At the annual meeting of the International Society for the Advancement of Spinal Surgery (3–5 April, Anaheim, USA), Jack E Zigler (Texas Health Center for Diagnostics and Surgery, Texas Back Institute, Plano, USA) reported results which “strongly support” the safety of the ProDisc-C device (Centinel Spine). In a study of 504 consecutive patients, Zigler and colleagues found that no secondary surgeries were required for device failure and a relatively low reoperation rate of 5.5%, including the learning curve for every participating surgeon.
The investigators report that secondary surgeries were required in 28/504 patients (5.5%). More specifically, 20/28 of these were operations for adjacent segment degeneration, five of which were adjacent to fusion levels. Three patients had total disc replacement (TDR) removals and anterior cervical discectomy and fusion (ADCF), including one migration, one subsidence, and one spondylosis. In addition, the investigators report one repositioning of a TDR, one incision and drainage for a wound infection, one haematoma drainage, two spinal cord stimulator implantations for pain control and, “most significantly,” according to Zigler, there were no reoperations for device failure.
Zigler and colleagues describe how cervical TDR cases involving the ProDisc-C device were identified at a multi-site, multi-surgeon spine speciality centre. They began with the first investigational device exemption (IDE) case performed in 2003 and included only patients ≥2 years postoperative by December 2017. Consecutive series of the first 504 ProDisc-C patients were analysed, involving 463 (92%) patients with one level, 39 patients (8%) with two levels, and two patients with three levels. The series included 112 hybrids.
The authors highlight two important factors in evaluating the safety of an implant: the rate of subsequent reoperations and the reasons for that surgery, in particular reasons that are related to possible problems with the implant. Zigler and colleagues therefore sought to investigate the reoperation rate for a case series of cervical TDR patients for 15 consecutive years at a single centre, involving the same device.
They reviewed the surgery log 2003–2017 to identify reoperations and for each one, recorded the reason, duration from index surgery and procedure type. The mean time from index operation to surgery log search for reoperations was 69.4 months (range of 24–169), they report.
During the presentation at ISASS 2019, Zigler described a repositioning case to demonstrate the safety of the ProDisc-C device. The patient he mentioned was discharged the day after surgery with some new right arm discomfort. The next day, he called reporting more severe right arm pain and tingling in his fingers. Imaging suggested foramenal encroachment, and the device was repositioned. Six months postoperatively, the patient reported 0/10 neck pain and 1.3/10 arm pain.
The authors note that one of the key strengths of the study was that its single-centre design eliminated many of the surgical and data collection variables that exist in multicentre analyses. They also address important weaknesses. Firstly, they mention that although most of the surgeons at the centre involved in the study are experienced in anterior cervical surgery, for many of them, ProDisc-C was the first arthroplasty device they were exposed to. Additionally, Zigler and colleagues note that besides the IDE patients, reoperations could have been performed elsewhere without the investigators’ knowledge. However, the company would have been alerted to this and this did not occur in the present study.
Talking to Spinal News International, Zigler commented on the significance of the study: “This is a complete data set on a large series of consecutive cases with a single implant. It also represents the early learning curve in cervical arthroplasty for all surgeons involved,” He continued: “A very low operation rate, and no instance of device breakage were two positive findings of the study.”