Causes

There are various possible causes for hip luxation after a TEP, whereby the main cause can be a malfunction of the operated patient after the operation. However, problems with the actual prosthesis or the surgical site can also be the reason for a luxation. It is important to distinguish whether adequate trauma or normal, everyday movement was the cause of the hip dislocation.

Although the risk of hip luxation with a hip prosthesis can be reduced, it can never be completely eliminated. For example, blows, falls or accidents in which the hip is exposed to high pressure can cause dislocation. Similarly, excessive movements that overstrain the prosthesis can also lead to dislocation, although depending on the access route during surgery, certain movements may be more likely to be the cause.

In the case of a side-front surgical approach, the risk of a hip luxation after a TEP is greatest in the case of strong external rotation, a rotation of the leg around the longitudinal axis with the foot pointing outwards, or adduction, i.e. leading the affected leg inwards. If the prosthesis was inserted from the side-back, excessive hip flexion and internal rotation are the main causes. Movements that correspond to this pattern are sitting down or standing up or deep bending. However, if these movements are everyday and controlled movements, a prosthesis that is not optimally seated or, for example, loosened in the event of an infection, may be the cause of hip luxation after TEP surgery, which must be surgically corrected.Finally, poorly developed and weak musculature of the patient can also lead to over-mobility in the joint and thus be the cause of dislocation in a total endoprosthesis. Less frequently, material defects are also considered.

Diagnosis

When treating a hip dislocation after a hip prosthesis, the medical history, inspection and instrumental methods lead to a diagnosis. First of all, the patient should be asked about a triggering factor, such as trauma or the previous movement. An inspection will then lead to a diagnosis if a shortened leg that is incorrectly rotated outwards or inwards is noticeable.

Important for the diagnosis is an x-ray of the hip in the anterior and lateral plane to assess the extent of hip luxation after TEP surgery and to be able to rule out loosening or misfitting of the prosthesis. If this is not sufficient, computer tomography can provide more accurate images and a reliable assessment of the hip luxation. After this, a decision is also made as to whether or not further surgery is necessary.

If no abnormalities are detected, the movement sequence and thus possibly the dislocation mechanism can be reconstructed in an image converter by means of moving X-ray images. In this way, the diagnosis of luxation with a hip prosthesis can be objectified. In addition, inflammation parameters in the blood should be measured to rule out infection (see: Complication of hip prosthesis surgery).