Editorial: Trends in internal fixation potential, limits and requirements

Abstract

In the last four decades, internal fixation has become a solid and reliable technology. Immediate painless functional after-treatment to allow functional recovery of the soft tissues of the limbs, thus reducing secondary problems of immobilization, was a big step in the right direction. Great advantage was gained from stable fixation in polytraumatized patients where stabilization of the skeleton permits better ventilation, improved general circulation, better handling and care, and “well being” of the patient to use a trendy word. The price for these advantages was some shortcomings, especially in local biology. Today we are reconsidering the merits of various techniques and are shifting the focus of attention from mechanics to biology under certain conditions. While recovery of function has been accepted as a major goal, the interest of the surgeons has been focused mainly on the demanding mechanical aspects of fracture treatment. Like a watchmaker, this precision of reduction could be demonstrated on radiographs and shared with colleagues; shortcomings could easily be blamed on the less gifted. These aspects fitted very well in a hierarchically oriented, highly disciplined setting. At present, the feeling is that we need vision and creativity to perform the next steps. The special emphasis on mechanics was triggered by biological studies which showed that stability, i.e. motionless fixation, avoided not only pain, thus allowing early function, but also resulted in the microscopically and radiologically fascinating pictures of internal welding or direct union. Frequently, the appearance of callus indicated that the surgeon had not achieved the goal of stable internal fixation. Callus per se was not considered deleterious, but as its appearance indicated in most cases some hidden or obvious problem callus was simply not “in”. When internal fixation was still in its infancy, biomechanical research demonstrated that bone was not only mechanically able to tolerate static compressive loads, but that compression, a major tool for achieving absolute, i.e. motionless stability, did not result in pressure necrosis. It could then be demonstrated experimentally that even minute amounts of instability, “micromotion”, triggered surface resorption of bone in contact with other bone fragments or with implants. In the context of internal fixation, the main function of both the implants and the reduced and compressed bone fragments was to act as a pre-tensioned structure. The deformation of the metal and the bone was extremely small, thus absolute stability was only maintained as long as not even a cell layer thickness of bone was resorbed or as long as the “inter-digitated” fracture surface could not settle, resulting in shortening of only a few micrometres whereby bone and implants lost their stabilizing function. The obvious contradiction between the observation of fracture healing in wild animals without any stabilization, on the one hand, and the observation that minute amounts of instability could jeopardize direct healing could possibly be explained by taking into account not only the amount of motion, but also the more important relative deformation, i.e. strain of the repair tissues. Soon it became obvious’that mechanics provided support and proper biomechanical conditions played an essential role, but biology was responsible for the reaction and, therefore, determined the outcome. In the last two decades, interest focused on soft tissue biology. Trauma and/or iatrogenic necrosis became the culprit of complications. Still, time and effort of the surgeon, resources of the community and very much the patience and faith of the unfortunate victim of trauma were strained. In the last decade, it became apparent that the real determinant of outcome was the biology of the bone itself. More and more the astonishing tolerance of bone healing to limited and elastic instability became obvious under the conditions of surgical fracture treatment. Fur-