A 52-year-old male patient presented with a history of right shoulder pain, which started about two weeks earlier, and was aggravated by lifting the arm. There was no restriction of movements, nor prior history of trauma.
The conoid tubercle of the right clavicle is elongated, with a flattened inferior surface directly pointing at the coracoid process of the scapula, forming an anomalous articulation [arrow, Fig. 3]. Sclerosis of the articular surfaces and osteophytes formation was noted. A comparison X-ray of the left shoulder revealed similar findings [arrow, Fig. 4].
Normally in humans, there is a coracoclavicular ligament (CCL) between the conoid tubercle of the clavicle and the superior surface of the horizontal part of the coracoid process of the scapula. The CCL is composed of two separate bands (conoid and trapezoid) in humans (Fig. 1), as opposed to a single band in primates [1]. On plain films, the conoid tubercle is a bony prominence off the inferior surface of the lateral third of the clavicle (arrows, Fig. 2). DA coracoclavicular joint (CCJ) is formed between a prominent conoid tubercle of the clavicle and the coracoid process of the scapula. It is a true synovial joint that is easily observed in some primates [2] because their shoulders are weight-bearing due to their locomotion and posture [1]. It is rarely seen in humans as a normal variant, as the human shoulder is a relatively weight-free structure. It may be found unilaterally or bilaterally, and is usually asymptomatic. It can be symptomatic due to trauma [3] or degeneration [4]. Posttraumatic ossification of the CCJ will lead to neurovascular impingement.
The plain radiographs of both shoulders in the current case show a bony outgrowth from the normal position of the conoid tubercle of the clavicle, forming an articulation with the coracoid process. There are associated degenerative changes in both joints. It is not clear if the presented symptoms are due to the degenerative changes.
Osteophytes, which are defined as lateral outgrowths of bone at the margin of the articular surface of a synovial joint, occur due to aging or as a response of the skeletal system to stress and injury. CT examination can confirm the presence of the abnormal joint and the existence of degenerative changes [4]. MRI will show not only the joint, but also its capsule.
A symptomatic CCJ can be treated by intracapsular injection of local anaesthetic - Xylocaine 2%, or by surgical resection [3, 5, 6].
Bilateral coracoclavicular joints with degenerative changes.
Based on the provided anteroposterior and lateral X-ray images of the shoulder, a noticeable bony outgrowth can be seen under the coracoid process on the lateral segment of the clavicle, forming a joint-like change with the coracoid process. This area corresponds to the normal site of the conoid tubercle but exhibits proliferative changes aligning with the articular surface of the coracoid process, suggestive of the formation of a coracoclavicular joint (CCJ).
Meanwhile, around the local joint surface, there are signs of bony proliferation or osteophyte-like changes (e.g., marginal sclerosis, mild irregularity of the joint space), indicating some degree of degenerative changes. This coracoclavicular joint morphology is uncommon in both shoulders. In this case, there is no obvious fracture on the imaging, nor is there any significant soft tissue swelling or calcification visible.
The coracoclavicular joint is more commonly seen in primates but is a rare congenital or anatomical variation in humans. The imaging in this case shows a bony outgrowth at the conoid tubercle of the clavicle forming a joint-like connection with the coracoid process, along with mild osteophyte formations that are consistent with degenerative changes. If the area is involved in inflammation, arthritis, or trauma, it may lead to shoulder pain or restricted movement.
Shoulder pain in middle-aged or older adults is often related to impingement under the acromion causing rotator cuff tendinopathy or partial tears. Although no obvious acromion morphological abnormalities or calcifications are noted on the images, it is clinically necessary to rule out the possibility of rotator cuff tissue damage.
AC joint degeneration is common in middle-aged and older patients, which can cause pain and local tenderness. Significant hypertrophy of the AC joint could be mistaken for a coracoclavicular joint or coracoclavicular ligament calcification. However, the main imaging changes in this case focus on the coracoclavicular region.
Plain radiographs of the shoulder may not reveal specific bony changes, but clinically one must still consider frozen shoulder, synovitis, or other functional disorders. No prominent signs are indicated on imaging.
Considering the patient's age, a two-week course of symptoms, no apparent history of trauma, and the imaging demonstrating a rare coracoclavicular joint formation along with degenerative changes, the most probable diagnosis is: “Coracoclavicular joint variant with accompanying degenerative changes.” This anatomical feature may have existed for years, but recent changes in use or mild strain might have triggered the current pain. Further clinical examination and additional tests (such as local anesthetic injection, MRI, etc.) are needed to confirm whether this structure is directly related to the present symptoms.
If it is definitively identified that degenerative changes in the coracoclavicular joint are the main source of pain and repeated conservative treatments fail, surgical resection or correction of the abnormal joint area may be considered to reduce pain and improve shoulder function.
During gradual progression, attention should be paid to maintaining proper shoulder movement patterns to prevent injury to other structures.
This report is a reference analysis based on existing imaging data and basic medical history. It does not replace a face-to-face diagnosis and examination by a clinician. If symptoms persist or worsen, please seek professional medical evaluation and treatment promptly.
Bilateral coracoclavicular joints with degenerative changes.
