Improved healing of large segmental defects in the rat femur by reverse dynamization in the presence of bone morphogenetic protein-2

Vaida Glatt, Micah Miller, Alan Ivkovic, Fangjun Liu, Nicola Parry, Damian Griffin, Mark Vrahas, Christopher H Evans

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Background: Large segmental defects in bone do not heal well and present clinical challenges. This study investigated modulation of the mechanical environment as a means of improving bone healing in the presence of bone morphogenetic protein (BMP)-2. Although the influence of mechanical forces on the healing of fractures is well established, no previous studies, to our knowledge, have described their influence on the healing of large segmental defects. We hypothesized that bone-healing would be improved by initial, low-stiffness fixation of the defect, followed by high-stiffness fixation during the healing process. We call this reverse dynamization. Methods: A rat model of a critical-sized femoral defect was used. External fixators were constructed to provide different degrees of stiffness and, importantly, the ability to change stiffness during the healing process in vivo. Healing of the critical-sized defects was initiated by the implantation of 11 mg of recombinant human BMP (rhBMP)-2 on a collagen sponge. Groups of rats receiving BMP-2 were allowed to heal with low, medium, and high-stiffness fixators, as well as under conditions of reverse dynamization, in which the stiffness was changed from low to high at two weeks. Healing was assessed at eight weeks with use of radiographs, histological analysis, microcomputed tomography, dual x-ray absorptiometry, and mechanical testing. Results: Under constant stiffness, the low-stiffness fixator produced the best healing after eight weeks. However, reverse dynamization provided considerable improvement, resulting in a marked acceleration of the healing process by all of the criteria of this study. The histological data suggest that this was the result of intramembranous, rather than endochondral, ossification. Conclusions: Reverse dynamization accelerated healing in the presence of BMP-2 in the rat femur and is worthy of further investigation as a means of improving the healing of large segmental bone defects. Clinical Relevance: These data provide the basis of a novel, simple, and inexpensive way to improve the healing of critical-sized defects in long bones. Reverse dynamization may also be applicable to other circumstances in which bonehealing is problematic.

Original languageEnglish (US)
Pages (from-to)2063-2073
Number of pages11
JournalJournal of Bone and Joint Surgery - Series A
Volume94
Issue number22
DOIs
StatePublished - Nov 21 2012
Externally publishedYes

Fingerprint

Bone Morphogenetic Protein 2
Femur
Bone and Bones
X-Ray Microtomography
External Fixators
Fracture Healing
Porifera
Thigh
Osteogenesis
Collagen
X-Rays

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

Cite this

Improved healing of large segmental defects in the rat femur by reverse dynamization in the presence of bone morphogenetic protein-2. / Glatt, Vaida; Miller, Micah; Ivkovic, Alan; Liu, Fangjun; Parry, Nicola; Griffin, Damian; Vrahas, Mark; Evans, Christopher H.

In: Journal of Bone and Joint Surgery - Series A, Vol. 94, No. 22, 21.11.2012, p. 2063-2073.

Research output: Contribution to journalArticle

Glatt, Vaida ; Miller, Micah ; Ivkovic, Alan ; Liu, Fangjun ; Parry, Nicola ; Griffin, Damian ; Vrahas, Mark ; Evans, Christopher H. / Improved healing of large segmental defects in the rat femur by reverse dynamization in the presence of bone morphogenetic protein-2. In: Journal of Bone and Joint Surgery - Series A. 2012 ; Vol. 94, No. 22. pp. 2063-2073.
@article{6cb12c3c720a4ede9b92080e5c8aeda1,
title = "Improved healing of large segmental defects in the rat femur by reverse dynamization in the presence of bone morphogenetic protein-2",
abstract = "Background: Large segmental defects in bone do not heal well and present clinical challenges. This study investigated modulation of the mechanical environment as a means of improving bone healing in the presence of bone morphogenetic protein (BMP)-2. Although the influence of mechanical forces on the healing of fractures is well established, no previous studies, to our knowledge, have described their influence on the healing of large segmental defects. We hypothesized that bone-healing would be improved by initial, low-stiffness fixation of the defect, followed by high-stiffness fixation during the healing process. We call this reverse dynamization. Methods: A rat model of a critical-sized femoral defect was used. External fixators were constructed to provide different degrees of stiffness and, importantly, the ability to change stiffness during the healing process in vivo. Healing of the critical-sized defects was initiated by the implantation of 11 mg of recombinant human BMP (rhBMP)-2 on a collagen sponge. Groups of rats receiving BMP-2 were allowed to heal with low, medium, and high-stiffness fixators, as well as under conditions of reverse dynamization, in which the stiffness was changed from low to high at two weeks. Healing was assessed at eight weeks with use of radiographs, histological analysis, microcomputed tomography, dual x-ray absorptiometry, and mechanical testing. Results: Under constant stiffness, the low-stiffness fixator produced the best healing after eight weeks. However, reverse dynamization provided considerable improvement, resulting in a marked acceleration of the healing process by all of the criteria of this study. The histological data suggest that this was the result of intramembranous, rather than endochondral, ossification. Conclusions: Reverse dynamization accelerated healing in the presence of BMP-2 in the rat femur and is worthy of further investigation as a means of improving the healing of large segmental bone defects. Clinical Relevance: These data provide the basis of a novel, simple, and inexpensive way to improve the healing of critical-sized defects in long bones. Reverse dynamization may also be applicable to other circumstances in which bonehealing is problematic.",
author = "Vaida Glatt and Micah Miller and Alan Ivkovic and Fangjun Liu and Nicola Parry and Damian Griffin and Mark Vrahas and Evans, {Christopher H}",
year = "2012",
month = "11",
day = "21",
doi = "10.2106/JBJS.K.01604",
language = "English (US)",
volume = "94",
pages = "2063--2073",
journal = "Journal of Bone and Joint Surgery - American Volume",
issn = "0021-9355",
publisher = "Journal of Bone and Joint Surgery Inc.",
number = "22",

}

TY - JOUR

T1 - Improved healing of large segmental defects in the rat femur by reverse dynamization in the presence of bone morphogenetic protein-2

AU - Glatt, Vaida

AU - Miller, Micah

AU - Ivkovic, Alan

AU - Liu, Fangjun

AU - Parry, Nicola

AU - Griffin, Damian

AU - Vrahas, Mark

AU - Evans, Christopher H

PY - 2012/11/21

Y1 - 2012/11/21

N2 - Background: Large segmental defects in bone do not heal well and present clinical challenges. This study investigated modulation of the mechanical environment as a means of improving bone healing in the presence of bone morphogenetic protein (BMP)-2. Although the influence of mechanical forces on the healing of fractures is well established, no previous studies, to our knowledge, have described their influence on the healing of large segmental defects. We hypothesized that bone-healing would be improved by initial, low-stiffness fixation of the defect, followed by high-stiffness fixation during the healing process. We call this reverse dynamization. Methods: A rat model of a critical-sized femoral defect was used. External fixators were constructed to provide different degrees of stiffness and, importantly, the ability to change stiffness during the healing process in vivo. Healing of the critical-sized defects was initiated by the implantation of 11 mg of recombinant human BMP (rhBMP)-2 on a collagen sponge. Groups of rats receiving BMP-2 were allowed to heal with low, medium, and high-stiffness fixators, as well as under conditions of reverse dynamization, in which the stiffness was changed from low to high at two weeks. Healing was assessed at eight weeks with use of radiographs, histological analysis, microcomputed tomography, dual x-ray absorptiometry, and mechanical testing. Results: Under constant stiffness, the low-stiffness fixator produced the best healing after eight weeks. However, reverse dynamization provided considerable improvement, resulting in a marked acceleration of the healing process by all of the criteria of this study. The histological data suggest that this was the result of intramembranous, rather than endochondral, ossification. Conclusions: Reverse dynamization accelerated healing in the presence of BMP-2 in the rat femur and is worthy of further investigation as a means of improving the healing of large segmental bone defects. Clinical Relevance: These data provide the basis of a novel, simple, and inexpensive way to improve the healing of critical-sized defects in long bones. Reverse dynamization may also be applicable to other circumstances in which bonehealing is problematic.

AB - Background: Large segmental defects in bone do not heal well and present clinical challenges. This study investigated modulation of the mechanical environment as a means of improving bone healing in the presence of bone morphogenetic protein (BMP)-2. Although the influence of mechanical forces on the healing of fractures is well established, no previous studies, to our knowledge, have described their influence on the healing of large segmental defects. We hypothesized that bone-healing would be improved by initial, low-stiffness fixation of the defect, followed by high-stiffness fixation during the healing process. We call this reverse dynamization. Methods: A rat model of a critical-sized femoral defect was used. External fixators were constructed to provide different degrees of stiffness and, importantly, the ability to change stiffness during the healing process in vivo. Healing of the critical-sized defects was initiated by the implantation of 11 mg of recombinant human BMP (rhBMP)-2 on a collagen sponge. Groups of rats receiving BMP-2 were allowed to heal with low, medium, and high-stiffness fixators, as well as under conditions of reverse dynamization, in which the stiffness was changed from low to high at two weeks. Healing was assessed at eight weeks with use of radiographs, histological analysis, microcomputed tomography, dual x-ray absorptiometry, and mechanical testing. Results: Under constant stiffness, the low-stiffness fixator produced the best healing after eight weeks. However, reverse dynamization provided considerable improvement, resulting in a marked acceleration of the healing process by all of the criteria of this study. The histological data suggest that this was the result of intramembranous, rather than endochondral, ossification. Conclusions: Reverse dynamization accelerated healing in the presence of BMP-2 in the rat femur and is worthy of further investigation as a means of improving the healing of large segmental bone defects. Clinical Relevance: These data provide the basis of a novel, simple, and inexpensive way to improve the healing of critical-sized defects in long bones. Reverse dynamization may also be applicable to other circumstances in which bonehealing is problematic.

UR - http://www.scopus.com/inward/record.url?scp=84870168305&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84870168305&partnerID=8YFLogxK

U2 - 10.2106/JBJS.K.01604

DO - 10.2106/JBJS.K.01604

M3 - Article

VL - 94

SP - 2063

EP - 2073

JO - Journal of Bone and Joint Surgery - American Volume

JF - Journal of Bone and Joint Surgery - American Volume

SN - 0021-9355

IS - 22

ER -