PTH improves titanium implant fixation more than pamidronate or renutrition in osteopenic rats chronically fed a low protein diet.
CONCLUSIONS
We evaluated the effects of parathyroid hormone (PTH), pamidronate, or renutrition on osseointegration of titanium implants in the proximal tibia of rats subject to prolonged low-protein diets. PTH improved mechanical fixation, microarchitecture, and increased pull-out strength. Pamidronate or renutrition had lesser effects. PTH can thus improve implant osseointegration in protein-malnourished rats.


BACKGROUND
Protein malnutrition impairs implant osseointegration in rats. PTH and pamidronate prevent deleterious effects of protein restriction introduced just prior to implantation. Whether these treatments improve osseointegration after chronic protein deprivation, i.e., in osteopenic bone at time of implantation, is unknown. We evaluated effects of PTH, pamidronate, or renutrition on resistance to pull-out of titanium rods implanted into the rat tibiae following isocaloric low-protein intake.


METHODS
Forty-one adult female rats received normal or isocaloric low-protein diets. Six weeks later, implants were surgically inserted into proximal tibiae. Following implantation, rats on low-protein diets were treated with PTH (1-34), pamidronate, saline vehicle, or normal protein diets, for another 8 weeks. Tibiae were removed for micro-computerised tomographic morphometry and evaluation of pull-out strength.


RESULTS
Pull-out strength decreased in rats on isocaloric low-protein diets compared with normal protein group (-33.4%). PTH increased pull-out strength in low-protein group, even compared to controls from the normal protein group. PTH and pamidronate increased bone volume/tissue volume, bone-to-implant contact, and trabecular thickness, whilst trabecular separation was reduced, with a shift to more plate-like bone surrounding the implants.


CONCLUSIONS
PTH reversed the deleterious effects of long-term protein undernutrition on mechanical fixation and bone microarchitecture and improved implant osseointegration more than pamidronate or renutrition, likely through changes to structure model index.
Division of Bone Diseases, Department of Rehabilitation and Geriatrics, Faculty of Medicine, Geneva University Hospitals, WHO Collaborating Center for Osteoporosis Prevention, 1211 Geneva 14, Switzerland. Romain.Dayer@hcuge.ch
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D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight / Q000502:physiology; D050071:Bone Density Conservation Agents / Q000494:pharmacology*; D001851:Bone Diseases, Metabolic / Q000209:etiology / Q000503:physiopathology*; D018753:Diet, Protein-Restricted / Q000009:adverse effects*; D004164:Diphosphonates / Q000494:pharmacology; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical / Q000379:methods; D005260:Female; D020007:Implants, Experimental; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D016348:Osseointegration / Q000187:drug effects*; D015675:Osteocalcin / Q000097:blood; D000077268:Pamidronate; D010281:Parathyroid Hormone / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014025:Titanium; D055114:X-Ray Microtomography / Q000379:methods
D050071:Bone Density Conservation Agents; D004164:Diphosphonates; D010281:Parathyroid Hormone; D015675:Osteocalcin; D007334:Insulin-Like Growth Factor I; D014025:Titanium; D000077268:Pamidronate