Rapid bone and blood flow formation in impacted morselized allografts: positron emission tomography (PET) studies on allografts in 5 femoral component revisions of total hip arthroplasty.

5 patients were revised with impaction of morselized frozen allograft and a cemented total hip arthroplasty (THA) because of loosening and osteolysis of a primary hip arthroplasty. Plain film radiographs of the stems showed stable implants in all patients 15-24 months after surgery. The clinical results were good. We used: 1) Positron Emission Tomography (PET) to evaluate vascularization and new bone formation in the allograft, 2) kinetic [18F]-fluoride PET to produce quantitative images, interpreted as new bone formation in the allograft surrounding the femur stem, 3) [15O]-water PET to quantify bone blood flow, and 4) [15O]-carbon monoxide to determine blood volume. After surgery, all patients were evaluated twice: at 1-8 days and 12 months and 3 patients were also studied at 4 months. As early as at 8 days after surgery, blood flow and bone formation had increased greatly adjacent to the allograft. At 4 months blood flow and bone formation were about the same, but activity was highest in the graft material. At 1 year after surgery, blood flow had declined to the levels of the contralateral femur diaphysis in most of the graft bed. These findings using the PET technique showed that angiogenesis and new bone formation occurred early after impaction of morselized bone allografts around the femoral component in revision THA. We found that PET is a sensitive method for evaluating neovascularization and bone formation in the graft beds.