Osteolysis - Causes, Symptoms and Therapy

Pathological osteolysis: When the bone substance dissolves

Osteolysis refers to the physiological bone metabolism process of bone loss that is normally in balance with bone formation (osteogenesis), or gradually increases with the natural aging process. If osteolysis has a pathological significance, it is a disease-related bone dissolution or bone decomposition of varying severity and due to various causes. Osteolytic processes are often associated with osteoporosis or bone marrow cancer. In addition to the treatment of the underlying disease, the administration of drugs from the group of bisphosphonates is of great importance to counteract the bone loss.

contents

• Pathological osteolysis: When the bone substance dissolves
• A short overview
• definition
• Causes and underlying diseases
• symptoms
• diagnosis
• treatment

A short overview

The following summary of key facts provides a brief summary of the following comprehensive article

• definitionOsteolysis is the physiological process of bone loss that occurs through so-called osteoclasts (scavenger cells) and forms part of the natural process of bone remodeling. The term "osteolysis" only becomes pathologically significant when it is referred to as pathologically increased bone loss.
• Causes and underlying diseases: Active bone resorption is caused due to various disorders or underlying diseases, such as osteoporosis or bone marrow cancer. But there are also forms without recognizable trigger. The multiple causes cause the occurrence of different forms and manifestations of bone decomposition.
• symptoms: The symptoms are very variable in the different forms and underlying diseases. In the advanced stage, various bone or joint pain may occur. Bones that have become unstable are more likely to break and can be the cause of excess calcium (due to the release of calcium in the bone loss process).
• diagnosisIn addition to the classic X-ray examination, nuclear medicine procedures, such as skeletal or bone marrow scintigraphy, can provide information about possible osteolysis and its sequelae.
• treatment: The treatment depends primarily on the underlying disease and its symptoms. In addition, bisphosphonates are often used to protect the bone substance and to inhibit its degradation.

definition

First of all, osteolysis is the natural physiological process of bone loss that is normally in equilibrium with bone formation (osteogenesis). This so-called bone remodeling process fulfills in a healthy person important functions for the maintenance and the constant renewal and adaptation of our bone and skeletal system.

Excessive bone loss (osteolysis in the medical sense) can have serious consequences. (Image: crevis / fotolia.com)

The osteoclasts are responsible for bone degradation at the cellular level. These are controlled by hormones of bone metabolism and act as bone-erosive "phagocytes". This decomposition process is counteracted to the same degree by the activity of bone-building osteoblasts. If, due to a variety of causes, this process is disrupted, this may be of pathological significance. In such cases one also speaks of active bone resorption or diseased bone dissolution.

Causes and underlying diseases

If the body breaks down more bone tissue than on, this does not necessarily lead to a general bone loss in the sense of a pathogenic osteolysis. For example, the natural aging process also causes a shift in the balance in bone metabolism. As a result, more than 50 years of age will lead to more bone loss processes even in healthy people, as new bone is built up in return.

The causes of pathogenic osteolysis are very diverse and can occur due to various disorders in the body, other underlying diseases or even without a recognizable trigger.

Disorders of bone remodeling

In the sense of an abnormal increase in bone loss in relation to the bone structure, this can occur in very different disorder processes and diseases. A relatively common disease associated with loss of bone tissue is osteoporosis (bone loss). In this osteopathy (bone disease) premature or accelerated bone degradation takes place, which leads to a reduction of the organic and mineral bone substance and thus to brittle bones. Often, hormonal causes are crucial, especially in postmenopausal women.

In addition, there is also a reduced bone mass when an osteomalce occurs. In contrast to osteoporosis, the breakdown of the bone substance here focuses on the mineral part. In most cases a calcium deficiency, in connection with a vitamin D deficiency or a disturbed Phosphatstoffwechsel, in this context the triggering factor.

These bone diseases can be systemic, meaning all bones can be affected.

The osteoclasts act as so-called phagocytes in the bone breakdown process. In pathological osteolysis, these cells often show excessive activity. (Image: Alex / fotolia.com)

Circumscribed osteolysis

In addition, other underlying diseases can cause a local loss of bone substance. Here, local osteoclast overactivities cause spatially limited degradation processes. This is commonly referred to as circumscribed osteolysis. In this disease, proper holes in the bone, which can act as punched out.

As a trigger for such processes are many diseases into consideration. These include, for example, bone tumors or bone cysts, chronic inflammatory diseases (chronic polyarthritis, osteomyelitis) or even hormonal disorders.

When it comes to cancer as a trigger, both benign and malignant bone tumors can be considered. However, cancers of other organs or malignant hematological tumors, such as various leukemia (white blood cancer), can lead to a circumscribed osteolysis.

Another condition that may be associated with local bone resorption is the isolated form of a multiple myeloma called plasmocytoma. This is a lymphoma disease in which a malignant tumor originates from the lymphocytes (bone marrow cancer). The typical picture of the punched out holes then arises at the places where the tumor cells grow in the bone. Often this is in the area of ​​the skull and one speaks in this context of a "shotgun skull".

Circumscribed (localized) osteolysis can be caused by a plasmocytoma (bone marrow cancer). (Image: fancytapis / fotolia.com)

Less common are metabolic diseases or hormonal disorders. For example, hyperthyroidism (hyperparathyroidism) causes osteolytic changes, including those in the jaw and face.

In addition, bone resorption can also occur in the area of ​​inserted endoprostheses or implants (periprosthetic osteolysis). A constant foreign body contact between the bone and the material used can lead to abrasion and thus to loss of its own bone substance. This can cause a loosening of the prosthesis or the dental implant. In addition, inflammatory processes and reactions of the immune system to infection can lead to bone loss processes - not only in the areas of the prostheses.

Also, such processes are observed in the area of ​​bone trauma and fractures, due to disorders in the healing process. For example, traumatic trauma can result from excessive weight lifting in the shoulder area (weight lifter's shoulder).

Idiopathic osteolysis

Very rarely, so-called idiopathic osteolysis can occur. The causes are unknown in these forms. One of these rare diseases is pharyngeal bone disease (Gorham-Stout syndrome), which results in the complete disintegration of a single bone.

According to different classifications, other rarely occurring hereditary (hereditary) idiopathic osteolyses are described. This includes, for example, multicenter osteolysis with or without nephropathy (kidney disease). This syndrome usually occurs as early as childhood and there is a progressive loss of bone matter with increasing age. Most of the hand and tarsal bones are affected. As a result, bone deformation causes physical restriction. Sometimes there are also mental deficits and abnormalities on the face.

In the area of ​​endoprostheses used, foreign body contact can lead to losses of bone substance. (Image: denissimonov / fotolia.com)

symptoms

Possible symptoms depend on the particular cause or underlying disease and their localization. Often complaints occur only in the advanced stage of the disease and it is not uncommon rather uncharacteristic symptoms, which are not readily attributable.

If bone dissolution is already advanced, the affected bones are unstable and, as a result, it is easier to break bones (fractures). In addition, the process releases more calcium, which can lead to excess calcium (hypercalcaemia). An example of this is osteolytic hypercalcaemia in a plasmocytoma. The discomfort of elevated levels of calcium in the blood are different. In addition to calcium deposits in various organs (for example, the kidney), the following symptoms may occur, among others:

• fatigue,
• Nausea and vomiting,
• muscle weakness,
• Arrhythmia,
• a pancreatitis,
• frequent urination,
• constipation,
• mental impairment (lack of concentration, depression).

You may also experience different pain in the diseased bones and body regions. These are often described as stress pain, chronic pain or rheumatoid joint pain.

Traditional X-ray studies help diagnose suspected osteolysis and possible consequences. (Image: angkhan / fotolia.com)

diagnosis

The diagnosis is based primarily on the causes and causative disorders and includes the age and personal information of the affected person on possible complaints.

Usually, classic X-ray examinations provide information about existing osteolysis. Fractured areas as well as existing fractures can be localized by X-ray images. If bone cancer is the cause of the decomposition processes, certain radiological signs can indicate whether it is a benign or malignant tumor.

Nuclear medicine examination methods can also help detect signs of bone disintegration. However, there is not always a high sensitivity of the examination for the different osteolytic processes. Corresponding possibilities offer the skeleton scintigraphy (also bone scintigraphy) or bone marrow scintigraphy. A scintigraphy of the skeleton represents the local bone metabolism, which can be elevated early in some diseases. Bone marrow scintigraphy displays the hematopoietic bone marrow and may also reveal very small osteolyses, such as those caused by tumor spread.

treatment

The therapy concept depends on the particular underlying disease, insofar as it could be diagnosed, and varies accordingly.

Frequently, in addition to other treatment approaches, a drug therapy with bisphosphonates is used. These drugs (for example pamidronate or zolendronate) are said to inhibit osteoclast activity by forming a kind of protective layer around the bones. This can delay the progressive bone loss and reduce the risk of fracture.

In addition, the active ingredients in the calcium metabolism, so that hypercalcemia is counteracted with harmful deposition processes of calcium in other organs. If the desired result occurs, pain is alleviated indirectly as well. In principle, those affected can choose between intravenous infusions or tablet intake. Sometimes calcitonin (for example synthetic salmon calcitonin) is used instead of corresponding bisphosphonates.

Also in the field of naturopathy, various measures can be used in addition. Here, the recommendations are based primarily on the clinical picture of the causative disorder. (tf, cs; updated on 27.11.2018)

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