Defining Clinically Relevant Proximal Junctional Kyphosis

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Figure
Left: Well-aligned adult with a normal C2-tilt, equal to the odontoid-hip-axis (OD-HA) of approximately 0°. Middle: Adult with ankylosing spondylitis and subsequent thoracic hyperkyphosis leading to an increase in C2-tilt. Right: Adult with ankylosing spondylitis and subsequent lumbar hypolordosis, increase in pelvic tilt, and increase in the C2-pelvic angle.

Table

Hart-International Spine Study Group proximal junctional kyphosis severity scale.

Characteristic	Points
Neurological deficit
None	0
Radicular pain	2
Myelopathy/motor deficit	4
Focal pain
None	0
VAS ≤4	1
VAS ≥5	3
Instrumentation problem
None	0
Partial fixation loss	1
Prominence	1
Complete fixation loss	2
Change in kyphosis/PLC integrity
0° to 10°	0
10° to 20°	1
>20°	2
PLC failure	2
Upper instrumented vertebra/adjacent vertebra fracture
None	0
Compression	1
Burst/chance fracture	2
Translation	3
Level of upper instrumented vertebra
Thoracolumbar junction	0
Upper thoracic spine	1