The Fate of the Bent Rod in Children With Osteogenesis Imperfecta.

BACKGROUND

Osteogenesis imperfecta (OI) is a genetic disorder characterized by brittle bones and long bone deformity. Realignment and intramedullary rodding with telescopic rods are indicated for progressive deformity and can help prevent fractures. Rod bending is a reported complication of telescopic rods and a common indication for revision; however, the fate of bent lower extremity telescopic rods in the setting of OI has not been reported.

METHODS

Patients with OI at a single institution who underwent lower extremity telescopic rod placement with at least 1-year follow-up were identified. Bent rods were identified, and for these bone segments, we collected the location and angle of bend, subsequent telescoping, refracture, increasing angulation of bend, and date of revision.

RESULTS

One hundred sixty-eight telescopic rods in 43 patients were identified. Forty-six rods (27.4%) bent during follow-up, with an average angulation of 7.3 (range: 1 to 24) degrees. In patients with severe OI, 15.7% of rods bent compared with 35.7% in nonsevere OI ( P =0.003). The proportion of bent rods was different between independent and nonindependent ambulators (34.1% and 20.5%; P =0.035). Twenty-seven bent rods (58.7%) were revised, with 12 rods (26.0%) revised early (within 90 d). The angulation of rods that were revised early was significantly higher than rods not (14.6 and 4.3 degrees, P <0.001). Of the 34 bent rods not revised early, the average time to revision or final follow-up was 29.1 months. Twenty-five rods (73.5%) continued to telescope, 14 (41.2%) increased in angulation (average 3.2 degrees), and 10 bones (29.4%) refractured. None of the refractures required immediate rod revision. Two bones had multiple refractures.

CONCLUSIONS

Bending is a common complication of telescopic rods in the lower extremities of patients with OI. It is more common in independent ambulators and patients with nonsevere OI, possibly because of the increased demand placed on the rods. Rods with a small bend and maintained fixation can telescope and need not be an indication for immediate revision.

LEVEL OF EVIDENCE

Level III-Retrospective review.