Tenotomy of gluteus medium and gluteus minimus is associated with dysplasia of the hip: an experimental study in rabbits.

[BACKGROUND] Atrophy of the gluteus medius and gluteus minimus has been reported in patients with developmental dysplasia of the hip (DDH). We aimed to investigate whether atrophy of the gluteus medius and gluteus minimus is associated with DDH.

[METHODS] Twenty white New Zealand rabbits were divided into 2 groups in our experiment. In group 1, one limb of each rabbit was randomly selected for tenotomy of the gluteus medius and gluteus minimus, with the other side serving as a sham control. In group 2, one limb of each rabbit was randomly selected for intramuscular injection of botulinum toxin to induce atrophy of the gluteus medius and gluteus minimus, with the other side serving as a sham control by injection of equal volumes of normal saline. Acetabulum and muscles were evaluated by ultrasound, X-ray imaging, shear wave elastography, and histology with hematoxylin-eosin (H&E) staining.

[RESULTS] Atrophy of the gluteus medius and gluteus minimus was observed on the experimental side in both groups. Early dysplastic changes in the hips on the tenotomy side was observed on the radiographs with an increased acetabular index (40.0 ± 6.7° vs 24.1 ± 1.9°, P < 0.001) compared with the control side in group 1. No dislocation of the hips was observed. No dysplasia of the hips was observed on the botulinum-toxin side in group 2 with similar acetabular index on both sides (25.0 ± 3.7° vs 24.1 ± 1.9°, P = 0.13).

[CONCLUSIONS] Tenotomy, not atrophy, of the gluteus medius and gluteus minimus is associated with early changes of DDH.