Background/Purpose:

Digital imaging combined with picture archiving and communication system (PACS) access allows detailed image retrieval and magnification. Calcium pyrophosphate dihydrate (CPPD) crystals preferentially deposit in fibrocartilages, the cartilage of the acromioclavicular (AC) joint being one such structure. We sought to determine if careful examination of the AC joints on magnified PACS imaging of routine chest films would be useful in identifying chondrocalcinosis (CC).

Methods:

Retrospective radiographic readings and chart reviews involving all 1920 patients aged 50 or more who had routine outpatient chest radiographs over a 4 month period were performed. CC was identified as linear or punctate cartilage calcifications. Knee radiographs were available for comparison in 489 patients. Medical records were reviewed to abstract demographics, chest film reports, and diagnoses. 

Results:

AC joint CC was identified in 1.1% (21/1920) of consecutive chest films. Patients with AC joint CC were 75 (± 11.6 S.D.) years of age versus 65 (±10.5 S.D.) in those without CC (p<0.0002, Wilcoxon rank sum). There was no significant gender difference in the prevalence of AC CC. 489 patients had knee films. 6 of these patients had AC joint CC and of these 5 also had knee CC (83%). Of the 483 without AC joint CC 62 (12%) had knee CC (p=0.002 Fischer's exact). Of the patients with AC joint CC only 14% had a diagnosis of CPPD recorded on the chart and none had AC joint calcification noted on the official radiology report. Patients with AC joint CC were more likely to have a recorded history of CPPD crystal disease than those without AC joint CC (14% versus 1%, p=0.0017 Fischer's exact). 

Conclusion:

By using digital imaging and PACS software magnification, AC joint CC is discernible on routine chest films. The prevalence of AC joint CC increases with age and is usually an indicator of associated knee CC. AC joint CC is most often overlooked by radiologists reading routine chest images. Rheumatologists (and radiologists) should consider scrutiny of available chest films for AC joint CC. A finding of AC joint CC should heighten suspicion of pseudogout or secondary osteoarthritis in appropriate clinical settings. And AC joint CC in a young patient should alert the clinician to the possibility of an associated metabolic condition. Moreover, such scrutiny is without cost other than less than a minute of time.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-prevalence-of-chondrocalcinosis-of-the-acromioclavicular-joint-on-chest-radiographs-and-correlation-with-calcium-pyrophosphate-dihydrate-crystal-deposition-disease/