Introduction
The prosthetic treatment of the hip joint is one of the most promising and frequently performed procedures in orthopedics. It is used in cases of osteoarthritis, inflammatory changes, necrosis, fractures, malpositions or malformations of the hip in order to alleviate pain for the patient and restore mobility. Unfortunately, the inserted joints do not last forever and after a few years without pain or complications, pain in the operated joint can occur. A possible complication is the loosening of the hip prosthesis. Most inserted prostheses do not loosen, but in individual cases the hip prosthesis may loosen.
Causes
Loosening of the hip prosthesis is caused by changes in the connection between prosthesis and bone in cementless hip prostheses or between bone cement and the bone in cemented hip prostheses. The changes can be caused by aseptic or septic processes. The main causes of aseptic prosthesis loosening are abrasion particles (e.g. from polyethylene, cement, ceramics, metal), which are released by abrasion between the artificial femoral head and the acetabulum as part of the daily stress on the joint.
Over the years, they can cause tissue reactions between bone and prosthesis. The detached particles of the prosthesis can also cause focal points of inflammation that cause the bone and prosthesis to diverge. These processes damage the bones and draw the adjacent soft tissue into sympathy. It is also possible, however, that a prosthesis did not show sufficient stability already at the time of implantation and therefore the prosthesis loosens even more over time. Septic processes that contribute to prosthesis loosening can be caused by minimal infection during surgery.
Symptoms
The cardinal symptom that leads to the examination in addition to the regular routine checks is pain. In combination with other signs that are typical for a loosening of the hip prosthesis, the suspicion of a loosening will become stronger. Pain is not the only parameter, because the intensity of pain varies depending on the location of the loosening of the hip prosthesis.
While cup loosening is often painful, stem loosening is very painful. Among other things, the pain also leads to a rapid shortening of the possible walking distance and a feeling of uncertainty or instability when walking. In addition, the patient may feel that he or she has lost control over the affected leg.
Another sign of loosening is a newly occurring difference in leg length. However, leg shortening is a sign that only occurs in an advanced stage. Further signs of loosening can be identified during a radiological examination using imaging techniques.
Bone is partly destroyed. At the same time, however, new bone formation occurs. The loosening of the hip prosthesis also causes the prosthesis to change its position, the shaft position changes and the acetabulum moves within the joint.
These changes can be detected just as easily as damage to the implant or the anchoring materials. The loosening of the hip prosthesis causes pain in the thigh. In contrast to cup loosening, which rarely causes pain, shaft loosening in particular causes severe pain in the thigh.
The pain in the thigh when the hip prosthesis is loosened is often pain when starting or under load when standing or walking. However, the pain from the thigh can also radiate into the groin, buttocks or knee joint of the affected side. However, not all pain in the thigh can be attributed to loosening of the hip prosthesis and the doctor will rule out other possible differential diagnoses through a conversation and examinations. The pain in the thigh could also be caused by nerve irritation, for example.
