Pitfalls and management of corrective spinal surgery in trisomy 9 mosaicism: a report of three cases

Purpose The aim of this case series is to present the outcomes of surgical correction of hyperkyphosis, and subsequent management of complications for three patients with a rare chromosomopathy, Trisomy 9 Mosaicism (T9M). Methods Case series with 2 year outcomes following index surgery. Results Case 1 presented at 9 years of age with 103° of kyphosis (T3-T10), which progressed to 118° despite bracing. Case 2 presented at 7 years of age with 113° of kyphosis (T3-T11). Case 3 presented at 4 years of age with 103° of kyphosis (T1-T11). Cases 1 and 2 underwent T2-L2 posterior instrumented spinal fusion (PISF). Upon follow up, radiographs for Cases 1 and 2 revealed severe, symptomatic proximal junctional kyphosis (PJK) of 71° and 50°, respectively, requiring surgical revision proximally to the C4 level. Case 3 underwent placement of magnetically controlled growing rods given young age and growth potential. Surgical levels for Case 3 were extended from C4-pelvis in an attempt to prevent development of symptomatic PJK. Most recent radiographs for Case 3 taken 21 months postoperatively demonstrate a stable 50° of kyphosis. PJK above C4 was noted but is stable and asymptomatic. Conclusion T9M often presents with progressive hyperkyphosis. Despite instrumentation above the upper end vertebra (UEV), PJK may be a common complication in this small patient population. This novel report on spine deformity correction in the T9M population may provide preliminary guidance for the treatment of hyperkyphosis in patients with T9M and help surgeons avoid common pitfalls. Level of evidence IV.