Interdependence Between Disc Space Height, Range of Motion and Clinical Outcome in Total Lumbar Disc Replacement

Study Design. Clinical and radiologic assessment obtained from an ongoing prospective trial following total lumbar disc replacement (TDR) with ProDisc II. Objective. To analyze the interaction between the parameters of disc space height (DSH), range of motion (ROM) and clinical outcome scores following TDR. Summary of Background Data. The interdependence between DSH, ROM and the clinical symptomatology has been well documented for patients with degenerative disc disease, fusion candidates and healthy control subjects. In the case of TDR, previously published data show conflicting results. Methods. All TDRs were performed monosegmentally at L4/5 or L5-S1. The clinical outcome assessment included the patient's subjective outcome evaluation, Visual Analogue Scale, and Oswestry Disability Index scores (ODI). The radiologic evaluation included measurement of the mean, anterior and posterior DSH, as well as the ROM. The parameters were correlated pre- and postoperatively with each other. Results. Data from 62 patients with an average follow-up of 42.4 months (range: 24.2-77.6 months) were included in this study. Visual Analogue Scale and ODI scores showed a significant and maintained improvement in comparison to preoperative levels (P < 0.0001). The DSH increased from 5.7 mm (range: 2-11.3 mm) to 11.2 mm (range: 8-13.4 mm), whereas ROM decreased from 8.1 (range: 0 degrees-23.1 degrees) to 5.1 (range: 0 degrees-12.8 degrees). This loss in ROM was significant following TDR at L5-S1 (P < 0.01). Preoperative DSH and ROM were positively correlated with postoperative segmental ROM (r = 0.45, P < 0.002 and r = 0.35, P < 0.01). The highest satisfaction rates were observed in the group of patients with the smallest preoperative DSH of < 4.5 mm (P < 0.024). Conclusion. A significant interdependence was observed between the parameters DSH, ROM and the clinical outcome following TDR. Whilst the DSH is restored, TDR leads to a significant decrease in postoperative ROM, particularly at the lumbosacral junction. Higher preoperative DSH and ROM revealed a beneficial effect on the postoperative segmental mobility. The subjective outcome evaluation indicates that TDR is a viable treatment option even in advanced stages of degenerative disc disease in the absence of other contraindications, in particular facet joint arthropathies.