Agarwal told OTW that he received a response, but it only corroborated the fact that the premise of [Pooria Hosseini et al.’s] study design “change the frequency of lengthening, without addressing the forces” was a misunderstanding of the concept he had proposed.
Hosseini Begs to Disagree
The authors of the European Spine Journal study, specifically Dr. Hosseini, explained the purpose of their study to OTW, “The purpose of our study was just assessing the lengthening intervals. We understand forces applied to the rod play a role in rod failure. However, there is no way to measure applied forces on the rods in a clinical retrospective study of our studied cohort.”
Dr. Hosseini had earlier written a response to Agarwal’s letter to the editor where he stated, “In response to your concerns about minimizing the distractions without consideration of applied forces; we did not recommend minimizing distraction intervals. We simply concluded that based on our study in a cohort of 138 patients, which was the largest sample size at the time of its publication, there was no statistical difference between rod fracture (RF) and no rod fracture (NRF) groups in relation with lengthening intervals. In our study we recognized that for assessment of shorter intervals (less than 6 months) we need to look at MCGR [magnetically controlled growth rods] cases to come up with better understanding of the effects of short versus long intervals, since they usually are lengthened more frequently.”
“Finally, in regards with stiffness, we totally agree with your comment. We also have concerns about the availability of stiffness assessment data at baseline. However, as it is mentioned in the limitations of the study, there are few missing data points that are mainly due to retrospective nature of the study. Assessment of spine flexibility at baseline is one of them.”
Looking Forward
Dr. Agarwal is considered to be an expert in both traditional and MAGnetic Expansion Control (MAGEC™) growth rods for scoliosis correction and their failure modes. The research coming out of Agarwal’s lab is showing that surgical technique, specifically the practice of employing shorter distraction magnitudes at shorter intervals could decrease complication risk, including fracture risk.
The MAGEC rod’s primary benefit is that it allows for noninvasive distraction of growth rods and a resultant reduction in the number of consecutive surgeries, and sometimes the possibility of reducing growth rod fracture or autofusion. Although the MAGEC leads to fewer complications than traditional rods, repeated unexpected failure of noninvasive distraction mechanism should encourage further research and innovation toward reducing them.
Agarwal and his team wrapped up their study by writing, “Better technical and clinical controls need to be set in place to avoid adverse events, which leads to unplanned open surgeries.”
