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Background Stability of threshold currents during long-term use of phrenic nerve stimulation has been questioned. Methods and Results Between January 5, 1988, and March 5, 2008, 49 patients with functional C2-tetraplegia received an Atrostim PNS (Atrotech Ltd., Tampere, Finland) as treatment of their respiratory insufficiency; a follow-up of 35 of such patients was carried out exclusively in our institution for 6.3 (4.44) 0.04–15.75 years (mean [standard deviation (SD)] range). The device employed four-pole sequential nerve stimulation, which provided four threshold currents subsequently evaluated for each phrenic nerve. Stimulation data were prospectively recorded. The differences between threshold currents recorded 1 year after implantation and the last recorded values were 0.33–0.43 (0.44–0.63) 0–2.9 mA. After having excluded the data of eight patients with values >1 mA (= mean + SD), we registered the differences for the remaining patients of 0.15–0.24 (0.14–0.24) 0–0.95 mA, which is just twice the adjustment accuracy of the device. Out of the eight problem cases one had, and two were suspected to have, surgical trauma; all three nerves recovered. In two cases the values steadily increasing over years might have been caused by unspecific foreign body reaction. Two cases with values >1mA for different durations at different electrodes might be caused by biofilm, and one patient displaying steadily increasing values lived, unwilling to live, only 2 years after the implantation. Conclusion Thus, there was no permanent nerve injury and in 77% of the presented cases threshold currents remained stable.

Background A computerized robotic surgical system was developed from 1986 by the Thomas J. Watson Research Center. In 1992 the system unit Orthodoc® and the milling robot Robodoc® were first used on humans. We present the results achieved with Robodoc-assisted total hip arthroplasty in 97 hips. Methods Between 1997 and 2002, 143 total hip replacements (128 patients) were performed using the Robodoc system. This is a consecutive series. Complete follow-up was possible in 97 hips at a mean follow-up period of 3.8 years. Results Technical complications directly related to the robotic device occurred in nine cases (9.3%). The pre-operative Merle d'Aubigne score was determined at 8.1 points compared to a post-operative mean score of 16.2. There was no sign of femoral stem loosening on radiographs. Conclusions Robotic-assisted total hip arthroplasty with the Orthodoc/ Robodoc system achieves equal results as compared to a manual technique. However, there was a high number of technical complications directly or indirectly related to the robot. Copyright © 2007 John Wiley & Sons, Ltd.

Background A robotic system for the implantation of a total hip arthroplasty (THA) is currently under development. One of the goals of this system is non-invasive patient fixation, aiding the robotic system by an infrared tracking system. To determine the extent of fixation that can be achieved by non-invasive methods, an in vitro study was performed. Methods In cadaver testing, different non-invasive fixation methods (Arthrex leg holder with tourniquet mechanism; arthroscopic leg holder with disposable foam inserts; gynaecological leg holder; Goepel knee crutch) were evaluated under load in different directions. Results Deviation was measured in the range 0.33–18.1 mm with up to 20 N load. The testing showed the pneumatic leg holder system to provide the highest stability, followed by an arthroscopic leg holder system with foam inserts. Conclusions Use of a leg holder with foam inserts produced a stability that should enable tracking of the remaining deviation by the navigation system. We will therefore use this method in our future development of the robotic milling tool. Copyright © 2007 John Wiley & Sons, Ltd.