Allogenic bone graft viability after hip revision arthroplasty assessed by dynamic [ 18 F]fluoride ion positron emission tomography

Abstract

The biological fate of allogenic bone grafts in the acetabular cavity and their metabolic activity after acetabular augmentation is uncertain but is most important for the stability of hip implants after hip revision arthroplasty. The aim of this study was to quantify regional bone metabolism after hip replacement operations. Dynamic [18F]fluoride ion positron emission tomography (PET) was used to investigate the metabolic activity of acetabular allogenic bone grafts and genuine bone, either 3-6 weeks (short-term group, n = 9) or 5 months to 9 years (long-term group, n = 10) after hip revision arthroplasty. Applying a three-compartment model, the fluoride influx constant was calculated from individually fitted rate constants (Knlf) and by Patlak graphical analysis (Kpat). The results were compared with genuine cancellous and cortical acetabular bone of contralateral hips without surgical trauma (n = 7). In genuine cortical bone, Knlf was significantly increased in short- (+140.9%) and long-term (+100.0%) groups compared with contralateral hips. Allogenic bone grafts were characterised by a significantly increased Knlf in the short-term group (+190.9%) compared with contralateral hips, but decreased almost to the baseline levels of contralateral hips (+45.5%) in the long-term. Values of Knlf cor-related with the rate constant K1 in genuine (r = 0.89, P<0.001) and allogenic bone regions (r = 0.79, P<0.001), indicating a coupling between bone blood flow and bone metabolism in genuine bone as well as allogenic bone grafts. Kpat values were highly correlated with Knlf measurements in all regions. In conclusion, [18F]fluoride ion PET revealed the presence of an increased host bone formation in allogenic bone grafts early after hip revision arthroplasty. In contrast to genuine cortical bone, allogenic bone graft metabolism decreased over time, possibly due to a reduced ability to respond to the same extent as genuine bone to elevated metabolic demands after surgery.

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

“…The signs of bone healing seen on the plain radiographs were supported by the swiftness of the healing process that we noted using PET. We have found one previous publication that analyzed the healing of a morselized bone allograft with PET (Piert et al 1999). The bonegraft that was not reduced by fat had become "slightly condensed" in an acetabular defect, which probably means that it was less tightly impacted than in our study.…”

Long-Term Precision of 18F-Fluoride PET Skeletal Kinetic Studies in the Assessment of Bone Metabolism

“…The dose of 90 MBq of fluoride used in the current study is approximately a third of that used in clinical practice for a whole-body 18 F-fluoride scan in the United Kingdom. Lower activities are associated with increasing variability (16), and enhanced precision of skeletal kinetic parameters may therefore be expected with higher 18 F-fluoride activity and more robust statistics within the ROI. The moderately small number of subjects who participated in the study resulted in relatively large statistical errors in the precision estimates.…”

“…This technique can be used to quantify therapeutic response in those with osteoporosis (3) and those with Paget's disease treated with bisphosphonates (8). It may also have a role in the assessment of physiologic events such as bone graft revascularization and osteogenesis after allogenic bone grafts (6,(16)(17)(18).…”

Use of mesenchymal stem cells to enhance bone formation around revision hip replacements

“…[12][13][14][15] Scintigraphic examination demonstrated that allograft showed increased activity compared with the surrounding bone, suggesting new bone formation within the grafts. 16 However, Piert et al 17 used Dynamic [18F] fluoride ion positron emission tomography (PET) to investigate the metabolic activity of allograft and concluded that the metabolic level was increased initially after surgery but decreased over time indicating allograft resorption. An animal study by Frei et al 18 also showed significant allograft resorption at 6 weeks, resulting in medullary canal widening and an unstable implant.…”