Table 1

Redefining lumbosacral transitional vertebrae (LSTV) classification through integrating the full spectrum of morphological alterations in a biomechanical continuum.²

Dysplastic L5 Transverse Process (TP)^*	Type I A	Type I B	Type I A F (i/c) or Type I B F(i/c)		Type I A F2 or Type I B F2	-
Dysplastic L5 Transverse Process (TP)^*	Unilateral TP ≤ 19 mm in width^*	Bilateral TPs ≤ 19 mm in width^*	With presence of ipsi/contra lateral rudimentary facet to the side of the L5 enlargement		With presence of bilateral rudimentary facets
Accessory articulations	Type II A	Type II B	Type II A F(i/c) or Type I B F(i/c)		Type II A 2F or Type II B 2F
Accessory articulations	Unilateral L5-S1 accessory articulation	Bilateral L5-S1 accessory articulations	With presence of ipsi/contra lateral rudimentary facet to the side of the diarthrosis		With presence of bilateral rudimentary facets	-
Sacralisation^**	Type II A	Type III B	Type III C		Type III A F (i/c) or Type III B F(i/c) or Type IIIC F	Type III A 2F or Type III B 2F or Type III C 2F
Sacralisation^**	Unilateral L5-S1 sacralisation	Unilateral complete sacralisation with contralateral L5-S1 pseudoarthrosis	Bilateral complete L5-S1 sacralisation		With presence of ipsi/contra lateral rudiemntary facet to the side of the sacralisation	With presence of bilateral rudimentary facets
Lumbarisation^**	Type IV A	Type IV B	Type IV C	Type IV D	Type IV A F(i/c) or Type IV B F(i/c) or Type IV C F or Type IV D F	Type IV A 2F or Type IV B 2F or Type IV C 2F or Type IV D 2F
Lumbarisation^**	Incomplete/partial lumbarisation of S1 as an accessory S1-2 articulation	Unilateral complete separation of S1 from sacral mass	Bilateral S1-2 accessory articulation	Complete sacralisation with residual four segment sacrum	With presence of ipsi/contra lateral rudimentary facet to the side of the diarthrosis	With presence of bilateral rudimentary facets

↵* Southworth and Bersack.²⁹ Modifications on the Castellvi's classifications are given in bold and italics.
↵** Situations with aymmetric augmentation of the auricular surface may be represented by adding the alphebets SR+ or SL+ for the corresponding right or the left sides.