2.2 Bone formation Lifecycle
Various factors are taking into consideration by the physician to determine the bone healing characteristics during a fracture. Some of the factors taken into account by physicians in making such a determination include fracture characteristics such as the gap size, location, displacement, and fragmentation of the site and patient characteristics, such as the age, gender, health conditions, weight and smoking habits of the patient. They may also identify certain mal-unions at the time of occurrence, as being susceptible to extended healing times and associated complications.
The process of bone healing generally takes from four to eights months for cortical bone and from three to six months for cancellous bone. Many fractures and voids take substantially longer to heal and some do not heal at all. Non-unions are fractures or voids that have not healed within nine months and have shown no sign of healing for the prior three months. In non-unions, the normal process of calcification fails to take place. The gap remains occupied by fibrocartilage and/or fibrous tissue and vascular penetration cannot proceed.
The following are the different stages of the bone healing process:
1. The first healing stage lasts approximately 48 hours, and is an inflammatory response in the tissue at the fracture site that stimulates the formation of stem (early stage) cells originating from bone marrow and from surface tissue at the fracture or void site. A sleeve of soft, cartilage-like new bone (periosteal callus) is formed on the outer surface (cortex) of each side of the effected bone.
2. In the second stage, as the inflammation subsides, the dead tissue at the bone ends is removed and stem cells begin to organize into a cellular matrix. The stem cells proliferate in the bone marrow cavity and evolve into cartilage cells and soft fracture callus (a matrix of fibrous tissue, cartilage and woven bone) in the outer and inne View More »