Biomechanical Properties of Porous Titanium Cages for Different Lumbar Interbody Fusion Surgeries / 医用生物力学

Objective To study the biomechanical properties of porous titanium cages used for different lumbar interbody fusion surgeries. Methods The three-dimensional (3D) finite element model of the lumbar spine was constructed, and mechanical parameters of porous materials were obtained by mechanical test. The biomechanical properties of porous titanium cages in anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), direct lateral interbody fusion (DLIF) were compared. Results After lumbar interbody surgery, the predicted range of motion (ROM) and the maximum stress in cage of DLIF model and ALIF model were substantially lower than those of PLIF model and TLIF model. The maximum stress in endplate of DLIF model, ALIF model and TLIF model were obviously lower than that of PLIF model. Conclusions DLIF with the porous cage showed advantages in biomechanical properties, which was simple to operate and suitable for minimally invasive surgery in clinical practice. DLIF performed the superior comprehensive properties.

Clinical and Radiological Outcomes of a New Cage for Direct Lateral Lumbar Interbody Fusion

OBJECTIVE: In Korea, direct lateral interbody fusion (DLIF) was started since 2011, using standard cage (6degrees lordotic angle, 18mm width). Recently, a new wider cage with higher lordotic angle (12degrees, 22mm) was introduced. The aim of our study is to compare the clinical and radiologic outcomes of the two cage types. METHODS: We selected patients underwent DLIF, 125 cases used standard cages (standard group) and 38 cases used new cages (wide group). We followed them up for more than 6 months, and their radiological and clinical outcomes were analyzed retrospectively. For radiologic outcomes, lumbar lordotic angle (LLA), segmental lordoic angle (SLA), disc angle (DA), foraminal height change (FH), subsidence and intraoperative endplate destruction (iED) were checked. Clinical outcomes were compared using visual analog scale (VAS) score, Oswestry disability index (ODI) score and complications. RESULTS: LLA and SLA showed no significant changes postoperatively in both groups. DA showed significant increase after surgery in the wide group (p<0.05), but not in the standard group. Subsidence was significantly lower in the wide group (p<0.05). There was no difference in clinical outcomes between the two groups. Additional posterior decompression was done more frequently in the wide group. Postoperative change of foraminal height was significantly lower in the wide group (p<0.05). The iED was observed more frequently in the wide group (p<0.05) especially at the anterior edge of cage. CONCLUSION: The new type of cage seems to result in more DA and less subsidence. But indirect foraminal decompression seems to be less effective than standard cage. Intraoperative endplate destruction occurs more frequently due to a steeper lordotic angle of the new cage.

Correction of Coronal Imbalance in Degenerative Lumbar Spine Disease Following Direct Lateral Interbody Fusion (DLIF)

OBJECTIVE: The authors have recently been using a surgical technique of minimally invasive direct lateral interbody fusion (DLIF) for correcting of coronal imbalance. The purpose of this study was to evaluate the surgical outcome and complication of DLIF. METHODS: We undertook retrospective analysis of a consecutive series of 8 DLIF procedures in Degenerative lumbar spine disease since May 2011. Four patients underwent DLIF only, and the others underwent combined DLIF and posterior fixation. Data on intra- and postoperative complications were collected. The pre- and postoperative X-rays were reviewed. We investigated coronal deformity, Cobb's angle, and apical vertebral translation (AVT). The mean follow-up period was months with a range of 2 to 8 months. RESULTS: A mean preoperative coronal Cobb's angle was 21.8degrees (range 11.5-32.4degrees). Following after DLIF, the mean Cobb's angle was decreased to 13.0degrees (range 2.9-21.5degrees). Following additional posterior screw fixation, mean Cobb's angle was further decreased to 7.4degrees (range 2.9-13.2degrees). A mean preoperative AVT was 2.0 cm(range 0.6-3.5 cm), and improved to 1.4 cm(range 0.3-2.4 cm) and 0.8 cm(range 0.2-1.8 cm) postoperatively (DLIF and, posterior fixation respectively). One patient (12.5%) showed cage migration during follow-up period. Two patients (25%) developed motor weakness, and 4 patients (50%) experienced postoperative thigh paresthesias or dysesthesias. During follow up period, motor weakness had resolved in 1 patient. Sensory symptoms were improved in all patients at the last follow-up. CONCLUSION: Degenerative lumbar disease can be effectively corrected by DLIF with acceptable complications.