Pathoanatomy and Clinical Symptoms

Degeneration is the most common joint disease, with an exponentially increasing incidence after the age of 50 years. Osteoarthritis occurs with approximately the same frequency in males and females, with primary generalized polyarthroses and erosive subtypes being characteristic in females. Aside from the spine, the hips, and the knees, the joints of the hand are predominantly affected by degenerative osteoarthritis.

Osteoarthritis generally has both a predisposing and a triggering factor. However, a small group of primary joint degenerations occur without any plausible cause ( Table 27.1 ).

Cartilaginous damage as the initial stage of osteoarthritis results from the following pathophysiologic processes:

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  There is initially a defined edematous swelling of the articular cartilage.

  
  
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  Small tears then appear in the superficial layers of articular cartilage. If the deep layers break open, the cartilag progressively loses height until the subchondral bone is exposed.

  
  
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  Reactive synovitis with granulation tissue and neoangiogenesis sets in, probably as a result of cartilaginous particles that have been rubbed off. Joint effusion is usually only minimal and can appear suddenly.

  
  
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  Vascularization also occurs in the subchondral bone matrix, from which the deep layers of cartilage are vascularized during regenerative processes.

Diagnostic Imaging

Disease Entities

Pathoanatomy and Clinical Symptoms

Osteoarthritis most commonly affects the proximal and distal interphalangeal joints, especially in women over the age of 45 years. Aside from a genetic disposition, no other causative factors for these degenerative forms are known (primary osteoarthritis). Only handedness and the extent of mechanical loading slightly influence the pattern of distribution and severity of degenerative changes. In addition to osteoarthritis of several finger joints, there are also degenerative changes at the radial side of the wrist, e.g., osteoarthritis of the scaphotrapeziotrapezoid (STT) and trapeziometacarpal (CMC I) joints. The other joints of the hand show no signs of degeneration.

Interphalangeal osteoarthritidis is usually painless. Joint function is maintained, except for morning stiffness and decreased grip strength. Soft-tissue nodules with mucoid contents (so-called mucoid cysts) arise on the dorsolateral aspect of the finger joints. These nodules communicate with the affected joint space and correspond histologically to ganglia. Arthrotic nodules on the proximal interphalangeal joints are called Bouchar nodules, and those on the distal interphalangeal joints are known as Heberden nodules, after the physicians who first described them.

Diagnostic Imaging

A typical sign of interphalangeal osteoarthritidis is the joint configuration. Since the condyle-shaped heads of the proximal and middle phalanges aremore resistant than the corresponding joint bases, in advanced stages of osteoarthritis a “seagull” deformity develops, with grinding down o the distal joint surfaces and a central spur remaining ( Table 27.3 , Fig.27.3 ).

Seagull deformities appear especially in erosive forms of osteoarthritis ( Fig. 27.11 ). They are also observed in hyperparathyroidism (see Fig. 31.8 ), in the final stages of rheumatoid arthritis (see Fig. 36.4a), and in psoriatic arthritis (see Fig. 37.2 ). Mostly, these diseases can be reliably differentiated by their different patterns of articular distribution and specific radiographic characteristics. In osteoarthritis, phalangeal subluxations to the radial or ulnar side are different from the palmar or dorsal deformities due to inflammatory tears of the tendons in rheumatoid arthritis.

Metacarpophalangeal (MP) joints II–V are seldom affected by degenerative changes in isolation ( Fig. 27.4 ). More frequent is the combination of advanced osteoarthritis in the interphalangeal joints with slight involvement in the MP joints – generally a narrowing of the joint spaces. In lesions of the MP joints resembling those of osteoarthritis, the following differential diagnoses must be considered:

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  The pattern of articular distribution in rheumatoid arthritis usually does not include the distal interphalangeal joints. There are also erosions, dislocations, and demineralization, but no osteophytes (see Fig. 36.3 ). The combination of rheumatoid arthritis with pre-existing Heberden nodules is possible, however.

  
  
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  Pronounced, hook-shaped osteophytes with flattening of the metacarpal heads and periarticular calcium deposits are typical of chondrocalcinosis (“pseudo gout,” CPPD deposition disease) and hemochromatosis (see Figs. 34.4 and 34.12 ).

  
  
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  Gout is typically manifested by means of marginal, cystic erosions and accompanying eccentric tophi with the density of soft tissues ( Fig. 34.1 ).

  
  
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  Wilson disease displays peculiar spicules.

Pathoanatomy and Clinical Symptoms

The trapeziometacarpal joint is a common location for degenerative changes, especially among women over 45 years of age. Clinically, the joint is swollen, and articular movement is accompanied by crepitation. Abduction and movements with axial pressure are painful. In advanced cases, there is a metacarpal subluxation to the radial and proximal aspects, resulting in consecutive adduction of the metacarpal I and hyperextension in the metacarpophalangeal joint. There is only a loose correlation between the clinical and the radiographic severity. Only half of the patients with osteoarthritis of the trapeziometacarpal joint have clinical symptoms.

Diagnostic Imaging

Radiographs of the wrist in two planes do not adequately depict the trapeziometacarpal joint. Because of the opposing position of the thumb in a palmar direction, the trapeziometacarpal joint can only be precisely visualized in the palmar-dorsal hyperpronated view (Chapter 1). This joint shows typical signs of osteoarthritis with narrowing of the articular space and increased subchondral sclerosis and osteophytes. The latter phenomena are more prominent on the trapezium than on the first metacarpal ( Figs. 27.5 , 27.11 ).

The classification shown in Table 27.4 is suitable for staging the severity.

Osteoproliferation in advanced osteoarthritis remodels the saddle shape of the trapezium joint surface into a half-cylindrical form. The joint surface of the trapezium is somewhat flatter in females, although there is no sex difference in the opposed joint surface of metacarpal I.