Osteolysis is a rare progressive condition that causes bone tissue to degenerate slowly, through the process of bone resorption. Bones in certain parts of the body lose important minerals, softening and becoming significantly weaker. There are several types of osteolysis, each involving unique mechanisms that trigger degeneration. Symptoms vary and are often minor, resulting in extreme bone damage before a person notices anything is wrong.

Bone Resorption

Bones are continually undergoing bone remodeling, and part of this process requires bone resorption, the breakdown of old bone to make way for new, healthy bone. As resorption begins, bone cells called osteoclasts secrete collagenase and other enzymes. As the osteoclasts dig into the bone, they release high levels of phosphate, magnesium, and, most importantly, calcium into the extracellular fluid. Other bone cells, osteoblasts, then deposit some of these minerals along new bones to strengthen them during the process of ossification. In children, ossification occurs more than resorption, but that changes in older individuals. Bone resorption without ossification causes weaker bones and is the primary mechanism of osteolysis.

Distal Clavicular Osteolysis

One of the more prominent forms of this condition is distal clavicular osteolysis, also known as weightlifter’s shoulder or acromioclavicular (AC) joint osteolysis. The AC joint is where the shoulder blade meets the clavicle on its outer end, and the AC ligament enables us to lift our arms above our heads. Distal clavicular osteolysis involves the breakdown of the bone in the distal end of the clavicle. In some cases, tiny fractures appear at the distal end of the bone as bone resorption takes place. In response, the affected shoulder may become stiff and painful. The condition is more prevalent among weightlifters and athletes who regularly perform significant weight training. It can also affect people who often lift heavy objects over their heads, such as factory or construction workers, and athletes who perform specific overhead movements, such as swinging a racket or swimming.

Causes of Distal Clavicular Osteolysis

Experts don’t yet fully understand the process through which distal clavicular osteolysis develops. However, most people believe it is the result of a combination of factors:

• Ongoing injuries to the AC joint or the clavicle
• Repetitive actions with heavy objects
• An underlying disease or infection
• Blunt force trauma to the clavicle
• Long-term wear on the joint in combination with an underlying condition, like rheumatoid arthritis

Additionally, researchers believe that weightlifters perform certain motions that overload this joint, which, over time, leads to microtrauma that doesn’t heal, resulting in bone degeneration.

Symptoms of Distal Clavicular Osteolysis

People with distal clavicular osteolysis usually experience mild symptoms at first that progressively worsen. Sharp pain in the AC joint or clavicle while moving the shoulder or arm is common. An individual may also feel an ongoing, dull ache even while not moving the affected area. Pressing on the end of the clavicle or collarbone may also cause discomfort. Inflammation often occurs on and around the AC joint. Progression of the pain is very slow, though continuing to use the joint can speed up the process. Some studies record bone degeneration of over an inch in severe cases.

Periprosthetic Osteolysis

Joint replacement surgery can cause periprosthetic osteolysis, which occurs when polyethylene or other materials in joint implants wear down the joint. As this occurs, debris builds up in the surrounding tissue, leading to inflammation that degenerates the bone. This is rare, though research shows that individuals who have received total hip replacement are particularly prone to the condition.

Symptoms of Periprosthetic Osteolysis

For many people, periprosthetic osteolysis is asymptomatic until very late in its progression. A characteristic symptom is the loosening of a prosthetic joint. Though infection is a common precursor, signs are not usually evident. If early symptoms do develop, they often involve varying levels of pain, stiffness, and weakness. Many experts recommend that people with joint replacements receive periodic x-rays to catch this largely asymptomatic complication early.

Acro-Osteolysis

A rare form of osteolysis affects the fingers and toes, the distal phalanges. Usually, this is due to an underlying condition that triggers significant inflammation. Acro-osteolysis occurs most often in people with rheumatic or inflammatory conditions, such as psoriatic arthritis, scleroderma, or juvenile idiopathic arthritis. People with certain infections and genetic conditions are also at higher risk of acro-osteolysis. Interestingly, there are also records of acro-osteolysis affecting unique groups of people: those with have high levels of parathyroid hormone, people who use vibratory power tools extensively, or those exposed to vinyl chloride.

Symptoms of Acro-Osteolysis

As with other forms of osteolysis, acro-osteolysis causes pain, weakness, and stiffness in the areas it affects. Additionally, it may occur alongside digital ischemia, a condition where tissues do not receive enough blood flow, leading to ulcerations like open sores as well as the death of skin cells. Some people notice color changes in their fingers as the condition progresses.

Diagnosis

Physicians use a variety of methods to diagnose osteolysis. Often, the diagnostic process begins when a patient mentions pain or weakness in the areas that osteolysis most commonly occurs. These signs, in combination with a history of factors that contribute to osteolysis, inform a doctor that x-rays and MRI scans are necessary. Scans are also useful in ruling out other causes of the symptoms.

Treatment Options

Each form of osteolysis has a different method of treatment. Distal clavicle osteolysis usually requires a fairly straightforward treatment: rest, ice, and nonsteroidal anti-inflammatory medications. Periprosthetic osteolysis often requires surgery because it is difficult to notice it before the bones undergo excess damage. Joint revision is the most common surgery for this purpose, and surgeons may support the bones around the area with various augments. Treating acro-osteolysis requires treating the underlying causes, though nonsteroidal inflammatory medications and short-term pain relief may be necessary. Physical therapy is helpful for all forms of osteolysis.