A commonly adopted method of grading the severity of spondylolisthesis is the Meyerding classification.
1. Type 1: dysplastic: congenital. Upper sacrum or arch of L5 permits the spondylolisthesis. No pars defect . 94% are associated with spinal bifida occulta. Some of these may progress (no way to accurately identify those that will progress).
2. Type 2: isthmic spondylolisthesis AKA spondylolysis: a failure of the neural arch as a result of a defect in the pars interarticularis (identifiable as a discontinuity in the neck of the “Scotty dog” on oblique LS-spine x-ray). May be seen in 5–20% of spine x-rays 1). Rarely produces central spinal canal stenosis since only the anterior part of the vertebral body shifts forward. May cause narrowing of the neural foramen.
a) lytic: fatigue fracture or insu ciency fracture of pars. In the pediatric age group may occur in athletes (especially gymnasts or football players); in some this may be an exacerbation of a pre-existing defect, in others it may be a result of repetitive trauma
b) elongated but intact pars: possibly due to repetitive fractures and healing
c) acute fracture of pars
3. Type 3: degenerative: due to long-standing intersegmental instability. Usually at L4–5. No break in the pars. Found in 5.8% of men and 9.1% of women (many of whom are asymptomatic)
4. Type 4: traumatic: due to fractures usually in areas other than the pars 2) 5. Type 5: pathologic: generalized or local bone disease, e.g. osteogenesis imperfecta
Five types were classified according to the Wiltse classification system 3):
see High grade spondylolisthesis —- Wiltse et al. categorized spondylolisthesis into six types:
Type I, or dysplastic, involves congenital dysplasia of the sacrum or L5 neural arch, with pars elongation or lysis which can develop later.
Type II, or isthmic, is a defect in the pars interarticularis, with pars lysis (type IIA), pars elongation (type IIB), or acute pars fracture (type IIC).
Type III, or degenerative, is a result of facet arthrosis leading to subluxation. see Lumbar degenerative spondylolisthesis
Type IV, or traumatic, is secondary to acute fracture of the posterior elements other than the pars.
Type V, or pathologic, is associated with incompetence of the posterior elements secondary to a systemic or local bony pathologic process.
Type VI, or post-surgical, is a result of loss of posterior elements due to surgery. This classification system combines both anatomical and etiological factors and it is not always easy to distinguish type I (congenital dysplastic) from type II (isthmic) since the latter can also be congenital. In addition, it does not provide any guidelines for treatment.
The most practical classification system in terms of prognosis and therapy is that of Marchetti and Bartolozzi.
In this system, spondylolisthesis is divided into two major groups, developmental or acquired.
Developmental spondylolisthesis is further divided into two types, both with lysis and elongation: low dysplastic and high dysplastic, depending on the severity of the bony dysplastic changes present on the L5 and S1 vertebrae and on the risk of slip progression. The low-dysplastic type is described as having a relatively normal lumbosacral profile, a normal appearing rectangular L5 vertebra, a normal S1 superior end plate, no pelvic retroversion or hyperlordosis, and very low risk of slip progression (up to 50%). Conversely, high-dysplastic spondylolisthesis is associated with lumbosacral kyphosis, a trapezoidal L5 vertebra, a dome-shaped superior end plate of S1, pelvic retroversion and hyperlordosis, and very high risk of slip progression (up to spondyloptosis). In order to decide on the best course of treatment, it is important to distinguish between low- and high-dysplastic spondylolisthesis, since the accepted treatment of the latter is surgical. Although Marchetti and Bartolozzi were the first to introduce the concept of low- and high-dysplastic developmental spondylolisthesis (HDDS), they did not include strict criteria to differentiate these two subtypes.