Intra- and interobserver variability of magnetic resonance imaging for quantitative assessment of abductor and external rotator muscle changes after total hip arthroplasty

MRI is an accurate and reliable test for evaluation of soft tissue structures in patients who have undergone THA. MRI evaluation of abductor muscles yields reproducible results on the THA side and on the NOS. Prosthesis artifacts limit evaluation of the gluteus minimus muscle on the THA side and cannot be recommended. Since interobserver variability was always higher than intraobserver variability, follow-up examinations should ideally be performed by the same reader in order to obtain clinically meaningful results.