The feasibility analysis of distal anchor at S1 for congenital lumbosacral deformities associated with sacral agenesis

English Keywords:Lumbosacral deformity  Sacral agenesis  Coronal imbalance  Trunk shift

English Abstract:

  【Abstract】 Objectives: To analyse the surgical outcome and condition of coronal balance for congenital lumbosacral deformities combined with sacral agenesis and evaluate the feasibility of distal anchor at S1. Methods: Six patients diagnosed with congenital lumbosacral deformities combined with sacral agenesis receiving surgical treatment with distal anchor at S1 from January 2009 to January 2018 were reviewed retrospectively. Lumbar Cobb angle, coronal balance distance(CBD) and pelvic obliquity angle(POA) were measured at baseline, immediate post-operation and follow-up in the long-cassette standing posteroanterior and lateral radiographs of the entire spine. Results: Six patients(3 boys and 3 girls) were recruited in our study with an average follow-up period of 3.83±1.47 years(1-6 years). The average age was 4.11±1.57 years(3-6 years). The lumbar Cobb angel was 39.20°±6.27° before surgery, 16.53°±14.16° after surgery and 22.48°±9.80° at the last follow-up, with significant difference(P<0.05). However, the coronal balance had a tendency of deterioration. The preoperative and immediate postoperative CBD were 18.30±16.85mm and 22.47±8.77mm, respectively. But it increased to 31.35±8.61mm at the last follow-up. If CBD>2cm was defined as coronal imbalance, 5 cases presented postoperative coronal imbalance with a high incidence of 83.3%. Compared with preoperation, postoperative and follow-up POA showed no significant difference(P>0.05). Conclusions: For congenital lumbosacral deformities combined with sacral agenesis, although distal anchor at S1 may immediately correct the deformity, coronal imbalance is prone to occur postoperatively. Therefore, pelvic fixation may be a better choice to avoid these problems.