At the heart of translational research is a clinical problem. In complex soft tissue reconstruction after leg trauma, the survivability of muscle flaps after they are re-raised is poorly understood. This issue arises late in the clinical pathway, after the effect of multitudinous variables with complicated interactions has been realised. To understand this modern problem, its origins must be explored. This includes such subjects as the evolution of leg reconstruction, the basis for modern flap selection, the development of techniques for the study of an animal model and the physiological response of muscle flaps to re-operation (in terms of vascularity and perfusion). This thesis aims to describe the behaviour of a muscle flap after injury to its anatomical vascular pedicle and to apply this knowledge to the problems of when and how a muscle flap should be re-raised to facilitate safe revision of the primary defect.
An historical literature review of the management of leg trauma was undertaken, followed by a retrospective review of reconstructed leg trauma at a single institution; the largest published series to date. Controlled trials in an animal muscle flap model were then performed, designed to examine the behaviour of muscle flaps after a simulated pedicle injury under varying but controlled conditions. Finally, a randomised controlled trial that compared two different approaches to re-raising muscle flaps was undertaken using the same animal model.
The reconstruction of leg trauma has evolved over 300 years with a progressive fall in amputation and mortality rates. The biggest impact was realised prior to World War I with the adoption of simple surgical measures such as debridement and antisepsis. In the modern era, outcomes shifted from mortality to morbidity-based measures. In contemporary reconstruction of leg trauma, the risk of a poor outcome can be described by a model that incorporates time to reconstruction, tissue vascularity and the germ theory of disease. There is no difference in outcome between muscle and fasciocutaneous flaps when variables that describe the severity of injury are controlled for. Muscle flaps can perfuse independent of the anatomical vascular pedicle by time-dependant neovascularisation at the inset. The change in muscle flap perfusion after simulated pedicle injury predicts failure of the flap. In designing an approach to re-raising muscle flaps, consideration should be given to pedicle flow, desired exposure, time since inset, type of muscle used and the state of the recipient bed.
Timely debridement of compound leg wounds has always been an important part of effective treatment and is likely to remain so. Flap selection is less important than recognising cases at high risk of a poor outcome and managing these cases aggressively. A model for the behaviour of a muscle flap at re-exploration can now be described based on experimental evidence in an animal model. In all instances where the distal portion of the flap is to be raised for exposure of the underlying fracture, splitting the flap is safer and provides greater exposure than incising the inset margin of the flap. This finding can now be applied to human trials wherein the perfusion response in the flap after pedicle compression is assessed and the relationship between the region of interest covered by the flap and the pedicle is considered. The ultimate goal is to reduce morbidity and improve the quality of life for patients affected by compound leg trauma. Although the problem of muscle flap failure after it is re-raised is not common, its consequences are dire. Understanding the behaviour of muscle flaps in humans is worthwhile because of this and also because of the burden of disease presented by compound leg trauma.