Allogenic versus autologous cancellous bone in lumbar segmental spondylodesis: a randomized prospective study

Abstract

The current gold standard in lumbar fusion consists of transpedicular fixation in combination with an interbody interponate of autologous bone from iliac crest. Because of the limited availability of autologous bone as well as the still relevant donor site morbidity after iliac crest grafting the need exists for alternative grafts with a comparable outcome. Forty patients with degenerative spinal disease were treated with a monosegmental spondylodesis (ventrally, 1 PEEK-cage; dorsally, a screw and rod system), and randomly placed in two groups. In group 1, autogenous iliac crest cancellous bone was used as a cage filling. In group 2 the cages were filled with an allogenic cancellous bone graft. Following 3, 6, 9 and 12 months, the clinical outcome was determined on the basis of: the Oswestry Low Back Pain Disability Questionnaire; patient satisfaction; patient willingness to undergo the operation again; and a visual analog scale for pain. The radiological outcome was based on both fusion rate (radiographs, computed tomography), and on the bone mineral density of the grafts. After 6 months, the X-rays of the patients in group 2 had a significantly lower rate of fusion. Aside from this, there were no further significant differences. After 12 months, radiological results showed a similar fusion rate in both groups. Donor site complications consisted of five patients with hematoma, and three patients with persistent pain in group 1. No implant complications were observed. If a bone bank is available for support and accepting the low risk of possible transmission of infectious diseases, freeze-dried allogenic cancellous bone can be used for monosegmental spondylodeses. The results demonstrated an equivalent clinical outcome, as well as similar fusion rates following a 12-month period. This is in despite of a delayed consolidation process.

Fig. 1

Radiographical fusion rate between the groups over time

Fig. 2

Fusion rate in computed tomography between the groups over time

Fig. 3

Two dimensional reconstructions (computed tomography) of a patient with fusion a at 3-month follow-up. Cage interposition at level L5/S1; no bridging bone but bone graft inside the cage; b at 12-month follow-up. Compared to the 3-month follow-up presenting increasing bone mass bridging the segment inside and anterior to the cage

Fig. 4

Mean bone mineral density inside the cage (CT) between the groups over time

Fig. 5

Oswestry low back pain disability index between the groups over time. Whiskers indicate a single standard deviation