Chang-Bae Kong1, Jae Hyup Lee2, Hae-Ri Baek3, Choon-Ki Lee4, Bong-Soon Chang4. 1. Department of Orthopedic Surgery, Korea Cancer Center Hospital, 215-4, Gongneung-dong, Nowon-gu, Seoul 139-706, Korea. 2. Department of Orthopedic Surgery, College of Medicine, Seoul National University, Seoul Metropolitan Goverment Seoul National University Boramae Medical Center, 41 Boramae-Gil, Seoul 156-707, Korea. Electronic address: spinelee@snu.ac.kr. 3. Department of Orthopedic Surgery, College of Medicine, Seoul National University, Seoul Metropolitan Goverment Seoul National University Boramae Medical Center, 41 Boramae-Gil, Seoul 156-707, Korea. 4. Department of Orthopedic Surgery, Seoul National University Hospital, 28 Yeonkeon-dong, Chongro-gu, Seoul 110-744, Korea.
Abstract
BACKGROUND CONTEXT: Hydroxyapatite (HA) is used as a bone graft extender for posterolateral spinal fusion in human. It is also useful as a recombinant human bone morphogenetic protein (rhBMP)-2 carrier because of its high affinity for rhBMP-2. PURPOSE: To assess the osteoinductivity of Escherichia coli-derived rhBMP-2 (E-BMP-2) using HA granules as a carrier and to evaluate the bone-forming ability depending on the different dosages of E-BMP-2. STUDY DESIGN: A mini-pig lumbar posterolateral fusion model using microcomputed tomography (μCT) scanning. PATIENT SAMPLE: Thirty-one adult male mini pigs were randomized into a single control group (n=8) without E-BMP-2 and two experimental groups with two different doses of E-BMP-2 (1 mg per side, n=8 and 3 mg per side, n=15). OUTCOME MEASURES: Outcome was measured by plain radiography, manual palpation, CT, three-dimensional μCT, and histologic examinations. METHODS: Bilateral intertransverse process arthrodesis was performed, and E-BMP-2 (0, 1.0, 3.0 mg per side) was implanted into the intertransverse space using HA granules as a carrier. RESULTS: Three mini pigs were removed because of death. Among 28 experimental subjects, 19 animals achieved solid bony union. The fusion rates were 37.5% for control group, 71.4% for 1 mg group, and 84.6% for 3 mg group. Fusion rates were significantly different among groups (p=.031). However, there was no statistically significant difference in fusion rates between 1 and 3 mg groups (p=.587). Thirty-eight intertransverse fusion masses of 19 subjects underwent μCT scanning. The bone volumes determined by μCT were 12,603±3,240 mm(3) for control group, 18,718±3,000 mm(3) for 1 mg group, and 26,768±7,256 mm(3) for 3 mg group, and the difference between groups was statistically significant (p<.001). CONCLUSIONS: This study shows that E-BMP-2 has osteoinductive activity in dose-dependent fashion, and porous HA granule is suitable for E-BMP-2 carrier in a porcine posterolateral fusion model. These preliminary findings suggest that E-BMP-2-adsorbed porous HA granules could be a novel effective bone graft substitute.
BACKGROUND CONTEXT: Hydroxyapatite (HA) is used as a bone graft extender for posterolateral spinal fusion in human. It is also useful as a recombinant humanbone morphogenetic protein (rhBMP)-2 carrier because of its high affinity for rhBMP-2. PURPOSE: To assess the osteoinductivity of Escherichia coli-derived rhBMP-2 (E-BMP-2) using HA granules as a carrier and to evaluate the bone-forming ability depending on the different dosages of E-BMP-2. STUDY DESIGN: A mini-pig lumbar posterolateral fusion model using microcomputed tomography (μCT) scanning. PATIENT SAMPLE: Thirty-one adult male mini pigs were randomized into a single control group (n=8) without E-BMP-2 and two experimental groups with two different doses of E-BMP-2 (1 mg per side, n=8 and 3 mg per side, n=15). OUTCOME MEASURES: Outcome was measured by plain radiography, manual palpation, CT, three-dimensional μCT, and histologic examinations. METHODS: Bilateral intertransverse process arthrodesis was performed, and E-BMP-2 (0, 1.0, 3.0 mg per side) was implanted into the intertransverse space using HA granules as a carrier. RESULTS: Three mini pigs were removed because of death. Among 28 experimental subjects, 19 animals achieved solid bony union. The fusion rates were 37.5% for control group, 71.4% for 1 mg group, and 84.6% for 3 mg group. Fusion rates were significantly different among groups (p=.031). However, there was no statistically significant difference in fusion rates between 1 and 3 mg groups (p=.587). Thirty-eight intertransverse fusion masses of 19 subjects underwent μCT scanning. The bone volumes determined by μCT were 12,603±3,240 mm(3) for control group, 18,718±3,000 mm(3) for 1 mg group, and 26,768±7,256 mm(3) for 3 mg group, and the difference between groups was statistically significant (p<.001). CONCLUSIONS: This study shows that E-BMP-2 has osteoinductive activity in dose-dependent fashion, and porous HA granule is suitable for E-BMP-2 carrier in a porcine posterolateral fusion model. These preliminary findings suggest that E-BMP-2-adsorbed porous HA granules could be a novel effective bone graft substitute.