In calcium pyrophosphate deposition (CPPD) disease, the typical joint involved in 'pseudo-osteoarthritis' pattern is the wrist. Which specific radiological finding distinguishes CPPD from calcium hydroxyapatite deposition disease (HADD)?
- A CPPD causes flocculent calcification in tendons; HADD causes calcification in articular cartilage
- B Chondrocalcinosis (calcification within the fibrocartilage and hyaline cartilage) is characteristic of CPPD, while HADD shows periarticular (bursal or tendon) calcification ✓
- C CPPD causes joint space narrowing, while HADD does not
- D Both diseases are radiologically indistinguishable
Explanation
CPPD deposits pyrophosphate crystals within fibrocartilage (menisci, triangular fibrocartilage, symphysis pubis, intervertebral discs) and hyaline cartilage, producing the X-ray finding of chondrocalcinosis — calcification within the articular cartilage substance. HADD (hydroxyapatite deposition) characteristically deposits within tendons (supraspinatus tendon in Milwaukee shoulder), bursae, and periarticular soft tissues, not within the cartilage matrix. CPPD shows rhomboidal positively birefringent crystals; HADD shows clumped ('chalk-like') calcification with no birefringence on polarised light microscopy.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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