Type I collagen alpha1 Sp1 polymorphism and the risk of cruciate ligament ruptures or shoulder dislocations

BACKGROUND: Cruciate ligament ruptures and shoulder dislocations are often caused by trauma, but predisposing intrinsic factors might also influence the risk. These injuries are more common in those with a previously injured sibling, an observation that might indicate a genetic predisposition. It is well known that polymorphisms in the collagen I gene are associated not only with osteoporosis and osteoporotic fracture risk, but also with osteoarthritis. HYPOTHESIS: Because collagen I is abundant in ligaments and tendons, the authors hypothesized that collagen I alpha1 Sp1 polymorphism also was related to the occurrence of cruciate ligament ruptures and shoulder dislocations. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: A total of 358 patients and 325 randomly selected population-based female controls were included in the study. Of the cases, 233 had a cruciate ligament rupture and 126 had had a shoulder dislocation. Age-adjusted odds ratios (ORs) with 95% confidence intervals (CIs) estimated by unconditional logistic regression were used as measures of association. RESULTS: Compared with the homozygous SS category, the heterozygous participants displayed a similar risk (OR, 1.06; 95% CI, 0.76-1.49), whereas the ss genotype was underrepresented in the injured population compared with the controls (OR, 0.15; 95% CI, 0.03-0.68). This latter estimate was similar for both cruciate ligament ruptures and shoulder dislocations, and was furthermore not modified by general joint laxity. CONCLUSION: The authors found a substantially decreased risk of these injuries associated with collagen type I alpha1 Sp1 polymorphism. The study might encourage other investigators to consider further research in the area of genes and soft tissue injuries.