[18F]-fluoride PET/CT analyses of postoperative bone mineralisation adjacent to femoral stems at THA: a randomised clinical trial.

Purpose: The long-term success of total hip arthroplasty (THA) is dependent on support from the periprosthetic bone bed. We present a randomised study using 18F-fluoride Positron Emission Tomography/Computerised Tomography (F-PET/CT) to analyse bone metabolism in periprosthetic bone adjacent to femoral stems following THA surgery. To compare bone metabolism to cemented Exeter and uncemented SP-CL stems, patients with hip osteoarthritis were randomly assigned for THA with either cemented or uncemented femoral components. The results were analysed with F-PET/CT.

Patients and methods: In 28 patients (28 cases) with hip osteoarthritis, a THA was performed. The patients received either an uncemented or a cemented femoral stem. The contralateral healthy femur was used as reference for normal bone metabolism. Patients' clinical scores, radiography and F-PET/CT were analysed at 4, 16 and 36 weeks postoperatively. PET results were analysed and presented in 13 regions of interest (ROI) adjacent to the whole stem-bone interface.

Results: Clinical results were good in all patients, and no major complications were recorded. At radiography, all stems were stable. PET analyses after 4 weeks showed that bone mineralising activity was significantly higher around the SP-CL stems, both compared to the Exeter group and to the contralateral healthy reference femur group. The SP-CL also had prolonged raised activity compared to the Exeter group.

Conclusions: A detailed analysis of bone formation patterns on the implant surface shows that early healing is associated with higher mineral deposition using the uncemented SP-CL stem.

Clinical trial registration: The study was registered at ClinicalTrials.gov (identifier NCT02320682).