Failure of Orthofix eight-Plate for the treatment of Blount disease

Hemiepiphysiodesis is a well-established treatment option for angular deformities of the knee. Recently, our institution began using the eight-Plate tension band device by Orthofix (McKinney, Tex) as an alternative to staples. However, several patients have returned with broken screws necessitating revision surgery.

Charts and radiographs of all patients who were treated with the eight-Plate (Orthofix) at our institution were reviewed. The diagnosis, age, amount of angular deformity, weight, and body mass index were analyzed with respect to eventual implant failure.

Implant failure occurred in 8 (26%) of 31 proximal tibia constructs. All 8 failures occurred in patients with Blount disease and involved breakage of the tibial metaphyseal screw. The mean time to failure was 13.6 months. Eight hardware failures in 18 Blount disease extremities represent a failure rate of 44%. No implant failures occurred in the remaining diagnoses. Neither age nor degree of deformity correlated with implant failure. The failure group was significantly heavier than the nonfailure group, and the patients with Blount disease were found to be heavier than the other patients. However, no significant difference in weight was found within the Blount group regarding implant failure. In all patients whose plates did not fail, rate of correction was equal to or better than previously reported hemiepiphysiodesis studies.

The eight-Plate (Orthofix) is a reasonable option for hemiepiphysiodesis but has an unacceptable failure rate in Blount disease (44%). There were no instances of failure in patients with other diagnoses. In Blount disease, stronger implants should be considered. Future implant designs should include stronger screws to decrease implant failure complications.