The contributions of dietary protein and mineral to the healing of experimental fractures. A biomechanical study
Einhorn, T.A.; Bonnarens, F.; Burstein, A.H.
Journal of Bone and Joint Surgery. American Volume 68(9): 1389-1395
1986
ISSN/ISBN: 0021-9355 PMID: 3782211 Document Number: 272859
We examined the contributions of dietary protein and mineral to fracture-healing by assessing the mechanical properties of fracture callus in rats that were fed a diet that was deficient in or enriched by these nutrients. In order to isolate the effects of diet on fracture-healing, we developed a method for producing a standard closed femoral fracture with minimum soft-tissue injury. Three groups of animals were studied. Group I was a control group, in which the rats did not undergo an operation. The rats in Group II underwent intramedullary pinning of the right femur, but no fracture was created. The rats in Group III underwent pinning identical to that used for Group II, after which a closed, transverse femoral fracture was produced. Immediately after surgery, the animals in each group were subdivided into five diet-treatment subgroups. Subgroup A received a regular diet; Subgroup B received a protein-free diet; and Subgroup C received a mineral-free diet that was lacking in calcium, phosphorus, and vitamin D. Subgroup D received a protein-supplemented diet that was composed of three times the calculated requirement of protein, and Subgroup E received a mineral-supplemented diet that was composed of three times the calculated requirements of calcium and phosphorus as well as a therapeutic dose of vitamin D, equivalent to that used in the treatment of osteomalacia. At the end of five weeks, the animals were killed and the right femur of each one was subjected to torsion-testing to failure. Values for angular deformation, stiffness, torsional strength, and absorption of energy were obtained. The results showed that supplementation of dietary protein or mineral in excess of the calculated requirements neither improved nor impaired fracture-healing. The stiffness of the fracture callus, which is acquired early in the course of normal fracture-healing, was found to develop independent of alterations in dietary protein or mineral. The strength of the fracture callus, which is acquired later in the course of normal fracture-healing, was found to be somewhat dependent on adequate dietary mineral but showed a much greater dependence on adequate dietary protein, as evidenced by significant reductions in both torsional strength and absorption of energy in the rats that had a fracture and were fed a diet that was low in protein. Clinical Relevance: Orthopaedic surgeons are frequently asked if increasing dietary calcium or other nutritional elements will improve fracture-healing. From the results of this study, it does not appear that supplementation of dietary protein or mineral in excess of the calculated requirements will alter the process of healing. Furthermore, even in the absence of these two nutrients, early events in fracture-healing will proceed. This may be explained by the fact that, in the early stages of healing, calcium and amino acids are mobilized from other body stores in response to a skeletal injury. However, fracture callus does not achieve normal strength in the absence of dietary mineral, and significant reductions occur in both strength and energy-absorptive capacities in the absence of dietary protein. This study emphasizes the importance of nutritional support, particularly adequate dietary intake of protein, during fracture-healing.