The use of 'hybrid' allografts in the treatment of fractures of the thoracolumbar spine: first experience

Harvesting autogenous bone grafts of the iliac crest carries complications and lengthens operative times. Allografts are preferred to avoid these problems. Fusion after using allogenic bone grafts has been well studied, by examining trabeculations and remodelling on anteroposterior and lateral radiographs. However, the question remains whether one can rely on radiographs alone to determine fusion. 'Hybrid' fresh-frozen allografts from the femur or tibia were used in 11 adult patients with a mean age of 56.4 years (range: 30-78 years) to stabilize the thoracolumbar spine after anterior decompression for trauma. In one case two adjacent levels were fractured, in another case two fractures occurred at different levels. Fresh-frozen allografts of the femur (in ten cases) and tibia (one case), filled with autogenous cancellous bone graft or pieces of rib, were used to reconstruct the anterior column of the spine. Stabilization was performed by means of a Kaneda device. Anteroposterior and lateral radiographs and, additionally, computed tomography (CT) examinations with reconstructions were used to study fusion. One patient died 1 month after surgery. At follow-up in ten patients, after a mean time of 30.2 months (range: 18-42 months), ten allografts showed a grade I fusion and one a grade III fusion. Additional data from the CT examination with reconstructions, however, showed cross-trabeculations in all cases, and a partially united allograft in the patient with a grade III fusion. Cross-trabeculations between the allograft and vertebral body was observed at 6 months, with remodelling occurring at approximately 2 years. Mean loss of correction was minimal, at 3.6 degrees (range 0 degree-16 degrees). Fresh-frozen femoral or tibial allografts worked effectively to maintain correction after trauma when combined with anterior instrumentation. CT examinations with sagittal and coronal reconstructions were more effective for evaluation of fusion compared with anteroposterior and lateral radiographs. The high fusion rate and the low morbidity achieved using allografts in this way supports the exclusive use of allografts in the anterior thoracic and lumbar spine in the future.