A Comparative Study Between Mechanical and a Viscoelastic Disc Prosthesis in the Lumbar Spine

TDR implants for the lumbar spine are currently most 2- or 3-piece devices with a purely mechanical function that provide/restore mobility. Lately interest is growing on non-mechanical implants that could possibly provide/restore mobility, but also produce counterforces on mobility as in healthy discs. No previous comparison between these two concepts has been performed, neither on clinical outcome, neither on specific differences on facet-joint load and wear.

A total of 250 patients are to be enrolled and treated. Inclusion criteria is unbearable pain and dysfunction from degenerative disc disease (DDD) that at one or two segments in the lover lumbar spine, that has not responded positively from at least one year of conservative treatment (that is combination of intense physical training and drugs). Patients with DDD below L3 vertebra are divided I three groups: 1. One segment DDD appropriate for treatment with TDR. 2. Two segments DDD appropriate for treatment with TDR. 3. One segment DDD appropriate for treatment with TDR and one segment DDD not appropriate for treatment with TDR, that will be treated with anterior fusion (ALIF) at the same surgical procedure, called "hybrids". Within all three groups there will be an equal randomization between the two prosthesis types. Clinical outcome will be evaluated from questionnaires sent out to patients after 12- and 24 months and 5- and 10 years after surgery. The questionnaire are the currently used ones from the Swedish Spine Registry (SweSpine) including VAS leg/back, EuroQol ,GA and ODI. Complications will be registered continuously and facet-joint load/health will be examined from flex-ext x-rays at 1 and 2 years. At the 2-year check up a 3D-CT will be performed to further evaluate the facet joints and their load under flex-ext.