Selection of fusion levels using the fulcrum bending radiograph for the management of adolescent idiopathic scoliosis patients with alternate level pedicle screw strategy: clinical decision-making and outcomes

Abstract

ObjectiveSelecting fusion levels based on the Luk et al criteria for operative management of thoracic adolescent idiopathic scoliosis (AIS) with hook and hybrid systems yields acceptable curve correction and balance parameters; however, it is unknown whether utilizing a purely pedicle screw strategy is effective. Utilizing the fulcrum bending radiographic (FBR) to assess curve flexibility to select fusion levels, the following study assessed the efficacy of pedicle screw fixation with alternate level screw strategy (ALSS) for thoracic AIS.MethodsA retrospective study with prospective radiographic data collection/analyses (preoperative, postoperative 1-week and minimum 2-year follow-up) of 28 operative thoracic AIS patients undergoing ALSS was performed. Standing coronal/sagittal and FBR Cobb angles, FBR flexibility, fulcrum bending correction index (FBCI), trunkal shift, radiographic shoulder height (RSH), and list were assessed on x-rays. Fusion level selection was based on the Luk et al criteria and compared to conventional techniques.ResultsIn the primary curve, the mean preoperative and postoperative 1 week and last follow-up standing coronal Cobb angles were 59.9, 17.2 and 20.0 degrees, respectively. Eighteen patients (64.3%) had distal levels saved (mean: 1.6 levels) in comparison to conventional techniques. Mean immediate and last follow-up FBCIs were 122.6% and 115.0%, respectively. Sagittal alignment did not statistically differ between any assessment intervals (p>0.05). A decrease in trunkal shift was noted from preoperative to last follow-up (p = 0.003). No statistically significant difference from preoperative to last follow-up was noted in RSH and list (p>0.05). No "add-on" of other vertebra or decompensation was noted and all patients achieved fusion.ConclusionsThis is the first report to note that using the FBR for decision-making in selecting fusion levels in thoracic AIS patients undergoing management with pedicle screw constructs (e.g. ALSS) is a cost-effective strategy that can achieve clinically-relevant deformity correction that is maintained and without compromising fusion levels.

Preventing Fusion Mass Shift Avoids Postoperative Distal Curve Adding-on in Adolescent Idiopathic Scoliosis

“…This is necessary to achieve satisfactory outcomes and prevention of adding-on, which we believe is a direct consequence of fusion mass shift. Our criteria of accepting a 20-mm fusion mass shift and fusion mass Cobb angle of 20°after surgery allows us to fuse as few lumbar segments as possible [30,42]. Our study also underscores and verifies the importance of our criteria.…”

“…The aim of surgical treatment of adolescent idiopathic scoliosis (AIS) is to achieve a balanced spine in the coronal and sagittal planes without listing (deviation in C7-center sacral vertical line) or truncal shifting [16,30,42]. In the selection of fusion levels, an ideal fusion mass requires parallel top and bottom endplates without substantial coronal shift, and appropriate sagittal alignment [30,42]. As proposed by Harrington [13,14], a simple way to achieve a parallel fusion mass is to instrument from a horizontal vertebrae above the curve to a horizontal vertebrae below the curve.…”

“…However, with these criteria, one or two levels beyond the primary curve at both ends are frequently included during surgery. With the development of modern pedicle screw instrumentation systems [18,27,45,54], better 3-dimensional deformity correction with a shorter fusion mass can be achieved [42].…”

“…The fulcrum-bending radiograph has been used as a clinical decision tool to determine selection of fusion levels and in predicting curve correction [2-5, 12, 15, 23-26, 28-30, 32, 38, 42, 47]. Essentially, fulcrum-bending radiographs help determine the shortest fusion segment that can achieve a fusion mass with parallel endplates and no shift in an effort to obtain a balanced spine [30,42]. There are two components of a fusion mass that determine the success or failure of the surgery, namely residual shift and Cobb angle [30].…”

A randomized double-blinded clinical trial to evaluate the safety and efficacy of a novel superelastic nickel–titanium spinal rod in adolescent idiopathic scoliosis: 5-year follow-up

“…Standard posterior 21 spinal exposure appropriate for the length of thoracic curve to be instrumented was performed Novel Super-Elastic Nickel-Titanium Rod RCT 8 based on fulcrum-bending radiographs. [45][46][47][48][49] . If possible, pedicle screws were applied to the upper and lower instrumented vertebra and the one adjacent vertebrae, thus a total of 4 screws were 2 used at both ends.…”