THE EIGHT PLATE – A NEW IMPLANT FOR TEMPORARY HEMIEPIPHYSEODESIS

Abstract

Introduction: Temporary hemiepiphyseodesis allows correction of angular deformities of the lower extremities in children before the end of growth. The eight plate is an alternative to Blount staples with the theoretical advantage of a more minimal approach, less risk of loosening with subsequent need for a re-operation and less compression of the growth plate due to the tension band mechanism. We report our results and experiences with this new implant.

Methods: Between August 2005 and May 2007 we implanted 74 eight plates (Orthofix International NV, Netherlands Antilles) in 32 patients. An idiopathic valgus deformity was the indication in 20 patients, an idiopathic varus in 4 patients, and a malalignment due to other reasons like infection, syndrome-association or trauma was seen in 8 patients. For the first part of this study we evaluated intra–and postoperative complications in patients with a minimum follow-up after the operation of 3 months. For the second part of the study we evaluated the results of correction after removal of the plate and analyzed long-standing radiographs using the malalignment test.

Results: Twenty-three patients treated with a total of 52 eight plates were included into the first part of this study. The mean follow-up after implantation was 9,5 months (range:3,4–22 months). One patient suffered from a significant postoperative haematoma which resolved spontaneously after 2 weeks and two patients showed a limited range of motion of the knee joint postoperatively. In both patients the range of motion was completely restored after 10 sessions of physical therapy. No other complication was seen during follow-up. Up to now 25 eight plates in 12 patients with 18 lower limb segments were removed. The mean age of the patients at the time of surgery was 12,2 years(rang: 6 – 13). The x-rays of these 18 lower extremities were reviewed and the alignment was analyzed. The mean preoperative mechanical axis deviation was 30,6mm (range: 8-50 mm). After hardware removal the mechanical axis showed a mean deviation from the center of the knee joint of 0,2 mm medial (range: 6mm lateral to 5 mm medial). The mean duration of implantation was 8,3 months (range: 4 to 16 months). Overcorrection was found in 2 patients, while a lack of correction at the end of growth was seen in one patient.

Conclusion: The eight plate is a safe and effective implant for temporary hemiepiphyseodesis. Especially loosening or implant failure, both commonly reported with the use of Blount staples, was not seen in our case series. Due to the minimal invasive approach with the need to implant only one eight-plate vs. two to four Blount staples and the sizes of the plates available the indications may be spread to a wider spectrum of deformities and ages.