A prospective randomized study comparing a cervical carbon fiber cage to the Smith-Robinson technique with allograft and plating: up to 24 months follow-up

Abstract

Introduction: Intervertebral carbon fiber cages may reduce graft collapse and promote bony fusion. Their safety and efficacy in the cervical spine have been investigated; however, no study has compared the outcomes of anterior cervical decompression and placement of a carbon fiber cage with placement of allograft and plate.

Methods: Forty consecutive patients who met inclusion criteria were enrolled and randomized to anterior cervical discectomy with carbon fiber cage alone (n=20) or with allograft with plating (n=20). Clinical and radiographic evaluations were performed at baseline and at 6 weeks, 3, 6, 12 and 24 months. Neck and arm pain as well as neck disability index (NDI) were assessed at every visit. The Short Form (SF)-36 was completed prior to operation and at 12-month intervals. Cervical radiographs were evaluated pre-op and at every follow-up for evidence of fusion and instability.

Results: No significant difference was found between the two randomized groups with respect to pre-operative age (mean 50 years), sex, employment status, duration of pain or cervical levels affected. The mean follow-up period was 14 months (range, 6-26 months). The clinical pain and disability improvements were similar for both treatments. Post-operative donor site pain was only present in the cage group, but not of significant long-term disability. At up to 24 months, NDI scores were significantly improved in both groups when compared with baseline. At 12 and 24 months, all SF-36 questionnaire responses were also improved in both the treatment groups. However, there was no statistically significant difference in outcomes between the two groups at any time. The fusion rate was 100% in both groups by 12 and 24 months, without evidence of instability. There were no differences in complications between both groups.

Conclusions: The outcomes after cervical decompression and placement of a carbon fiber cage appear to be similar to cervical decompression with allograft and plating by the Smith-Robinson technique.

Fig. 1

Mean NDI scores for both treatment groups at pre-op and each subsequent follow-up. The whisker represents one standard deviation. The number of patients available for review is listed below the follow-up time as number of allograft and plate patients/cervical cage patients. No statistically significant difference is noted between both groups at any time. Both groups demonstrate statistically significant improvement of scores at both 12 and 24 months versus pre-op (P<0.05). No statistically significant difference in scores is noted at 12 and 24 months in either group.

Fig. 2

Mean Short Form (SF)-36 scores for both the allograft and plate group (A) and the cervical cage group (B) at pre-op and every 12-month follow-up period. The whisker represents one standard deviation. The subscores are defined as follows: PF, physical functioning; RP, role of physical disability; BP, bodily pain; GH, general health; VT, vitality; SF, social functioning; RE, role of emotional disability and MH, mental health. At pre-op, no statistically significant difference is noted in scores between both groups except for GH which is significantly higher in the cervical cage group (P<0.05). No statistically significant difference is noted between both groups at any follow-up.

Fig. 3

(A) Lateral radiograph of a C6–7 cervical cage fusion at 12 months after surgery demonstrating a bridging post of bone through the cervical cage connecting the vertebral bodies. Note that the cage is radiolucent and creates no imaging artifact. The three tantalum markers note the location and orientation of the cage. (B) Lateral radiograph of a C4–5, C5–6 two-level cervical cage fusion at 12 months after surgery demonstrating bony fusion at both levels.