Fracture Healing: An Overview of Existing Concepts
Curr Orthop Pract. 2016;27(2):192-197.
Healing of bone fractures has been studied for over several centuries. A number of fracture treatment modalities have been advocated, adapted, discarded, and reintroduced again. Effectiveness of many newer modalities has not been proven unequivocally. By convention, the process of bone fracture healing is divided into separate phases, but these phases are not distinct biologic entities, as one blends into another. The process of bone regeneration is subject to modification by factors such as physical attributes of the fracture itself and the condition of the individual sustaining the fracture. The operative treatment of fractures is universally practiced, but in some circumstances it may not represent the best option.
Fracture healing is the cornerstone of orthopaedics. Healing of bone fractures has been studied by surgeons and laboratory scientists over several centuries. Many fracture treatment modalities have been advocated, discarded, and adopted again, most as the results of empirical observations, and several have endured the tests of time. Among these are fracture reductions, plaster casting, bracing, intramedullary nail fixation, and compression plating. Effectiveness of many other modalities to date have not been unequivocally proven.
There are two universally recognized phenomena. The bones heal because they are broken, and bone is the only tissue capable of complete regeneration. By convention the process of bone fracture healing has been divided into three distinct phases: reactive, reparative and remodeling. However, the distinction between phases cannot be delineated accurately as one phase blends into another. To further complicate the matter, the process of bone regeneration is subject to modifications by factors such as the angle of displacement, physical attributes of the fracture itself, and the general conditions of the individual sustaining the fracture. Nonunions, malunions, and delayed unions still occur with some frequency. The pathogenesis of these complications is only partially understood.When complications occur they present challenges to orthopaedic surgeons. To deal with these effectively, the biology of bone fracture healing is best kept in mind.
The present review summarizes cumulative experiences with studies on fracture healing. It encompasses both clinical observations and laboratory studies.
In treating fractures, it is impossible to separate the fracture from the individual in whom it occurs. The most important factors are the overall state of the patient's health, nutrition, and the bone health before the injury. The present treatise deals with the biology of fracture healing in healthy, average individuals and experimental animals not compromised by osteopenia or osteoporosis. To do otherwise would require a deviation from the subject at hand, an extensive review of the literature and separate paper devoted to each topic. This is beyond the scope of the present endeavor
When one of the body's 206 dynamic living bones break, the fracture is repaired by a cascade of unique biologic events. Fracture healing is a dynamic process governed by a variety of physiologic agents and cellular elements. In the last several decades, our knowledge of the healing process has expanded partially as the result of the advancements made in other areas of medicine and biology. The ability to recognize important growth factors, improve delivery methods, and the ability to isolate and manipulate mesenchymal stem cells has led to a proliferation of research studies, many performed in rodents. Although the fact is not frequently emphasized, many studies show that it is more difficult to induce new bone formation in humans than it is in laboratory animals, particularly rodents. The heterotopic bone model in rodents, currently the gold standard for osteoinductivity for grafts intended for human use, is not analogous to conditions in humans. Heterotopic bone formation in humans is a pathologic entity.
The present hierarchy of laboratory testing related to fracture healing ranges from cell culture assay to rodent bone induction assay. The availability of much of this technical information unfortunately does not fully elucidate the mechanism of fracture healing. To successfully manage bone fractures and complications thereof, one must remain aware of the cascade nature of the process and strive to exploit it rather than work against it.
Bone is a unique tissue. Other than liver it is the only tissue capable of complete regeneration. If this capacity is utilized fully, the result will be an uneventful healing of most fractures. However, to fully exploit the circumstances, one must constantly examine the existing concepts and alter and modify these when appropriate. In a clinical setting, this is best done by learning from the patient. To this end, a quotation fromWilliam Osler is appropriate, ''Let not your conception of disease come from words heard in the lecture room or read from the book. See and then reason and compare and control. But see first.''
In dealing with fracture healing, is it possible to surpass the natural sequence of events? It may be possible, but it is not likely. Induction of accelerated bone fracture healing by chemical, physical, hormonal, and other means has been a rapidly growing area to the point where a plethora of information is presented to orthopaedic surgeons, some overwhelming, some competitive, and some with commercial overtones. Clinical evidence of the efficacy of many of these modalities is not clear, and neither are the indications, dosage, timing and the mode of action. In view of the lack of clear indications, orthopaedics will have to make a choice. A right choice can be made only on the basis of well-established findings and clinical experience.
Treatment of fractures is an all-encompassing endeavor. It takes into account the peculiarities of man and his uniqueness. It must also take into account the world in which we live, and the metamorphosis that fracture treatment has undergone in the last decades. Despite all scientific and technological advances, the comment of Paracelsus, made over 500yr ago, that the character of a physician may have more influence on the patient than the actual treatment, still holds true. A method of fracture treatment successful in the hands of one individual, might result in a failure in the hands of another. The message is clear, in dealing with patients with fractures, we should not be exclusively technicians, but physicians in the true sense of the word. At times, this may be difficult to achieve, under the external pressures exerted by the current medical environments. In this connection a distinction between science and technology should be clear. Science is systematized knowledge derived from observation, study, and experimentation carried out to determine the nature or principles of the subjects under scrutiny. Technology is the study and application of the practical or industrial arts. Technology of metal and plastic manufacturing has dominated orthopaedic surgery since the last half of the 20th century, but the price for this has been high. Concomitant with the great technological advances brought about by compression plates, screws, and intramedullary rods came some undesirable side effects. Instead of a therapeutic option some of the plating and rodding techniques became dogma.
Today the treatment of fractures has become a subject of public concern. Many of its tenets are seriously questioned and are likely to be altered for no other than economic reasons. Under the pressure of moral, social, and economic conflicts traditional percepts may no longer prevail. Just how medical ethics will emerge into in the next decades is unpredictable, but one thing is certain. Treatment of fractures will come under scrutiny. However, hopefully, even under pressure, what each individual physician judges to be the best option for managing patients with fractured bones will prevail.