Two major complications of hip replacement are loosening and infection. Reliable differentiation between these pathological processes is difficult since both may be accompanied by similar symptoms. Our aim was to assess the diagnostic ability of triple-phase bone scanning (TPBS) and positron-emission tomography (PET) to detect and differentiate these complications in patients with a hip arthroplasty. Both TPBS and PET were performed in 63 patients (92 prostheses). The radiotracer for PET imaging was ¹⁸F-fluorodeoxyglucose (FDG). Image interpretation was performed according to qualitative and quantitative criteria although the final diagnosis was based upon either surgical findings or clinical follow-up.

The sensitivity, specificity and accuracy of PET was 0.94, 0.95 and 0.95 respectively, compared with 0.68, 0.76 and 0.74 for TPBS. We found that an image interpretation based exclusively upon quantitative criteria was inappropriate because of its low selectivity. The histological examination indicated that increased periprosthetic uptake of FDG in patients with aseptic loosening was caused by wear-induced polyethylene particles and the subsequent growth of aggressive granulomatous tissue.

In 21 children with myelomeningocele who underwent kyphectomy for congenital kyphosis of the lumbar spine, aortography revealed no case in which the aorta followed the spinal curvature. Many anomalies of the intercostal and segmental arteries were demonstrated which were only in part associated with deformities of the respective vertebral bodies. The kidneys, which were frequently malformed, often lay within the kyphosis and were therefore at risk of operative damage. We conclude that the aorta is not at risk and that aortography is not usually necessary before kyphectomy, except in patients who have undergone prior abdominal surgery. Non-invasive methods (ultrasound, CT or MRI) should be used to detect malpositions and malformations of the kidneys.