Does a new "topping-off" device lead to a better clinical outcome compared to standard fusion? Does this device prevent the development of adjacent instability? Does radiological adjacent instability correlate with clinical outcome?

Primary efficacy endpoint:

The baseline and follow-up values after 6 weeks after the operation as well as 6 and 12 months after baseline of the SF-36 (Short-Form-36)-Measured Outcome regarding the Physical Component Summary (PCS).

Key secondary endpoint(s):

1. Mental Component Summary (MCS) and individual dimensions and subscales of the SF-36
2. Individual dimensions of the Oswestry Disability Index (ODI)
3. Time until radiological adjacent instability and comparison to the clinical outcome
4. Capacity of work at the time of surgery and after surgery, time until return to work

Assessment of safety:

1. Treatment complication in control and intervention groups (SAE-management)
2. A rating committee will provide consistency of the procedure and the assessment of data (e.g. by intraoperative photos, surgery reports, x-rays) to minimize bias

Key inclusion criteria:

1. Male or female >30 years of age
2. Lumbar spine pathology with indication for monosegmental PLIF
3. Radiological signs of a degeneration of the adjacent segment without instability

Key exclusion criteria:

1. Radiological signs of existing instability of the adjacent segment 2. Normal endplates and no disc desiccation in MRI in the adjacent seg-ment 3. Previous surgery of the lumbar spine

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