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  • Does Minimally Invasive Posterior Instrumentation (PPI) Prevent Proximal Junctional Kyphosis (PJK) in Adult Spinal Deformity (ASD) surgery? A Prospectively Acquired Propensity Matched Cohort Analysis

    Final Number:

    Praveen V. Mummaneni; Michael Y. Wang; Virginie Lafage; John E. Ziewacz; Jamie Terran; David O. Okonkwo; Juan S. Uribe; Richard G. Fessler; Raqeeb M. Haque; Justin S. Smith; Adam S. Kanter; Paul Park; Frank LaMarca; Christopher I. Shaffrey; Vedat Deviren; Gregory Mundis; International Spine Study Group

    Study Design:
    Clinical Trial

    Subject Category:

    Meeting: Congress of Neurological Surgeons 2013 Annual Meeting

    Introduction: Proximal junctional kyphosis (PJK) is an unwanted complication of ASD surgery. Multiple theories exist why PJK occurs. One potential contributor is damage to the paraspinal musculature and intervertebral stabilizers frequently disrupted during exposure and screw placement. This study aims to investigate the effect of PPI vs. Open screw placement on PJK development.

    Methods: 280 pts in 2 prospective databases (MIS n=85; OPEN n=195) were retrospectively reviewed, divided in 2 separate approaches and propensity matched for pelvic incidence – lumbar lordosis (PI-LL) and change of LL. Inclusion criteria: age >45, Cobb >20°, min 1 yr follow up. Groups defined as: 1)cMIS- lateral interbody fusion (LIF) with PPI (n= 31) and 2)Hybrid (HYB)- LIF followed by open posterior instrumentation (n=31). PJK was defined as Proximal junctional angle (PJA) >10° and change post op >10°.

    Results: A mean of 4.1 levels were fused (range 2-6). The mean age was 64 years and mean BMI was 26.1. Mean follow-up was 27.5 months. There was no preop difference between groups for LL-PI or SVA. Both groups showed significant improvement in LL (cMIS: 33°-41°; HYB: 35°-44°; p<0.001) and PI-LL (cMIS:19.7°-12.4°; HYB: 19.6°-7.4°) and significant difference in PT. SVA remained physiologic for cMIS (29-26mm) and improved in HYB (54-31 mm; p=0.024). The cMIS group had a smaller change in PJA (+1.3°) than HYB (+6°) (p=0.005). PJK developed in 19.4% of HYB patients and 0% in cMIS (p<0.01). One patient in the Hybrid group required vertebroplasty for PJK. Both groups saw significant improvement in ODI (cMIS 39 to 20.1; HYB 46.7 to 30; p<0.001).

    Conclusions: The addition of PPI seems to have a protective effect on the development of PJK. The analysis controlled for preoperative sagittal alignment as well as for correction of PI-LL. HYB was effective in restoring sagittal global alignment and cMIS in maintaining it.

    Patient Care: Improve our understanding of surgical treatment strategies for adults with spinal deformity.

    Learning Objectives: By the conclusion of this session, participants should be able to: (1) Understand that development of proximal junctional kyphosis remains a significant potential complication following adult deformity surgery; (2) Appreciate that minimally invasive pedicle screw placement may be protective against development of proximal junctional kyphosis.


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