Fixation of distal femoral osteotomy with an intramedullary rod: Early failure of carbon fibre composite implant in rabbits

A novel composite material with an ultra-high strength and a low elastic mo dulus, comprising a carbon fibre reinforced liquid crystalline polymer (LCP /CF) has been developed. An experimental osteotomy of the distal femur in n ineteen rabbits weighing on average 4.8 (3.7-6.3) kg was fixed with an intr amedullary LCP/CF rod of 3.2 mm in diameter and 50 mm in length. The initia l mechanical properties of the rods had a mean shear strength of 180 MPa, a flexural strength of 450 MPa, and a flexural modulus of 40 GPa. The rods w ere implanted for periods of 3, 6, 12, 24, and 52 weeks, The healing of the osteotomy was analyzed by radiographic, histological, microradiographic, a nd oxytetracycline fluorescence studies. The strength retention of the LCP/ CF rods was measured by mechanical testing. Solid union of the osteotomy wa s seen within 6 weeks. The implants retained their original strength proper ties up to 52 weeks. In three rabbits, a non-union with granulation tissue and carbon fibre particles was noticed at the osteotomy site, where disrupt ion of the implant surface was seen at the level of the osteotomy. Further studies with a special interest in the fabrication process of the LCP/CF-im plants are needed.