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Objectives: The purpose of this study is to assess the role of the Hartshill horseshoe cage for lumbar and lumbosacral interbody fusion through anterior Robinson–Smith construct. Materials: About 25 adults (11 males and 14 females), aged 29 to 56 years were the subject materials. Disease entities were post-traumatic internal derangement, isthmic and degenerative spondylolisthesis and lumbar scoliosis (DLS). The fusion levels were L${}_{4-5}$ in 21 and L₅–S₁ in four patients, braced postoperatively for 2–3 months. Results: Fusion took place at least five months on average (4–7 months). No complications were encountered. In one DLS patient who had multi-segment posterior instrument-aided stabilization (T${}_{11}$–S₁), the lowest pedicle screw became loosened gradually, but cage was maintained intact without loosening. Conclusion: Hartshill horseshoe cage offered a conducive biomechanical environment for anterior interbody fusion.

Purpose: Anterior cervical discectomy and fusion is considered as a standard procedure for treating cervical degenerative disc disease. This retrospective study aimed to analyze the radiographic outcome of using a novel cushion titanium cage (Baui Z-Brace Dynamic Fusion Cage). Methods: Fifty-seven patients who received either single-, double-, or three-level interbody fusion surgeries were enrolled. Data from initial status after surgery and postoperative follow-ups for five years were obtained. The patients were divided into three groups according to different levels of cage implantation: 1-level ($n=27$), 2-level ($n=25$), and 3-level ($n=6$). Follow-up time and fusion rate of radiographs were subjected to evaluation. Results: The lateral view of plain radiographs manifests no evident cage subsidence ($>3$mm) and dislodgment in 1-, 2-, and 3-level cage implantation. The follow-up time is three years in 1-level and two years in 2- and 3-level. The CT scans at the final follow-up among different levels of cage implantation manifested bony fusion. The measurement of the Hounsfield unit indicates the bone growth inside the cage compared with control case, demonstrating solid bony fusion among groups at the final follow-up. Conclusions: The data confirm that the specialized Z-shaped structure of the cushion titanium cage may provide the interfragmentary motion stimulating innate bony fusion for sustained improvement.

Peri-implant debris certainly lead to osteolysis, necrosis, pseudotumor formation, tissue granulation, fibrous capsule contractions, and even implant failure. For the three-dimensional (3D) printed cage, impaction during cage insertion is one of the most potential sources of fracture debris. A finite-element study was carried out to reduce the impact-induced debris of the 3D-printed cage. This study focused on the design strategy of solid and cellular structures along the load-transferring path. Using the finite-element method, the cellular structure of the transforaminal lumbar interbody fusion (TLIF) cage was systematically modified in the following four variations: a noncellular cage (NC), a fully cellular (FC) cage, a solid cage with a cellular structure in the middle concave (MC) zone, and a strengthened cage (SC) in the MC zone. Three comparison indices were considered: the stresses at the cage-instrument interfaces, in the MC zone, and along the specific load-transferring path. The NC and FC were the least and most highly stressed variations at the cage-instrument interfaces and in the MC zone, respectively. Along the entirely load-transferring path, the FC was still the most highly stressed variation. It showed a higher risk of stress fracture for the FC cage. For the MC and SC, the MC zone was consistently more stressed than the directly impacted zone. The further strengthened design of the SC had a lower peak stress (approximately 29.2%) in the MC zone compared with the MC. Prior to 3D printing, the load-transferring path from the cage-instrument interfaces to the cage-tissue interfaces should be determined. The cage-instrument interfaces should be printed as a solid structure to avoid impact-induced fracture. The other stress-concentrated zones should be cautiously designed to optimize the coexistence strategy of the solid and cellular structures.

This study investigates and compares the mechanical response of interbody and posterolateral fusion along with the transpedicular screw fixation for the degenerative spondylolisthesis under different load conditions using finite element (FE) analysis. Image processing, computer aided design (CAD), and computer aided engineering techniques were applied to build a three-dimensional model of a functional spinal unit (L4–L5) with transpedicular screw fixation for the posterolateral fusion FE model. Additionally, the intervertebral disc was replaced by two cages to represent the interbody fusion FE model. A unit moment of 1 Nm was applied on the top of L4 in different directions to simulate the flexion, extension, lateral bending, and axial rotation, respectively. The lower of L5 was fixed in all directions for constraint. The simulated results revealed that using cages obviously decreased (13%–58%) the stress imposed upon the instrumentations. The stress concentration occurred at the locking nut on the transpedicular screw head, the middle part of the bone plate, and the thread of transpedicular screw near the head. These findings were comparable to clinical observations. With the limited data, our results suggested interbody fusion in combination with transpedicular screw fixation demonstrated less stress on the instrumentations than the posterolateral fusion with only transpedicular screw fixation.