Despite improvements in the prophylactic and the therapeutic measures, soft-tissue damage and consecutive infection remain the major dilemma in the healing process of long bone fractures. Osteomyelitis is a consequence of local contamination by germs combined with a local and/or systemic immunodeficiency. Additionally, blood supply in the traumatized bone is disturbed which means systemic applied antibiotics do not reach the fractured region. In consequence, the further course may lead to severe disability including soft-tissue and/or segmental bone defects, impairment of joint motion, or even amputation. Once osteomyelitis has occurred, removal of the implant and aggressive debridement of the infected bone as well as soft tissue, combined with heavy local and systemic antibiotic therapy often represent the only option of treatment.

Bacteria introduced at the time of surgical implantation from the lower layers of the patients own skin which are not reached by skin disinfection, or at the time of injury in open fractures, compete with the patients immune system. This is often described as a race for the surface. Certain bacteria can colonize the surface of an implant and form a protective biofilm composed of proteins and polysaccharides, protecting the bacteria from the patients immune system as well as from the action of systemically applied antibiotics.

An antibiotic coating on an implant may prevent the bacteria from colonizing on the implants surface. In addition a coating with high local antimicrobial concentrations could protect the site of injury and avoid side effects resulting from long term high dose systemic antibiotic therapy.

The UTN PROtect combines the established UTN with a fully resorbable coating consisting of a fully amorphous polylactide (PDLLA) carrier containing gentamicin sulphate. Gentamicin was chosen due to its aminoglycoside, broad antibacterial spectrum, the bactericidal effect (non-proliferating bacteria), its synergistic effect in combination with cephalosporins, and because it is well established for local application in orthopedics (bone cement, PMMA-beads, collagen sponges). The total amount of antibiotic contained on one implant ranges from around 2040 mg, depending on the size of the implant. The gentamicin is released from the coating immediately after implantation with an initial burst that achieves a high peak concentration in the first hours and fades out over a period of 6 weeks. After coating the implant is packaged and sterilized by gamma irradiation and delivered sterile to the clinics.

The UTN PROtect will be the basis for all future generations of coated expert nails. A coated expert lateral femoral nail has already been used successfully as custom-made device.

Mechanical properties of the nail are not affected by the coating. Tests on cadavers and plastic bones proved the coating to be resistant to the abrasive forces present during insertion into a narrow and moist bone canal. The surgical technique does not differ from the regular standard of care in UTN implantation.

A clinical study run by AO Clinical Investigation and Documentation (AOCID) is ongoing. Preliminary data of the present results seem very encouraging, showing a superior outcome in comparison with published data. No adverse side effects due to the coated implant were detected. However, the study needs to complete before final results can be assessed.