Transcript Biomechanical risk factors for PJK

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Biomechanical risk factors for proximal junctional kyphosis: a detailed
numerical analysis of surgical instrumentation variables
Marco Cammarata, BEng1,2, Carl-Éric Aubin, PhD, PEng1,3,
Xiaoyu Wang, PhD1,3, Jean-Marc Mac-Thiong, MD, PhD2,3
1. Department of Mechanical Engineering, École Polytechnique de
Montréal, Canada
2. Research Center, Hôpital du Sacré-Cœur de Montréal, Canada
3. Research Center, Sainte-Justine University Hospital Center,
Canada
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A total of 576 numerical simulations and a sensitivity analysis were
performed for six adult spinal deformity instrumentation cases to
assess four biomechanical indices related to the development of
PJK:
– Immediate postoperative proximal junctional kyphotic angle;
– Thoracic kyphosis;
– Proximal junctional intervertebral flexion forces;
– Proximal junctional intervertebral flexion moment;
The individual effect of four instrumentation variables on each of the
above indices was evaluated:
– Proximal dissection procedure;
– Implant type at the upper instrumented vertebra;
– Sagittal thoracic rod curvature;
– Proximal diameter of the proximal transition rod;
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Each of the followings biomechanically helps reducing the risk of
PJK:
– Preserving more intervertebral elements at the proximal end of
the instrumentation;
– Using transverse process hooks instead of pedicle screws at the
upper instrumented vertebra;
– Using tapered transition rods at the proximal end of the
instrumentation.
Monoaxial and multiaxial screws at upper instrumented vertebra had
similar effects on the four biomechanical indices.
Resulting average, minimum,
and maximum values of
each biomechanical index
(PJ: proximal junctional; TK:
thoracic kyphosis; UIV: upper
instrumented vertebra)
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Typical results for one
case (#2): FSU: intact
functional spinal unit;
BCF: bilateral complete
facetectomy; PLD:
posterior ligaments
dissection; FAS: fixed
angle screw; MAS:
multiaxial screw; TPH:
transverse process hook;
PJ: proximal junctional;
UIV: upper instrumented
vertebra.
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