Spontaneous ankylosis in erosive osteoarthritis of the finger joints: a case series of eight postmenopausal women.

Osteoarthritis of the hands is very common, particularly in elderly people. Little is known though, is the subset of erosive osteoarthritis (EOA), which predicts a poorer prognosis and causes much more discomfort. Even less known is the fact that this subset can evolve into spontaneous ankylosis. We describe eight women (average age 62.6, range 54-74 years) with EOA and spontaneous ankylosis of the proximal interphalangeal (PIP) and/or distal interphalangeal (DIP) joints. In total, 21 PIP joints (0-7 per patient) were found with EOA and nine PIP joints (0-3 per patient) with ankylosis. In one patient, ankylosis of the PIP was already seen at the first presentation. In the other cases, it took an average of 77.4 months (range 34-119) for EOA to develop into ankylosis of the PIP. For DIP joints, the numbers were 17 joints (1-4 per patient) with EOA and three joints (0-1 per patient) with ankylosis, respectively. In one patient, ankylosis of the DIP was already seen at the first presentation. Ankylosis was found significantly more often on the left hand (n = 10) compared to the right hand (n = 2; p < 0.0005), while all the patients were right handed. No difference in handedness was found for the occurrence of EOA. Although rare, PIP or DIP joint with EOA can-over the course of several painful years-develop into a spontaneous pain-free ankylosis. Ankylosis was more commonly found in the left hand than in the right hand, probably due right handedness.