AddBIO: Clinical results – Zolidd improves function of orthopedic external fixation pins

AddBIO AB, a subsidiary of Accelerator Nordic AB, has developed Zolidd®, a proprietary add-on for bone implants that enhances the bone holding power by local administration of bisphosphonate, a drug that increases local bone density. A randomized clinical trial shows
that Zolidd improves the function of orthopedic external fixation pins.

External fixation with threaded pins is an easy and practical method for (minimally invasive) fracture fixation. It is mainly used for temporary fixation, because of problems with loosening and pin-tract infection, especially in spongeous (porous) bone. This problem can be largely overcome by the use of a hydroxyapatite (HA) coating. HA enables bone formation directly on the pin surface, which reduces loosening, but creates new problems such as difficult and painful removal. In the present study, implants with bisphosphonate were compared to implants coated with HA, as well as plain stainless steel implants.

“The study shows that local bisphosphonate improves the fixation in spongeous bone to the same degree that HA does. However, removal was as easy as with uncoated pins”, says Professor Per Aspenberg, Linköping University Hospital, co-author of the study and co-founder of AddBIO.

”This is an important study. Zolidd has now been shown to outperform presently used devices in both orthopedic and dental indications. This is very encouraging when we take the next steps in commercializing Zolidd”, says Ulf Sewerin, CEO of AddBIO AB.

Zolidd is the first application from a platform technology designed for local administration of drugs from medical implants, developed by Professor Per Aspenberg, Linköping University, and Professor Pentti Tengvall, Gothenburg University. A nanometer-thin protein layer is attached to the implant
surface and a bisphosphonate drug is embedded therein. When placed in the bone, the drug is released, with the effect of locally increasing bone density and strength. In the present study, a Zolidd prototype was used.

Twenty patients underwent correction of knee joint angles (tibial osteotomy with hemicallotasis): The bone was cut off below the knee, fixed with external fixation in the desired angle, and allowed to heal. Each patient received two fixation pins in the spongeous bone very close to the knee joint and two in the hard shaft of the bone, one of each prepared with Zolidd. Torques were measured at placement and at removal after three months, and compared to each other and to historic data. No loosening, no pin-track infections, and no increased pain was reported with Zolidd-coated pins.

The study was conducted at Hässleholm hospital, Sweden, by Sören Toksvig-Larsen, Hässleholm hospital and LundUniversity, and Per Aspenberg, Linköping University, Sweden.

It has now been published online in Acta Orthopaedica http://informahealthcare.com/doi/abs/10.3109/17453674.2013.797315

For additional information, contact Maria Wrethag, CEO Accelerator Nordic AB, +46 76 119 1983.