Stress-shielding compared with load-sharing anterior cervical plate fixation: a clinical and radiographic prospective analysis of 50 patients.

OBJECT: In a prospective analysis the authors evaluated the clinical and radiographic outcome of 50 consecutive patients who underwent anterior cervical discectomy and fusion and fixation in which either a stress-shielding or a load-sharing plate (Orion and Premier, respectively) was placed. Data obtained in the two cohorts were analyzed to determine whether clinical or radiographic differences would emerge. METHODS: All patients underwent either one- or two-level fusion in which freeze-dried allogenic tricortical iliac crest bone graft was used. In the first cohort of 25 patients entered into the study, fixation was achieved using a stress-shielding anterior cervical plate (ACP) system, whereas in the second cohort of 25 patients a load-sharing plate system was employed. Patients were evaluated during a follow-up period that ranged from 12 to 35 months. Outcome was determined using a standard questionnaire by which the authors gauged the level of pain, disability, and satisfaction following surgery. The success of surgical fusion and the magnitude of the translation were determined by radiographic evaluation. There was no statistically significant difference between the two cohorts with respect to age, sex, smoking rate, and postoperative complications. With regard to pain and functionality, there was a significant difference (p < 0.05) in favor of the load-sharing system. The fusion rates with the load-sharing and stress-shielding systems were 96 and 92%, respectively, and this difference was not significant. There was no significant difference between the two cohorts with regard to overall satisfaction. The magnitude of vertical translation was significantly greater in the stress-shielding ACP group (p < 0.05) for treatment at one level but not at two. Clinical and radiographic data were available in all patients. CONCLUSIONS: Load-sharing ACP systems exhibited superior clinical results compared with stress-shielding ACPs in this series of patients. The symptomatic pseudarthrosis rate was lower in the load-sharing ACP-treated patients, although this was not statistically significant.