Patella alignment abnormality in patients with developmental dysplasia of the hip

The purpose of this study was to assess the influence of developmental dysplasia of the hip (DDH) on patella alignment.

The radiographic data of all the patients who met the inclusion criteria from January 2015 to July 2017 were reviewed, including the quadriceps angle (QA), patellar lateral tilt (PTA), sulcus angle (SA), lateral shift of patella (LSP), and lower limbs alignment. The patients were divided into three groups in accordance with lateral center-edge angle (LCE) and femoral neck torsion angle (FNTA): group A (LCE > 25° and FNTA < 40°), group B (LCE < 20° and FNTA < 40°), and group C (LCE < 20° and FNTA > 40°).

One hundred thirty-eight patients with 230 hips (115 females and 23 males) were recruited with an average age of 22 years. There were significant differences between group A and group C as well as group B and group C in QA, SA, PTA, LSP, and lower limbs alignment (p < 0.01). There were no differences in SA, PTA, LSP, and lower limbs alignment (p >0.05) and significant differences in QA (p < 0.01) between group B and group C. The "Pearson's" correlation analysis of the data in total of group B and group C showed that FNTA and LCE and QA and LCE were negatively correlated, whereas FNTA and QA, PTA, SA, and lower limbs alignment as well as SA, PTA, and lower limbs alignment were positively correlated.

Patients with DDH not only have hip joint change, but also have the patella alignment abnormality, which may lead to patella instability. In the clinic, we should pay attention to the hip development of the patella instability patients for excluding DDH. Level of Evidence: Prognostic level III.