Prosthetic Disc Nucleus: Treatment ..
This study documented the presence of large areas of strain maxima adjacent to the implant for all modes of loading. We have previously performed a similar analysis on a fixed-core TDR and evaluated the von Mises strains of the cancellous bone. The results of that study indicated that strains typically remained under 1% after implantation, with the exception of a small area during flexion. This is likely the result of the larger contact surface area for a TDR compared with the Fernström sphere, especially at 0 mm of subsidence. This is further indicated by the decreasing area of strain maxima that was observed for increasing levels of subsidence. As the implant nested further into the cancellous bone, the area of contact increased, which resulted in a more distributed load. Even though increased subsidence resulted in reduced areas of strain maxima, the fully nested models still depicted strains substantially greater than the intact state. Despite the large areas of strain maxima above 1% documented for all modes of loading, the clinical results depict reasonable levels of subsidence and satisfactory clinical outcomes., This suggests that the initial strains experienced by the bone after implantation may not be relevant when one is investigating long-term subsidence of spinal arthroplasty devices. Alternatively, the disparity between the clinical outcomes and high peak strain documented in this study may be explained by increased load bearing in the annulus fibrosus. Specifically, because the Fernström prosthesis maintains the majority of the annulus, continued subsidence may offset the axial loading from the device to the surrounding annulus. The current model did not take this phenomenon into consideration.
with the prosthetic disc nucleus PDN ..
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An intervertebral disc nuclear prosthesis ought, ..
Nuclear replacement is an emerging surgical treatment for degenerative disc disease (DDD) and low back pain (LBP). While clinical experience is most extensive with the prosthetic disc nucleus PDN (Raymedica, Minneapolis, Minnesota), strict indications apply for the implantation of this device. The purpose of this study was to ascertain what percentage of patients treated surgically for degenerative disc disease with other surgical procedures would have been candidates for nuclear replacement implantation.
The PDN prosthetic disc-nucleus device
The major complication found with use of the previous PDN generational products is posterior device herniation causing compressive radiculopathy, which usually requires revision, consisting of removal of the device and placement of a smaller one, TDR, or a fusion., , – In the earliest and latest series this complication occurred in 8–12% of the patients, respectively., , , However, in the interim, extrusion rates were as high as 26% and 38%, because the risk factors for extrusion were not completely appreciated. A series with no herniation in 45 patients has been reported, albeit with only two-thirds of the patients returning for a 6-month follow-up and with use of the nuclear replacement device for a different indication (adjunct to microdiscectomy for disc herniation). In face of potential complications, not all patients with DDD would qualify for nuclear replacement. Careful patient selection is stressed by all authors as essential for surgical and clinical success., , –
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