Background: Anterior spinal growth tethering (ASGT) has been shown to alter spinal growth with the potential to correct scoliosis while maintaining spine flexibility. The purpose of this study was to report the 2 to 4-year outcomes of ASGT in skeletally immature patients with thoracic scoliosis. Methods: We conducted a retrospective review of patients with thoracic scoliosis who underwent ASGT with a minimum of 2 years of follow-up. Patient demographics, perioperative data, and radiographic outcomes are reported. A “successful” clinical outcome was defined as a residual curve of <35° and no posterior spinal fusion indicated or performed at latest follow-up. Results: Seventeen patients met the inclusion criteria. The etiology was idiopathic for 14 and syndromic for 3. The mean follow-up was 2.5 years (range, 2 to 4 years). Preoperatively, all patients were at Risser stage 0, with a mean age at surgery of 11 ± 2 years (range, 9 to 14 years). There was an average of 6.8 ± 0.5 vertebrae tethered per patient. The average thoracic curve magnitude was 52° ± 10° (range, 40° to 67°) preoperatively, 31° ± 10° immediately postoperatively, 24° ± 17° at 18 months postoperatively, and 27° ± 20° at latest follow-up (51% correction; range, 5% to 118%). Revision surgery was performed in 7 patients: 4 tether removals due to complete correction or overcorrection, 1 lumbar tether added, 1 tether replaced due to breakage, and 1 revised to a posterior spinal fusion. In 3 additional patients, posterior spinal fusion was indicated due to progression. Eight (47%) of the patients had a suspected broken tether. Ten (59%) of the 17 were considered clinically successful. Conclusions: Despite most patients having some remaining skeletal growth at the time of review, the results of the current study demonstrate that at mid-term follow-up, ASGT showed a powerful, but variable, ability to modulate spinal growth and did so with little perioperative and early postoperative risk. Fusion was avoided for 13 of the 17 patients. The overall success rate was 59%, with a 41% revision rate. Understanding the parameters leading to success or failure will be critical in advancing a reliable definitive nonfusion treatment for progressive scoliosis in the future. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Background: Anterior vertebral body tethering (AVBT) has been introduced as a means of correcting scoliosis without fusion. The purpose of this study was to compare outcomes for patients with thoracic idiopathic scoliosis between a group of patients who underwent AVBT and a matched cohort of patients treated with posterior spinal fusion and instrumentation (PSF).Methods: A retrospective study of patients who underwent AVBT and PSF for idiopathic scoliosis was conducted. The inclusion criteria were determined on the basis of the AVBT cohort: primary thoracic idiopathic scoliosis with a curve magnitude between 40° and 67°, Risser stage of ≤1, age of 9 to 15 years, no prior spine surgery, index surgery between 2011 and 2016, and minimum follow-up of 2 years. Demographic, radiographic, clinical, and patient-reported outcomes and revisions were compared between groups.Results: There were 23 patients in the AVBT cohort and 26 patients in the PSF cohort. The mean follow-up (and standard deviation) was similar between groups: 3.4 ± 1.1 years for the AVBT group and 3.6 ± 1.6 years for the PSF group (p = 0.6). Preoperatively, the groups were similar in all measurements of radiographic and clinical deformity, with mean main thoracic curves of 53° ± 8° for the AVBT group and 54° ± 7° for the PSF group (p = 0.4). At the time of final follow-up, the AVBT cohort had significantly more residual deformity, with a mean thoracic curve of 33° ± 18° compared with 16° ± 6° for the PSF group (p < 0.001). There were 9 revision procedures in the AVBT cohort (with 3 conversions to PSF and 3 more pending) and none in the PSF cohort. Revisions occurred at a mean postoperative time of 2.3 years (range, 1.2 to 3.7 years). Twelve patients (52%) had evidence of broken tethers; of these patients, 4 underwent revision. The post-intervention patient-reported outcomes were similar.Conclusions: Both AVBT and PSF resulted in postoperative correction; however, 2-year correction was better maintained in the PSF group. There were no differences in post-intervention patient-reported outcomes. AVBT resulted in less deformity correction and more revision procedures than PSF, but resulted in the delay or prevention of PSF in the majority of patients.Level of Evidence: TherapeuticLevel III. See Instructions for Authors for a complete description of levels of evidence.

Retrospective analysis of prospectively collected multicenter series. To evaluate the sagittal profile of surgically treated adolescent idiopathic scoliosis (AIS) patients. With the increasing popularity of segmental pedicle screw spinal instrumentation, thoracic kyphosis (TK) is often sacrificed to achieve coronal and axial plane correction. Radiographs of AIS patients with a Lenke type 1 deformity and minimum 2-year follow-up after selective thoracic fusion (lowest instrumented vertebra of T11, T12, or L1) were evaluated. Changes in TK were correlated with changes in lumbar lordosis (LL). Patients were divided according to approach (open/thoracoscopic anterior vs. posterior). Analysis of variance was used to compare pre and postoperative radiographic measures. Two hundred fifty-one patients (age: 14 +/- 2 years) were included. Sixty seven percentages of the patients had anterior surgery (97 open anterior, 71 thoracoscopic) and 33% (83 patients) had posterior spinal fusion. A decrease in postoperative TK was significantly correlated (P < or = 0.001) with a decrease in LL at first erect (r = 0.3), 1 year (r = 0.4) and 2 years (r = 0.4), independent of surgical approach. LL decreased significantly at the first erect regardless of approach (P = 0.003); however, at 2-year postoperative TK and LL were significantly decreased after a posterior approach (P < or = 0.001) when compared with an anterior approach that added kyphosis. The decrease in LL (5.6 degrees +/- 9.7 degrees) was nearly twice the decrease in TK (2.8 degrees +/- 11.4 degrees) in the posterior group at 2-years. Given that thoracic AIS is often associated with a preexisting reduction in TK, ideal surgical correction should address this deformity. Procedures which further reduce TK also reduce LL. It is unclear if the loss of LL from thoracic scoliosis correction will compound the loss of LL that occurs with age and lead to further decline in sagittal balance. With this concern, we recommend a posterior column lengthening and/or an anterior column shortening to achieve restoration of normal TK and maximal LL.

The influence of axial plane rotation. The purpose of the current study was to define a methodology for measuring the 3-D segmental sagittal alignment of the spine in patients with adolescent idiopathic scoliosis (AIS) and to assess the effect of axial plane rotation on differences between 3-D and 2-D measures of deformity. Methods: Preoperative and postoperative EOS images of 120 consecutive patients with AIS (primary thoracic curves) treated with segmental thoracic pedicle-screw instrumentation were analyzed in the “3-D sagittal plane.” The technique measured 3-D kyphosis or lordosis in the specific plane of sagittal motion for each spinal motion segment. The kyphosis (+) and lordosis (−) values of the segments from T5 to T12 were summed to give the 3-D measurement of T5-T12 kyphosis. These values were compared with the standard 2-D measurements of T5-T12 kyphosis on lateral radiographs, and a correlation analysis with regard to axial plane rotation of the apex was performed. Results: The average age (and standard deviation) of the patients was 14 ± 2 years. The mean preoperative Cobb angle on the standard 2-D view was 55° ± 10° and on the 3-D view was 52° ± 9° (p ≤ 0.001). On the 3-D view, the mean preoperative T5-T12 kyphosis was 6° ± 14°, and the kyphosis significantly increased to 26° ± 6° postoperatively (p < 0.001). The T5-T12 kyphosis on the standard 2-D view measured 18° ± 13° preoperatively and 27° ± 6° postoperatively (p < 0.001). The difference between the 2-D and 3-D measurements of T5-T12 kyphosis strongly correlated with apical vertebral rotation (r = 0.85; p < 0.01). Conclusions: Routine 2-D measurements of thoracic kyphosis erroneously underestimate the preoperative loss of kyphosis in AIS because of errors associated with axial plane rotation, an inherent component of thoracic scoliosis. Level of Evidence: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence....

Background: Spinal growth modulation by tethering the anterolateral aspect of the spine, as previously demonstrated in a nonscoliotic calf model, may be a viable fusionless treatment method for idiopathic scoliosis. The purpose of the present study was to evaluate the radiographic, histologic, and biomechanical results after six and twelve months of spinal growth modulation in a porcine model with a growth rate similar to that of adolescent patients. Methods: Twelve seven-month-old mini-pigs underwent instrumentation with a vertebral staple-screw construct connected by a polyethylene tether over four consecutive thoracic vertebrae. The spines were harvested after six (n = 6) or twelve months (n = 6) of growth. Monthly radiographs, computed tomography and magnetic resonance imaging scans (made after the spines were harvested), histologic findings, and biomechanical findings were evaluated. Analysis of variance was used to compare preoperative, six-month postoperative, and twelve-month postoperative data. Results: Radiographs demonstrated 14° ± 4° of coronal deformity after six months and 30° ± 13° after twelve months of growth. Coronal vertebral wedging was observed in all four tethered vertebrae and progressed throughout each animal's survival period. Disc wedging was also created; however, in contrast to the findings associated with vertebral wedging, the tethered side was taller than the untethered side. Magnetic resonance images revealed no evidence of disc degeneration; however, the nucleus pulposus had shifted toward the side of the tethering. Midcoronal undecalcified histologic sections showed intact bone-screw interfaces with no evidence of implant failure or loosening. With the tether cut, stiffness decreased and range of motion increased in lateral bending away from the tether at both time-points (p < 0.05). Conclusions: In this porcine model, mechanical tethering during growth altered spinal morphology in the coronal and sagittal planes, leading to vertebral and disc wedging proportional to the duration of tethering. The resulting concave thickening of the disc in response to the tether was not anticipated and may suggest a capacity for the nucleus pulposus to respond to the compressive loads created by growth against the tether. Clinical Relevance: Multilevel flexible tether placement may provide a growth-modulating mechanism for scoliosis correction while maintaining disc health. Understanding the response of the growing vertebrae and discs in this proposed method of fusionless scoliosis treatment remains paramount.

The standard of care for progressive spinal deformity that is greater than 45–50 degrees in growing children is deformity correction with spinal fusion and instrumentation. This sacrifice both spinal motion and further spinal growth of the fused region. Idiopathic scoliosis in particular is associated with disproportionate anterior spinal column length compared to the posterior column (hypokyphosis) that is associated with the coronal (scoliosis) and axial plane (rib and lumbar prominence) deformities. In theory, application of compression to the convex and anterior aspects of vertebrae could decrease both anterior and lateral growth via the Hueter-Volkmann principle, while allowing growth on the concave and posterior aspect resulting in spinal realignment created by altered growth. Animal models and preliminary clinical experience suggest spinal growth can be modulated in this way using a flexible tether applied to the convex side of scoliotic vertebral column. Experimental studies suggest disc health is preserved with a flexible tether as disc motion is maintained during the growth period. Anterolateral tethering been performed via a thoracoscopic spinal approach clinically for a number of years and the early clinical outcomes are beginning to appear in the literature. Initial results of anterolateral tethering in growing patients with spinal deformities are encouraging, however the results 3–4 years after the procedure are somewhat mixed. Further research is ongoing and many remain optimistic that improvements in technology and understanding will continue to lead to better patient outcomes.