Because of the deformity, there may eventually be osteoarthritis (Fig. 40.8). Another common result is retardation of growth after bone infection, particularly of the phalanges; individual fingers may be short and stubby and long bones may be uneven in length.

There is no evidence that any treatment, be it surgical, antibiotic, or chemotherapeutic, in any way affects the outcome of the disease. Protection of the joint during the acute stage, keeping affected bones and joints weight-free, and the removal of effusions all improve the end result. If weight-bearing is permitted, unequal involvement of the distal femoral epiphyseal plate is not uncommon and destruction of the medial and lateral side may result in a genu valgum. The destruction of epiphyseal centers leads to uneven growth and premature fusion; this epiphyseal involvement is another feature differentiating the disease from bacterial osteomyelitis.

Whenever obscure joint or skeletal deformities are recognized in a patient who has spent much time in the tropics, particularly where smallpox was once endemic, the possibility of this infection should be investigated. Most patients, however, will remember the clinical illness only too well.

Complications

The major complications are those of secondary bacterial infection (apart from the deformities which are the end result of the disease and which have already been described). Secondary infection may result from aspiration of an effusion, or spread from skin lesions near a joint, or may follow the spontaneous development of a sinus through which the infection has tracked. It is certain that the mortality of patients with smallpox osteomyelitis is not worse than that of other smallpox patients in whom the skeleton has not become involved. Prophylactic antibiotics have been used but none has proved efficient either in preventing the development of variola bone and joint infection or in altering its natural history and prognosis.

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Fig. 40.8A-C. The end result of smallpox osteomyelitis of the elbow. (A) Severe bilateral osteoarthritis associated with growth deformities in each elbow. Both have some remaining movement. (B) One elbow is completely ankylosed; the other has limited movement. (C) Complete fusion of both elbow joints.