Size and separability of the calcaneal and the medial and lateral plantar nerves in the distal tibial nerve.

The tibial nerve (TN) has three main terminal branches: the medial and lateral plantar nerves and the calcaneal branch (CB), which innervates the foot sole. The design and implantation of nerve cuff electrodes with separate channels for each of these three terminal branches would provide significant sensory information, which can be used in functional electrical stimulation systems to assist standing or to correct foot drop. Detailed quantitative anatomical data about fascicular size and separability of the terminal branches of TN are needed for the design and implantation of such cuff electrodes. Therefore, the branching pattern, the fascicular separability and the fascicular size of the TN posterior to the medial malleolar-calcaneal axis were examined in this study, using ten human TN specimens. The TN branching patterns were highly dispersed. For the CBs, multiple branches were identified in five (50%) of the specimens. For the TN, the bifurcation point was located within the tarsal tunnel in eight (80%) of the cases. The distance proximal to the medial malleolar-calcaneal axis for which the TN could be split ranged form 0 to 41 mm. Quantitative and qualitative data were obtained for the fascicular size and separability of the TN. Only the CB of the TN proved separable for a sufficient length for nerve cuff electrode implantation. The results suggest the use of a two-channel cuff with one common channel for the lateral and medial plantar nerves, having multiple electrodes for selective recording, and one channel for the CB.

Phase II trial to evaluate the ActiGait implanted drop-foot stimulator in established hemiplegia.

OBJECTIVE: To evaluate a selective implantable drop foot stimulator (ActiGait) in terms of effect on walking and safety. DESIGN: A phase II trial in which a consecutive sample of participants acted as their own controls. SUBJECTS: People who had suffered a stroke at least 6 months prior to recruitment and had a drop-foot that affected walking were recruited from 3 rehabilitation centres in Denmark. METHODS: Stimulators were implanted into all participants. Outcome measures were range of ankle dorsiflexion with stimulation and maximum walking speed and distance walked in 4 minutes. Measurements were applied before implantation, at 90 days and at a long-term follow-up assessment. Changes over time and with and without stimulation are reported. Safety was evaluated by nerve conduction velocity and adverse events. RESULTS: Fifteen participants were implanted and 13 completed the trial. Long-term improvements were detected in walking speed and distance walked in 4 minutes when stimulated, and the orthotic effect of stimulation showed statistically significant improvement. The device did not compromise nerve conduction velocity and no serious device-related adverse events were reported. Technical problems were resolved by the long-term follow-up assessment at which further improvement in walking was observed. CONCLUSION: This trial has evaluated the safety and performance of the device, which was well accepted by patients and did not compromise safety.

Testing repeatability of forces when using neurosurgical spatulas.

Virtual reality systems seems to be useful for training the use of brain spatulas without damaging brain tissue but the success of such a system is dependant on the human ability to discriminate pressures applied with the spatula. This paper describes an experiment designed to explore some central issues related to this ability: are surgeons better than laypeople, are the abilities in Virtual Reality (VR) and real world (RW) comparable, and will visual feedback enhance the ability. A group of surgeons and a control group of laypeople were tested in VR and RW. The results showed that surgeons performed better than the control group in RW but worse in VR, and that visual feedback improved the surgeons' abilities more than the control group. The results indicated that visual feedback is important for the success of such a virtual training system.

Modelling of interaction between a spatula and a human brain.

This paper describes a method for surgery simulation, or more specifically a learning system of how to use a brain spatula. Improper use of brain spatulas can lead to brain tissue lesions such as tearing of brain tissue and ischemia. The idea is to provide surgeons with a tool which can teach them the correlation between deformation and applied force. The system includes a Finite Element based model of the brain in a Virtual Reality setup with haptic feedback. The physical model links the shape of the deformable model with the associated force. The interaction between the spatula and the brain model is handled by a collision response method which aims at smoothing the discrete haptic feedback. The experimental results are promising even though the used force feedback device is somewhat constraining the realism.

Training brain retraction in a virtual reality environment.

A computer based virtual reality system is presented allowing the user to train skills related to brain retraction. The system is designed and the core training system implemented and tested. The initial test shows promising results.

A case of late-onset primary hyperoxaluria type 1.

Primary hyperoxaluria type 1 (PH1) is an inherited metabolic disorder characterized by recurrent urolithiasis and nephrocalcinosis frequently leading to progressive renal insufficiency during the second decade of life. Systemic organ involvement as a result of the accumulation of calcium oxalate crystal deposits in vessel walls often is observed. We report a case of a 56-year-old woman with late-onset of PH1 who developed rapidly progressive renal failure and severe systemic oxalosis with skin and eye involvement despite intensified hemodialytic therapy during the waiting period for combined liver and kidney transplantation. This case illustrates the difficulties in treatment of PH1-induced end-stage renal disease. Combined liver and kidney transplantation should be offered to these patients as soon as possible to reverse the underlying metabolic defect and to restore renal function.