Differential fracture healing resulting from fixation stiffness variability: A mouse model

Michael J. Gardner, Sara M. Putnam, Ambrose Wong, Philipp N. Streubel, Akhilesh Kotiya, Matthew J. Silva

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Background The mechanisms underlying the interaction between the local mechanical environment and fracture healing are not known. We developed a mouse femoral fracture model with implants of different stiffness, and hypothesized that differential fracture healing would result. Methods Femoral shaft fractures were created in 70 mice, and were treated with an intramedullary nail made of either tungsten (Young's modulus = 410 GPa) or aluminium (Young's modulus = 70 GPa). Mice were then sacrificed at 2 or 5 weeks. Fracture calluses were analyzed using standard microCT, histological, and biomechanical methods. Results At 2 weeks, callus volume was significantly greater in the aluminium group than in the tungsten group (61.2 vs. 40.5 mm3, p = 0.016), yet bone volume within the calluses was no different between the groups (13.2 vs. 12.3 mm 3, ). Calluses from the tungsten group were stiffer on mechanical testing (18.7 vs. 9.7 N/mm, p = 0.01). The percent cartilage in the callus was 31.6% in the aluminium group and 22.9% in the tungsten group (p = 0.40). At 5 weeks, there were no differences between any of the healed femora. Conclusions In this study, fracture implants of different stiffness led to different fracture healing in this mouse fracture model. Fractures treated with a stiffer implant had more advanced healing at 2 weeks, but still healed by callus formation. Although this concept has been well documented previously, this particular model could be a valuable research tool to study the healing consequences of altered fixation stiffness, which may provide insight into the pathogenesis and ideal treatment of fractures and non-unions.

Original languageEnglish (US)
Pages (from-to)298-303
Number of pages6
JournalJournal of Orthopaedic Science
Volume16
Issue number3
DOIs
StatePublished - May 2011

Fingerprint

Fracture Healing
Bony Callus
Tungsten
Aluminum
Femoral Fractures
Elastic Modulus
X-Ray Microtomography
Nails
Femur
Cartilage
Bone and Bones
Research

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine

Cite this

Differential fracture healing resulting from fixation stiffness variability : A mouse model. / Gardner, Michael J.; Putnam, Sara M.; Wong, Ambrose; Streubel, Philipp N.; Kotiya, Akhilesh; Silva, Matthew J.

In: Journal of Orthopaedic Science, Vol. 16, No. 3, 05.2011, p. 298-303.

Research output: Contribution to journalArticle

Gardner, Michael J. ; Putnam, Sara M. ; Wong, Ambrose ; Streubel, Philipp N. ; Kotiya, Akhilesh ; Silva, Matthew J. / Differential fracture healing resulting from fixation stiffness variability : A mouse model. In: Journal of Orthopaedic Science. 2011 ; Vol. 16, No. 3. pp. 298-303.
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abstract = "Background The mechanisms underlying the interaction between the local mechanical environment and fracture healing are not known. We developed a mouse femoral fracture model with implants of different stiffness, and hypothesized that differential fracture healing would result. Methods Femoral shaft fractures were created in 70 mice, and were treated with an intramedullary nail made of either tungsten (Young's modulus = 410 GPa) or aluminium (Young's modulus = 70 GPa). Mice were then sacrificed at 2 or 5 weeks. Fracture calluses were analyzed using standard microCT, histological, and biomechanical methods. Results At 2 weeks, callus volume was significantly greater in the aluminium group than in the tungsten group (61.2 vs. 40.5 mm3, p = 0.016), yet bone volume within the calluses was no different between the groups (13.2 vs. 12.3 mm 3, ). Calluses from the tungsten group were stiffer on mechanical testing (18.7 vs. 9.7 N/mm, p = 0.01). The percent cartilage in the callus was 31.6{\%} in the aluminium group and 22.9{\%} in the tungsten group (p = 0.40). At 5 weeks, there were no differences between any of the healed femora. Conclusions In this study, fracture implants of different stiffness led to different fracture healing in this mouse fracture model. Fractures treated with a stiffer implant had more advanced healing at 2 weeks, but still healed by callus formation. Although this concept has been well documented previously, this particular model could be a valuable research tool to study the healing consequences of altered fixation stiffness, which may provide insight into the pathogenesis and ideal treatment of fractures and non-unions.",
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N2 - Background The mechanisms underlying the interaction between the local mechanical environment and fracture healing are not known. We developed a mouse femoral fracture model with implants of different stiffness, and hypothesized that differential fracture healing would result. Methods Femoral shaft fractures were created in 70 mice, and were treated with an intramedullary nail made of either tungsten (Young's modulus = 410 GPa) or aluminium (Young's modulus = 70 GPa). Mice were then sacrificed at 2 or 5 weeks. Fracture calluses were analyzed using standard microCT, histological, and biomechanical methods. Results At 2 weeks, callus volume was significantly greater in the aluminium group than in the tungsten group (61.2 vs. 40.5 mm3, p = 0.016), yet bone volume within the calluses was no different between the groups (13.2 vs. 12.3 mm 3, ). Calluses from the tungsten group were stiffer on mechanical testing (18.7 vs. 9.7 N/mm, p = 0.01). The percent cartilage in the callus was 31.6% in the aluminium group and 22.9% in the tungsten group (p = 0.40). At 5 weeks, there were no differences between any of the healed femora. Conclusions In this study, fracture implants of different stiffness led to different fracture healing in this mouse fracture model. Fractures treated with a stiffer implant had more advanced healing at 2 weeks, but still healed by callus formation. Although this concept has been well documented previously, this particular model could be a valuable research tool to study the healing consequences of altered fixation stiffness, which may provide insight into the pathogenesis and ideal treatment of fractures and non-unions.

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