Current strategies for the restoration of adequate lordosis during lumbar fusion

Table 3 Theoretical values for positional pelvis and spinal parameters related to pelvis incidence

PI class	PI (°)	PTth (°)	LLth (°)
I	< 38	4	PI + 18
II	38-47	8	PI + 13
III	48-57	12	PI + 9
IV	58-67	16	PI + 6
V	68-77	20	PI + 2
VI	> 78	24	PI - 5

PT: Pelvis tilt; LL: Lumbar lordosis; PT_th: Theoretical PT; LL_th: Theoretical LL. As examples, for PI measured to 40°, expected PT should be 8° and LL should be 53°; for PI measured to 52°, expected PT should be 12° and LL should be 61°; and for PI measured to 64°, expected PT should be 16° and LL should be 70°.