A type 2B classification of spondylolisthesis described which etiology?

• A. Dysplastic
• B. Degenerative
• C. Isthmic due to elongation of pars
• D. Isthmic due to pars fracture

Answer: (C)

The key idea is how spondylolisthesis is categorized by the underlying cause. In this scheme, a type that is labeled isthmic points to problems with the pars interarticularis. Within that isthmic group, a subtype described as elongation of the pars interarticularis means the slip arises from a gradual lengthening of that bony bridge rather than an acute fracture. So describing the etiology as isthmic due to elongation of the pars interarticularis matches the type II B scenario. Other etiologies—dysplastic (congenital facet misalignment), degenerative (wearing of the joints), or traumatic (acute pars fracture or other injury)—don't capture this elongation mechanism.