Insertion of an annular disc implant at lumbar discectomy

4.1 A non‑randomised comparative study of 102 patients (30 patients treated by discectomy plus annular disc implant and 72 patients treated by discectomy only) reported no reherniations in the implant group within 2 years after surgery and 5 reherniations in the discectomy‑only group: 3% (2/72) within 3 months and 4% (3/72) between 4 months and 2 years after surgery (level of significance not stated). A non‑randomised comparative cohort study of 76 patients (30 patients from the same implant cohort as in the previous study and 46 patients treated by discectomy only) reported no reherniations 2 years after surgery in the implant group and 7% (3/46) in the discectomy‑only group (no significant difference).

4.2 The non‑randomised comparative study of 102 patients reported improvement in Oswestry Disability Index (ODI) scores in both groups. In the implant group, the ODI score decreased from 62.7 before surgery to 31.4 after 6 weeks and 11.6 after 24 months. In the discectomy‑only group, the ODI score decreased from 49.4 before surgery to 30.7 after 6 weeks and 19.8 after 24 months. The scores were significantly different between the 2 groups at baseline (before surgery) (p=0.0004) but not at 6 weeks and 24 months.

4.3 The non‑randomised comparative study of 102 patients reported that back pain scores and leg pain scores (both measured on 100‑point visual analogue scales, with higher scores indicating more severe pain) improved in both groups. Back pain scores improved from 66.3 before surgery to 10.5 after 24 months in the implant group and from 43.1 to 19.1 in the discectomy‑only group (level of significance not stated). Leg pain scores improved from 79.8 before surgery to 8.9 after 24 months in the implant group and from 58.8 to 21.2 in the discectomy‑only group (level of significance not stated). The scores for back and leg pain were significantly different between the 2 groups at baseline (before surgery; p≤0.0001). The scores for leg pain (but not for back pain) were significantly different between the 2 groups at 12 months and 24 months (p<0.05).

4.4 The non‑randomised comparative cohort study of 76 patients reported a mean loss of disc height from 8.60 mm to 7.63 mm (0.97 mm loss) in the implant group compared with 8.30 mm to 6.90 mm (1.40 mm loss) in the discectomy‑only group 12 months after surgery (p=0.054). A case series of 45 patients reported a decrease of the mean disc height to 93% of baseline 12 months after surgery (p<0.01).

4.5 The specialist advisers identified a key efficacy outcome as recurrence of herniation in the long term.