Bone pain

Bone pain (also known medically by several other names) is pain coming from a bone, and is caused by damaging stimuli. It occurs as a result of a wide range of diseases or physical conditions or both, and may severely impair the quality of life.

Bone pain belongs to the class of deep somatic pain, often experienced as a dull pain that cannot be localized accurately by the patient. This is in contrast with the pain which is mediated by superficial receptors in, e.g., the skin. Bone pain can have several possible causes ranging from extensive physical stress to serious diseases such as cancer.

Bones contain nerves. The periosteal layer (an outer membrane) of bone tissue is highly pain-sensitive and an important source of pain in several disease conditions causing bone pain, like fractures, osteoarthritis, etc. However, in certain diseases, the endosteal and haversian nerve supply seems to play an important role, e.g. in osteomalacia, osteonecrosis, and other bone diseases.^{[citation needed]} Thus, there are several types of bone pain, each with many potential sources or origins of cause.

Causes

A number of diseases can cause bone pain, including the following:

• Endocrine, such as hyperparathyroidism, osteoporosis, kidney failure.
• Gastrointestinal or systemic, such as celiac disease and non-celiac gluten sensitivity (both often occur without obvious digestive symptoms), inflammatory bowel disease (including Crohn's disease and ulcerative colitis).
• Hematologic, such as Cushing's syndrome, histiocytosis, multiple myeloma and sickle cell anaemia.
• Infectious, such as Lyme disease and osteomyelitis.
• Neurological, such as spinal cord injury and vertebral degeneration.
• Oncologic, such as bone metastasis, oncogenic osteomalacia and leukemia.
• Rheumatic, such as ankylosing spondylitis, rheumatoid arthritis, gout.
• Others, such as fractures, osteoarthritis, Paget's disease of bone (also termed osteitis deformans or just Paget's disease).

Pathophysiology

Stimulation of specialized pain-sensitive nerve fibers (nociceptors) that innervate bone tissue leads to the sensation of bone pain. Bone pain originates from both the periosteum and the bone marrow which relay nociceptive signals to the brain creating the sensation of pain. Bone tissue is innervated by both myelinated (A beta and A delta fiber) and unmyelinated (C fiber) sensory neurons. In combination, they can provide an initial burst of pain, initiated by the faster myelinated fibers, followed by a slower and longer-lasting dull pain initiated by unmyelinated fibers.

Nociceptors responsible for bone pain can be activated via several mechanisms including deterioration of surrounding tissue, bone destruction, and physical stress which shears the bone, vascular, muscle, and nervous tissue.

Treatment

The use of anesthetics within the bone has been a common treatment for several years. This method provides a direct approach using analgesics to relieve pain.

Another commonly used treatment is radiotherapy, which can be safely administered in low doses. Radiotherapy uses radioactive isotopes and other atomic particles to damage the DNA in cells, leading to cell death. By targeting cancer tumors, radiotherapy can decrease tumor size and even destroy the tumor. A form of radiotherapy often used in bone cancer is systemic radioisotope therapy, where the radioisotopes target sections of the bone specifically undergoing metastasis.

In bone fractures, surgical treatment is generally the most effective. Analgesics can be used with surgery to help ease pain of damaged bone.

Research

Mice and other animal models are being heavily used to determine the neuron tissue densities in bone and mechanisms for maintenance of bone pain. This information is pertinent to determining the biological and physiological components of pain in the bone. By creating a detailed map relating the types of nerves going through the different sections of bone, it is possible to pin-point locations in the bone that are at a higher risk of being susceptible to bone pain.

Treatments focusing on biological components such as cannabinoid receptors are being tested for effectiveness. Through testing in mouse models, it has been shown that activation of the CB-1 receptor helps reduce reactions associated with acute pain, indicating that it alleviates bone pain. Thus, a new target for potential treatments is activation of the CB-1 receptor.

Modern research and techniques are attempting to provide longer-lasting and more effective methods of treating bone pain by developing and applying new physiological knowledge of nervous tissue within the bone. If thorough understanding of the intra-neuronal mechanisms relating to pain can be developed, then new and more effective treatment options can be created and tested. Thus, it is critical to fully understand the mechanism which dictates bone pain.^{[citation needed]}

Names

Bone pain is also known by the following names:

References