Trimethylene carbonate-caprolactone conduit with poly-p-dioxanone microfilaments to promote regeneration after spinal cord injury

Spinal cord injury (SCI) is often associated with scarring and cavity formation and therefore bridging strategies are essential to provide a physical substrate for axonal regeneration. In this study we investigated the effects of a biodegradable conduit made from trimethylene carbonate and c-caprolactone (TC) containing poly-p-dioxanone microfilaments (PDO) with longitudinal grooves on regeneration after SCI in adult rats. In vitro studies demonstrated that different cell types including astrocytes, meningeal fibroblasts, Schwann cells and adult sensory dorsal root ganglia neurons can grow on the TC and PDO material. For in vivo experiments, the TC/PDO conduit was implanted into a small 2-3 mm long cavity in the C3-C4 cervical segments immediately after injury (acute SCI) or at 2-5 months after initial surgery (chronic SCI). At 8 weeks after implantation into acute SCI, numerous 5HT-positive descending raphaespinal axons and sensory CGRP-positive axons regenerated across the conduit and were often associated with PDO microfilaments and migrated host cells. Implantation into chronically injured SCI induced regeneration mainly of the sensory CGRP-positive axons. Although the conduit had no effect on the density of OX42-positive microglial cells when compared with SCI control, the activity of GFAP-positive astrocytes was reduced. The results suggest that a TC/PDO conduit can support axonal regeneration after acute and chronic SCI even without addition of exogenous glial or stem cells

Intraoperative quantification of floating mass transducer coupling quality in active middle ear implants: a multicenter study

Purpose!#!Evaluating the effectiveness of intraoperative auditory brainstem responses (ABRs) to stimulation by the Vibrant Soundbridge (VSB) active middle ear implant for quantifying the implant's floating mass transducer (FMT) coupling quality.!##!Methods!#!In a diagnostic multicentric study, patients (> 18 years) who received a VSB with different coupling modalities were included. Pre- and postoperative bone conduction thresholds, intraoperative VSB-evoked ABR thresholds (VSB-ABR) using a modified audio processor programmed to preoperative bone conduction thresholds, postoperative vibrogram thresholds, and postoperative VSB-ABR thresholds were measured. Coupling quality was calculated from the difference between the pure tone average at 1000, 2000, and 4000 Hz (3PTA) vibrogram and postoperative 3PTA bone conduction thresholds.!##!Results!#!Twenty-three patients (13 males, 10 females, mean age 56.6 (± 12.5) years) were included in the study. Intraoperative VSB-ABR response thresholds could be obtained in all except one patient where the threshold was > 30 dB nHL. Postoperatively, an insufficient coupling of 36.7 dB was confirmed in this patient. In a Bland-Altman analysis of the intraoperative VSB-ABRs and coupling quality, the limits of agreement exceeded ± 10 dB, i.e., the maximum allowed difference considered as not clinically important but the variation was within the general precision of auditory brainstem responses to predict behavioral thresholds. Five outliers were identified. In two patients, the postoperative VSB-ABR thresholds were in agreement with the coupling quality, indicating a change of coupling before the postoperative testing.!##!Conclusion!#!The response thresholds recorded in this set-up have the potential to predict the VSB coupling quality and optimize postoperative audiological results