Comparison of posterolateral lumbar fusion rates of Grafton Putty and OP-1 Putty in an athymic rat model.
METHODS
Posterolateral lumbar spine fusions in athymic rats.


OBJECTIVE
To compare spine fusion rates of two different osteoinductive products.


BACKGROUND
Many osteoinductive bone graft alternatives are available. Grafton (a demineralized bone matrix [DBM]) and Osteogenic Protein-1 (OP-1, an individual recombinant bone morphogenetic protein) are two such alternatives. The relative efficacy of products from these two classes has not been previously studied. The athymic rat spine fusion model has been validated and demonstrated useful to minimize inflammatory responses to xenogeneic or differentially expressed proteins such as those presented by DBMs of human etiology.


METHODS
Single-level intertransverse process fusions were performed in 60 athymic nude rats with 2 cc/kg of Grafton or OP-1 Putty. Half of each study group was killed at 3 weeks and half at 6 weeks. Fusion masses were assessed by radiography, manual palpation, and histology.


RESULTS
At 3 weeks, manual palpation revealed a 13% fusion rate with Grafton and a 100% fusion rate with OP-1 (P = 0.0001). At 6 weeks, manual palpation revealed a 39% fusion rate of with Grafton and a 100% fusion rate with OP-1 (P = 0.0007). Similar fusion rates were found by histology at 3 and 6 weeks. Of note, one or two adjacent levels were fused in all of the OP-1 animals and none of the Grafton animals.


CONCLUSIONS
Significant differences between the ability of Grafton and OP-1 to induce bone formation in an athymic rat posterolateral lumbar spine fusion model were found.
Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, CT 06520-8071, USA.
David A
DA
Bomback
Jonathan N
JN
Grauer
Roberto
R
Lugo
Nancy
N
Troiano
Tushar Ch
TCh
Patel
Gary E
GE
Friedlaender
D030201:Activin Receptors, Type I; D000818:Animals; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D005990:Glycerol / Q000494:pharmacology*; D006801:Humans; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D023421:Models, Animal; D010012:Osteogenesis / Q000187:drug effects*; D011506:Proteins / Q000494:pharmacology*; D011859:Radiography; D051381:Rats; D011923:Rats, Nude; D013123:Spinal Fusion
C525819:BMP7 protein, human; C525821:Bmp7 protein, rat; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; C497176:Grafton demineralized bone matrix gel; D011506:Proteins; C425423:ACVR1 protein, human; D030201:Activin Receptors, Type I; D005990:Glycerol