Absence of Ligamentum Teres in Developmental Dysplasia of the Hip

Background: Ligamentum teres is hypertrophied and should be resected in developmental dysplasia of the hip (DDH). We have observed a relatively high prevalence of absence of ligamentum teres (ALT) in severe DDH. The purpose of this study was to determine: (1) the percentage of ALT in DDH; (2) the risk factors correlating with ALT; and (3) the pathologic characteristics of DDH with ALT. Methods: In 2012, 123 patients were hospitalized for open reduction of DDH. Clinical records were retrospectively reviewed. The distribution of ALT was discerned. The risk factors correlating with ALT were analyzed. The pathologic changes of the DDH with ALT were observed. Results: For the 123 patients, there were 14 males and 109 females with a mean age of 2.2 +/- 1.7 years old. Forty-one cases were diagnosed with bilateral DDH, and 27 of them had open reduction for both hips. Thus, 150 hips were included. According to the Tonnis grading, there were 1 grade I, 43 II, 67 III, and 39 IV patients. During operation, the ligamentum teres was confirmed absent in 24 patients (28 hips, 18.67%), 22 of the hips with ALT was Tonnis grade IV (78.57%). It was present in the other 99 patients (122 hips). The difference of ALT among different grade (chi(2) = 43.959, P= 0.000) and different age (chi(2) = 10.748, P= 0.008) showed statistical significance, respectively. Logistic regression revealed only grading was the correlation factor of ALT (P= 0.000). Pathologically, the femoral head was extremely small. The cartilage surface showed erosion-like change. The acetabulum was also diminutive but could match the femoral head well. Conclusions: At our institution, 18.67% of DDH needing open reduction was combined with ALT. The degree of dislocation was the only correlation factor of ALT. If the Tonnis grade was high, the hip was often associated with ALT.