Biomechanical Evaluation of a Novel Apatite-Wollastonite Ceramic Cage Design for Lumbar Interbody Fusion: A Finite Element Model Study

Objectives. Cage design and material properties play a crucial role in the long-term results, since interbody fusions using intervertebral cages have become one of the basic procedures in spinal surgery. Our aim is to design a novel Apatite-Wollastonite interbody fusion cage and evaluate its biomechanical behavior in silico in a segmental spinal model. Materials and Methods. Mechanical properties for the Apatite-Wollastonite bioceramic cages were obtained by fitting finite element results to the experimental compression behavior of a cage prototype. The prototype was made from hydroxyapatite, pseudowollastonite, and frit by sintering. The elastic modulus of the material was found to be 32 GPa. Three intact lumbar vertebral segments were modelled with the ANSYS 12.0.1 software and this model was modified to simulate a Posterior Lumbar Interbody Fusion. Four cage designs in different geometries were analyzed in silico under axial loading, flexion, extension, and lateral bending. Results. The K2 design had the best overall biomechanical performance for the loads considered. Maximum cage stress recorded was 36.7 MPa in compression after a flexion load, which was within the biomechanical limits of the cage. Conclusion. Biomechanical analyses suggest that K2 bioceramic cage is an optimal design and reveals essential material properties for a stable interbody fusion

Core curriculum (CC) of spinal surgery: a step forward in defining our profession

Objective: The aim our study was to establish a core curriculum (CC) for spine surgery incorporating knowledge, skills and attitudes to help define spine surgery as a medical specialty and serve as a guide for specific spine surgery training. Methods: A committee was established to prepare the CC. Five modules were established; Basic Sciences, Spinal Trauma, Degenerative Spine Diseases, Destructive Spine Pathologies and Spinal Deformity. Prepared CC modules were evaluated in a consensus meeting, translated and reevaluated in a second consensus meeting before being accepted as final. Results: In the five modules, 54 subject headings (19 for Basic Sciences, 10 for Spinal Trauma, 4 for Degenerative Spine Diseases, 4 for Destructive Spine Pathologies and 17 for Spinal Deformity) and 165 specific subjects (59 for Basic Sciences, 32 for Spinal Trauma, 10 for Degenerative Spine Diseases, 23 for Destructive Spine Pathologies and 41 for Spinal Deformity) were defined. Learning outcomes and entry and exit criteria were defined for all subjects. Conclusion: This CC may form the basis of spinal surgery training, defining spinal surgery as a medical specialty and help us spine surgeons to develop better defined identities

Implant Complications After Magnetically Controlled Growing Rods for Early Onset Scoliosis: A Multicenter Retrospective Review

Background:Traditional growing rods have a reported wound and implant complication rate as high as 58%. It is unclear whether the use of magnetically controlled growing rods (MCGR) will affect this rate. This study was performed to characterize surgical complications following MCGR in early onset scoliosis.Methods:A multicenter retrospective review of MCGR cases was performed. Inclusion criteria were: (1) diagnosis of early onset scoliosis of any etiology; (2) 10 years and younger at time of index surgery; (3) preoperative major curve size >30 degrees; (4) preoperative thoracic spine height 6 mo). Distraction technique and interval of distraction was surgeon preference without standardization across sites.Results:Fifty-four MCGR patients met inclusion criteria. There were 30 primary and 24 conversion procedures. Mean age at initial surgery was 7.3 years (range, 2.4 to 11 y), and mean duration of follow-up 19.4 months. Twenty-one (38.8%) of 54 patients had at least 1 complication. Fifteen (27.8%) had at least 1 revision surgery. Six (11.1%) had broken rods (2 to 4.5 and 4 to 5.5 mm rods); two 5.5 mm rods failed early (4 mo) and 4 late (mean=14.5 mo). Six (11.1%) patients experienced 1 episode of lack or loss of lengthening, of which 4 patients subsequently lengthened. Seven patients (13.0%) had either proximal or distal fixation-related complication at average of 8.4 months. Two patients (3.7%) had infections requiring incision and drainage; 1 early (2 wk) with wound drainage and 1 late (8 mo). The late case required removal of one of the dual rods.Conclusions:This study shows that compared with traditional growing rods, MCGR has a lower infection rate (3.7% vs. 11.1%). MCGR does not appear to prevent common implant-related complications such as rod or foundation failure. The long-term implication remains to be determined.Level of Evidence:Level IV