Influence of bone cements on bone-screw interfaces in the third metacarpal and third metatarsal bones of horses.
OBJECTIVE
To compare biomechanical strength, interface quality, and effects of bone healing in bone-implant interfaces that were untreated or treated with calcium phosphate cement (Ca-cement), magnesium phosphate cement (Mg-cement), or polymethylmethacrylate (PMMA) in horses.


METHODS
6 adult horses.


METHODS
4 screw holes were created (day 0) in each third metacarpal and third metatarsal bone of 6 horses. In each bone, a unicortical screw was placed in each hole following application of Ca-cement, Mg-cement, PMMA, or no treatment (24 screw holes/treatment). Screws were inserted to 2.82 N m torque. Horses were euthanized and bones were harvested at day 5 (16 screw holes/treatment) or day 182 (8 screw holes/treatment). Radiography, biomechanical testing, histomorphometry, and micro-computed tomography were performed to characterize the bone-implant interfaces.


RESULTS
Use of Mg-cement increased the peak torque to failure at bone-implant interfaces, compared with the effects of no treatment and Ca-cement, and increased interface toughness, compared with the effects of no treatment, Ca-cement, and PMMA. Histologically, there was 44% less Ca-cement and 69% less Mg-cement at the interfaces at day 182, compared with amounts present at day 5. Within screw threads, Ca-cement increased mineral density, compared with PMMA or no treatment. In the bone adjacent to the screw, Mg-cement increased mineral density, compared with PMMA or no treatment. One untreated and 1 Ca-cement-treated screw backed out after day 5.


CONCLUSIONS
In horses, Mg-cement promoted bone-implant bonding and adjacent bone osteogenesis, which may reduce the risk of screw loosening.
Hirvinen
Laura J M
LJ
Comparative Orthopedic Research Laboratories, Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA.
Litsky
Alan S
AS
Samii
Valerie F
VF
Weisbrode
Steven E
SE
Bertone
Alicia L
AL
D000704:Analysis of Variance; D000818:Animals; D001843:Bone Cements; D001863:Bone Screws; D002130:Calcium Phosphates; D005593:Fracture Fixation, Internal / Q000662:veterinary*; D017102:Fracture Healing / Q000502:physiology*; D006736:Horses / Q000502:physiology / Q000601:surgery*; D008274:Magnesium; D050279:Metacarpal Bones / Q000000981:diagnostic imaging / Q000601:surgery*; D008682:Metatarsal Bones / Q000000981:diagnostic imaging / Q000601:surgery*; D010012:Osteogenesis / Q000502:physiology; D019904:Polymethyl Methacrylate; D055114:X-Ray Microtomography
D001843:Bone Cements; D002130:Calcium Phosphates; D019904:Polymethyl Methacrylate; D008274:Magnesium