How to Select the Lower Instrumented Vertebra in Traditional Growing Rods Index Surgery

Abstract

Background: There are still no consensus criteria on how to select the lower instrumented vertebra (LIV) for traditional growing rods (TGRs) at index surgery. The aim was to evaluate whether the criteria used for adolescent idiopathic scoliosis fusion adapts to early onset scoliosis (EOS).Methods: Retrospective analysis of prospectively longitudinal collected data in a consecutive cohort of patients with EOS treated with TGR, expanding from index surgery to 2 years after graduation. The LIV was analyzed regarding its relation to the stable vertebra (SV), substantially touched vertebra (STV), and not STV (NSTV). Failure of LIV selection was considered when revision surgery with distal extension was needed during follow up, due to adding on (DLIV tilt . 108).Results: A total of 25 patients met inclusion criteria. Mean age was 8.6 6 3 (at index surgery), 15.1 6 1.8 (at graduation), and 17.8 6 1.6 (at final follow up). The most frequent LIV at index surgery was L3 (13/25); in 13 cases, STV was selected as LIV; in 7, it was NSTV; and in 5, SV on the standard postero-anterior radiographs. During follow up, a significant increase in the mean LIV tilt (P ¼ .049) and distal junctional angle (P ¼ .017) was found. Nine of the 25 patients (36%) developed adding on: 20% (1/5) of those with LIV at SV, 38.5% (5/13) at STV, and 42.8% (3/7) at NSTV. Of those 9 cases of adding on, only four needed distal extension (mean LIV tilt ¼ 17.68): 2 STV patients (15.4%), and 2 NSTV patients (28.6%). None of the patients with the LIV chosen at SV needed distal extension due to adding on.Conclusions: The cranial the selection of the LIV above the SV, the higher the risk of adding on and of revision surgery with distal extension during follow up. Saving motion segments could be justified by choosing STV as LIV because the need for distal extension is not high, and it can be scheduled during lengthening procedures or at graduation surgery.Level of Evidence: 4. Clinical Relevance: Choosing the LIV in TGR index surgery is crucial to have a secure distal foundation, control and correct the deformity during growth, and save distal segments to allow growth and mobility.

Is Final Fusion Necessary for Growing-Rod Graduates: A Systematic Review and Meta-Analysis

“…1,2 Both the implants need to be anchored to the proximal and distal fixation points usually constituted by 2 vertebrae cranially between T2 to T4 and 2 vertebrae caudally, usually the stable or the last touch vertebra. [3][4][5][6] Sub-periosteal dissection is avoided in the segments lying in between the cranial and caudal fixation points to maintain the growth potential in these segments and periodic distractions achieve the necessary lengthening of the trunk.…”

Lowest instrumented vertebrae in early onset scoliosis: is there a role for a more selective approach?

“…LIV selection is a common topic of discussion and area of research in the treatment of AIS [ 1 , 2 , 4 , 8 , 10 – 18 ]. In contrast, there is a relative paucity of literature assessing LIV selection in EOS with research efforts instead focused on implant type, complications, and spinal growth [ 5 , 7 , 19 – 21 ]. Upper implant level selection and technique has also received deserved attention as implant failure is more frequent at the upper foundation [ 22 ].…”

“…There has been less emphasis on LIV selection in early-onset scoliosis (EOS) treated with distraction-based growth-friendly instrumentation (GFI) [ 5 , 6 ]. The variability of curve patterns and diagnoses found within this population may complicate the process of LIV selection [ 7 ]. It is also possible that the size and space requirements of the implants used in GFI limit LIV selection options [ 6 ].…”

“…Key factors influencing LIV decisions include the last touched vertebrae (TV), curve flexibility on pre-operative bending films, rotation at the apex, curve magnitude, and clinical exam [ 1 , 2 , 8 , 9 ]. In contrast, there is a paucity of literature evaluating LIV selection in EOS, and little is known about the factors influencing LIV decisions in this patient population [ 5 – 7 ].…”

Concave Side Apical Control in Early Onset Scoliosis Managed with Growing Rods

“…[1,2] These implants require to be anchored to the cranial and caudal fixation sites commonly formed by two vertebrae proximally and two vertebrae distally, and intermittent distractions attain the required lengthening of the body. [3][4][5][6] TGRs were commonly applied in severe cases of EOS during the last decades but required periodic operative distraction under general anesthesia associated with comparatively elevated rates of infection. [7,8] MCGRs were presented approximately 10 years ago and were first published in 2012.…”