Abstract
Endoprosthetic reconstruction for pathologic acetabular fractures is associated with a high risk of periprosthetic joint infection. In this setting, bone defect reconstruction utilising co-delivery of a synthetic bone substitute with an antibiotic, is an attractive treatment option from both, therapeutic and prophylactic perspective. We wished to address some concerns that remain regarding the possible presence of potentially wear inducing particles in the periprosthetic joint space subsequent to this procedure.
We analysed a drain fluid sample from an endoprosthetic reconstruction of a pathologic acetabular fracture with implantation of a gentamicin eluting, biphasic bone graft substitute, consisting of 40% hydroxyapatite (HA) and 60% calcium sulphate (CERAMENT G), into the residual peri-acetabular bone defect. This sample was divided into two 1.5ml subsamples, to one of which 100mg HA particles were added as control before burning off all organic substance at very high temperature. These heat treated samples were then examined with scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX) and compared to a reference sample consisting of HA particles only.
On SEM, hydroxyapatite particles were readily recognisable in the control and reference samples, whereas only very few particles over 2μm were apparent in the ”pure” drain sample. EDAX revealed that very large amounts of salts were present in both drainage samples. The pure drainage sample however, contained markedly lower amounts of calcium and phosphate compared to reference and control samples. No HA particles as such, were seen in the pure sample, however their presence cannot be excluded with absolute certainty, as some particles might have been hidden within the large salt conglomerates.
We could not find clear evidence that the drain fluid really contained HA particles. More thorough investigations are needed and future analyses with prior removal of the high salt content would likely yield more conclusive results.
