To investigate the stress and strain feature at the acetabular cup-bone interface at different heights of the Crowes Ⅱ/Ⅲ DDH acetabular implant.

The hip CT scan data of three Crowe Ⅱ/Ⅲ DDH patients were used for acetabular three-dimensional model reconstruction, then the cup models were implanted at vertical distance of 15, 21, 30mm respectively from the inferior edge of the acetabulum. The model was transformed into a three-dimensional finite element mesh model, and applied a static load to record the stress and strain at the cup-bone interface. The differences of the stress and strain at the cup-bone interface were analyzed by paired-sample t test or Wilcoxon rank test.

The minimal value of maximal stress was appeared at the vertical height of 21 mm, patient A 10.03 Mpa, patient B 17.67 Mpa and patient C 14.99 Mpa. At the height of 15mm and 30mm, the maximal values of maximal stress of the cup were as follows: patient A 20.64 and 12.03 Mpa, patient B 22.06 and 23.02 Mpa, patient C 34.72 and 17.88 Mpa. Paired-samples t test revealed no significant difference in the stress and strain at the cup-bone interface(P>0.0167, P value was corrected). There was no specific pattern on the strain of the acetabulum and the bone tissue at different heights.

For total hip arthroplasty in the patients with Crowe Ⅱ/Ⅲ DDH, the cup model implanted upward appropriately can decrease the maximal stress of the cup model.