Perren’s Strain Theory and Fracture Healing

Abstract

The healing process of fractures depends on their biomechanical environment. The distinct knowledge and understanding of the biomechanical influence on fracture healing is the basis of the definition of the treatment strategy. The primary goal in treating a fracture is to achieve prompt and functional recovery of the injured limb. The healing process is based on the biological and mechanical situation of the fracture and its environment, defined by the interplay of rigidity and elasticity of fracture fixation. These mechanical properties directly influence the biological process of fracture healing. In cases of less rigid fixation, a callus formation can be observed that bridges the fracture gap. This healing process is supported by relative stability. Contrary to that, absolute stability aims to minimize callus formation leading to direct fracture healing. Stephan M. Perren summarized these observations in his strain theory. Strain is the deformation of elements within a material that leads to breakage if a certain degree is reached. With certain fixation methods, strain within the fracture gap can be modulated leading to different degrees of stability and different biological healing processes. Each treatment has its advantages and disadvantages that should be taken into consideration individually when defining fracture treatment strategies.