Reversal of the detrimental effects of chronic protein malnutrition on long bone fracture healing

Objective: To determine whether dietary intervention in the immediate postf racture period will reverse the detrimental influence of protein deprivatio n on fracture healing in the rat. Design: Adult Sprague-Dawley rats were maintained on a diet containing eith er a normal or reduced protein concentration. After five weeks, both femora of each rat were pinned with an intramedullary 0.625-millimeter K-wire. A closed fracture of the right femur was created one week later, by use of a hand-held device. Groups of rats were killed and the femora harvested at 14 days for histologic study and at twenty-eight and fifty-six days for mecha nical tearing. Intervention: Control rats (Group I) were maintained on a 20 percent protei n diet. Malnourished (Group II) animals were maintained on a 6 percent prot ein diet during the six-week prefracture period and throughout the fifty-si x-day postfracture period. Malnutrition was confirmed by measurement of ser um concentrations of transferrin, immunoglobulin, and albumin. Renourished (Group III) animals were started on the 6 percent protein diet but were fed a 20 percent protein diet in the fifty-six-day postfracture period. Results: When compared with control, well-nourished rats, malnourished anim als had callus composed primarily of fibrous-type tissue and had decreased periosteal and external callus as well as callus strength. The callus from renourished animals histologically resembled that from well-nourished anima ls with large amounts of periosteal and external callus. Based on mechanica l testing results, callus from malnourished animals showed reduced strength and stiffness as compared with control renourished animals. Tn renourished animals, the cross-sectional area of the fracture callus, as well as callu s stiffness and strength, were greater than those in malnourished and well- nourished animals. Conclusion: Protein deprivation has a profound detrimental effect on fractu re healing. The identification of a protein-reduced state and its reversal could result in improved fracture healing and presumably a better clinical outcome in malnourished patients.