Revision surgery after total hip or knee arthroplasty is an ongoing issue due to an increasing number of primary surgeries. Patients seek physicians due to pain. The cause is divided between loosening, infection or chronic pain. Some are operated on the suspicion of a chronic infection. However, postoperative microbiological testing does not always correlate with the suspicion and the operation may have been superfluous.

The objective is to employ a highly advanced diagnostic algorithm based on state of the art diagnostic techniques in order to improve the basis of preoperative diagnosis. Through this approach treatment can be given according to the causal problem.

The aim of the project is to improve the preoperative diagnosis of infections and persistent pain in patients with prosthesis-related problems. Prosthesis infection is of chronic nature. Recent research has shown that one important explanation of this is the formation of encapsulated 'bacterial communities' on the surface of the prosthesis, where bacteria are well protected against antibiotic treatment. Surgery is therefore necessary for this patient group. But it is important to make diagnosis more accurate than it currently is today. In contrast, patients with persistent pain, but no indication of infection or prosthetic loosening, are best served by avoiding surgery, and instead receiving a treatment that is directed against the chronic pain condition. Based on the pain research carried out at Aalborg University, an understanding of chronic pain and treatment principles that would be beneficial for this patient group have been developed.

The investigators want to:

1. describe the postoperative course of specific serologic markers for primary and secondary total hip arthroplasty (THA) and total knee arthroplasty (TKA).
2. describe the bacteriologic diversity through revision of THA and TKA using cultivation techniques and molecular biological analysis comprehensive fluorescence in-situ hybridization (FISH), cloning and phylogeny, quantitative polymerase chain reaction (qPCR) and gene expression profiling.
3. describe pain and sensitization with new diagnostic technology in patients with stem loosening, suffering from infection and pain.
4. apply to a new diagnostic algorithm for the diagnosis of infection and pain following THA and TKA, which includes pain assessment, diagnostic X-ray, bone scintigraphy, PET scan, percutaneous biopsy, specific serologic parameters and molecular biological analysis.
5. describe the effect of the diagnostic algorithm, compared with a descriptive retrospective cohort of patients who have undergone revision of THA or TKA.

Inclusion Criteria:

• Patients undergoing primary uncemented total hip-joint replacement surgery
• Patients undergoing primary hybrid total hip-joint replacement surgery
• Patients undergoing total knee-joint replacement surgery

Exclusion Criteria:

• Patients younger than 18 years old
• Unability to speak or read Danish
• Pregnancy or lactating
• Bilateral disease
• Cancer
• Inability to give informed consent

Primary care clinic.