Total hip replacement is the well-established surgical method for treatment of hip osteoarthritis and related diseases. The outcome of the procedure is commonly satisfactory and most patients will not need any revision surgery. However, the procedure has its complications, including (1) periprosthetic infection, (2) mechanical loosening caused by wear particles and (3) adverse reaction caused by metal ions released from metal-on-metal bearing surfaces. The unsolved clinical problem is related to the differential diagnosis of these conditions. The purpose of this prospective clinical study is to compare the efficacy of two techniques of PET/CT imaging in the differential diagnosis of these complications. Positron Emission Tomography (PET)/Computed Tomography (CT) imaging, performed during a single day, will include the head-to-head comparison of 18F-Fluoro-D-Glucose (18F-FDG) PET/CT and 68Gallium-citrate (68Ga-citrate) PET/CT imaging.

(68Ga) gallium citrate is a novel PET tracer aimed for detection of skeletal infections. It has not been previously applied to diagnose periprosthetic joint infections in arthroplasty patients. This exploratory prospective study, representing the first of its kind, examines the use of 68Ga-citrate as a diagnostic tool of periprosthetic infections aside with 18F-FDG tracer as the standard reference.

The first study group (n=10) will include total hip replacement patients without infection. The recruited patients should suffer from pain and/or functional impairment due to adverse reaction to metal debris (ARMD) caused by metal-on-metal bearings. The diagnosis of ARMD should be based on metal artifact reduction sequence magnetic resonance imaging (MARS-MRI). The patients will undergo the same-day comparison of the two PET/CT tracers.

The second study group (n=10) will include total hip replacement patients with bacteriologically confirmed periprosthetic joint infection. The third group (n=10) will include patients with aseptic loosening of total hip prosthesis.

Inclusion Criteria:

• Adult patients with uncemented total hip replacement
• American Society of Anesthesiology score I-III
• Group 1: local symptoms and MRI findings of the operated hip fulfilling the criteria of ARMD due to metal-on-metal bearings of the hip prosthesis, infection ruled out
• Group 2: bacteriologically verified periprosthetic infection of the hip prosthesis
• Group 3: local symptoms and radiographic findings of the hip prosthesis fulfilling the criteria of aseptic mechanical implant loosening, infection ruled out

Exclusion Criteria:

• any related condition of the index hip which requires immediate surgical intervention, such as a septic infection or a periprosthetic fracture
• any systemic disorder or condition (ASA IV) which makes the patient an unlikely candidate for revision surgery of the affected hip implant