Anterior vertebral body tethering : a single center cohort with 5+ years of follow-up

Introduction: Vertebral Body Tethering (VBT) is a new surgical technique for the treatment of Adolescent Idiopathic Scoliosis where limited data for mid-to long-term outcomes exists. We aimed to fill this critical gap by evaluating outcomes in a cohort of patients with 4-7 years of post-operative follow-up.   Methods: We performed a retrospective review of clinical and radiologic data from our first thirty-one consecutive patients treated with VBT, all of whom had at least four years of follow-up (mean: 5.7±0.7 yrs.). We assessed various parameters related to deformity correction, suspected broken tethers, and surgical revisions at all available timepoints. A successful postoperative outcome was defined by a residual deformity of ≤ 30° at latest follow-up without conversion to Posterior Spinal Fusion (PSF). Results: Of the patients who met the inclusion criteria, two were lost to follow-up, seven required revisions, sixteen exhibited at least one suspected broken tether, and two were converted to a PSF. Only two broken tethers were identified more than four years postoperatively (mean: 2.68 years). The average main thoracic and thoracolumbar deformities were 22° and 23° at latest follow-up. A successful postoperative outcome was observed in 64% of patients despite an average increase of 4° in main thoracic and 8° in thoracolumbar deformities. Conclusion: Although some deformity correction was lost, we remain optimistic regarding outcomes as 93% of patients avoided PSF and only two new suspected broken tethers were identified beyond four years. Additional long-term follow-up data will be required to continue to elucidate the efficacy of VBT

Temporal milestones during childhood : identification of a maturational spurt

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The transition of the human skeleton from immature to mature is characterized by a series of predictable milestones in both growth (e.g., peak height velocity) and development (e.g., ossification of the adductor sesamoid). As such, the treatment of many skeletal growth and/or developmental disorders often includes a detailed skeletal assessment to predict the attainment of future milestones; however, differences in actual growth and development and those predicted from prior assessments are often less precise then that required for positive patient outcomes. A lack of estimate precision may be related to the 'Linear Paradigm'--a long-held assumption that skeletal maturation should progress linearly throughout childhood and adolescence (a detailed discussion can be found in Chapter One). Thus, the complex characterization of skeletal maturation, including the identification of a maturational 'spurt', akin to the pubertal growth spurt, may provide greater prognostic value than that which is provided under the Linear Paradigm. Chapters Two, Three, and Four (i.e., Aim 1) aimed to characterize longitudinal assessments of skeletal maturation throughout childhood and adolescence by leveraging existing data from the Fels Longitudinal Study. Chapter Two highlights the strengths and weakness of distinct statistical methodologies for milestone estimates of height and also provides the statistical justification for the longitudinal methodologies used in throughout the remainder of this dissertation. Chapter Three explores the longitudinal relationship, particularly related to the tempo of skeletal maturation, between chronological age and skeletal age throughout childhood and adolescence. This chapter provides a comprehensive characterization of the maturational spurt, which includes the identification of three discrete longitudinal maturational trajectories (i.e., childhood only maturational spurt, adolescent only maturational spurt, and both a childhood and adolescent maturational spurt). Chapter Four explores the clinical significance of modeling longitudinal changes in the tempo of skeletal maturation with two distinct higher order polynomial models. Aim 2 (i.e., Chapter Five) focuses on refining existing skeletal maturity phenotypes associated with relevant ontogenetic milestones of the maturational spurt. This chapter highlights the skeletal phenotypes associated with peak maturational velocity in participants that exhibited a maturational spurt in adolescence only and also establishes multivariate statistical models that can be used by pediatric practitioners to predict the timing of peak maturational velocity. Because the tempo of skeletal maturation is influenced by racial and/or ethnic background, Aim 3 (i.e., Chapter 6) characterizes relevant ontogenetic milestones associated with the maturational spurt in participants of African American, Asian American, and Hispanic descent from the Bone Mineral and Density in Childhood Study. Taken together, the data presented herein highlight the non-linear nature of normal skeletal maturation, which provides robust evidence toward a shift in the maturational paradigm. Additionally, these data provide pediatric clinicians with a more detailed understanding of the progression of skeletal maturation, particularly during adolescence, which will increase patient-specific treatment resulting in improved patient outcomes and quality of life for those suffering from skeletal growth and/or developmental disorders

Estimating peak height velocity in individuals: a comparison of statistical methods

Background Estimates pertaining to the timing of the adolescent growth spurt (e.g. peak height velocity; PHV), including age at peak height velocity (aPHV), play a critical role in the diagnosis, treatment, and management of skeletal growth and/or developmental disorders. Yet, distinct statistical methodologies often result in large estimate discrepancies. Aim The aim of the present study was to assess the advantages and disadvantages of three modelling methodologies for height as well as to determine how estimates derived from these methodologies may differ, particularly those that may be useful in paediatric clinical practice. Subjects and methods Height data from 686 individuals of the Fels Longitudinal Study were modelled using 5th order polynomials, natural cubic splines, and SuperImposition by Translation and Rotation (SITAR) to determine aPHV and PHV for all individuals together (i.e. population average) by sex and separately for each individual. Estimates within and between methodologies were calculated and compared. Results In general, mean aPHV was earlier, and PHV was greater for individuals when compared to estimates from population average models. Significant differences between mean aPHV and PHV for individuals were observed in all three methodologies, with SITAR exhibiting the latest aPHV and largest PHV estimates. Conclusion Each statistical methodology has a number of advantages when used for specific purposes. For modelling growth in individuals, as one would in paediatric clinical practice, we recommend the use of the 5th order polynomial methodology due to its parameter flexibility