1. Prospective clinical study of spine growth modulation using
titanium clip-screw device:
Disc heights at 2 and 3 years
Bylski-Austrow DI, Glos DL, Jain VV, Reynolds JE, Wall EJ

2. Previous clip-screw studies
Titanium clip-screw device in USA FDA IDE clinical study
Six patients with progressive early AIS (IRB approved)
Maximum of n=6 defined by FDA for safety study
Safety and curvature results to 2 years have been reported
SRS 20151, ORS 2016, In rev, Spine Deformity 2016
Disc heights at 1 year PO showed increase on the concave curve side, with increase in symmetry of disc heights side-to-side
ICEOS 2014, #222

3. Purpose Specific aims Hypotheses
Determine disc heights on concave and convex sides in the first cohort in a prospective clinical safety FDA IDE study of a titanium clip-screw device
Hypotheses
Disc heights decrease with PO time
Disc height differences side-to-side correlate with curvatures

4. Methods
Six AIS patients underwent thoracoscopic placement of clip-screw devices (IRB approved)
Inclusion criteria: Thoracic curves (Lenke 1A or 1B), Cobb angle 25 to 40, age >10 years, Risser 0 and open triradiates
Disc heights measured for every patient at instrumented levels with visible intervertebral boundaries using clinical PACS system and image analysis software (Photoshop, Adobe)
Calibration ring in all pre-op radiographs
Disc heights by side compared to pre-op
Statistics
t-tests, one-tail
ANOVA, mixed model, 2-way: subject, time (SAS 12.1)

5. Methods: Radiographic
Coronal and sagittal radiographs obtained using digital radiographic system
Open triradiate cartilages documented
Calibration ring in pre-op radiographs

6. Results Disc heights were measurable in 5 of 6 subjects
One patient was eliminated due to both inability to discern most disc boundaries and conversion, prior to 2 years PO, to posterior spinal fusion (PSF)
On average, disc heights did not change from pre-op to 3 years PO for concave or convex (treated) curve sides

7. Difference in disc height vs curvature
By subject and time, local disc height changes depended on response to treatment Differences in disc height side-to-side were highly correlated with curvature (p = )

8. Discussion Limitations Comparisons
This was a safety study, a pilot clinical trial. Therefore, sample size was intentionally small, not powered to detect changes in any outcome variable. Disc height was not specifically an outcome variable of the base study
Radiographic measures were limited by the resolution of planar digital images of 3D curves, longitudinal linear measurements based on pre-op calibration scale, and need to eliminate the subject with the most axially rotated, and progressive, curve
Correlations between disc heights in the thoracic spine and disc health are not well established
Comparisons
Compared to the previous study: Disc heights at 1 year showed an increase in symmetry primarily by height increase on concave side.2 In the present study, mean concave height was slightly increased at 2 years, but not at 3 years
To related methods: To the authors’ knowledge, this is the first spine growth modulation clinical study to report disc heights
These results may be now compared to those reported for the scoliosis disease process,3 bracing studies,4,5 and, when reported, to other proposed methods of spine growth modulation

9. Conclusions Main finding Clinical significance
Disc heights did not decrease from immediately pre-operative to 3 years PO in a prospective human clinical study of experimental growth modulation with a titanium clip-screw construct for early progressive AIS
Paired side to side differences in disc height were associated with changes in curvature with PO time
Greatest mean change in disc height was <5%
Clinical significance
Excessive disc compression may be associated with disc degeneration long-term
Defining magnitude, location, and extent of disc compression by construct type is important to defining the mechanism of spine growth modulation and the likelihood of any concomitant disc effects for each proposed system

10. References Acknowledgments
Wall EJ, SRS 2015 #112, ORS 2016; #113
Bylski-Austrow, ICEOS 2014; #22
Grivas TB, Studies Health Tech & Informatics 2006; 123: 80-83
Will RE, Stokes IA, Spine 2009; 34;25:
Volz R, Dolan LA, Scoliosis 2013; 8 Suppl 1: O38
Acknowledgments
Main study regulatory status: FDA Investigational Device Exemption (IDE); Sponsor: SpineForm LLC Grant funding for main study: Ohio Third Frontier ( ), FDA R01 1-R01 FD ( )
Disclosures: DI Bylski-Austrow: SpineForm LLC: Unpaid consultant, Other financial or material support. DL Glos: None. VV Jain: SpineForm: Unpaid consultant; Medtronic Sofamor Danek: Unpaid consultant. JE Reynolds: SpineForm LLC: Paid consultant; Stock or stock options. EJ Wall: SpineForm: Other financial or material support; Research support; Stock or stock options; Unpaid consultant; OrthoPediatrics: Paid consultant; CCP-HO, PRISM, ROCK: Board or committee member
Device approved for use in European Union (CE Mark) for the labeled indications. The intended use of the system is guided spinal growth treatment of progressive idiopathic scoliosis (IS). The test article is intended for anterior-lateral fixation across the growth plates from T3 to L1 with placement through video-assisted thoracoscopic surgery. Main thoracic curvatures, but not disc heights, were an outcome measure specified a priori in the prospective clinical safety study protocol