Does the Use of Minimally Invasive Pedicle Screw Fixation Lower the Rate of PJK and Reoperation for PJF?

Presented at SMISS Annual Forum 2014
By Paul Park MD
With Juan S. Uribe MD, FACS, Neel Anand MD, Vedat Deviren MD, Richard G. Fessler MD, PhD, Michael Wang MD, Praveen Mummaneni MD, David O Okonkwo , Adam Kanter MD, Christopher Shaffrey MD, Gregory M. Mundis MD, Pierce Nunley MD, Stacie Nguyen MPH, Kai-Ming Fu MD,

Disclosures: Paul Park MD B; Biomet, Globus, Medtronic, Nuvasive. F; Globus Juan Uribe MD, FACS A; Nuvasive. B; Nuvasive. C; Nuvasive. D; Nuvasive. F; Nuvasive, Neel Anand MD None, Vedat Deviren MD A; AOSpine, Globus, Nuvasive. B; Nuvasive. F; Nuvasive., Richard Fessler MD, PhD None, Michael Wang MD None, Praveen Mummaneni MD B; Globus, David O Okonkwo None, Adam Kanter MD None, Christopher Shaffrey MD None, Gregory Mundis MD A; ISSGF, Nuvasive. B; K2M, Medicrea, Misonix, Nuvasive. C; K2M, Nuvasive. F; Nuvasive., Pierce Nunley MD None, Stacie Nguyen MPH None, Kai-Ming Fu MD B; Globus, Depuy Synthes, Sibone, 4web,

Introduction:
Disruption of the paraspinal muscles and joints may contribute to proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) requiring reoperation. Minimally invasive (MIS) pedicle screw fixation has been theorized to lower the PJK rate by reducing paraspinal soft tissue injury.

Aims/Objectives:
The purpose of this study was to compare rates of PJK and reoperations for PJF in a propensity matched patient cohorts who had posterior minimally invasive (MIS) versus open pedicle screw placement to correct moderate degrees of adult deformity.

Methods:
Two multi-center databases were queried. Inclusion criteria for the databases were age >18 yrs and one of the following criteria: coronal scoliosis ≥20°, SVA >5cm, PT >25º, or thoracic kyphosis >60º. Patients were categorized into 3 groups by surgical approach. The MIS group were those who had lateral interbody fusion (LIF) and/or MIS TLIF with posterior percutaneous instrumentation. Hybrid (HYB) group were those who had LIF followed by open posterior instrumentation. Open (OPEN) group were those who had a traditional posterior exposure for screw placement +/- osteotomies. Patients were propensity matched for SVA, PI-LL mismatch, and levels fused. 114 patients were included with 38 in each group. All patients had 2 year minimum follow-up. PJK was defined as proximal junctional angle >10° and change post-op >10°.

Results:
Mean age was 60.8(MIS), 62.4(HYB), and 53.5(OPEN)yrs (p=0.018). Pre-op SVA and PI-LL were similar and remained so at 2 year follow-up (Table 1). Mean levels fused were 4.7(MIS), 5.4(HYB), 6.8(OPEN) (p=0.002). Radiographic PJK rates were similar. However, 0(0%) cases in MIS vs 6(15.8%) in HYB (p=0.01) and vs 3(7.9%) in OPEN (p=0.07) required re-operation. Mean PJK angle in these patients were 21.3° for HYB and 23.1° for OPEN.

Conclusions:
In this comparative study, MIS pedicle screw fixation resulted in a similar rate of radiographic PJK in patients who were propensity matched for SVA and PI-LL mismatch (pre-op SVA<5cm, PI-LL of 10-20 degrees) and levels fused. There was a trend toward MIS cases requiring less reoperation for PJK.