engleski

Translational vs rotational dynamization of the implants used for anterior cervical fusion

Surgical treatment of spondylogenic radiculomyelopathy consists of anterior neuro-decompression and instrumented fusion. Although rigidity of spinal fixator is often desirable, it is potential cause of construct failure due to prevention of subsidence. Purpose of the study was to detect possible dynamization of the implants, to compare speed and quality of fusion following fixation with semi constrained cervical plate and dynamic fixation system. An Independent Matched-Cohort Study including trial (dynamic) group monitored prospectively and operated on from January 2001 till December 2001 (No= 15) and control (H plate) group chosen from historic group of patients operated on from January 1991 till December 2000 (No= 15). Patients were matched by sex, age and number of operated levels. X-rays were performed on the end of surgery, on the second postoperative day and 6 weeks following surgery. Fusion was graded by 2 independent investigators according to Tribus criteria. Rotation of the screws was calculated as the difference between screw-plate angles (grade), and translation of the screws as difference of distances between upper and lower screws (mm). Two independent researchers measured angles and translation of the screws. Trial group consisted of 9 males and 6 females mean-age 52.6 ± 8.42 years, and control group 9 males and 6 females mean-age 51.8 ± 8.06 years. Groups were well matched by number of decompressed intervertebral levels. The angle of rotation in the trial group was 0°, and in the control group 7.2°± 3.04°. The translation of the screws in the trial group was 2.67mm ± 0.79 mm, and in the control group 0 mm. Fusion on 6 week follow-up examination was significantly better in trial group (2.18 ± 0.59 vs. 1.59 ± 0.49 ; p=0.0013). One patient in the control group had a gap between graft and end plate at one-year follow-up examination that fused during the second year of follow-up. One patient in trial group (with 4 level fusion) and two in control group had non-union. Seven patients in the trial group had heterotopic ossification on the adjacent segment with ankylosis in one patient. Our results showed that subsidence was allowed with both fixation systems, in the non-fixed moment arm system due to rotation of the screws and in the dynamic system due to translation. In the translation dynamic systems fusion was faster and more effective. The DOC dynamic fixator provocated heterotopic ossification in half of the patients in the adjucent mobile segment.

surgical procedure; cervical vertebrae; spondylogenic radiculomyelopathy; anterior neurodecompression; instrumented fusion

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