Selective epiphysiodesis of the triradiate cartilage for treatment of residual experimental acetabular dysplasia.

BACKGROUND

The purpose of the study is to evaluate the effect of a selective epiphysiodesis of the ilioischial limb of the triradiate cartilage (TC) in an experimental dysplastic hip.

MATERIALS AND

METHODS

A hip dysplasia was obtained in 23 New Zealand rabbits 3 weeks old by immobilizing the knee in extension with a K-wire, in 4 groups: (1) control group; (2) K-wire maintained until sacrifice; (3) K-wire removed 1 week later without epiphysiodesis; and (4) K-wire removed 1 week later with selective epiphysiodesis of the ilioischial limb of the TC. Radiographic evaluation was performed previous to knee immobilization, after K-wire removal and after sacrifice. Acetabular index (AI), Sharp's angle, ACM angle, acetabular floor thickness ratio (AFTR) were measured and presence of dysplasia, subluxation, or dislocation was noted. The acetabular version, the acetabular sector angles, and the pelvis rotation were obtained using CT evaluation. A morphology score was developed and a morphometric study of both proximal femur and acetabulum was performed.

RESULTS

No differences between groups in the radiographic assessment before immobilization or K-wire removal were found. All cases in group 2 showed dysplasia, subluxation, or dislocation of the hip. The radiographic assessment of group 4, compared with group 3, showed a lower AI (P=0.027), Sharp's angle (P=0.005), ACM angle (0.049), and AFTR (P=0.017). No differences between groups 1 and 4 regarding AI (P=0.08), Sharp's angle (P=0.484), and AFTR (P=0.639) were obtained. The morphology score was lower in group 4 than in groups 2 and 3. Group 4 showed a deeper acetabulum than group 2 (P=0.008) and group 3 (P=0.033), while it was similar to group 1 (P=0.364).

CONCLUSIONS

A selective epiphysiodesis of the ilioischial limb of the TC in a dysplastic hip normalized the radiographic measurements of the acetabulum and the acetabular deepness, and it improved the previous gross morphology of the capsule, labrum, and ligamentum teres in rabbits.

LEVEL OF EVIDENCE: Level II-therapeutic study.