Predictability of the Fulcrum Bending Radiograph in Scoliosis Correction with Alternate-Level Pedicle Screw Fixation

Cheung, Kenneth M.C.; Natarajan, Deepa; Samartzis, D; Wong, Yat-Wa; Cheung, Wai-Yuen; Luk, K.D.K.

doi:10.2106/jbjs.h.01831

Cited by 55 publications

(30 citation statements)

References 7 publications

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“…It is well known that to achieve a certain degree of correction, the more rigid the curve, the more correction ability is required [2,10]. In our study, a similar significant high correlation was noted between Angle XF to that of FBCI and XFI.…”

Section: Discussionsupporting

confidence: 83%

The “X-Factor” Index: a new parameter for the assessment of adolescent idiopathic scoliosis correction

et al. 2010

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The correction rate (CR) and fulcrum bending correction index (FBCI) based on the fulcrum bending radiograph (FBR) were parameters introduced to measure the curve correcting ability; however, such parameters do not account for contributions by various, potential extraneous ''X-Factors'' (e.g. surgical technique, type and power of the instrumentation, anesthetic technique, etc.) involved in curve correction. As such, the purpose of the following study was to propose the concept of the ''X-Factor Index'' (XFI) as a new parameter for the assessment of the correcting ability of adolescent idiopathic scoliosis (AIS). A historical cohort radiographic analysis of the FBR in the setting of hook systems in AIS patients (Luk et al. in Spine 23:2303-2307, 1998) was performed to illustrate the concept of XFI. Thirty-five patients with AIS of the thoracic spine undergoing surgical correction were involved in the analysis. Plain posteroanterior (PA) plain radiographs were utilized and Cobb angles were obtained for each patient. Pre-and postoperative PA angles on standing radiograph and preoperative fulcrum bending angles were obtained for each patient.The fulcrum flexibility, curve CR, and FBCI were determined for all patients. The difference between the preoperative fulcrum bending angle and postoperative PA angle was defined as Angle XF , which accounted for the correction contributed by ''X-Factors''. The XFI, designed to measure the curve correcting ability, was calculated by dividing Angle XF by the fulcrum flexibility. The XFI was compared with the curve CR and FBCI by re-evaluating the original data in the original paper (Luk et al. in Spine 23:2303-2307, 1998. The mean standing PA and FBR alignments of the main thoracic curve were 58.3°and 24.5°, respectively. The mean fulcrum flexibility was 58.8%. The mean postoperative standing PA alignment was 24.7°. The mean curve CR was 58.0% and the mean FBCI was 101.1%. The mean XFI was noted as 1.03%. The CR was significantly positively correlated to curve flexibility (r = 0.66; p \ 0.01).The FBCI (r = -0.47; p = 0.005) and the XFI (r = -0.45; p = 0.007) were significantly negatively correlated to curve flexibility. The CR was not correlated to Angle XF (r = 0.29; p = 0.089).The FBCI (r = 0.97; p \ 0.01) and the XFI (r = 0.961; p \ 0.01) were significantly positively correlated to Angle XF . Variation in XFI was noted in some cases originally presenting with same FBCI values. The XFI attempts to quantify the curve correcting ability as contributed by ''X-Factors'' in the treatment of thoracic AIS. This index may be a valued added parameter to accompany the FBCI for comparing curve correction ability among different series of patients, instrumentation, and surgeons. It is recommended that the XFI should be used to document curve correction, compare between different techniques, and used to improve curve correction for the patient.

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Section: Discussionsupporting

confidence: 83%

The “X-Factor” Index: a new parameter for the assessment of adolescent idiopathic scoliosis correction

et al. 2010

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“…However, a significant correlation has been found between the number of implants and the curve correction using a multi-center database of AIS patients [11]. It has also been reported that increasing the number of implants can improve the correction of curves with higher stiffness, as determined by the fulcrum bending radiograph [10]. The discrepancies between the results of this work and the clinical studies may be explained by the fact that there exist considerable differences on how the increased control provided by adding additional implants have been explored.…”

Section: Discussionmentioning

confidence: 99%

“…Basic deformity reduction techniques associated with the modern segmental spinal instrumentation systems for posterior spinal fusion involve vertebral translation, rod derotation, apical vertebral derotation, bilateral apical vertebral derotation, direct vertebra derotation, compression and distraction, and in situ rod contouring [7,8]. In order to apply certain correction techniques and to have a better control on the deformed spine, there has been a noticeable trend among spine surgeons to use more and more pedicle screws [9][10][11]. Nowadays, pedicle screws are frequently placed bilaterally at each vertebra included in the fusion, but some surgeons recommend fewer screws [12].…”

Section: Introductionmentioning

confidence: 99%

“…In spite of the demonstrated benefits of pedicle screws, the associated complications, risks, and the hardware costs are not negligible [13,14]. Several clinical studies have been carried out to compare the deformity-correction effects of spinal instrumentations with the same fusion levels but different number (density) of implants [9][10][11]. Studies have also been conducted to evaluate intervertebral and implant-vertebra force levels [15].…”

Section: Introductionmentioning

confidence: 99%

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Biomechanical comparison of alternative densities of pedicle screws for the treatment of adolescent idiopathic scoliosis

2011

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Purpose The objective of this computational study was to compare the biomechanical effects of different implant densities in terms of curve reduction and the force levels at the implant-vertebra interface and on the intervertebral elements. Methods Eight cases were randomly picked among patients who have undergone a posterior spinal instrumentation for adolescent idiopathic scoliosis (AIS). For each case, two computer simulations were performed, one with the actual surgery implant pattern and another with the same fusion levels but an alternative implant pattern proposed by an experienced surgeon. The two implant patterns for each case were respectively put into higher and lower implant density group. The spinal correction and the force levels at bone-implant interface and on the intervertebral elements were analyzed and compared between the two groups. Results There were on average 13% more pedicle screws and 30% more bilaterally placed pedicle screws in the higher versus lower density group. The difference in the density of screws (92% vs. 79%) did not lead to significant difference in terms of the resulting main thoracic (MT) Cobb angle, and the MT apical axial vertebral rotation. The average and maximum implant-vertebra force levels were about 50 and 65%, respectively higher in the higher versus lower density group, but without consistent distribution patterns. The average intervertebral forces did not significantly differ between the two groups. Conclusions With the same fusion levels, lower density screws allowed achieving similar deformity correction and it was more likely to have lower screw-vertebra loads.

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“…Since the FBCI took curve flexibility into account, it was considered a better method than the correction rate for comparing curve corrections with different instrumentation system. Cheung et al [19] prospectively assessed the predictive value of the FBR in AIS curve correction in the context of alternate level pedicle screw fixation of the MT curve. A mean FBCI of 122% was obtained, and they draw the conclusion that pedicle screw constructs have a better ability to correct scoliosis compared to hooks and hybrid constructs.…”

Section: Discussionmentioning

confidence: 99%

Coronal deformity correction in adolescent idiopathic scoliosis patients using the fulcrum-bending radiograph: a prospective comparative analysis of the proximal thoracic, main thoracic, and thoracolumbar/lumbar curves

Dumonski

Samartzis

et al. 2010

Eur Spine J

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The aim of the prospective, comparative radiographic analysis was to determine the role of the fulcrum-bending radiograph (FBR) for the assessment of the proximal thoracic (PT), main thoracic (MT), and the thoracolumbar/lumbar (TL/L) curves in patients undergoing posterior spinal pedicle screw fixation and fusion for adolescent idiopathic scoliosis (AIS). The FBR demonstrated statistically better correction than other preoperative methods for the assessment of frontal plane correction of the MT curves. The fulcrum-bending correction index (FBCI) has been considered a superior method than the correction rate for comparing curve correction undergoing posterior spinal fusion because it accounts for the curve flexibility. However, their applicability to assess the PT and TL/L curves in AIS patients remains speculative. The relation between FBR and correction obtained by pedicle screws fixation is still unknown. Thirty-eight consecutive AIS patients who underwent pedicle screw fixation and posterior fusion were included in this study. The assessment of preoperative radiographs included standing posterior-anterior (PA), FBR, supine side-bending, and postoperative standing PA and lateral plain radiographs. The flexibility of the curve, as well as the FBCI, was calculated for all patients. Postoperatively, radiographs were assessed at immediate (i.e. 1 week), 3-month, 6-month, 12-month, and 2-year follow-up. Cobb angles were obtained from the PT, MT, and TL/L curves. The study consisted of 9 PT, 37 MT, and 12 TL/L curves, with a mean age of 15.1 years. The mean FBR flexibility of the PT, MT, and the TL/L curves was 42.6, 61.1, and 66.2%, respectively. The mean operative correction rates in the PT, MT, and TL/L curves were 43.4, 69.3, and 73.9%, respectively, and the mean FBCI was 103.8, 117.0, and 114.8%, respectively. Fulcrum-bending flexibility was positively correlated with the operative correction rate in PT, MT, and TL/ L curves. Although the correction rate in MT and TL/L curves was higher than PT curves, the FBCI in PT, MT, and TL/L curves was not significantly different (p \ 0.05). The FBR can be used to assist in the assessment of PT, MT, and TL/L curve corrections in AIS patients. When curve flexibility is taken into account by FBR, the ability of pedicle screws to correct PT, MT, and TL/L curves is the same.

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Predictability of the Fulcrum Bending Radiograph in Scoliosis Correction with Alternate-Level Pedicle Screw Fixation

Cited by 55 publications

References 7 publications

The “X-Factor” Index: a new parameter for the assessment of adolescent idiopathic scoliosis correction

The “X-Factor” Index: a new parameter for the assessment of adolescent idiopathic scoliosis correction

Biomechanical comparison of alternative densities of pedicle screws for the treatment of adolescent idiopathic scoliosis

Coronal deformity correction in adolescent idiopathic scoliosis patients using the fulcrum-bending radiograph: a prospective comparative analysis of the proximal thoracic, main thoracic, and thoracolumbar/lumbar curves

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