Purpose of study: Long bone chronic osteomyelitis may result in limb length discrepancy by shortening of the affected bone when the physis is damaged. Little is known about the rates of overgrowth of infected long bones. This study documents the relative rates of overgrowth and undergrowth in a large series of chronic osteomyelitis patients.

Methods: Forty-two consecutive patients presenting to our unit with chronic osteomyelitis of a long bone were included. There were no exclusion criteria. The mean age at presentation was 10.3 years. The mean duration of symptoms was 18.2 months prior to presentation. For 37 (88%) of patients the cause of osteomyelitis was haematogenous.

Results: Three (7%) patients had shortening of the long bone compared to the unaffected side (average 2.5cm), whilst 13 (31%) patients had overgrowth of the affected bone (average overgrowth 2.2cm). The tibia was most commonly affected (20/42, 48%), followed by the femur (8/42, 19%) and the humerus (6/42, 14%). The average proportion of long bone involved on X-ray was 59%. At least one physis was affected in 8/42 (12%) patients (2 had undergrowth, 1 overgrowth).

Conclusions: This large prospective series of patients shows the effect of osteomyelitis on the growth of long bones, in particular an overgrowth rate of 31%. The mechanism for this is probably related to the duration of symptoms. In areas of the world with poor access to health care, there is consequently a prolonged period of increased blood supply as a result of inflammation.

This increased blood supply may make overgrowth limb length discrepancy more likely than undergrowth.