The correct diagnosis is Subluxed Terminal Phalanx in Osteoarthrosis
The hands look as old as the reported age, in part because the skin appears thin and wrinkled, so that the veins on the dorsa stand out prominently. The thumbs appear somewhat "jammed" onto the palms, especially on the left, where a bumpy first metacarpophalangeal joint replaces a normally more gradual curvature. The fingers, however, catch our attention: both fifth fingers appear stiff and out-deviated in a fashion that recalls the digiti quinti sign of mild hemiparesis.1 Both index fingers show flexion and ulnar deviation at the distal interphalangeal joint (Figure); the left middle finger displays a very similar deformity. The proximal interphalangeal joint of the right middle finger looks a bit pushed-upward into a faint shadow of the boutonniere deformity of rheumatoid arthritis (RA),2 but the overall appearance of the hands does not suggest RA. We concluded that the deformities all related to age and ordinary osteoarthrosis.
One entity to consider is mallet finger, analogous to mallet toe, wherein rupture of the extensor tendon leads to unopposed flexion of the terminal phalanx.3,4 However, there was no antecedent injury, nor any known disorder of tendons that should predispose to rupture. Such tendon disorders include enthesopathies and the iatrogenic links to some quinolones—chiefly implicated in Achilles tendon rupture—and to the "it weakens everything" suspicion that attaches to chronic systemic corticosteroid ingestion. Furthermore, our patient has an element of ulnar deviation that is more conspicuous, at least in these images, than the flexion deformity. Mallet finger should not produce this.
It would seem highly unlikely that a single patient would have fractures of 3 separate phalanges, unless a single injury were implicated—perhaps via a landing on outstretched fingers during a fall or a motor vehicle crash. Much more familiar, and more likely in a younger woman around menopausal age, would be the braced-hand Colles fracture of the wrist.
Rotation can occur in phalangeal fractures,3 but not typically this far distally. There is no way to create a convincing single scenario that would also explain the distorted bases of the thumbs and the "outrigger" fifth fingers.4
Several "What's Your Diagnosis?" columns have addressed RA in the hands.2,5-7 There is no single feature pathognomonic of rheumatoid hand; the most suggestive features include major metacarpophalangeal joint involvement and joint disease that is much more significant in the proximal interphalangeal joints than in the distal. In the present case, the abnormalities do not include a "knuckle sign." Apart from the thumbs, there is not even a forme fruste of the opera glass deformity of arthritis mutilans,7 which is most typically rheumatoid although reported in other conditions as well. Ulnar deviation of the digits is often cited as evidence for RA, but it can occur in plain osteoarthrosis as well.
Here the distal interphalangeal joints are relatively selectively involved. Such localization favors 3 differential diagnoses: the ubiquitous osteoarthrosis and the less common gouty and psoriatic arthritides.4
Not Shying Away
Distinct diagnosis of the hand can feel overpoweringly difficult to non-rheumatologist primary care physicians. Or one can venture inferences, but only about nonmusculoskeletal problems.8 However, simple assessment tools for functional disorders9 as well as for joint problems ease our task.10
The Gait, Arms, Legs, and Spine (GALS) screening test advocated by the Arthritis Foundation especially counters any intimidation factor. We do our own competence a disservice, and create a self-fulfilling prophecy, if we try to recognize only the grossest aberrations in the structure of the hand.
We constantly need to remember that function and performance can outstrip the deficits predicted from the pathologic anatomy alone, depending on motivation, cognitive state, resourcefulness, and adaptive equipment. This lesson strikes us as particularly vivid when a person with the familiar gnarled hand of end-stage RA4 manages to feed, dress, and perhaps toilet himself or herself, and to write legibly or use a computer, beyond all reasonable expectation based on the structure one observes. Conversely, problems with manual dexterity are common in osteoarthrosis, especially with distal interphalangeal and base-of-thumb joints.10