Abstract—Neuromuscular electrical stimulation (NMES) is a potential deep vein thrombosis (DVT) preventative measure that is often over-looked. NMES could be used postoperatively in conjunction with pharmacological prophylaxis to further reduce the incidence rate of DVT following orthopaedic surgery. However, the use of NMES in the recovery period following orthopaedic surgery on patients with metallic hip/knee implants has not been tested to date. The presence of a metallic implant may interfere with the NMES generated electric field causing hypersensitivity at the implant site. This may essentially limit the use of NMES postoperatively. Consequently, patient tolerance of NMES must be assessed before any treatment can be administered. Five hip replacement patients and 5 knee replacement patients participated in this study that were at least 3 weeks post-op. NMES was applied to the calf muscles of each patient using skin surface electrodes and the stimulation intensity was slowly increased. Comfort was assessed by asking the patient to indicate the stimulation intensity corresponding to 4 thresholds: when they first felt the stimulus sensation (sensory threshold), when a muscle contraction was observed (motor threshold), when stimulation became uncomfortable (pain threshold) and when the stimulation became unbearable (pain tolerance). Patients also indicated their overall comfort level on a visual analogue scale and completed a short verbal interview detailing their experience of the NMES treatment. Results indicated that the presence of a metallic implant did not give rise to hypersensitivity to NMES. Patients found the application of calf muscle NMES comfortable and acceptable as a treatment. We conclude that use of NMES on postoperative orthopaedic patients can be safely considered as a DVT prevention method. Manuscript received April 1, 2010. This work was supported in part by the Irish Research Council for Science, Engineering & Technology EMBARK Initiative scholarship. B. J. Broderick is with the School of Engineering and Informatics, National University of Ireland Galway, University Road, Galway, Ireland and the National Centre for Biomedical Engineering Science, National University of Ireland Galway, University Road, Galway, Ireland. C. Kennedy is with the Department of Orthopaedics, Galway University Hospitals, Newcastle Road, Galway, Ireland. P. P. Breen is with the School of Engineering and Informatics, National University of Ireland Galway, University Road, Galway, Ireland and the National Centre for Biomedical Engineering Science, National University of Ireland Galway, University Road, Galway, Ireland. S. R. Kearns is with the Department of Orthopaedics, Galway University Hospitals, Newcastle Road, Galway, Ireland. G. ÓLaighin is with the School of Engineering and Informatics, National University of Ireland Galway, University Road, Galway, Ireland and the National Centre for Biomedical Engineering Science, National University of Ireland Galway, University Road, Galway, Ireland (phone: +353-91- 492728; fax +353-91-494511; e-mail: gearoid.olaighin@nuigalway.ie). I. INTRODUCTION EEP vein thrombosis (DVT) and its sequelae, pulmonary embolism (PE), remain a serious medical concern [1-3]. In the case of lower limb orthopaedic surgery, anesthesia, circulation interruption, bed rest and the alteration in the blood constituents due to the inflammation inherently associated with surgery, all create an ideal situation for the development of DVT [4]. Studies have demonstrated the effectiveness of mechanical and pharmacological DVT prophylactic measures post orthopaedic surgery [2, 5]. However, situations where medication is contraindicated (active bleeding or risk of hemorrhage) and the low compliance problems of intermittent pneumatic compression devices have encouraged surgeons to seek alternatives [2, 6, 7]. Neuromuscular electrical stimulation (NMES) has been used as a neural prosthesis for assisting the restoration of lost function in patients with hemiplegia but has also been used for therapeutic tasks, such as improving blood circulation [8, 9]. A controlled electrical stimulus applied over motor points in the body using skin surface electrodes causes a fused contraction of skeletal muscle. If NMES is targeted to the calf muscles, it can increase venous blood flow by activating the skeletal muscle pump. A previous study by Faghri et al. detailing the use of NMES on patients undergoing total hip and knee arthroplasties perioperatively demonstrated an improvement in lower leg circulation and a reduction in venous stasis [4]. Total hip and knee replacement patients are still at high risk of DVT in the days following surgery but the effect NMES therapy has on DVT rates during this period has not been evaluated. Patient comfort and tolerance of NMES during the study by Faghri et al. was not considered, as the patients were anesthetized for the duration of the application of stimulation [4]. However, before a postoperative NMES therapy can be evaluated, patient comfort and tolerance of NMES must be investigated. The presence of a metallic implant may interfere with the NMES generated electric field giving rise to hypersensitivity the implant site. This may limit the use of NMES postoperatively to patient groups whose implants are far enough away from the stimulus site so as not to cause problems. As a result, patient tolerance of NMES must be assessed before any treatment can be administered. The Influence of Orthopaedic Implants on Patient Tolerance of Neuromuscular Electrical Stimulation (NMES) Barry J. Broderick, Member, IEEE, Cian Kennedy, Paul P. Breen, Member, IEEE, Stephen R. Kearns and Gearóid ÓLaighin, Senior Member, IEEE D 32nd Annual International Conference of the IEEE EMBS Buenos Aires, Argentina, August 31 - September 4, 2010 978-1-4244-4124-2/10/$25.00 ©2010 IEEE 5823