Mechanical failures of eight-plateguided growth system for temporary hemiepiphysiodesis.

BACKGROUND: For decades, the Blount staple has been used to perform temporary hemiepiphysiodesis for angular deformity correction in children with open growth plates. Recently, the eight-PlateGuided Growth System (Orthofix, McKinney, TX) has gained popularity for use in this procedure. The eight-Plate is said to be superior to the Blount staple, as it is less likely to break or migrate out of the bone. However, some centers have observed mechanical failures of the eight-Plate cannulated screws.
METHODS: The purpose of our study was to conduct a multicenter survey to determine which factors increase the risk of mechanical failure with this device. We distributed a questionnaire in 2007 to 841 members of the Pediatric Orthopaedic Society of North America that asked about their experience with the eight-Plate and whether they had observed any mechanical failures. Follow-up surveys were distributed to determine the background of the failed cases.
RESULTS: Of the 445 (53%) surgeons who responded, 314 (71%) reported that they use the eight-Plate in their practice. Forty-eight (15%) of the 314 surgeons who use the eight-Plate observed a total of 65 cases of mechanical failure. In every case, the screws failed, not the plate. The average body mass index of these patients was 37.8 kg/m (range, 19.2 to 70.2 kg/m).
CONCLUSIONS: Overweight and obese patients with Blount disease were among those most likely to experience eight-Plate screw failure. Fractures occurred almost always in the metaphyseal screw-not where the head meets the shank but where the shank enters the lateral cortex, presumably because of 3-point bending. No broken plates were reported. In high-risk cases, we now consider using 2 parallel eight-Plates or using solid (not cannulated) screws for plate fixation. LEVEL OF EVIDENCE: Level IV.