Influence of screw density on thoracic kyphosis restoration in hypokyphotic adolescent idiopathic scoliosis

Luo, Ming; Jiang, Hui; Wang, Wengang; Li, Ning; Shen, Mingkui; Xu, Genzhong; Xia, Lei

doi:10.1186/s12891-017-1877-6

Cited by 11 publications

(8 citation statements)

References 44 publications

(48 reference statements)

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“…Recently, there have been many attempts to restore thoracic kyphosis using pedicle screws. [20][21][22] Modern correction techniques can better restore kyphosis and might change the incidence of PJK in patients with an all-screw construct. A study comparing the patients in the present study with recently operated patients would be necessary to confirm our findings.…”

Section: Discussionmentioning

confidence: 99%

Incidence of Proximal Junctional Kyphosis With Pedicle Screws at Upper Instrumented Vertebrae in Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

Ogura

Glassman

Sucato

et al. 2020

Global Spine Journal

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Study Design: Longitudinal cohort. Objectives: Posterior spinal fusion (PSF) using all-pedicle screw constructs has become the standard procedure in the treatment of adolescent idiopathic scoliosis (AIS). However, there have been several reports that all-pedicle screw constructs or the use of pedicle screws at the upper instrumented vertebrae (UIV) increases the incidence of proximal junctional kyphosis (PJK). We aimed to evaluate the impact of instrumentation type on the incidence of PJK following PSF for AIS. Methods: We performed a stratified random sampling from 3654 patients enrolled in a multicenter database of surgically treated AIS to obtain a representative sample from all Lenke types. Patients were then allocated into 3 groups based on the instrumentation type: all-pedicle screw (PS), hook at UIV with pedicle screws distally (HT), and hybrid constructs (HB). We measured proximal junctional angle (PJA) and defined PJK as PJA ≥ 10° and PJA progression of >10° at the final follow-up. Results: Fifteen (4.3%) of 345 cases had PJK. PJK was significantly more common in PS (11%) compared with HB (1%) and HT (0%) ( P < .001). PJK patients were similar to non-PJK patients regarding age, sex, curve type, UIV, and preoperative coronal Cobb angle. Thoracic kyphosis was significantly higher in the PJK group before surgery. Patients who developed PJK had a statistically significantly larger negative sagittal balance compared with the non-PJK group. Conclusion: The incidence of PJK was 4.3% and was more common in all-pedicle screw constructs. Using hooks at UIV might be a treatment strategy to limit PJK.

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Section: Discussionmentioning

confidence: 99%

Incidence of Proximal Junctional Kyphosis With Pedicle Screws at Upper Instrumented Vertebrae in Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

Ogura

Glassman

Sucato

et al. 2020

Global Spine Journal

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“…Several factors influence thoracic kyphosis corrections included preoperative thoracic kyphosis, main thoracic curve flexibility, anchor density of concave side, rod materials and facetectomy levels [27–29]. Although statistical radiographic differences of thoracic kyphosis correction were observed between low-density and other two groups, clinical significances of thoracic kyphosis correction were not reached since the mean differences were only 5°-10° between the three groups.…”

Section: Discussionmentioning

confidence: 99%

The correlations between the anchor density and the curve correction of adolescent idiopathic scoliosis surgery

Yeh

Niu

Chen

et al. 2019

BMC Musculoskelet Disord

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BackgroundThe optimal anchor density in adolescent idiopathic scoliosis (AIS) surgery to achieve good curve correction remains unclear. The purpose of the study is to analyze the correlations between three-dimensional curve correction and anchor density in the pedicle screw-based posterior fusion of AIS.MethodsOne hundred and twenty-seven AIS patients receiving primary posterior fusion with pedicle screw instrumentation were retrospectively reviewed. Anchor density (AD) was defined as the screws number per fused spinal segment. The correlations between three-dimensional curve correction radiographic parameters and anchor density were analyzed with subgroup analysis based on different curve types, curve magnitudes, and curve flexibilities. The differences of curve correction parameters between the low-density (AD ≤1.4), middle-density (1.4 < AD ≤1.7) and high-density (AD > 1.7) groups were also calculated. Independent t-test, analysis of variance (ANOVA), and Pearson’s correlation coefficient were used for statistical analysis.ResultsThere were no correlations between the anchor density and the coronal curve correction or apical vertebral rotation (AVR) correction. In the sagittal plane, mild positive correlations existed between anchor density and thoracic kyphosis correction in all patients (r = 0.27, p = 0.002). Subgroup analysis revealed similar mild positive correlations in Lenke 1 (r = 0.31, p = 0.02), Lenke 1–3 (r = 0.27, p = 0.01), small curves (40°-60°, r = 0.38, p < 0.001), and flexible curves (flexibility > 40%, r = 0.34, p = 0.01).There were no differences between low-density (mean 1.31), middle-density (mean 1.55), and high-density (mean 1.83) in terms of coronal or axial curve correction parameters. Low-density group has longer fused level (mean difference 2.14, p = 0.001) and smaller thoracic kyphosis correction (mean difference 9.25°, p = 0.004) than high-density group.ConclusionIn our study, the anchor density was not related to coronal or axial curve corrections. Mild positive correlations with anchor density were found in thoracic kyphosis correction, especially in patients with smaller and flexible curves. Low anchor density with longer fusion level achieves similar curve corrections with middle or high anchor density in adolescent idiopathic scoliosis surgery.

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“…They include: The surgeon themselves: Variation in surgeons’ choice of techniques and differences between different surgeons’ techniques, including variation in rod contouring [ 12 , 25 , 26 , 27 , 28 , 29 , 30 ]. Implant density and implant choice: Higher screw density on the concave side with thicker and cobalt chrome rods have been associated with restoration of kyphosis to greater than 20 degrees [ 31 ]. Reduction in the implant density, however, also means the load exerted on each anchor is increased.…”

Section: Discussionmentioning

confidence: 99%

“…Implant density and implant choice: Higher screw density on the concave side with thicker and cobalt chrome rods have been associated with restoration of kyphosis to greater than 20 degrees [ 31 ]. Reduction in the implant density, however, also means the load exerted on each anchor is increased.…”

Section: Discussionmentioning

confidence: 99%

Correction of Thoracic Hypokyphosis in Adolescent Scoliosis Using Patient-Specific Rod Templating

et al. 2023

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The emphasis of surgical correction in adolescent idiopathic scoliosis (AIS) has been given to coronal plane correction of deformity without addressing the sagittal plane thoracic hypokyphosis. Thoracic hypokyphosis has been implicated in cervical malalignment, increased incidence of proximal and distal junctional kyphosis, spinopelvic incongruence, and increased incidence of low back pain. The surgeon, variability in surgical technique, and difference in rod contouring have been implicated as factors resulting in less-than-adequate restoration of thoracic kyphosis. We hypothesised that predictable correction of hypokyphosis could be achieved by using a reproducible surgical technique with patient-specific rod templating. We describe a technique of correction of AIS with dual differential rod contouring (DDC) using patient-specific rod templating to guide intraoperative rod contouring. The pre- and post-operative radiographs of 61 patients treated using this technique were reviewed to compare correction of hypokyphosis achieved with that predicted. Analysis revealed that we achieved a kyphosis within +/− 5.5 of the predicted value. The majority of patients had a post-operative kyphosis within the optimal range of 20–40 degrees. We concluded that patient-specific rod templating in DDC helps surgeons to consistently achieve sagittal correction in AIS close to a predicted value while achieving a very good coronal plane correction.

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Influence of screw density on thoracic kyphosis restoration in hypokyphotic adolescent idiopathic scoliosis

Cited by 11 publications

References 44 publications

Incidence of Proximal Junctional Kyphosis With Pedicle Screws at Upper Instrumented Vertebrae in Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

Incidence of Proximal Junctional Kyphosis With Pedicle Screws at Upper Instrumented Vertebrae in Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

The correlations between the anchor density and the curve correction of adolescent idiopathic scoliosis surgery

Correction of Thoracic Hypokyphosis in Adolescent Scoliosis Using Patient-Specific Rod Templating

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