PURPOSE Magnetic-controlled growing rods (MCGRs) are now routinely used in many centres to treat early-onset scoliosis (EOS). MCGR lengthening is done non-invasively by the external remote controller (ERC). Our experience suggests that there may be a discrepancy between the reported rod lengthening on the ERC and the actual rod lengthening. The aim of this study was to investigate this discrepancy. METHODS This was a prospective series. Eleven patients who were already undergoing treatment for EOS using MCGRs were included in this study. RESULTS One hundred and ninety-two sets of ultrasound readings were obtained (96 episodes of rod lengthening on dual-rod constructs) and compared to their ERC readings. Only 15/192 (7.8%) readings were accurate; 27 readings (14.9%) were false positive; and 8 readings (4.2%) were an underestimation while 142 readings (74.0%) were an overestimation by the ERC. Average over-reporting by the ERC was 5.31 times of the actual/ultrasound reading. When comparing interval radiographs with lengthening obtained on ultrasound, there was a discrepancy with an average overestimation of 1.35 times with ultrasound in our series. There was a significant difference between ERC and USS (p = 0.01) and ERC and XR (p = 0.001). However, there was no significant difference between USS and XR (p > 0.99). CONCLUSION The reading on the ERC does not equate to the actual rod lengthening. The authors would recommend that clinicians using the MCGR for the treatment of early-onset scoliosis include pre- and post-extension imaging (radiographs or ultrasound) to confirm extension lengths at each outpatient extension. In centres with ultrasound facilities, we would suggest that patients should have ultrasound to monitor each lengthening after distraction but also 6-month radiographs. These slides can be retrieved under Electronic Supplementary Material.

中文翻译：

---

外部遥控器的读数是否与磁控生长棒中的实际长度相对应？

目的磁控生长棒（MCGR）现在在许多中心被常规使用，以治疗早发性脊柱侧凸（EOS）。MCGR延长是通过外部遥控器（ERC）无创地完成的。我们的经验表明，ERC上报告的拉长和实际拉长之间可能存在差异。这项研究的目的是调查这种差异。方法这是一个预期的系列。本研究包括11名已经使用MCGR接受EOS治疗的患者。结果获得了192组超声读数（在双杆结构上杆伸长了96次），并将其与ERC读数进行了比较。只有15/192（7.8％）的读数是准确的；假阳性的读数为27（14.9％）；和8个读数（4。2％）被低估了，而142个读数（74.0％）被ERC高估了。ERC的平均超额报告是实际/超声波读数的5.31倍。当比较间隔X线照片与超声获得的延长时，在我们的系列中，超声存在平均高估1.35倍的差异。ERC和USS（p = 0.01）和ERC和XR（p = 0.001）之间存在显着差异。但是，USS和XR之间没有显着差异（p> 0.99）。结论ERC上的读数并不等于实际的拉杆长度。作者建议使用MCGR治疗早发性脊柱侧弯的临床医生应包括延伸前和延伸后的影像学检查（放射线照相或超声检查），以确认每次门诊延伸时的延伸长度。在设有超声检查设备的中心，我们建议患者应进行超声检查，以监测分心后的每次延长以及6个月的X射线照片。这些幻灯片可以在电子补充材料下找到。