Does Bone Scanning Predict Bone Union in Vascularized Bone Grafts

Abstract

Using a free fibula osteoseptocutaneous flap for a segmental long defect is the standard technique in recent reconstructive surgery. For postoperative monitoring of vascular patency, an overlying skin flap is useful. However, does the skin paddle of a fibula osteoseptocutaneous flap really reveal the real state of vascularized bone grafts? Between 1993 and 2001, 27 segmental bony long defects were reconstructed with fibula osteoseptocutaneous flaps. The defects were 18 in the tibia, 7 in the femoral, and one in each of the radius and humerus. The defects ranged from 6- to 15-cm. All of the vascularized fibula grafts were inserted into the bone marrows of the recipient bones as inlayed grafts with rigid fixations. Technetium-99 methylene diphosphate (MDP) bone scans were used to assess the viability of the transplanted fibula. It was performed to the donor legs one week preoperatively in nine normal patients to serve as the baseline for comparison with bone scans performed one week postoperatively. Intensity of phase three (delayed bone image) was graded from 0 to 5. Plain X-rays of the recipient limbs were taken at two-month intervals for assessment of bone union. In this series, all 27 skin flaps were clinically judged viable. In Tc-99 bone scan studies, 4 patients were rated as grade 0, 3 patients were grade 1, one patient was grade 2, 8 patients were grade 3, 9 patients were grade 4, 2 patients were grade 5. The bone union time between grade 0 and grade 1, grade 0 and grade 3, grade 0 and grade 4, was statistically significant difference (Mann-Whitney Test) (p＜0.05). The grade zero group the average union time was around 17 months, longer than the expectation. In spite of outer viable skin flaps, phase three bone scan is valuable to predict bone union time, because it is the better way to estimate the viability of osteocytes of vascularized bone grafts.