Bone fracture

Signs and symptoms

Although bone tissue itself contains no nociceptors, bone fracture is painful for several reasons:

Damage to adjacent structures such as nerves or vessels, spinal cord, and nerve roots (for spine fractures), or cranial contents (for skull fractures) may cause other specific signs and symptoms.

Pathophysiology

The natural process of healing a fracture starts when the injured bone and surrounding tissues bleed, forming a fracture hematoma. The blood coagulates to form a blood clot situated between the broken fragments. Within a few days, blood vessels grow into the jelly-like matrix of the blood clot. The new blood vessels bring phagocytes to the area, which gradually remove the non-viable material. The blood vessels also bring fibroblasts in the walls of the vessels and these multiply and produce collagen fibres. In this way the blood clot is replaced by a matrix of collagen. Collagen's rubbery consistency allows bone fragments to move only a small amount unless severe or persistent force is applied.

At this stage, some of the fibroblasts begin to lay down bone matrix in the form of collagen monomers. These monomers spontaneously assemble to form the bone matrix, for which bone crystals (calcium hydroxyapatite) are deposited in amongst, in the form of insoluble crystals. This mineralization of the collagen matrix stiffens it and transforms it into bone. In fact, bone is a mineralized collagen matrix; if the mineral is dissolved out of bone, it becomes rubbery. Healing bone callus on average, is sufficiently mineralized to show up on X-ray within 6 weeks in adults and less in children. This initial "woven" bone does not have the strong mechanical properties of mature bone. By a process of remodeling, the woven bone is replaced by mature "lamellar" bone. The whole process may take up to 18 months, but in adults, the strength of the healing bone is usually 80% of normal by 3 months after the injury.

Several factors may help or hinder the bone healing process. For example, any form of nicotine hinders the process of bone healing, and adequate nutrition (including calcium intake) will help the bone healing process. Weight-bearing stress on bone, after the bone has healed sufficiently to bear the weight, also builds bone strength.

Although there are theoretical concerns about NSAIDs slowing the rate of healing, there is not enough evidence to warrant withholding the use of this type analgesic in simple fractures.

Effects of smoking

Smokers generally have lower bone density than non-smokers, so have a much higher risk of fractures. There also is evidence that smoking delays bone healing.

Diagnosis

A bone fracture may be diagnosed based on the history given and the physical examination performed. Radiographic imaging often is performed to confirm the diagnosis. Under certain circumstances, radiographic examination of the nearby joints is indicated in order to exclude dislocations and fracture-dislocations. In situations where projectional radiography alone is insufficient, Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) may be indicated.

Classification

In orthopedic medicine, fractures are classified in various ways. Historically they are named after the physcian who first described the fracture conditions, however, there are more systematic classifications in place currently.

Mechanism

Soft-tissue involvement

Displacement

Fracture pattern

Fragments

Anatomical location

An anatomical classification may begin with specifying the involved body part, such as the head or arm, followed with more specific localization. Fractures that have additional definition criteria than merely localization often may be classified as subtypes of fractures, such as a Holstein-Lewis fracture being a subtype of a humerus fracture. Most typical examples in an orthopedic classification given in previous section cannot be classified appropriately into any specific part of an anatomical classification, however, as they may apply to multiple anatomical fracture sites.

OTA/AO classification

The Orthopaedic Trauma Association Committee for Coding and Classification published its classification system in 1996, adopting a similar system to the 1987 AO Foundation system. In 2007, they extended their system, unifying the two systems regarding wrist, hand, foot, and ankle fractures.

Classifications named after people

Treatment

Treatment of bone fractures are broadly classified as surgical or conservative, the latter basically referring to any non-surgical procedure, such as pain management, immobilization or other non-surgical stabilization. A similar classification is open versus closed treatment, in which open treatment refers to any treatment in which the fracture site is opened surgically, regardless of whether the fracture is an open or closed fracture.

Pain management

In arm fractures in children, ibuprofen has been found to be as effective as a combination of acetaminophen and codeine.

Immobilization

Since bone healing is a natural process that will occur most often, fracture treatment aims to ensure the best possible function of the injured part after healing. Bone fractures typically are treated by restoring the fractured pieces of bone to their natural positions (if necessary), and maintaining those positions while the bone heals. Often, aligning the bone, called reduction, in good position and verifying the improved alignment with an X-ray is all that is needed. This process is extremely painful without anesthesia, about as painful as breaking the bone itself. To this end, a fractured limb usually is immobilized with a plaster or fiberglass cast or splint that holds the bones in position and immobilizes the joints above and below the fracture. When the initial post-fracture edema or swelling goes down, the fracture may be placed in a removable brace or orthosis. If being treated with surgery, surgical nails, screws, plates, and wires are used to hold the fractured bone together more directly. Alternatively, fractured bones may be treated by the Ilizarov method which is a form of external fixator.

Occasionally smaller bones, such as phalanges of the toes and fingers, may be treated without the cast, by buddy wrapping them, which serves a similar function to making a cast. By allowing only limited movement, fixation helps preserve anatomical alignment while enabling callus formation, toward the target of achieving union.

Splinting results in the same outcome as casting in children who have a distal radius fracture with little shifting.

Surgery

Surgical methods of treating fractures have their own risks and benefits, but usually surgery is performed only if conservative treatment has failed, is very likely to fail, or likely to result in a poor functional outcome. With some fractures such as hip fractures (usually caused by osteoporosis), surgery is offered routinely because non-operative treatment results in prolonged immobilisation, which commonly results in complications including chest infections, pressure sores, deconditioning, deep vein thrombosis (DVT), and pulmonary embolism, which are more dangerous than surgery. When a joint surface is damaged by a fracture, surgery is also commonly recommended to make an accurate anatomical reduction and restore the smoothness of the joint.

Infection is especially dangerous in bones, due to the recrudescent nature of bone infections. Bone tissue is predominantly extracellular matrix, rather than living cells, and the few blood vessels needed to support this low metabolism are only able to bring a limited number of immune cells to an injury to fight infection. For this reason, open fractures and osteotomies call for very careful antiseptic procedures and prophylactic use of antibiotics.

Occasionally, bone grafting is used to treat a fracture.

Sometimes bones are reinforced with metal. These implants must be designed and installed with care. Stress shielding occurs when plates or screws carry too large of a portion of the bone's load, causing atrophy. This problem is reduced, but not eliminated, by the use of low-modulus materials, including titanium and its alloys. The heat generated by the friction of installing hardware can accumulate easily and damage bone tissue, reducing the strength of the connections. If dissimilar metals are installed in contact with one another (i.e., a titanium plate with cobalt-chromium alloy or stainless steel screws), galvanic corrosion will result. The metal ions produced can damage the bone locally and may cause systemic effects as well.

Other

Evidence for ultrasound to speed healing in newly broken bones is insufficient to justify routine use. Vitamin D supplements combined with additional calcium marginally reduces the risk of hip fractures and other types of fracture in older adults; however, vitamin D supplementation alone did not reduce the risk of fractures.

Complications

Some fractures may lead to serious complications including a condition known as compartment syndrome. If not treated, eventually, compartment syndrome may require amputation of the affected limb. Other complications may include non-union, where the fractured bone fails to heal or mal-union, where the fractured bone heals in a deformed manner.

Complications of fractures may be classified into three broad groups, depending upon their time of occurrence. These are as follows –

1. Immediate complications – occurs at the time of the fracture
2. Early complications – occurring in the initial few days after the fracture
3. Late complications – occurring a long time after the fracture

Children

In children, whose bones are still developing, there are risks of either a growth plate injury or a greenstick fracture.