Hip Prosthesis Failure: Causes of Aseptic Loosening and Periprosthetic Infections.
Material Wear (Aseptic Loosening)
This is the leading cause of hip prosthesis revision, especially in the medium and long term. It occurs when the prosthesis fails to fix properly, either because the cement mantle has failed or due to the absence of adequate bone growth around the implant in non-cemented prostheses.
The reason for this loosening depends on many factors. For example, in non-cemented prostheses, if adequate stability is not achieved during Primary Fixation, abnormal micromovement can occur around the implant, leading to long-term loosening and patient pain. For cemented prostheses, factors can range from inadequate cementation technique to polyethylene wear and the subsequent inflammatory reaction to its particles.
The main symptom observed in these patients is pain that appearing during movements involving the prosthesis. When the loosening is severe, the pain stops being mechanical and becomes chronic, as it is felt constantly due to the inflammation caused by prosthetic instability.
Another important symptom is a feeling of "failure" or instability, as if the Osteoarthritis had returned. This happens because the reduced range of motion in the joint causes the muscles to lose trophism (wasting).
Periprosthetic Hip Infection (Septic Loosening)
This is one of the most feared prosthesis failures for both joint surgeons and patients because its treatment is complex, lengthy, and impacts the patient's quality of life. When we perform a partial or total hip replacement, we are implanting an inert element through the skin, our natural protective barrier. The skin houses bacteria that coexist with us harmlessly as long as they remain on the epidermal surface.
During the process of making the surgical incision and implanting the prosthesis, bacteria or fungi can enter and cause an infection. It is important to clarify that with any surgical procedure, there is a risk of germs entering at a deep level. We take multiple preventive measures to avoid this; however, it is difficult to have total control over all variables, and thus it can likely never be avoided in absolutely every case.
These microorganisms can reach the surface of the implant and create a perfect environment to protect themselves from the immune system, creating an infection that is impossible to eliminate without removing the implant in most cases. This is especially true for chronic cases or those caused by germs entering the joint from infections in other parts of the body via the bloodstream.
Infections mainly manifest during the immediate postoperative period with pain, excessive swelling, fever, and drainage from the surgical wound, potentially leading to septicemia. Progressive pain that prevents the patient from advancing in recovery is also common. In chronic cases, the patient may frequently present a small, round, or puncture-like wound that drains constantly.
