Type 3 finger length pattern, where the fourth finger is longer than the second finger, may be a valid non-invasive biomarker for risk of chronic joint pain and osteoarthritis (OA) of the hand, research reveals.
This type of finger pattern is an indicator of prenatal exposure to high androgen levels, which are known to be involved in the development of the skeleton, the researchers note.
“For example, androgens have been shown to influence HOX-gene expression during development of chondrocytes in the fingers”, they explain.
“This might not only result in differences in development of the finger length, but possibly also result in a more susceptible cartilage to osteoarthritis later in life.”
The team, led by Marjolein de Kruijf (Erasmus Medical Center, Rotterdam, the Netherlands), determined the finger length pattern of 4784 individuals, all of whom were aged at least 45 years and participating in The Rotterdam Study, a large prospective population-based study.
In all, 1233 people had the type 3 finger length pattern, which was more prevalent in men than women, at 35% versus 18%. The rates of radiographic knee, hip or hand OA were 36% for men and 25% for women. And 50% of women and 37% of men had chronic joint pain.
Participants with this type of finger pattern were significantly more likely than those with type 1 or 2 patterns – where the fourth finger is shorter than the second finger or the second finger is the same as the index finger – to have hand OA, at an odds ratio (OR) of 1.64.
And this significantly increased risk remained after patients with severe OA of the second digit, which can lead to shortening of the digit, had been excluded from the analysis, at an OR of 1.43.
There was no association between type 3 finger length pattern and radiographic knee or hip OA. But in a meta-analysis of the current results plus those of previous publications, and restricted to symptomatic knee OA only, de Kruijf and co-workers found a highly significant association, at an OR of 1.70.
The researchers also report that type 3 finger pattern was significantly associated with chronic joint pain, at an OR of 1.18. And this association became stronger with chronic joint pain affecting more than two sites, at an OR of 1.41. There was little change in the strength of these associations when patients with severe OA in the second digit were excluded from the analysis.
“This suggests that not the OA […], but the chronic pain might explain the association found”, the team points out in Arthritis Care and Research.
All of the associations were independent of other known risk factors for OA, such as age, gender and body mass index.
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