J Korean Neurosurg Soc.  2017 May;60(3):348-354. 10.3340/jkns.2016.0707.002.

Difference in Spinal Fusion Process in Osteopenic and Nonosteopenic Living Rat Models Using Serial Microcomputed Tomography

• Park SB
• Yang HJ
• Kim CH
• Chung CK

• KMID: 2382770
• DOI: http://doi.org/10.3340/jkns.2016.0707.002

Abstract

OBJECTIVE
To identify and investigate differences in spinal fusion between the normal and osteopenic spine in a rat model.
METHODS
Female Sprague Dawley rats underwent either an ovariectomy (OVX) or sham operation and were randomized into two groups: non-OVX group and OVX group. Eight weeks after OVX, unilateral lumbar spinal fusion was performed using autologous iliac bone. Bone density (BD) was measured 2 days and 8 weeks after fusion surgery. Microcomputed tomography was used to evaluate the process of bone fusion every two weeks for 8 weeks after fusion surgery. The fusion rate, fusion process, and bone volume parameters of fusion bed were compared between the two groups.
RESULTS
BD was significantly higher in the non-OVX group than in the OVX group 2 days and 8 weeks after fusion surgery. The fusion rate in the non-OVX group was higher than that in the OVX group 8 weeks after surgery (p=0.044). The bony connection of bone fragments with transverse processes and bone formation between transverse processes in non-OVX group were significantly superior to those of OVX group from 6 weeks after fusion surgery. The compactness and bone maturation of fusion bed in non-OVX were prominent compared with the non-OVX group.
CONCLUSION
The fusion rate in OVX group was inferior to non-OVX group at late stage after fusion surgery. Bone maturation of fusion bed in the OVX group was inferior compared with the non-OVX group. Fusion enhancement strategies at early stage may be needed to patients with osteoporosis who need spine fusion surgery.

Keyword

Osteoporosis; Ovariectomy; Spine; Fusion; Rat

MeSH Terms

Animals
Bone Density
Female
Humans
Models, Animal*
Osteogenesis
Osteoporosis
Ovariectomy
Rats*
Rats, Sprague-Dawley
Spinal Fusion*
Spine
X-Ray Microtomography*

Figure

• 

  Fig. 1 Experimental groups and time schedule. Eighteen rats underwent bilateral OVX (OVX group), and another 18 rats underwent a sham operation (non-OVX group). Eight weeks after OVX, all rats underwent unilateral spinal fusion using autologous iliac bone. Sequential micro-CT evaluations in all rats were obtained every 2 weeks for 8 weeks after surgery. Bone density of all rats was assessed at 2 days and 8 weeks after fusion surgery. OVX: ovariectomy, micro-CT: microcomputed tomography.

• 

  Fig. 2 Assessment of fusion processes using three-dimensional (3D) images. The scheme and 3D reconstructed images show nonfusion (A) and fusion (B). Fusion was defined as the simultaneous presence of bridging bone and the connection of bridging bone to both upper and lower TPs. The shape of the bone fragments in 3D reconstructed image A (asterisk) does not appear as compact as that in 3D reconstructed image B (asterisk). VB: vertebral body, TP: transverse process.

• 

  Fig. 3 Comparison of the fusion process between two groups. This graph shows the difference between non-OVX and OVX groups in fusion rate (A), and the ratios of the presence of a bony connection with the TP (B) and bridging bone between TPs (C) at postoperative weeks 2, 4, 6 and 8 (asterisk, p<0.05). OVX: ovariectomy, TP: transverse process.

• 

  Fig. 4 Micro-CT scanning of fusion masses. The figures show 3D reconstructed images from both groups after surgery. The picture in the upper row shows serial 3D reconstructed images from a rat in the non-OVX group. The grafted bone materials were inserted on the fusion bed between the L4 and L5 TPs. The shape of the bridging bone 8 weeks after surgery (asterisk) was more compact than that in the early period after surgery. The picture in the lower row is a 3D reconstructed image from a rat in the OVX group. The shape of the grafted bone at 8 weeks was less compact in the OVX group (arrow) than in the non-OVX group. Micro-CT: microcomputed tomography, OVX: ovariectomy, TP: transverse process.

Reference

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