[Sonographic changes after total hip joint replacement]

The value of ultrasonographic imaging after total hip arthroplasty (THA) has not been described in the literature so far.

The typical postoperative sonographical findings are to be presented thus creating a basis for detecting pathological alterations.

73 consecutive patients after THA were sonographically and clinically examined at the beginning and the end of the clinical rehabilitation phase. Laboratory tests detecting signs of inflammation and coagulation disorders were also performed.

In the early postoperative phase collection of liquid and its delayed resorption are the most important findings. The haematoma of the joint is usually organised within three weeks after the operation. It could be visualised in all patients as a region of homogeneous, slightly echogenic appearance--not clearly distinguishable from the surrounding tissue and not compressible. Areas of low echogenicity were rarely seen. The forming of a neo-capsule could be detected from the ninth postoperative week onwards. Peri-articular ossification was not seen in this study. A loosening of prosthetic material did not occur. In the area of surgical approach irregularly shaped slightly echogenic and hardly compressible zones representing large haematomas could be found. The volume of these lesions could not be measured exactly due to their highly irregular shape. We did not observe large areas of seroma or liquid haematoma interfering with the rehabilitation process.

Experienced examiners are capable of demonstrating the sonographic features representing signs of the healing process. Thus pathological developments can be detected and adequate therapeutic measures be taken. Future studies will have to show to which degree ultrasonography can become relevant in the diagnosis of endoprosthetic loosening.