Bone graft substitutes in active or suspected infection. Contra-indicated or not?

Treatment of infection in clinical orthopaedic and trauma care is a time consuming and costly endeavour. More than once, it will lead to extraction of implant material and additional surgical interventions. Currently, debridement, implantation of PMMA beads impregnated with antibiotics most often with implant exchange are the gold standard for deep infection treatment. Recently bone graft substitute materials such as calcium phosphate, collagen fleeces and bioglasses have appeared for specific use in infection treatment. Although these materials show great potential, their supporting level of evidence is still limited. This review paper provides an overview of current understanding and therapies for infection treatment and provides concepts for the use of new developed biomaterials in infection treatment. Furthermore, the benefits and risks of using biomaterials in infection treatment are discussed and the level of evidence of a number of new materials is presented.

The use of a bioresorbable nano-crystalline hydroxyapatite paste in acetabular bone impaction grafting.

Calcium phosphates such as TCP-HA granules are considered promising bone graft substitutes. In the future, they may completely replace allograft bone for impaction grafting procedures. Mechanically, acetabular reconstructions with TCP-HA granules show high stability, however this is partly caused by excessive cement penetration, which is unfavourable from a biological perspective. It has been hypothesised that mixtures of morselised cancellous bone grafts (MCB) and/or TCP-HA granules with a nano-crystalline hydroxyapatite paste (Ostim) may reduce cement penetration while maintaining adequate implant stability and biocompatibility of the graft mixture. To investigate this hypothesis, destructive lever-out tests and in vivo animal test were performed with various combinations of materials. Mechanically, the addition of 10% Ostim to mixtures of MCB and/or TCP-HA granules reduced cement penetration and resulted in a mechanical stability comparable to pure allograft (the current gold standard). Biologically, the application of Ostim with MCB or TCP-HA granules did not hamper the biocompatibility of the materials. Ostim was mostly osseous-integrated with MCB or TCP-HA granules after 8 weeks. Also, non-osseous-integrated Ostim remnants were observed. In tartrate resistant acid phosphatase stained sections, these few non-osseous integrated Ostim remnants were actively being resorbed by osteoclasts. In conclusion, Ostim HA-paste could be a valuable addition when TCP-HA ceramic granules are being used for acetabular bone impaction grafting procedures.