Intermediate clinical and radiological results of cervical TDR (Mobi-C) with up to 2 years of follow-up

Abstract

The interest in cervical total disc replacement (TDR) as an alternative to the so-far gold standard in the surgical treatment of degenerative disc disease (DDD), e.g anterior cervical discectomy and fusion (ACDF), is growing very rapidly. Many authors have established the fact that ACDF may result in progressive degeneration in adjacent segments. On the contrary, but still theoretically, preservation of motion with TDR at the surgically treated level may potentially reduce the occurrence of adjacent-level degeneration (ALD). The authors report the intermediate results of an undergoing multicentre prospective study of TDR with Mobi-C prosthesis. The aim of the study was to assess the safety and efficacy of the device in the treatment of DDD and secondary to evaluate the radiological status of adjacent levels and the occurrence of ossifications, at 2-year follow-up (FU). 76 patients have performed their 2-year FU visit and have been analyzed clinically and radiologically. Clinical outcomes (NDI, VAS, SF-36) and ROM measurements were analyzed pre-operatively and at the different post-operative time-points. Complications and re-operations were also assessed. Occurrences of heterotopic ossifications (HOs) and of adjacent disc degeneration radiographic changes have been analyzed from 2-year FU X-rays. The mean NDI and VAS scores for arm and neck are reduced significantly at each post-operative time-point compared to pre-operative condition. Motion is preserved over the time at index levels (mean ROM = 9 degrees at 2 years) and 85.5% of the segments are mobile at 2 years. HOs are responsible for the fusion of 6/76 levels at 2 years. However, presence of HO does not alter the clinical outcomes. The occurrence rate of radiological signs of ALD is very low at 2 years (9.1%). There has been no subsidence, no expulsion and no sub-luxation of the implant. Finally, after 2 years, 91% of the patients assume that they would undergo the procedure again. These intermediate results of TDR with Mobi-C are very encouraging and seem to confirm the efficacy and the safety of the device. Regarding the preservation of the status of the adjacent levels, the results of this unconstrained device are encouraging, but longer FU studies are needed to prove it.

Figures

Fig. 1

The controlled motion of the Mobi-C® prosthesis. The five degrees of freedom are represented: two translational (dotted line arrows) and three rotational (full-line arrows)

Fig. 2

Neutral and dynamic post-operative X-rays of illustrative one-level C5–C6 prosthesis (a) and of a two-level C5–C6/C6–C7 case (b)

Fig. 3

Mean NDI score before and after the surgery (1, 3, 6, 12 or 24 months), for the 76 patients (a) and for the subgroup of patients with pre-op NDI ≥ 30% (b). Mean (±SEM) are given for each time-point. * Significant difference (P < 0.05) versus pre-op

Fig. 4

Cervical VAS score before and after the surgery (1, 3, 6, 12 or 24 months), for the 76 patients (a) and for the subgroup of patients with pre-op cervical VAS ≥ 20 pts (b). Mean (±SEM) are given for each time-point. * Significant difference (P < 0.05) versus pre-op

Fig. 5

Arm VAS score before and after the surgery (1, 3, 6, 12 or 24 months), for the 76 patients (a) and for the subgroup of patients with pre-op arm VAS ≥ 20 pts (b). Mean (±SEM) are given for each time-point. * Significant difference (P < 0.05) versus pre-op

Fig. 6

SF-36 quality of life score before and after the surgery (1, 3, 6, 12 or 24 months). PCS physical component scale; MCS mental component scale. Mean (±SEM) are given for each time-point

Fig. 7

Analgesic requirement in the overall population before and after the surgery (1, 3, 6, 12 or 24 months)

Fig. 8

Mean range of motion (ROM) from flexion/extension at the index level before and after the surgery (1, 3, 6, 12 or 24 months). Mean (±SEM) are given for each time-point

Fig. 9

Distribution of the ROM at the index levels measured 2 years after the surgery. Results are expressed as percent of the 76 analyzed segments