Early changes of fracture healing on MRI

Abstract

Objective To observe MRI presentations of fracture healing process in the early stage.Methods Six New Zealand rabbits were used in the experiment. A union model of long oblique fracture of 1 mm in bone defect and 10 mm in vertical length was created on the right radius. A model of 10 mm bone defect was created on the left radius. X-ray and MRI examinations were performed in 1 w, 2 w, 4 w, 6 w, 8 w, 12 wafter the surgery and CT examination was performed in 4 w, 12 w after the surgery. The imaging presentations at the fracture sites were observed on T1, T2, FS-T2, PD, FS-PD sequences. Results The soft tissue around the fracture site presented high signals on T2, FS-T2, PD, FS-PD sequences in the early stage of fracture healing. The signals decreased as time went on, but turned intermediate at 6 w after surgery. The signals of bone marrow turned from high to intermediate on T1, T2 and PD sequences early after the surgery,but turned high again with the healing of medullary cavity. On FS-T2 and FS-PD sequences, bone marrow presented intermediate signals mixed with high signals, but the high signals subsided as time went by. Early changes of callus formation could be observed by MRI. Callus formation at the site of fracture showed intermediate signals in FS-T2 and FS-PD images obtained at 2 w after the surgery in the fracture union model. The changes above could not be observed in the bone defect model. Conclusions Callus formation may be predicted earlier by MRI than by X ray, especially on FS-T2 and FS-PD sequences. The MRI presentations of early fracture healing are to be confirmed by pathological examinations. Key words: Fracture healing; Magnetic resonance image; Animal experimentation