Nucleus replacement devices may yield excellent long-term results in select patients
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Use of a nucleus replacement device may provide “excellent” long-term clinical and radiological outcomes in select patients, according to researchers of published results.
“The results of this study support the hypothesis that nucleus replacement using a biomechanically robust implant in well selected patients with discogenic back pain can essentially restore normal spinal function. Such results, however, depend largely on the accuracy of diagnosis, as well as the long-term performance of the [nucleus replacement device],” Jeff D. Golan, MD, told Healio. “Additional research on nucleus replacement technologies is essential to develop the ideal device and technique of implantation, and to refine criteria for selecting patients most likely to benefit.”
Golan and colleagues gathered clinical outcome and imaging data to assess the performance of the Dascor Disc Arthroplasty Device (Disc Dynamics Inc.) in an extended period. Researchers evaluated VAS for back pain, Oswestry Disability Index scores and analgesic medication use scores in 26 patients who received the device between 2006 and 2009. Researchers also systematically evaluated disc height, Modic changes, Pfirrmann grade and any implant-associated findings with MRI at the index and adjacent disc levels.
Of the 14 patients with long-term data available, results showed a mean improvement of VAS, Oswestry Disability Index scores and analgesic medication use scores compared with baseline values. Researchers also found 46% of patients developed radiological adjacent segment degeneration on MRI vs. 54% of patients who did not. Golan noted one patient needed secondary surgery for adjacent segment disease 8 years later, while the other patients demonstrated adjacent segment changes equivalent to those reported in other published studies on natural history of degenerative changes.
“Another cohort of eight patients chose not to complete clinical or radiological follow-up,” Golan said. “This group had poor results, as six patients went on to require revision surgery and two others underwent surgery at adjacent levels. It is unclear why some had excellent response, while others did not.”
Perspective
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Lumbar arthroplasty, unlike cervical total disc replacement, hasn’t lived up to its lofty expectations. Lumbar total disc replacement has developed a niche in the treatment of axial, mechanical low back pain. But lumbar total disc replacement has seen limited adoption, partly due to the necessity of utilizing the anterior retroperitoneal approach with its associated morbidity and difficulties with revision. Lumbar nucleus replacement was designed to address this shortcoming by addressing the presumptive pain generator, a degenerated nucleus pulposus, through a less invasive approach. Nucleus replacement devices have also failed to meet expectations, without a single device gaining FDA approval.
The Dascor device, featured in the manuscript by Jeff D. Golan, MD, and colleagues, is a polyurethane filled balloon placed via a minimally invasive approach. Unfortunately, this device has been plagued with the complications common to nucleus replacement devices, namely displacement and subsidence leading to reoperation. The Golan study reports a reoperation rate of 43% at the index level and 21% at the adjacent levels, which is unacceptably high. Nucleus replacement offers the enticing combination of motion preservation coupled with a minimally invasive approach, but it remains functionally elusive.
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