The acromioclavicular (AC) joint, located at the top of the shoulder, plays a role in shoulder movement and overall stability. This joint connects the collarbone (clavicle) to a part of the shoulder blade (acromion). AC joint hypertrophy is a common condition that affects this area, characterized by an enlargement of the joint.
What is AC Joint Hypertrophy
The AC joint is a gliding, or plane-style synovial joint, allowing for slight gliding movements and enabling the scapula to rotate on the thorax and adjust to the changing shape of the rib cage during arm movements. It also helps transmit forces from the upper extremity to the clavicle. The joint’s small and sometimes incongruent surfaces make it susceptible to both trauma and degenerative changes.
Hypertrophy refers to an enlargement of the AC joint, often involving thickening of bone, cartilage, or the formation of bone spurs (osteophytes). These changes can narrow the joint space. This condition commonly arises from degenerative changes, similar to osteoarthritis, which involves cartilage breakdown.
Repetitive stress on the shoulder, such as that experienced by weightlifters or individuals performing frequent overhead activities, can contribute to AC joint hypertrophy. Previous injuries or trauma to the AC joint, like dislocations or separations, also increase the likelihood of this condition. Degenerative changes can begin as early as the second decade of life, with joint space narrowing commonly observed by the sixth decade.
Recognizing the Symptoms
Individuals with AC joint hypertrophy often experience pain at the top of the shoulder. This pain can be aching, sharp, or dull, and may worsen with certain movements. Activities such as reaching overhead, performing cross-body movements (like reaching for a seatbelt), or sleeping on the affected side can aggravate discomfort.
Other indicators may include clicking, popping, or grinding sensations within the joint, medically known as crepitus. The area around the AC joint might also feel tender to the touch. Sometimes, a visible bump or deformity, an osteophyte, may be present at the top of the shoulder.
The pain from AC joint hypertrophy can sometimes radiate down the arm or into the neck. Persistent pain and limited motion might lead to muscle weakness in the shoulder. Some individuals also report increased discomfort at night, which can disrupt sleep patterns.
Diagnosis and Treatment Options
Diagnosing AC joint hypertrophy begins with a physical examination. A healthcare professional will palpate the joint for tenderness and assess the shoulder’s range of motion. Imaging studies are then used to confirm the diagnosis and assess the condition’s extent.
X-rays are used to visualize degenerative changes such as joint space narrowing and bone spurs. Magnetic Resonance Imaging (MRI) provides detailed images of soft tissues, detecting capsular hypertrophy, fluid accumulation, and bone marrow edema. Computed Tomography (CT) scans offer a more detailed assessment of bony structures. Diagnostic injections, typically involving a corticosteroid mixed with a local anesthetic, administered directly into the AC joint, can confirm it as the source of discomfort if pain relief follows.
Treatment options for AC joint hypertrophy include non-surgical and surgical interventions. Conservative non-surgical approaches are often the first line of treatment. These include rest, modifying activities to avoid aggravating movements, and applying ice to the affected area to reduce inflammation. Over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen or naproxen are recommended to alleviate pain and swelling.
Physical therapy is important for conservative management, focusing on strengthening surrounding shoulder and scapular muscles and improving overall shoulder biomechanics. Corticosteroid injections into the AC joint can provide temporary pain relief. If conservative treatments do not provide sufficient relief after several months, surgical intervention may be considered.
A common surgical procedure for AC joint hypertrophy is the distal clavicle excision, also known as the Mumford procedure. This procedure involves removing a small portion of the end of the clavicle where it meets the acromion. This creates space between the bones, preventing them from rubbing together and alleviating pain. The Mumford procedure can be performed using either an open technique or a minimally invasive arthroscopic approach, with arthroscopic methods often leading to quicker recovery.
Managing the Condition Long-Term
Long-term management of AC joint hypertrophy involves lifestyle adjustments to minimize stress on the joint and prevent symptom worsening. Modifying exercise routines is often recommended, such as adjusting weightlifting techniques to avoid aggravating movements. Exercises that work similar muscle groups with less joint irritation may be suggested.
Maintaining proper posture is also beneficial, as it can help align the shoulder and reduce undue strain on the AC joint. Strengthening the surrounding shoulder and scapular muscles through targeted exercises helps improve joint stability and function. Physical therapy programs focus on improving range of motion and building muscle strength.
Ongoing pain management strategies include ice therapy, particularly after activities that might increase discomfort. Regular follow-ups with healthcare professionals are important to monitor the condition’s progression, adjust treatment plans, and explore new management strategies. While AC joint osteoarthritis is a chronic degenerative condition that can worsen over time, proactive management helps preserve mobility and improve overall quality of life.