Failure to lengthen consensus for the magnetically controlled growing rod (MCGR).

Abstract

MCGR lengthening has become an important innovation in treating patients with EOS. An alternative to traditional growing instrumentation, a single surgical procedure is necessary for insertion of the construct, followed by non-invasive lengthening in the outpatient setting. With every new technology emanates a new complication to troubleshoot. Failure to lengthen in the MCGR is a significant cause of revision surgery. Currently, no consensus exists on how to define a MCGR lengthening failure, what steps are necessary after a failure to lengthen, and what factors determine these next steps. The primary goal of this study was to establish a consensus on how to define and navigate a MCGR that fails to lengthen. A series of 3 surveys were distributed to 49 early onset scoliosis surgeons with 37 responses between December 2021 and April 2022. Consensus was defined as at least 70% agreement. 37 of 49 surgeons (75%) responded to the first survey, and all 37 surgeons responded to the following two surveys (100%). Consensus statements were reached on 25% of questions (3/12) from survey 1, 40% of questions (4/10) on survey 2, and 100% of questions (5/5) on survey 3. The questions that reached consensus are detailed in Table 1. Consensus steps to navigate a rod that fails to lengthen 1 mm (97%) in the office include retrying during the same visit (78%), changing technique in the office (88%), and not adjusting the interval between lengthening appointments (78%). Table 1 Items that reached consensus from each survey (12 total) Survey Question Response, Consensus Percentage 1 If a rod does not lengthen, do you try again in that office visit?​ Yes, 78% 1 All modes of XR are equivalent when determining failure to lengthen? Yes, 70% 1 If you are unsuccessful at lengthening, you should change the lengthening interval? No, 78% 2 Re-lengthening a rod following a failure to lengthen one should change their technique? Yes, 88% Reposition patient, 100% Alternate rods, 90% No traction in OR, 92.6% 2 Is a MCGR non-operational following 3 consecutive visits where the rod failed lengthening? Yes, 100% 2 Considerations when determining next steps with a non-operational rod? Skeletal Age, 100% Curve Progression, 97% Curve Stiffness, 93.8% Family Convenience, 83% Chronologic Age, 77% Time from Last Lengthening, 70% 2 Can an APP follow your protocol for a rod that has failed to lengthen? Yes, 81% 3 Are you comfortable using either clunk or stall to describe the phenomena of the internal clutch failing within the actuator when lengthening? Yes, 97.3% 3 Clunk/stall try again before an adjustment? Yes, 81% 3 Define failure to lengthen? Less than 1 mm length achieved, 97% 3 After two failure to lengthen events do you discuss next surgical steps?​ Yes, 97% 3 Once a rod had been classified as non-operational (no longer lengthening despite interventions) do you consider the underlying diagnosis when making next step decisions? Yes, 97% CONCLUSION: Best clinical practice guidelines using a Delphi method established a consensus on defining failure to lengthen in a MCGR (less than 1 mm), appropriate responses to failure to lengthen (re-attempt to lengthen and re-position patient) and a definition for a non-functional MCGR (failure to lengthen 3 consecutive times). This consensus will help standardize research on this important problem. V-expert opinion.