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 prob lems. Fusion after using allogenic bone grafts has been well studied, by ex amining trabeculations and remodelling on anteroposterior and lateral radio graphs. However, the question remains whether one can rely on radiographs a lone to determine fusion. 'Hybrid' fresh-frozen allografts from the femur o r 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 decompre ssion for trauma. In one case two adjacent levels were fractured, in anothe r case two fractures occurred at different levels. Fresh-frozen allografts of the femur (in ten cases) and tibia (one case), filled with autogenous ca ncellous bone graft or pieces of rib, were used to reconstruct the anterior column of the spine. Stabilization was performed by means of a Kaneda devi ce. Anteroposterior and lateral radiographs and, additionally, computed tom ography (CT) examinations with reconstructions were used to study fusion. O ne 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 g rade I fusion and one a grade III fusion. Additional data from the CT exami nation with reconstructions, however, showed cross-trabeculations in all ca ses, and a partially united allograft in the patient with a grade III fusio n. Cross-trabeculations between the allograft and vertebral body was Observ ed at 6 months, with remodelling occuring at approximately 2 years. Mean lo ss of correction was minimal, at 3.6 degrees (range 0 degrees -16 degrees), Fresh-frozen femoral or tibial allografts worked effectively to maintain c orrection after trauma when combined with anterior instrumentation. CT exam inations 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 th is way supports the exclusive use of allografts in the anterior thoracic an d lumbar spine in the future.