Management of Spinal and Thoracic Deformity in Patients with Myelomeningocele Using Vertical Expandable Prosthetic Titanium Rib Ajeya P. Joshi, David Limon, R. Zach Garza, Khadija Tayabali, Vishwas Patil, William Koeck, Hope Trevino, James W. Simmons, Robert M. Campbell, Jr.

Introduction and Objectives There are significant challenges to the treatment of spinal deformities associated with myelomeningocele due to the high complication rates of the defect Vertical Expandable Prosthetic Titanium Rib (VEPTR) is an effective medium-term treatment for the many spinal and thoracic deformities associated with thoracic insufficiency syndrome (TIS) Objective: Analyze the efficacy of treatment of patients with spinal deformities, associated TIS, and myelomeningocele using VEPTR implants

Methods Retrospective review of 17 patients at a single institution with spinal deformity, associated TIS, and a history of myelomeningocele that received VEPTR treatment Sitting radiographs measured for coronal and sagittal profile such as Cobb angle, pelvic obliquity, space available for lungs (SAL), thoracic kyphosis, and lumbar lordosis Charts reviewed for surgical history, assisted ventilation rate (AVR), vital signs, capillary blood gasses (CBG), and complications All data were collected before and after initial implantation, after a subsequent alteration to the devices used (this does not include device expansion, use of a larger device with growth, etc.), where applicable, and before and after spinal fusion surgery, where applicable

Methods Space Available for Lungs (SAL) Assisted Ventilation Rate (AVR) To find hemithoracic height, the distance from the superior, medial apex of the hemithorax to the midpoint of the hemidiaphragm was measured bilaterally The height of the concave hemithorax was divided by the height of the convex hemithorax to give SAL Perfectly symmetrical hemithoraces would express an SAL of 1 A measure of a patients ventilator dependency status 0 = breathing room air 24 hr/day 1 = use of supplemental O2 (e.g. nasal cannula) 2 = nighttime ventilator use (including CPAP) 3 = occasional daytime ventilator use 4 = fully ventilator dependent

Results Demographic Summary # Mean Cobb angle at pre-op Mean SAL at pre-op Mean age at VEPTR implant (years) Average follow-up (years) 7 males 8 females 72.71o .691 5.5 6.4 Relative to pre-op values: * = p<.05 ** = p<.01 *** = p<.0001 † = possibly due to small sample size at post #2 * ** *** ** *** †

Results 4x4 MM ANOVA of the Effects of Implant Timepoint and Implant Progression on Thoracic Kyphosis   Sum Sq Mean Sq NumDF DenDF F.value Pr(>F) kyphotime 177.3612 59.1204 3 30.93646 0.2609597 0.8529460 imps 2758.1349 919.3783 13.20727 4.0581709 0.0302784 kyphotime:imps 3651.1425 608.5237 6 2.6860471 0.0323725 Further testing revealed that receiving an initial bilateral implant improved TK values (moved them closer to a normal value) relative to patients that initially received a unilateral implant, but later had a bilateral implant (p<.001). Additionally, patients with some form of bilateral implant improved over the course of the study, while those with unilateral implants actually worsened. 4x4 MM ANOVA of the Effects of Implant Timepoint and Implant Progression on AVR Value   Sum Sq Mean Sq NumDF DenDF F.value Pr(>F) avrtime 2.956874 0.9856247 3 28.46601 1.336227 0.2821911 imps 11.477241 3.8257469 13.58100 5.186627 0.0133705 avrtime:imps 7.927657 1.3212761 6 28.42296 1.791275 0.1366591 Further testing showed that removal of a bilateral construct to leave only unilateral devices decreased AVR value relative to all other construct progressions. However, this was somewhat confounded, because all those who kept a unilateral implant throughout the study had an AVR of 0 before their implantation, so it is difficult to compare relative effects of bilateral versus unilateral implant progressions.

Conclusions VEPTR implant associated with Complications Improved Cobb angle, SAL, pelvic obliquity, lumber, thoracic, and total spine height Improvement of thoracic kyphosis and lumbar lordosis toward normal values Advantages to use of bilateral implants in many cases VEPTR treatment is effective for relief of many structural spinal and thoracic issues associated with myelomeningocele, including improvement of thoracic deformities associated with TIS VEPTR treatment has minimal effects on the potential for spinal and thoracic growth Complications Every patient experienced at least 1 instance of an adverse event, typically manageable 10/17 patients experienced device-related infection 1 patient experienced wound dehiscence 29 device dislodgements in 11 patients 3 patients underwent spinal fusion surgery There was no difference in the incidence of AEs and infection rates between the different implant progression types Two deaths occurred, both unrelated to surgery