Abstract
In vitro experiments have shown, that stabilisation of the fibula in complete fractures of the lower leg give more stability compared to a single stabilisation of the tibia. However it is not known how this biomechanical conditions influence the bone healing process. To investigate the effect of fibula stability in tibia fracture healing tibial osteotomies in rats with and without fibula fractures were compared.
Male wistar rats (n=18) were operated by a transverse osteotomy of the proximal tibia of the left leg. Fracture was stabilised by intramedullary nailing. In 8 cases an additional closed fibula fracture was performed. The healing period was 21 days.
Each whole leg was examined by x-ray. After explantation of the tibia and removing of the nail and the fibula, the tibia was examined by CT-Scan, three-point-bending and histological evaluation.
Animals, who had a fibula fracture along with the tibia fracture presented with delayed healing. Density in CT-scan was 30% lower (p=0,0002) in animals with a fibula fracture (405mg/ccm, SD:64) compared to those without a fibula fracture (mean=577mg/ccm, SD:17). In three point bending the bending stiffness was 79% lower (p=0,0006) in animals with a fibula fracture (mean=252Nmm/mm, SD:118) compared to animals without a fibula fracture (mean=1219Nmm/mm, SD:478). The breaking force was 59% lower (p=0,0004) in animals with a fibula fracture (mean=17,5N, SD:6) compared to animals without a fibula fracture (mean=42,4N, SD:14).
Complete fractures of the lower leg healed considerably worse than solitary fractures of the tibia. We conclude that the missing of rotational stability of our k-wire fixation of the tibia with a unfixed fibula fracture is one of the reasons for the delay in fracture repair. The results support the in vitro findings of the biomechanical importance of the fibula for the stability of tibia fractures.
