This in vivo biomechanical study was undertaken to analyze the consequences for sagittal balance and lumbar spine movement in three different lumbar disc prostheses. A total of 105 patients underwent total disc replacement in three different centers. The Maverick Ò prosthesis was used in 46 patients, the SB Charité Ò device was used in 49 patients and the Prodisc Ò device was utilized in 10 patients. The analysis was computer assisted, using Spineview Ò and Matlab Ò softwares. The intra and inter-observer reliability and measurement uncertainty was performed. The analysis of lateral X-ray films in flexion-extension allowed to measure the prosthesis positioning, the range of motion (ROM), the localization of the mean center of rotation (MCR), the vertebral translation and the disc height, for each prosthesis device. The sagittal balance was analyzed on a full spine film. The parameters studied were described by Duval-Beaupè re. The results were compared to the data found in literature, and compared to 18 asymptomatic volunteers, and 61 asymptomatic subjects, concerning the sagittal balance. The prostheses allowed an improvement of the ROM of less than 2°. The ROM of L5-S1 prostheses ranged from 11.6 to 15.6% of the total lumbar motion during flexion-extension. At L4-L5 level, the ROM decreased when there was an arthrodesis associated at the L5-S1 level. There was no difference of ROM between the three prostheses devices. The MCR was linked to the ROM, but did not depend on the prosthesis offcentering. The disc height improved for any prosthesis, and decreased in flexion or in extension, when the prosthesis was offcentered. An increase of translation indicated a minor increase of the ROM at L4-L5 level after Maverick Ò or SB Charité Ò implantation. The L5-S1 arthrodesis was linked with an increase of the pelvic tilt. The lumbar lordosis curvature increased between L4 and S1, even more when a prosthesis was placed at the L3-L4 level. Total disc arthroplasty is useful in the surgical management of discogenic spinal pathology. The three prostheses studied allowed to retorate the disc height, the ROM, without disrupting the sagittal balance, but induced modification of the lumbar curvature.

The short and intermediate term clinical outcomes are better with RSA than with HA. The complication rate is higher with HA. Nevertheless, scapular notching occurred in more than 20% of patients with RSA, suggesting that care should be taken when using this prosthesis in young, active patients.

This literature review confirms that the use of rhBMP-2 following FDA-approved recommendations (i.e. one-level ALIF surgery with an LT-cage) is safe. The rate of complications is low and the AEs had been identified by the FDA during the pre-marketing clinical trials. The clinical efficiency of rhBMP-2 is equal or superior to that of allogenic or autologous bone graft in respect to fusion rate, low back pain disability, patient satisfaction and rate of re-operations. For all other off-label use, the safety and effectiveness of rhBMP-2 have not been established, and further RCTs with high level of evidence are required.

4; retrospective study.

Magnetic Resonance Imaging (MRI) appears as a good surrogate to Computed Tomography (CT) scan as it does not involve radiation. In this context, a 3D anatomical and perfusion MR imaging protocol was developed to follow the evolution of bone regeneration and the neo-vascularization in femoral bone defects in rats. For this, three different biomaterials based on Pullulan-Dextran and containing either Fucoidan or HydroxyApatite or both were implanted. In vivo MRI, ex vivo micro-CT and histology were performed 1, 3 and 5 weeks after implantation. The high spatially resolved (156 × 182 × 195 µm) anatomical images showed a high contrast from the defects filled with biomaterials that decreased over time due to bone formation. The 3D Dynamic Contrast Enhanced (DCE) imaging with high temporal resolution (1 image/19 s) enabled to detect a modification in the Area-Under-The-Gadolinium-Curve over the weeks post implantation. The high sensitivity of MRI enabled to distinguish which biomaterial was the least efficient for bone regeneration, which was confirmed by micro-CT images and by a lower vessel density observed by histology. In conclusion, the methodology developed here highlights the efficiency of longitudinal MRI for tissue engineering as a routine small animal exam.