Approach to Spondylolisthesis

Wiltse Classification (“Did Tim Pass”)

I – Dysplastic
– IA – axially oriented facets; IB – sagitally oriented facets
– dysplastic facets permit forward translation – higher chance for neural compression as the intact posterior elements move forwards

II – Isthmic
– IIA – lytic defect in pars; IIB – elongated (partially healed lytic lesion)

III – Degenerative

IV – Traumatic

V – Post-Surgical

– children get isthmic spondylolysis and spondylolisthesis at L5/1; adults get degenerative spondy at L4/5
– an acquired disorder; possibly a stress fracture of the pars after repetitive microtrauma
– increase in slippage is seen during adolescent growth spurt; progression is unlikely after adolescence; therefore, like in adolescent scoliosis, get an idea of how skeletally mature they are when deciding about risk of progression.
– initial slippage of 50% is predictive of further slippage
– slip angle measures lumbosacral kyphosis and is associated with a higher risk of progression
– look for a rounded off sacrum or trapezoidal L5 body – higher chance of progression

Grade I and II slips that are asymptomatic (found spuriously)
– observation semiannually until age 15, then annually until the end of growth
– may give them advise about avoiding hyperextension activities and contact sports
– a 20% slip that progresses to 35% is not necessarily an indication for fusion – assess the above factors and watch – look at skeletal maturity, high slip angle, rounded sacrum or trapezoidal shape of L5 as useful markers of progression.
closesly. A 20% slip that progresses to 50% is probably an indication that you better get on an fuse it.

Grade I and II slips with pain
– activity restriction, NSAIDs, local measures, stretching exercises
– if continues to have pain – thoracolumbar orthosis
– if pain persists with orthosis, can do a L5-S1 posterolateral in-situ fusion with bone graft followed by single or double leg hip spica cast

Grade III or IV slips with or without symptoms
– gets a L4-S1 posterolateral in situ fusion with bone graft as a preventative measure for further progression if they are asymptomatic. Must extend fusion up to L4 because of the biomechanical disadvantage of the fusion mass.

– instrumented fusions are becoming popular but do not have the long-term track record of the standard posterolateral uninstrumented in-situ fusion. Instrumented reduction is hazardous to the nerve roots
– if they have documented MOTOR weakness, you should probably decompress them, which also means that you are going to go midline and destablize them – they need to be instrumented.
* when you position them prone in the OR, position them with their hips and legs EXTENDED – if you allow them to flex like they normally do, their lumbosacral kyphosis worsens, and they are apt to get a cauda equina syndrome. Cauda equina can occur with reductions and with in-situ fusions as well – requires sacroplasty

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