dupuytren disease group had significantly lower phalanx and combined 2D:4D. These findings suggest that endogenous prenatal androgens could contribute to the development of Dupuytren disease, leading to its characteristic clinical presentation predominantly in men and affecting the ulnar rays.

Severity of Diabetes Mellitus and Total Hip or Knee Replacement: A Population-Based Case-Control Study

It is generally thought that people with diabetes mellitus (DM) are more likely to suffer from osteoarthritis (OA) due to an increased body mass index (BMI), resulting in mechanical destruction of cartilage. However, previous studies have suggested a coexisting metabolic causality.To evaluate the risk of hip or knee replacement, as a proxy for severe OA, in patients with DM. We additionally evaluated the risk of total joint replacement (TJR) with various proxies for increased DM severity.A population-based case-control study was performed, using the Clinical Practice Research Datalink (CPRD). Cases (n = 94,609) were defined as patients >18 years who had undergone TJR between 2000 and 2012. Controls were matched by age, gender, and general practice. Conditional logistic regression was used to estimate the risk of total knee (TKR) and total hip replacement (THR) surgery associated with use of antidiabetic drugs (ADs). We additionally stratified current AD users by proxies for DM severity.Current AD use was significantly associated with a lower risk of TKR (OR = 0.86 (95% CI = 0.78-0.94)) and THR (OR = 0.90 (95% CI = 0.82-0.99)) compared to patients not using ADs. Moreover, risk of TKR and THR was decreased with increasing HbA1c.This study does not support the theory that DM patients are more likely to suffer from severe OA as compared to patients without diabetes. Moreover, risk of severe OA necessitating TJR decreases with increasing DM severity. This is possibly due to dissimilarities in methodology, a decrease in eligibility for surgery, or variability of OA phenotypes.

State of the evidence

PURPOSE OF REVIEW

This review focuses on recent studies of osteoarthritis epidemiology, including research on prevalence, incidence, and a broad array of potential risk factors at the person level and joint level.

RECENT FINDINGS

Studies continue to illustrate the high impact of osteoarthritis worldwide, with increasing incidence. Person-level risk factors with strong evidence regarding osteoarthritis incidence and/or progression include age, sex, socioeconomic status, family history, and obesity. Joint-level risk factors with strong evidence for incident osteoarthritis risk include injury and occupational joint loading; the associations of injury and joint alignment with osteoarthritis progression are compelling. Moderate levels of physical activity have not been linked to increased osteoarthritis risk. Some topics of high recent interest or emerging evidence for association with osteoarthritis include metabolic pathways, vitamins, joint shape, bone density, limb length inequality, muscle strength and mass, and early structural damage.

SUMMARY

Osteoarthritis is a complex, multifactorial disease, and there is still much to learn regarding mechanisms underlying incidence and progression. However, there are several known modifiable and preventable risk factors, including obesity and joint injury; efforts to mitigate these risks can help to lessen the impact of osteoarthritis.

Use of thiazolidinediones and the risk of elective hip or knee replacement: a population based case-control study

AIMS

Osteoarthritis (OA) is the most common musculoskeletal condition in the elderly population. However, no disease modifying drug exists for this disease. In vivo animal studies have suggested that thiazolidinediones (TZD) may be used as disease modifying osteoarthritis drugs (DMOADs). To our knowledge, this has not yet been examined in humans before. The aim was to determine the risk of total joint replacement (TJR) in patients using TZDs compared with diabetic patients using other antidiabetic drugs.

METHODS

A population based case-control study was performed using the Clinical Practice Research Datalink (CPRD). Cases (n = 94 609) were defined as patients >18 years of age who had undergone total knee (TKR) or hip replacement (THR) between 2000 and 2012. Controls were matched by age, gender and practice/surgery. Conditional logistic regression analyses were used to estimate the risk of TKR and THR with the use of TZDs in patients currently using one or more antidiabetic drugs. In order to determine effect with prolonged use, we also stratified TZD users by total number of prescriptions prior to surgery. We statistically adjusted our analyses for lifestyle factory, comorbidities and concomitant drug use.

RESULTS

There was no difference in risk of TKR (OR 1.09, 95% CI 0.93, 1.27) and THR (OR 0.92, 95% CI 0.76, 1.10) when TZD users were compared with other AD users. Furthermore, we did not find an association with prolonged use of TZDs and TJR.

CONCLUSION

Despite promising results from animal in vivo studies, this study did not find any evidence for a disease modifying osteoarthritic effect of TZDs.