Scoliosis

Neurofibromatosis type 1 (NF1) is a common autosomal dominant genetic disorder occurring in 1:4000 worldwide.  Scoliosis is perhaps the most common skeletal problem in patients with NF1 with a prevalence of 1069%. There are two types: dystrophic and non dystrophic scoliosis.  Dystrophic scoliosis appears to have a poorer prognosis.  Dystrophic changes develop over time and may not necessarily appear at initial presentation.  Therefore the development and validation of a radiographic scheme to classify dystrophic scoliosis is needed to aide in distinguishing dystrophic from non dystrophic scoliosis and allow early detection and intervention and is our first objection. The second objective rests on the fact that NF1 has marked variability of clinical expression.  There is evidence that other genes may play a role in NF1 expression. Current research has identified candidate genetic SNP markers that can predict progressive and non-progressive curves in Adolescent Idiopathic Scoliosis (AIS) with a high degree of reliability.  If the same genetic markers are present in non-dystrophic scoliosis then this will allow earlier, more accurate prognostication, and perhaps improve treatment. Thus our hypothesis is that  NF1 patients with non-dystrophic or dystrophic scoliosis have the same genetic markers as patients with AIS. 

Background: Multilevel posterior spine fusion is associated with significant intraoperative blood loss. Tranexamic acid is an antifibrinolytic agent that reduces intraoperative blood loss. The goal of this study was to compare the percent of total blood volume lost during posterior spinal fusion (PSF) with or without tranexamic acid in patients with adolescent idiopathic scoliosis (AIS).

Methods: Thirty-six AIS patients underwent PSF in 2011-2014; the last half (n=18) received intraoperative tranexamic acid. We retrieved relevant demographic, hematologic, intraoperative and outcomes information from medical records. The primary outcome was the percent of total blood volume lost, calculated from estimates of intraoperative blood loss (numerator) and estimated total blood volume per patient (denominator, via Nadler’s equations). Unadjusted outcomes were compared using standard statistical tests.

Results: Tranexamic acid and no-tranexamic acid groups were similar (all p>0.05) in mean age (16.1 vs. 15.2 years), sex (89% vs. 83% female), body mass index (22.2 vs. 20.2 kg/m2), preoperative hemoglobin (13.9 vs. 13.9 g/dl), mean spinal levels fused (10.5 vs. 9.6), osteotomies (1.6 vs. 0.9) and operative duration (6.1 hours, both). The percent of total blood volume lost (TBVL) was significantly lower in the tranexamic acid-treated vs. no-tranexamic acid group (median 8.23% vs. 14.30%, p = 0.032); percent TBVL per level fused was significantly lower with tranexamic acid than without it (1.1% vs. 1.8%, p=0.048). Estimated blood loss (milliliters) was similar across groups.

Conclusions: Tranexamic acid significantly reduced the percentage of total blood volume lost versus no tranexamic acid in AIS patients who underwent PSF using a standardized blood loss measure.

Level of Evidence: 3. Institutional Review Board status: This medical record chart review (minimal risk) study was approved by the University of Minnesota Institutional Review Board.