An injection-molded internal supporting rib has been produced to control the flexibility of silicone rubber encapsulated electrodes designed to electrically stimulate the auditory nerve in human subjects with severe to profound hearing loss. The rib molding dies, and molds for silicone rubber encapsulation of the electrode, were designed and machined using AutoCad and MasterCam software packages in a PC environment. After molding, the prototype plastic ribs were iteratively modified based on observations of the performance of the rib/silicone composite insert in a clear plastic model of the human scala tympani cavity. The rib-based electrodes were reliably inserted farther into these models, required less insertion force and were positioned closer to the target auditory neural elements than currently available cochlear implant electrodes. With further design improvements the injection-molded rib may also function to accurately support metal stimulating contacts and wire leads during assembly to significantly increase the manufacturing efficiency of these devices. This method to reliably control the mechanical properties of miniature implantable devices with multiple electrical leads may be valuable in other areas of biomedical device design.

Objective: Delayed sexual maturation and low body weight is common in cystic fibrosis (CF). Concomitant data on sex hormones and concomitant body composition are lacking in men with CF. Design: Cross-sectional study. Subjects and methods: Serum levels of testosterone, 17b-oestradiol (E 2 ), 25-hydroxyvitamin D (25(OH)D), sex hormone-binding globulin (SHBG) and LH were measured by RIA and total and regional lean body mass (LBM), fat body mass (FBM), bone mineral content and bone mineral density (BMD) were assessed by dual-energy X-ray absorptiometry, in men with CF (n ¼ 40; age 24:7^5:4 years) and age-matched healthy controls ðn ¼ 28; age 25:7^3:7Þ: Only men without acute disease exacerbation or systemic glucocorticoid treatment were included. Results: Mean levels of hormonal serum parameters differed significantly between healthy controls ðtestosterone ¼ 20:2^5:5 nmol=l; E 2 ¼ 95:0^20:2 pmol=l; 25ðOHÞD ¼ 62:8^28:3 nmol=lÞ and patients ðtestosterone ¼ 15:9^4:1 nmol=l; E 2 ¼ 60:7^19:4 pmol=l; 25ðOHÞD ¼ 39:5^17:8 nmol=l; P , 0:001Þ while no difference was found for SHBG or LH. Eleven (for E 2 , 19 of 40, for 25(OH)D, 20 of 40) out of 40 patients had serum testosterone levels 2 S.D. below the mean of normal. Men with CF showed a relative shift from FBM to LBM and a different body fat distribution compared with healthy controls ðP , 0:01Þ: Testosterone was not correlated with weight, total or regional LBM or FBM, but significantly with BMD ðr ¼ 0:32; P , 0:05Þ independently from body height and 25(OH)D levels. E 2 was correlated with regional and total FBM ðr ¼ 0:48; P , 0:05Þ: In a multiple regression analysis of the joint effect of testosterone and body components on E 2 , a testosteroneindependent effect was found for FBM. Conclusions: CF patients with stable disease have moderately reduced serum testosterone levels. This might already imply detrimental effects on bone. The change in LBM of patients appears to have no direct association with sex hormone levels while low FBM might cause reduced net conversion of serum testosterone to E 2 with possible effects on FBM distribution.

Lumbar spinal fusion is a complex biologic process. The results of the current study demonstrate the reproducibility of a rabbit fusion model and the ability of ultrasound to induce a statistically significant increase in fusion rate, stiffness, area under the load displacement curve, and load to failure of the fusion mass. These results provide a basis for continued evaluation of biologic improvement of spinal arthrodesis with the use of ultrasound.

This study demonstrates the reproducibility of a rabbit fusion model, and the ability of a pulsed electromagnetic field to induce a statistically significant increase in stiffness, area under the load-displacement curve, and load to failure of the fusion mass. This investigation provides a basis for continued evaluation of biologic enhancement of spinal arthrodesis with the use of a pulsed electromagnetic field.