Scapholunate advanced collapse: A manifestation of calcium pyrophosphate deposition disease

A 76-year-old male with a medical history of obesity and arterial hypertension presented with pain in the left wrist with edema, redness, and functional limitation since a week ago. There was no involvement of other joints.

The posteroanterior left wrist radiograph (Fig. 1) shows a widening of the scapholunate interval, known as the Terry-Thomas sign, in honour of the famous British comedian who had a distinctive gap between upper incisors. Additionally, there is osteoarthritis of the radioscaphoid articulation with reduced joint space and markedness subchondral sclerosis contrasting with the absence of osteophytes. These findings are consistent with scapholunate dissociation with scapholunate advanced collapse (SLAC). In addition, linear calcifications can be observed in the triangular fibrocartilage and the scapholunate space, suggesting chondrocalcinosis, which a CT scan performed later also showed (Fig. 2).

The lateral left wrist radiograph (Fig. 3) demonstrates dorsal tilt of the lunate with increased scapholunate and capitolunate angle, consistent with the dorsal intercalated segment instability (DISI).

Given the findings, the diagnostic hypothesis of calcium pyrophosphate deposition disease was raised, confirmed by the presence of calcium pyrophosphate crystals in synovial fluid by polarized light microscopy.

Calcium pyrophosphate deposition disease (CPPD) is a crystalline arthropathy characterized by calcium pyrophosphate crystals in joints and peri-articular structures. It is a common disease associated with various metabolic disorders and mainly affects middle-aged or elderly people [1-4].

The formation of calcium pyrophosphate crystals occurs in the cartilage's pericellular matrix, and their passage to the synovial fluid triggers an inflammatory process responsible for acute disease crises [1-3].

Contrarily, chondrocalcinosis represent any cartilage calcification, often asymptomatic [5].

The CPPD commonly affects the knee, wrist, pubic symphysis, and spine (namely intervertebral discs and odontoid process) [1,3,5]. The involvement is mostly mono/oligoarticular, being polyarticular in only 11% of cases [3].

It is a clinically heterogeneous disease that can manifest as acute arthritis, chronic arthropathy, or asymptomatically, presenting as incidental findings of chondrocalcinosis. Acute arthritis (formerly pseudogout) is usually self-limiting, manifesting with the pain of inflammatory pattern, stiffness, erythema, and oedema [1]. Differently, chronic CPPD arthritis clinically resembles rheumatoid arthritis, with a predominance of radiological features of osteoarthritis [2].

Although identifying calcium pyrophosphate crystals in synovial fluid is necessary, the diagnosis is also supported by characteristic radiological findings [2,4]. Different imaging modalities can be used, but radiography remains the first-line method for diagnosis and monitoring [5]. Typical radiological findings of CPPD include calcifications and arthropathy. Calcifications may involve the hyaline cartilage, fibrocartilages, synovium, bursas, articular capsules, meniscus, tendons, and ligaments. CPPD arthropathy has the same characteristics as osteoarthritis (reduced joint space, subchondral osteosclerosis, and geodes); however, CPPD differs in that: it affects joints usually spared by osteoarthritis, articular surface can be jagged, numerous geodes appear, and there are few or no osteophytes [3,4].

In the wrist, the involvement of the scaphotrapezial joint, lunotriquetral ligament, scapholunate ligament, and triangular fibrocartilage complex is typical. A scapholunate ligament tear results in dorsal intercalated segment instability (DISI) with the lunate rotating into abnormal extension and the scaphoid rotating into abnormal flexion [3,6]. Classic radiographic findings of DISI include increased scapholunate interval (>4mm), increased scapholunate (>60°) and capitolunate (>30°) angles, and the cortical ring sign produced by the shortened distal pole of the scaphoid. With the progression of DISI, there is degeneration and collapse of the carpal known as scapholunate advanced collapse (SLAC). In SLAC advanced stages, the capitate can migrate proximally [6,7].

The treatment of CPPD is symptomatic, but surgery is indicated in cases of carpal instability. Our patient refused surgery, opting for conservative medical treatment with partial improvement.

Written informed patient consent for publication has been obtained.