Posterior tibial tendon (PTT) dysfunction is recognized as an etiology leading to acquired flatfoot in adults, causing significant functional loss. Many risk factors and systemic conditions have been proposed in literature. However, many patients present PTT dysfunction without any of these characteristics. This suggests that there could be a genetic influence associated with posterior tibial tendinopathy. The purpose of the present study is to investigate the association of the À1607 polymorphism in the promoter gene of MMP-1 and posterior tibial tendinopathy. The test group included 50 women, who presented PTT dysfunction grade 2 or 3, and who were submitted to surgical treatment, with histopathological examination of the tendon and magnetic resonance image (MRI) confirming tendinopathy, while the control group was 100 asymptomatic women who presented intact PTT at MRI. The results were analyzed using the chi-square test. The data showed a 75% incidence of the allele 1G and 62% of the genotype 1G/1G at the control group while, at the test group, they showed a 78% incidence of the allele 2G and 72% of the genotype 2G/2G (p < 0.001). The À1607 polymorphism of promoter gene of MMP-1 is associated with the posterior tibial tendinopathy in the studied population. It is three times more often in females, the peak incidence happening at the age of 55 and it is more common in Caucasian, obese, diabetics, rheumatics and hypertensive patients.2 It affects 3.3% of English women.3 Several risk factors, like impingement at fibrous-osseous groove, insertions abnormalities, hypovascularity area within the tendon and congenital flat foot, have been proposed in literature.
4-11However, many patients present PTT dysfunction without any of these risk factors and systemic conditions. This suggests that there could be a genetic influence associated with it, making individuals more prone to posterior tibial tendinopathy.Collagen type I is responsible for building thick fibers that give resistance to the tendon tissue. While collagen type IV is the main component of the basal membrane, collagen types III and V originate thin fibrils that interwine with collagen type I. Collagen types III and V are both responsible for the elasticity of the tendon tissue. The type I collagen molecule is a heterotrimer consisting of two alfa-1(I) and one alfa-2(I) chains. Some studies have shown that normal PTT has, in its extracellular matrix, 95% of collagen type I and small amounts of collagen type III, IV, and V. 12,13 These components confers parallel bundles on the tendon structure and allow elastic and mechanical resistance to PTT.According to biochemical studies, posterior tibial tendinopathy has shown, in its extracellular matrix, an increase of 53.6% in collagen type III and 26.4% of collagen type V and a decrease of 40.4% in the alfa-1 chain and 42.5% in the alfa-2 chain of collagen type I. Authors have concluded that this different biochemical pattern found in the posterior tibial tendinopathy is a possible explanation to decrea...
