Osteolysis is bone erosion, the bone is dissolving or lost. There is a localized area of inflammation, hyperemia, microfracture, bone resorption, and eventually arthritis of the AC joint. The condition affects the distal end of the clavicle due to micro stress fractures. It typically affects younger male patients. It occurs from activities that require overhead heavy lifting, repetitive motion, and the use of a jack hammer. The condition is also common in weight lifters.
During the examination, you will find localized pain, swelling, and tenderness over the AC joint area. Additionally, the provider will find a positive cross body adduction test. An x-ray will show erosion of the outer end of the clavicle. The acromion is okay. There may be osteopenia, osteolysis, tapering and cystic changes of the clavicle. An MRI may be obtained to rule out additional shoulder pathology. An MRI will show a high signal in the distal clavicle.
Imaging
Acromioclavicular Joint Radiography- Zanca View
Direction of the x-ray beam: The beam is directed with the cephalad angle of 10 degrees. Clavicular osteolysis can be assessed using the Zanca view. The acromion will be normal with the abnormality isolated to the distal clavicle. The Zanca view is also used for diagnosis of arthritis of the AC joint. It will show osteophytes and joint space narrowing. The findings of the x-rays may not represent the patient’s real symptoms.
Differential Diagnosis
Erosion or absence of the distal ends of the clavicle may be seen in a wide range of conditions.
Bilateral Erosions
- Hyperparathyroidism
- Rheumatoid arthritis
- Scleroderma
Unilateral Erosion
- Post-traumatic Osteolysis
- Myeloma
- Metastases
- Osteomyelitis
Treatment consists of rest, NSAIDs, ice, and activity modification. Injections may be given blindly or with ultrasound guidance. If pain persists despite conservative methods, surgery may be considered. An arthroscopic or open resection of the distal clavicle may be performed. An arthroscopy allows for evaluation of the shoulder joint. In open surgery, repair the trapezius and deltoid fascia adequately. Surgery is successful in about 90% of cases. The surgeon will resect 5-10mm of bone and keep the posterior-superior ligament intact because it maintains horizontal stability of the clavicle.
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