LAUSR

The isotope bone scan (Fig. 1) demonstrates significantly reduced radiotracer activity in the right lower limb in keeping with critical ischaemia following the patient’s hip replacement surgery. Increased activity at the left knee joint was due to osteoarthritis. The preand post-operative radiographs (Fig. 2) show a right intracapsular proximal femoral fracture sustained following a low energy fall and the subsequent implanted femoral prosthesis. Both radiographs demonstrate arterial calcification, signifying peripheral vascular disease. The isotope scan was undertaken shortly following surgery to investigate for skeletal metastases secondary to the known pulmonary adenocarcinoma of mucinous sub-type. Due to the marked asymmetry of uptake between the lower limbs on isotope bone scan, an urgent CT angiogram was arranged, confirming occlusion of the right superficial femoral (Fig. 3a) and popliteal arteries (Fig. 3c). The patient was managed conservatively with heparin. Skeletal scintigraphy is the most commonly utilised radionuclide study to evaluate skeletal metastatic disease due to its widespread availability, relatively fast acquisition time and high sensitivity. A Technetium-99m-labelled diphosphonate tracer is used, which rapidly accumulates in bone following administration [1–3]. Radiotracer uptake is dependent on multiple factors including blood flow and bone formation as well as patient hydration, renal function and age [4]. In a single-phase scan, imaging is often delayed beyond 2-h to allow for improved soft tissue clearance and target to background contrast. A triplephase acquisition obtains additional early blood flow and blood pool images to assess hyperaemia and articular permeability respectively [4]. Vascular injuries are a rare postoperative complication following hip replacement surgery,