Reversal of the Detrimental Effects of Chronic Protein Malnutrition on Long Bone Fracture Healing

OBJECTIVETo determine whether dietary intervention in the immediate postfracture period will reverse the detrimental influence of protein deprivation on fracture healing in the rat. DESIGNAdult Sprague-Dawley rats were maintained on a diet containing either 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 mechanical testing. INTERVENTIONControl rats (Group I) were maintained on a 20 percent protein diet. Malnourished (Group II) animals were maintained on a 6 percent protein diet during the six-week prefracture period and throughout the fifty-six–day postfracture period. Malnutrition was confirmed by measurement of serum 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. RESULTSWhen compared with control, well-nourished rats, malnourished animals 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 animals with large amounts of periosteal and external callus. Based on mechanical testing results, callus from malnourished animals showed reduced strength and stiffness as compared with control renourished animals. In renourished animals, the cross-sectional area of the fracture callus, as well as callus stiffness and strength, were greater than those in malnourished and well-nourished animals. CONCLUSIONProtein deprivation has a profound detrimental effect on fracture 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.