Internal Fixation of Bone Fracture
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Broken bones have always been challenging to manage due to the severity of the acute disability, the level of the pain and the functionally important negative consequences which can ensue, ensuring fracture treatment an important place in medical care. Fracture treatments have included amputation, immobilisation, replacement, internal fixation and traction. Infection is and was a significant risk in open fractures which might have important soft tissue damage, typically managed in the past by amputation. The surgeon who developed immunisation, Lister, promoted the concept of openly reducing and internally fixing patellar fractures.
In the 1880s and 1890s the use of plates, screws and wires was introduced but was compromised by infection, implant design, allergy to the metals and a poor understanding of the biology underlying fracture healing. The techniques and principles of fracture fixation developed in the 1950s and more recent scientific advancement in mechanical and biological understanding of fractures and their healing have led to modern methods of assessing, managing and fixing fractures.
The blood supplies through the solid bone and that through the surrounding membrane are both disrupted by a fracture and good fracture healing depends on having an adequate blood supply. Inflammation, soft callus, hard callus and remodelling are the four stages of bone fracture repair and a fracture exhibits the cardinal signs of inflammation which include redness, swelling, pain and heat. When a bone fractures the area bleeds and collects as a haematoma at the site. New blood vessels form and cells multiply secondary to immigration of inflammatory cells.
Bone Fracture Repair Biology
The haematoma around the site of the fracture attracts chondroblasts, cells which manufacture cartilage, and the fracture area becomes invaded by fibrous tissue. This increases the stability of the blood clot at the fracture and starts the progress towards stiffening. The soft callus which forms initially is then converted into hard bone via the hard callus phase by cartilage gradually becoming bone and bone forming below the membrane covering the bone. Once a more solid connection develops between the fragments the fracture is rated as united, after which time it gradually develops into lacunar or mature bone via a remodelling process.
Indirect fracture repair or secondary bone union is the process whereby fibrous bone is changed into mature lamellar bone, the typical way that fractures heal. In secondary healing the formation of callus occurs in a fracture which is not rigidly fixed and which has some displacement. The healing bone biology can be altered by reducing the fracture closely, i.e. getting the fragments in close contact and then fixing it internally. Removing the stresses applied to the fracture is achieved by the close approximation and stabilisation of the break and this can lead to the missing out of the callus stages in a direct healing across the break. As long as inappropriate levels of force are not applied to the site whilst healing the process completes, a process named primary bone union or direct bone healing.
Once the internal fixation of the fracture has been applied, the technique used will determine which way the fracture will heal due to the mechanical environment provided. If the operative fixation provides for some fracture movement and does not stabilise the fracture completely then healing with secondary or indirect healing will be the result. If the fixation provides for very little movement between the fragments and therefore a highly stable site, direct or primary healing will be the result.
Types of Fixation - Pins and Wires
Many devices are used for fixing fractures and these include screws, plates, nails and wires, the choice of which depends on the severity, position and type of fracture. The simplest types of fixation of fracture are the use of wires and pins and the most commonly used are indicated by the name of the surgeon who designed them. Steinmann pins are between three and six millimetres in diameter and K-wires (Kirschner wires) are between 0.6 and three millimetres in diameter. The lack of stiffness of a normal wire means that K-wires are easy to bend so are used as an adjunct to more secure fixation. They can be used to perform the initial fracture stabilisation while the more permanent fixation is being planned, without damaging the site.
Article Source: Articlelogy.com
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