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Effects of low intensity pulsed ultrasound with and without increased cortical porosity on structural bone allograft incorporation.

Santoni BG, Ehrhart N, Turner AS, Wheeler DL - J Orthop Surg Res (2008)

Bottom Line: The +CTL and -CTL groups did not receive LAP or LIPUS treatments.All animals were humanely euthanized four months following graft transplantation for biomechanical and histological analysis.LAP may provide an option for increasing porosity, and thus potential in vivo osseous apposition and revitalization, without adversely affecting the structural integrity of the graft.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, School of Biomedical Engineering, Orthopaedic Bioengineering Research Laboratory, Colorado State University, Fort Collins, CO 80523, USA. bgsant@engr.colostate.edu

ABSTRACT

Background: Though used for over a century, structural bone allografts suffer from a high rate of mechanical failure due to limited graft revitalization even after extended periods in vivo. Novel strategies that aim to improve graft incorporation are lacking but necessary to improve the long-term clinical outcome of patients receiving bone allografts. The current study evaluated the effect of low-intensity pulsed ultrasound (LIPUS), a potent exogenous biophysical stimulus used clinically to accelerate the course of fresh fracture healing, and longitudinal allograft perforations (LAP) as non-invasive therapies to improve revitalization of intercalary allografts in a sheep model.

Methods: Fifteen skeletally-mature ewes were assigned to five experimental groups based on allograft type and treatment: +CTL, -CTL, LIPUS, LAP, LIPUS+LAP. The +CTL animals (n = 3) received a tibial ostectomy with immediate replacement of the resected autologous graft. The -CTL group (n = 3) received fresh frozen ovine tibial allografts. The +CTL and -CTL groups did not receive LAP or LIPUS treatments. The LIPUS treatment group (n = 3), following grafting with fresh frozen ovine tibial allografts, received ultrasound stimulation for 20 minutes/day, 5 days/week, for the duration of the healing period. The LAP treatment group (n = 3) received fresh frozen ovine allografts with 500 mum longitudinal perforations that extended 10 mm into the graft. The LIPUS+LAP treatment group (n = 3) received both LIPUS and LAP interventions. All animals were humanely euthanized four months following graft transplantation for biomechanical and histological analysis.

Results: After four months of healing, daily LIPUS stimulation of the host-allograft junctions, alone or in combination with LAP, resulted in 30% increases in reconstruction stiffness, paralleled by significant increases (p < 0.001) in callus maturity and periosteal bridging across the host/allograft interfaces. Longitudinal perforations extending 10 mm into the proximal and distal endplates filled to varying degrees with new appositional bone and significantly accelerated revitalization of the allografts compared to controls.

Conclusion: The current study has demonstrated in a large animal model the potential of both LIPUS and LAP therapy to improve the degree of allograft incorporation. LAP may provide an option for increasing porosity, and thus potential in vivo osseous apposition and revitalization, without adversely affecting the structural integrity of the graft.

No MeSH data available.


Related in: MedlinePlus

(A) Undecalcified static image (2×) of distal host (H)/graft (G) junction in the LAP treatment group illustrating perforations in the cranial and caudal cortices that have filled to varying degrees with new appositional bone. Cranially (Cr) in (A), the perforation is almost entirely filled with new bone and extends the entire length of the conduit. (B) Dynamic histomorphometric whole specimen composite of (A) (2×) illustrating extensive uptake of both calcein and tetracycline Fluorochrome labels that extend the length of the 10 mm conduits in the cranial and caudal cortices.
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Figure 4: (A) Undecalcified static image (2×) of distal host (H)/graft (G) junction in the LAP treatment group illustrating perforations in the cranial and caudal cortices that have filled to varying degrees with new appositional bone. Cranially (Cr) in (A), the perforation is almost entirely filled with new bone and extends the entire length of the conduit. (B) Dynamic histomorphometric whole specimen composite of (A) (2×) illustrating extensive uptake of both calcein and tetracycline Fluorochrome labels that extend the length of the 10 mm conduits in the cranial and caudal cortices.

Mentions: Perforations present in the LAP and LIPUS+LAP undecalcified slides filled to varying degrees with immature woven bone after 4 months of healing. Animals within both groups exhibited perforations that were entirely filled with new immature tissue while some animals within those same groups had bone regeneration isolated to the inner surface of the longitudinal perforation. In either case, the appositional bone extended the entire length of the 10 mm perforation in LAP and LIPUS+LAP treatment groups (Fig. 4). Mineralizing tissue extended the entire length of the conduits resulting in graft MAR that was significantly greater in these two treatment groups relative to the -CTL (p < 0.001). LIPUS therapy alone also significantly increased allograft MAR (p < 0.001), though activity was localized at the periphery of the graft rather than mid-cortex as in LAP treated grafts. MAR in the callus was always larger than in the host or allograft for all treatment groups (Figure 5, Table 3). Limbs treated with LIPUS, LAP and LIPUS+LAP had 3-fold greater MAR in the periosteal callus than in -CTL allografts (p < 0.001).


Effects of low intensity pulsed ultrasound with and without increased cortical porosity on structural bone allograft incorporation.

Santoni BG, Ehrhart N, Turner AS, Wheeler DL - J Orthop Surg Res (2008)

(A) Undecalcified static image (2×) of distal host (H)/graft (G) junction in the LAP treatment group illustrating perforations in the cranial and caudal cortices that have filled to varying degrees with new appositional bone. Cranially (Cr) in (A), the perforation is almost entirely filled with new bone and extends the entire length of the conduit. (B) Dynamic histomorphometric whole specimen composite of (A) (2×) illustrating extensive uptake of both calcein and tetracycline Fluorochrome labels that extend the length of the 10 mm conduits in the cranial and caudal cortices.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2414658&req=5

Figure 4: (A) Undecalcified static image (2×) of distal host (H)/graft (G) junction in the LAP treatment group illustrating perforations in the cranial and caudal cortices that have filled to varying degrees with new appositional bone. Cranially (Cr) in (A), the perforation is almost entirely filled with new bone and extends the entire length of the conduit. (B) Dynamic histomorphometric whole specimen composite of (A) (2×) illustrating extensive uptake of both calcein and tetracycline Fluorochrome labels that extend the length of the 10 mm conduits in the cranial and caudal cortices.
Mentions: Perforations present in the LAP and LIPUS+LAP undecalcified slides filled to varying degrees with immature woven bone after 4 months of healing. Animals within both groups exhibited perforations that were entirely filled with new immature tissue while some animals within those same groups had bone regeneration isolated to the inner surface of the longitudinal perforation. In either case, the appositional bone extended the entire length of the 10 mm perforation in LAP and LIPUS+LAP treatment groups (Fig. 4). Mineralizing tissue extended the entire length of the conduits resulting in graft MAR that was significantly greater in these two treatment groups relative to the -CTL (p < 0.001). LIPUS therapy alone also significantly increased allograft MAR (p < 0.001), though activity was localized at the periphery of the graft rather than mid-cortex as in LAP treated grafts. MAR in the callus was always larger than in the host or allograft for all treatment groups (Figure 5, Table 3). Limbs treated with LIPUS, LAP and LIPUS+LAP had 3-fold greater MAR in the periosteal callus than in -CTL allografts (p < 0.001).

Bottom Line: The +CTL and -CTL groups did not receive LAP or LIPUS treatments.All animals were humanely euthanized four months following graft transplantation for biomechanical and histological analysis.LAP may provide an option for increasing porosity, and thus potential in vivo osseous apposition and revitalization, without adversely affecting the structural integrity of the graft.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Mechanical Engineering, School of Biomedical Engineering, Orthopaedic Bioengineering Research Laboratory, Colorado State University, Fort Collins, CO 80523, USA. bgsant@engr.colostate.edu

ABSTRACT

Background: Though used for over a century, structural bone allografts suffer from a high rate of mechanical failure due to limited graft revitalization even after extended periods in vivo. Novel strategies that aim to improve graft incorporation are lacking but necessary to improve the long-term clinical outcome of patients receiving bone allografts. The current study evaluated the effect of low-intensity pulsed ultrasound (LIPUS), a potent exogenous biophysical stimulus used clinically to accelerate the course of fresh fracture healing, and longitudinal allograft perforations (LAP) as non-invasive therapies to improve revitalization of intercalary allografts in a sheep model.

Methods: Fifteen skeletally-mature ewes were assigned to five experimental groups based on allograft type and treatment: +CTL, -CTL, LIPUS, LAP, LIPUS+LAP. The +CTL animals (n = 3) received a tibial ostectomy with immediate replacement of the resected autologous graft. The -CTL group (n = 3) received fresh frozen ovine tibial allografts. The +CTL and -CTL groups did not receive LAP or LIPUS treatments. The LIPUS treatment group (n = 3), following grafting with fresh frozen ovine tibial allografts, received ultrasound stimulation for 20 minutes/day, 5 days/week, for the duration of the healing period. The LAP treatment group (n = 3) received fresh frozen ovine allografts with 500 mum longitudinal perforations that extended 10 mm into the graft. The LIPUS+LAP treatment group (n = 3) received both LIPUS and LAP interventions. All animals were humanely euthanized four months following graft transplantation for biomechanical and histological analysis.

Results: After four months of healing, daily LIPUS stimulation of the host-allograft junctions, alone or in combination with LAP, resulted in 30% increases in reconstruction stiffness, paralleled by significant increases (p < 0.001) in callus maturity and periosteal bridging across the host/allograft interfaces. Longitudinal perforations extending 10 mm into the proximal and distal endplates filled to varying degrees with new appositional bone and significantly accelerated revitalization of the allografts compared to controls.

Conclusion: The current study has demonstrated in a large animal model the potential of both LIPUS and LAP therapy to improve the degree of allograft incorporation. LAP may provide an option for increasing porosity, and thus potential in vivo osseous apposition and revitalization, without adversely affecting the structural integrity of the graft.

No MeSH data available.


Related in: MedlinePlus