How do you diagnose Calcium Pyrophosphate Dihydrate (CPPD) disease at the wrist?

Diagnosis of Calcium Pyrophosphate Deposition (CPPD) Disease at the Wrist

The diagnosis of CPPD at the wrist requires a combination of conventional radiography and ultrasound, with synovial fluid analysis being the gold standard for definitive diagnosis.

Diagnostic Approach

Initial Imaging

• Conventional radiography should be the first imaging modality used when CPPD is suspected at the wrist 1
• Standard radiographic examination should include posterior-anterior and lateral views in neutral position, supplemented by oblique views 2
• Look for punctate and linear radiodense areas in fibrocartilage and hyaline cartilage, which are characteristic of chondrocalcinosis 3
• Radiography has high specificity (100%) but limited sensitivity (53.1%) for detecting CPPD at the wrist 4

Ultrasound Examination

• Ultrasound is recommended as a complementary imaging modality with significantly higher sensitivity (94%) than radiography for detecting CPPD crystals 1, 4
• Standard ultrasound examination of the wrist should include:
  • Dorsal transverse scans (both radial and ulnar) 1
  • Dorsal longitudinal scans (radial, median, and ulnar) 1
  • Volar transverse and longitudinal scans 1
• Use high-frequency transducers (10 MHz or higher) to detect even minor crystal deposits 1
• Position the patient in sitting position with the hand on top of the thigh or on an examining table 1

Synovial Fluid Analysis

• Synovial fluid analysis remains the gold standard for definitive diagnosis of CPPD 1, 5
• If joint aspiration is needed, ultrasound guidance should be used when aspiration based on anatomical landmarks is challenging 1
• Examine synovial fluid using:
  • Non-polarized light microscopy initially to screen for CPPD crystals based on their characteristic morphology 6
  • Compensated polarized light microscopy for definitive identification, showing weakly positive birefringent crystals (though this pattern only occurs in about 20% of samples) 6, 3

Specific Radiographic Features to Look For

• Trapezioscaphoid joint abnormalities are present in 43.7% of CPPD wrists compared to 14.4% in control wrists 7
• Associated features include first carpometacarpal arthropathy and subchondral cysts in the scaphoid or trapezium 7
• These features may suggest CPPD diagnosis even when chondrocalcinosis is obscured or absent 7

Clinical Considerations

• The wrist is one of the common target sites for CPPD, along with the knee 1
• When performing imaging for CPPD, both symptomatic areas and disease-specific target sites should be examined 1
• Consider CPPD in patients with acute or chronic wrist pain, especially in those over 65 years (prevalence 10-15% in age group 65-75 years) 3
• Early disease (onset before age 60) requires evaluation for underlying metabolic conditions, particularly hyperparathyroidism, hemochromatosis, hypomagnesemia, and hypophosphatasia 3

Diagnostic Algorithm

1. Begin with conventional radiography of the wrist 1
2. If radiography is negative or equivocal but CPPD is still suspected, proceed to ultrasound examination 1, 4
3. If imaging findings suggest CPPD, consider synovial fluid aspiration and analysis for definitive diagnosis 1, 6
4. In cases where joint aspiration is difficult, use ultrasound guidance 1

Common Pitfalls and Caveats

• Relying solely on radiography may miss CPPD due to its limited sensitivity (53.1%) 4
• Ultrasound can detect CPPD in 93.7% of cases compared to 53.1% with radiography alone 4
• The agreement between ultrasound and radiography for detecting chondrocalcinosis is only moderate (κ coefficient = 0.33) 4
• CPPD can mimic other conditions such as osteoarthritis, rheumatoid arthritis, or neuropathic joint disease, leading to misdiagnosis 6, 3
• Patient information (medical history, physical examination, laboratory findings) should always be considered alongside imaging findings 1