Classification of Spondylolysis and Spondylolisthesis

Michael Sullivan

The condition of slippage of the fifth lumbar vertebra on the sacrum has been known for many years, by obstetricians particularly. The condition was described by Herbeneaux in France at the end of the 18th century and then by two other people at almost the same time: Rokitansky in Vienna and Kilian in Britain in about 1853. However, it was Neugebauer, working as a gynecologist and obstetrician in Warsaw, who coined the modern term by combining the Greek words spondylo, meaning spine, and olisthesis, meaning slippage, to form the word spondylo-olisthesis. Of course, this was well before the days of x-rays, and so he described the physical characteristics. His original papers, in fact, show patients with what is now called dysplastic spondylolisthesis, typified by shortening of the trunk and a crease across the abdomen.

Junghauns in 1930 then proposed the term “pseudo” spondylolisthesis for what we now call degenerative spondylolisthesis. However, immediately after World War II, three surgeons independently introduced classifications, which were not very dissimilar. The three surgeons were MacNab in 1950, Wiltse in 1957, and Newman in 1963.

The International Society for the Study of the Lumbar Spine (ISSLS) had its first meeting in Montreal in 1974. Harry Farfen was the host, Leon Wiltse was made the first president, and I was made the first secretary. The outcome of this was that the second meeting in 1975 was held in London at The Royal College of Surgeons; I was privileged to host the meeting. The same three surgeons, namely MacNab, Wiltse, and Newman, presented three papers at that meeting. All three gave their expert opinion on classification of spondylolisthesis. At the end of the meeting, the committee asked these three eminent spinal surgeons to unite to produce a common classification to be presented at the following year’s ISSLS meeting in Bermuda. It is their classification that is most widely accepted around the world. When anything is done through a committee, there has to be some compromise and this is the case in their classification.

They classified spondylolisthesis into five types, with three subtypes in Type 2:

Type 1. Dysplastic

Type 2. Isthmic

Type 3. Degenerative

Type 4. Traumatic

Type 5. Pathological

The three subgroups of Type 2, Isthmic, are

2A. Lytic fatigue fracture of the pars

2B. Elongation but intact pars

2C. Acute fracture

DYSPLASTIC SPONDYLOLISTHESIS

Type 1 spondylolisthesis is associated with congenital dysplasia of the upper sacrum and neural arch, which Newman classified as “congenital type.” There is a weakness of the posterior elements and therefore a gradual sliding forward of the fifth lumbar vertebra on the sacrum. This weakness of the posterior elements allows L5 to slide forward, and as it slides forward, it slowly compresses the neural elements. When 25% slippage occurs, either the posterior elements must give way with elongation or fracture; or if neither of these situations occurs and the slip continues, the slippage transects or certainly completely compresses the cauda equina. The fundamental feature of dysplastic spondylolisthesis is the presence of the dysplastic posterior elements. Fracture into the pars interarticularis occurs in the isthmic type, and this is where confusion tends to occur. The presentation of dysplastic spondylolisthesis is quite different from the other types. It occurs during the adolescent growth spurt. The children with this condition have a short trunk compared to the length of the lower limbs. As the pelvis tilts, they acquire: a crease across the front of the abdomen (Fig. 9.1), a strange gait because of the marked hamstring
spasm, and also the inability to bend (Fig. 9.2). The slippage is often eccentric and therefore leads to an apparent scoliosis.