Proximal Fusion Constructs in MIS Scoliosis Surgery are Successful without Interbody or Intertransverse Fusion

Presented at SMISS Annual Forum 2018
By S. Burks
With J. Godzik , Konrad Bach MD, J. Uribe , M. Wang ,

Disclosures: S. Burks None J. Godzik None, Konrad Bach MD None, J. Uribe None, M. Wang None,

Introduction:

Minimally invasive techniques are increasingly utilized in adult deformity surgery as surgeon familiarity improves and long-term data is published. Concerns raised in such cases include pseudoarthrosis at levels where interbody grafts are not utilized. Previous studies have not specifically examined the status of the rostral aspect of the surgical construct, which is commonly instrumented without interbody or intertransverse fusion.

Aims/Objectives:

Assess the fusion status of percutaneously instrumented rostral segments in deformity constructs. Evaluate the rate of proximal junctional kyphosis in hybrid deformity cases where the rostral levels are instrumented percutaneously.

Methods:

A retrospective analysis was performed on all patients who underwent hybrid minimally invasive deformity corrections in two academic spine centers over a ten-year period. Inclusion criteria were at least 2 rostral levels instrumented percutaneously ranging from T8-L2 as upper end of the construct. Fusion assessment was made using computed tomography when possible or dynamic radiographs. Common radiographic parameters and clinical variables were assessed pre- and post-operatively.

Results:

A total of 34 patients fit inclusion criteria. Baseline characteristics included: M:F 14:20, average age of 65.1 years, and BMI 30.2. The number of levels fused on average was 7.4 with an average of 3.4 instrumented percutaneously between T8 and L2, representing a total of 115 rostral levels instrumented percutaneously. Fusion assessment was performed using CT in 70 levels and radiographs in 45 levels. Among the 115 rostral levels instrumented percutaneously robust fusion was seen in 20 (17.4%) with 49 (42.6%) exhibiting some evidence of fusion. Pseudoarthosis was seen in 2 (1.7%) of rostral segments. There were no instances of proximal hardware revision. The number of patients with radiographic PJK was 8 (22.9%). Follow-up imaging was obtained at a mean of 26.7 months. Deformity parameters were captured in all patients with standing scoliosis radiographs.

Conclusions:

In the present series of adult scoliosis patients undergoing thoracolumbar deformity correction, rostral segments instrumented percutaneously have a very low rate of pseudoarthorsis (less than 2%) with clear evidence of bony fusion occurring in >60% of patients. The rate of PJK was acceptably low.