The Design Of Lumbar Anterior Carbon Fiber Reinforced Interbody Fusion Devices And The Related Study

Objective: Based on the lumbar anatomic character of Chinese people, a lumbar anterior carbon fiber reinforced interbody fusion device (ACFR-Cage) was designed to enhance its ability in restoration of the original shape of interbody space and reconstruction of lumbar lordosis, as well as to augment the segmental immediate stability and to increase the possibility of the long-term bone fusion. The related biomechanical and histological study on ACFR-Cage were undertaken.Methods: ACFR-Cage suitable for lumbar disc of Chinese people was designed and manufactured, whose related study in biomechanics and histology was performed. This study was divided into three parts. Part one: The design of ACFR-Cage and carbon fiber artifact ligament (CFAL) fixation device. On basis of related literature, data on the shape and size of ACFR-Cage for Chinese people were obtained and prototype of ACFR-Cage was made. The artifact ligament made of carbon fiber was also manufactured. The material and functional characters of ACFR-Cage and CFAL fixation system were described. Part two: The biomechanical study of ACFR-Cage and CFAL fixation device. This part consists of two experiments. One experiment is planned to evaluate and compare the immediate stability of cadaver lumbar spine constructs using different implants and various fixation instrumentations. Eight L3-S1 cadaveric human lumbar spines (L4-L5 level with partial discectomy and instrumented or not) were tested, dividing into seven groups: 1) intact; 2) with a single iliac bone graft; 3) with a stand-alone ACFR-Cage ;4) an ACFR-Cage plus pedicle screw(PS) fixation; 5) an ACFR-Cage plus translaminar facet screw(TLFS) fixation; 6) with an ACFR-Cage plus anterior CFAL fixation device;7)a laterally-implanted ACFR-Cage preserving anterior longitudinal ligament(ALL). Specimens were loaded in each anatomic plane and the stress, displacement, stiffness and ultimate strength of segmental construct were tested under axial compression, flexion, extension, later bending and torsion respectively. The results were statistically analyzed. The other experiment was performed to evaluate the initial resistance to dislocation ofACFR-Cage and iliac bone graft. Six motion segments(Ll/2 level) were randomly divided into two groups: iliac bone graft group and ACFR-Cage group. The pullout force of the two groups was recorded in the axial compressive preload of 200N. The results were analyzed. Part three: Biological study of specially-made ACFR-Cage and CFAL in dogs. 12 dogs were divided into three groups, including control group(n=3), experiment group(n=6) and CFAL-implanted group(n=3). After anterolateral discectomy, iliac graft was harvested and implanted into disc space in control group and ACFR-Cage impacted with the cancellous bone in experiment group. The fusion segment was instumented with metacarpus plate anterolaterally in both groups. At 3-month and 6-month point, interbody fusion was observed by X -ray, CT examination method and histology. In the third group, CFAL was implanted in paravertebral muscle tissue in dog. At 3-month point, histological study was performed.Results: The ACFR-Cage is stable in physical and chemical quality and suitable for Chinese lumbar disc in morphology. The stress and displacement measurements in stand-alone ACFR-Cage group were less than in iliac graft group in various loading direction such as axial compression, flexion, extension and lateral bending(P<0.01). But the displacement and torsion stress measurements in both groups were greater than intact group in extension and rotation, indicating that implanting stand-alone ACFR-Cage can increase stability in lumbar fusion segment in all loading directions except extension and rotation and require supplemental fixation. ACFR-Cage combined with PS instrumentation outperformed the other fixation methods in segmental stability during all loading directions (P < 0.05). Compared to stand-alone ACFR-Cage group, the stress and displacement in extension was decreased and the stiffness in rotation was increased in ACFR-C...