To evaluate the long-term follow up in terms of safety and usability of the Urgent-SQ system (implantable tibial nerve stimulator) based on 1 year, 9 year and novel results 18 years after first implantation in 2002. The Urgent-SQ system consists of an external stimulator and an internal body. The external stimulator is an external electromagnetic pulse generator and has radio-frequency transmission. The internal body of the Urgent-SQ consists of an electromagnetic pulse receiver and a body with two leads containing monopolar electrodes. [1]

This 18-year follow up study included all patients (n=7) who were included in the 1-year and 9-year follow up studies. [1, 2] These patients underwent an implantation procedure with the Urgent-SQ between 2002 and 2004. In total, eight patients were implanted with the Urgent-SQ system. One of the implanted patients experienced after 6 months of follow up unexplainable loss of efficacy. This patient underwent explantation of the implant, was excluded of all studies and considered unsuccessful. [2]  
During the current study, patients were interviewed through a discussion with a physician by phone. This discussion consisted of questions regarding efficacy, durability and safety of the Urgent-SQ system. The results were compared to the former published papers (1-year and 9-year follow up). Table 1. summarizes the questions patients were asked

5/7 patients (60% female) did respond, mean age at 18 year follow up was 72 years ± 8 (range 65-82). Two patients could not be contacted  and were considered lost to follow up. Both patients were responders after 1 year of follow up. During 9 year follow up one of them was still using the system. 
All five patients, who were included in this follow up study, did not use the system anymore due to external stimulator deficiency (n=2) or loss of effect (n=3). Patients who reported external stimulator deficiency were satisfied with the treatment and used it frequently until deficiency occurred. After quitting the therapy the complains of urge/ urge-incontinence increased again in all patients (n=5). Patients now are on different treatment modalities varying from botulin toxin injections, medication and alternative medicine.
Regarding safety, all patients (n=5) reported no explantations or other surgical interventions during the extended follow up period. Other serious adverse events or adverse event due to the implant, external stimulator or implant procedure were not mentioned. Patients did not report any local problems at the site of the implant, such as discomfort or pain during rest or exercise. Most of the patients (3/5) could feel the implant from the outside. None of the patients (n=5) reported discomfort during palpation. These results are largely in line with the published 9 year follow up data. There was one patient who reported sporadic spontaneous sensory response during 9 year follow up, but this was not reported during the current interview. Table 2. shows the results regarding response, pain in patients who still use the Urgent-SQ system comparing to 1 year and 9 year follow up studies.

In this study, the primary goal was to evaluate safety and usability of the that time  experimental Urgent-SQ implant after a maximum of 18 years after implantation. Patients (n=5) reported no (serious) adverse events during follow up period. None of the patients (n=5) who were included in this study reported any complaints or discomfort at the implant site. Therefore, we conclude that the Urgent-SQ is a well-tolerated and safe implant on the longer term. 
The advantages of home-based treatment for OAB with a tibial implant could not be confirmed by this study beyond 9 years. However, this study is an open label follow up study, without technical support from the sponsor, a large implant with 2 leads and had a small number of patients with a few patients loss to follow up. With this in mind, still we can conclude the Urgent-SQ has a great safety profile without SAE on the longer-term. The results for long term efficacy of tibial nerve stimulation via an implant is difficult to interpret beyond 9 years. Patients did subjectively report a worsening of symptoms after technical failure of the external stimulator. Taken this all together, in the future a technical improved, smaller, less vulnerable implant with long term technical support could hopefully confirm the benefit of home-based treatment of OAB with a tibial implant.

This abstract demonstrates the results of longest follow up study conducted for a tibial nerve implant. The Urgent-SQ implant shows a high safety profile without any new adverse or serious adverse events during the maximum 18-year follow up period. Technical failure of the external stimulator (40%) is the dominant factor of therapy failure beyond 9 years. None of the patients in this cohort are currently using the Urgent-SQ implant in their treatment of OAB. Due to unavailability of the external stimulator, no revisions were possible.

Janssen, D.A., F. Farag, and J.P. Heesakkers, Urgent-SQ implant in treatment of overactive bladder syndrome: 9-year follow-up study. Neurourol Urodyn, 2013. 32(5): p. 472-5.
van der Pal, F., et al., Implant-Driven Tibial Nerve Stimulation in the Treatment of Refractory Overactive Bladder Syndrome: 12-Month Follow-up. Neuromodulation, 2006. 9(2): p. 163-71.