"type I: enlarged and dysplastic transverse process (at least 19 mm)"
"Ia: unilateral"
"Ib: bilateral"
"type II: pseudoarticulation of the transverse process and sacrum with incomplete lumbarisation/sacralisation; enlargement of the transverse process with pseudoarthrosis"
"IIa: unilateral"
"IIb: bilateral"
"type III: transverse process fuses with the sacrum and there is complete lumbarisation or sacralisation, enlarged transverse process with complete fusion"
"IIIa: unilateral"
"IIIb: bilateral"
"type IV: type IIa on one side and type IIIa on the contralateral side"
"type II: pseudoarticulation of the transverse process and sacrum with incomplete lumbarisation/sacralisation; enlargement of the transverse process with pseudoarthrosis"