Two-year observation of artificial intervertebral disc replacement: results after supplemental ultra-high strength bioresorbable spinal stabilization.

Object: This 2-year experimental study was conducted to investigate the efficacy of a bioactive three-dimensional (3D) fabric disc for lumbar intervertebral disc replacement. The authors used a bioresorbable spinal fixation rod consisting of a forged composite of particulate unsintered hydroxyapatite/poly-L-lactide acid (HA/PLLA) for stability augmentation. The biomechanical and histological alterations as well as possible device-related loosening were examined at 2 years postoperatively.

Methods: Two lumbar intervertebral discs (L2-3 and L4-5) were replaced with the 3D fabric discs, which were augmented by two titanium screws and a spanning bioresorbable rod (HA/PLLA). The segmental biomechanics and interface bone ingrowth were investigated at 6, 15, and 24 months postoperatively, and results were compared with the other two surgical groups (3D fabric disc alone; 3D fabric disc with additional anterior instrumentation stabilization). The 3D fabric disc and HA/PLLA-spinal segments demonstrated segmental mobility at 15 and 24 months; however, the range of motion (ROM) in flexion-extension decreased to 49 and 40%, respectively, despite statistically equivalent preserved torsional ROM. Histologically there was excellent osseous fusion at the 3D fabric disc surface-vertebral body interface. At 2 years posttreatment, no adverse tissue reaction nor aseptic loosening of the device was observed.

Conclusions: Intervertebral disc replacement with the 3D fabric disc was viable and when used in conjunction with the bioresorbable HA/PLLA spinal augmentation. Further refinements of device design to create a stand-alone type are necessary to obviate the need for additional spinal stabilization.