Growth Preserving Spinal Surgery for Scoliosis in Children with Osteogenesis Imperfecta Lawrence Karlin, MD, Amer Samdani, MD, Anna McClung, BSN, RN, Michael Troy, BA

Introduction Surgeons treating children with osteogenesis imperfecta (OI) are faced with the major challenge of obtaining and maintaining secure fixation in the fragile bone. This study was undertaken to determine the feasibility in this population of performing growth sparing surgery, a method that places significant stresses on the bone- instrumentation site.

Methods Retrospective review of Growing Spine Study Group (GSSG) data base Inclusion criteria: – OI diagnosis and scoliosis – Previous/on-going growth sparing spinal surgery – 2 year minimum follow-up following initial procedure Demographic, clinical, radiographic data analyzed for surgical results and complications

Results 5 children – 3 boys with Sillence Type III – 1 girl Type I – 1 girl Type I-IV combination initial surgery – 7.3y ( ) Average follow-up – 6.6y (5-9) Average #surgical procedures – 1 patient stopped treatment after 1 lengthening – 4 patients - 11 procedures (5-15) – 1 final fusion Instrumentation – Spine based growth rods - 4 – VEPTR - 1

Results-Radiographic In 4 of 5 patients final T1-T12 height >180mm In 4 patients that continued treatment – Milder type OI: T1-T12 height increased an average of 11.8mm/yr or 9 mm/lengthening – Type III OI: T1-T12 height increased an average of 6.5 mm/y or 3.7 mm/lengthening

Results-Radiographic Initial major curvature80° (60°-99°) Initial Correction32% (45°-64°) Most Recent Correction 4 patients that continued treatment Patient that stopped treatment 39% (38°-55°) 32% increase (100°) Average T1-T12 height increase144mm( ) to 194mm ( ) Average T1-S1 height increase222mm( ) to 309mm( )

Complications Medical:3 minor(atelectasis,uti,hyponatremia) Neurologic: intra-op monitor change-resolved Wound infection: 0 Instrumentation:10 (9 anchor site failures, 1 prominent screw) – 4/10 un-planned surgeries – 3 un-planned in OI type III

O.I. Type III At age 4y2m Matthew’s thoracic scoliosis had progressed to 62°and his lumbar to 52°(a). The surgical plan was to obtain secure anchor sites before applying the stress of deformity correction. At the initial surgery the anchor sites at T2-4 and L2-3 were instrumented and fused©. After 4 months the rods were placed and correction obtained though some persistent thoracolumbar kyphosis was accepted(d,e). a b d c e

a b c O.I Type III The rods and connectors were exchanged at 2 ½ years(a). By 7 years it was apparent that the upper anchors had migrated(b). The CT images show that the hooks were within bone, but their position was clearly posterior and proximal to the original site(c,d). The instrumentation was revised at the time of a surgical decompression and fusion for symptomatic basilar impression. Over 8 years the T1-T12 height increased form 120 mm to 180 mm and the T1-S1 height from 206 mm to 263. The thoracic deformity correction has been maintained and the lumbar improved (e). e d

Conclusions In this small series of OI patients, growth sparing surgery was tolerated without major complications. When treatment was continued correction of the deformity was maintained. As anticipated the most frequent complication was loss of fixation. The length gained in OI type III patients was extremely variable and prognosis in these patients remains guarded.