The challenge of fractures through the ages has been how to manage the severe pain, immediate disability and long term sequelae of these acutely presenting emergencies, making broken bones clear priorities due to the large number of incidences. The variety of fracture treatments includes traction, joint replacement, immobilisation, amputation and internal fixation. Open fractures with significant soft tissue injury and damage were and remain at risk of infection which was commonly treated with amputation in the past. Lister, who pioneered immunisation, developed the ideas of the open reduction of patella fractures and their internal fixation.

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 maintenance of an adequate blood supply is vital for healing and a fracture disrupts both blood supply through the bone and that of the membrane surrounding the bone, the periosteum. The four stages of bone repair are inflammation, soft callus formation, hard callus formation and remodelling. Clinical signs of inflammation are pain, swelling, redness and heat, with a haematoma forming from the considerable bleeding which occurs at the fracture site. Inflammatory cells migrate in, which stimulate formation of new blood vessels and general cell multiplication.

The Biology of Bone Fracture Repair

Around the fracture site the inflammatory phase is succeeded by fibrous tissue and cartilage producing cells, gradually growing fibrous tissue into the haematoma. The blood clot becomes stiffer with these changes and this is the steady process of stabilising which occurs during bone healing. Soft callus is transformed into hard bone via the hard callus stage as the cartilage is changed into bone and bone forms under the bone membrane. The fracture is judged to be united once a solid connection forms between the fragments and then the bone develops into mature, lacunar bone via a process of remodelling.

The normal way which fractures heal involves transformation of fibrous bone to lamellar or mature bone, this process being known as secondary bone union or indirect fracture repair. If a fracture is not fixed rigidly and is displaced to some extent then in secondary healing it heals by forming callus at the site. If the fragments are realigned very closely and then fixed with metal fixation the biology of the healing bone is different as the stabilisation and close connection of the break reduces the stresses operating across it. The allows the bone to heal without going through the callus process as the bone cells grow directly across the fracture, ensuring healing provided than high stresses are not permitted to the break. This process is known as direct bone healing and primary bone union.

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.

Fixation with Pins and Wires

Fractures are fixed by a variety of devices which include pins, wires, nails, plates and screws, depending on the location and severity of the fracture and the type of fixation provided. Pins and wires are the simplest methods of fracture fixation and the commonest ones are named after the people who developed them. Kirschner or K-wires are narrow wires varying in diameter from 0.6 to 3.0 millimetres and Steinmann pins vary from 3 to 6 millimetres in diameter. K-wires are not stiff and can be easily bent as a typical wire can, so they are mostly an addition to other methods of fracture stabilisation. These techniques can initially fix a fracture in preparation for more definitive techniques later, with minimal soft tissue and bone damage occurring.