The efficacy of direct current stimulation for lumbar intertransverse process fusions in an animal model.

STUDY DESIGN: Posterolateral lumbar intertransverse process fusion using a rabbit model with autologous bone graft and direct current stimulation was compared with fusion achieved by using autologous bone graft alone. OBJECTIVES: To determine the efficacy of direct current electrical stimulation for the posterolateral lumbar intertransverse process fusion technique by using a 20-microA current and the more recently developed 60-microA current delivered by an implantable direct current stimulator. SUMMARY OF BACKGROUND DATA: Previous studies have demonstrated a positive effect of direct current electrical stimulation on posterior spinal fusion techniques. However, until recently, the environment of an intertransverse fusion was not well simulated. The current research examined the posterolateral lumbar intertransverse process fusion technique with direct current electrical stimulation using a rabbit model. This appears to parallel human fusion techniques more closely and allows for lower cost and technical ease. METHODS: In this study, 44 adult New Zealand white rabbits underwent an L5-L6 intertransverse process fusion. All the fusions used an autologous bone graft obtained from bilateral posterior iliac crests. A device was implanted in all the rabbits subcutaneously, and they were divided randomly into three groups: a sham or nonfunctioning group, a 20-microA low-current stimulator group, and a 60-microA higher-current stimulator group. Spinal fusion was evaluated radiographically, histologically, and manually as well as by biomechanical testing 5 weeks after surgery. RESULTS: Radiographic grades, manual palpation, biomechanical strength, and stiffness showed an increasing trend from sham or inactive stimulator groups to low-current and then to high-current stimulator groups. Histologic analysis revealed that the higher-current stimulator showed that, statistically, the healing response of the host tissue to the autograft had increased significantly, as compared with the sham. CONCLUSIONS: Direct current electrical stimulation is efficacious in improving both the healing rate and strength in this posterolateral lumbar fusion model. In addition, it appears that this effect is enhanced by increasing the stimulation current from 20 microA to 60 microA.

Relationship between tympanic membrane perforations and retained ventilation tubes.

OBJECTIVES: To determine the effects of prolonged ventilation tube retention on tympanic membrane healing and the efficacy of patching procedures used concomitantly at the time of tube removal. DESIGN: Retrospective chart review. SETTING: Tertiary referral academic institution. PATIENTS: Seventy-six patients aged 12 years and younger, with a total of 99 ears identified from January 1989 to December 1994. All patients underwent ventilation tube removal for prolonged tube retention or infection unresponsive to medical management. A minimum of 6 months of follow-up was required for inclusion. INTERVENTION: Ventilation tube removal under general anesthesia, with or without concomitant patching. OUTCOME MEASURES: All medical charts were reviewed for age, sex, indications for tube removal, tube retention time, type of patch used (if any), type of tube, outcome after removal, other medical problems, and previous surgical history. RESULTS: The perforation rate was significantly higher in children with tubes retained beyond 36 months (P=.02). History of previous adenoidectomy predicted poor outcome, with a rate of 47% vs 17% in patients with no such history (P=.002). Patching did not improve healing. No other patient factors significantly influenced the perforation rate. CONCLUSIONS: Ventilation tube retention longer than 36 months resulted in an increased perforation rate after surgical removal. Paper patching at the time of tube removal does not improve healing. Prospective studies are needed to confirm these findings and to determine the efficacy of other patching techniques.