The Memory Metal Minimal Access Cage: A New Concept in Lumbar Interbody Fusion—A Prospective, Noncomparative Study to Evaluate the Safety and Performance

Abstract

Study Design/Objective. A single-centre, prospective, non-comparative study of 25 patients to evaluate the performance and safety of the Memory Metal Minimal Access Cage (MAC) in Lumbar Interbody Fusion. Summary of Background Data. Interbody fusion cages in general are designed to withstand high axial loads and in the meantime to allow ingrowth of new bone for bony fusion. In many cages the contact area with the endplate is rather large leaving a relatively small contact area for the bone graft with the adjacent host bone. MAC is constructed from the memory metal Nitinol and builds on the concept of sufficient axial support in combination with a large contact area of the graft facilitating bony ingrowth and ease in minimal access implantation due to its high deformability. Methods. Twenty five subjects with a primary diagnosis of disabling back and radicular leg pain from a single level degenerative lumbar disc underwent an interbody fusion using MAC and pedicle screws. Clinical performance was evaluated prospectively over 2 years using the Oswestry Disability Index (ODI), Short Form 36 questionnaire (SF-36) and pain visual analogue scale (VAS) scores. The interbody fusion status was assessed using conventional radiographs and CT scan. Safety of the device was studied by registration of intra- and post-operative adverse effects. Results. Clinical performance improved significantly (P < .0018), CT scan confirmed solid fusion in all 25 patients at two year follow-up. In two patients migration of the cage occurred, which was resolved uneventfully by placing a larger size at the subsequent revision. Conclusions. We conclude that the Memory Metal Minimal Access Cage (MAC) resulted in 100% solid fusions in 2 years and proved to be safe, although two patients required revision surgery in order to achieve solid fusion.

Pain and disability after first-time spinal fusion for lumbar degenerative disorders: a systematic review and meta-analysis

“…After assessment of full text, twenty-five studies fulfilled the eligibility criteria and were included for qualitative analysis. Boissiere et al [47], Kok et al [54], and Pereira et al [60] were excluded for the quantitative analysis because of an overlap in study population with Barrey et al [46], Kok et al [55], and Franke et al [68], respectively. Tables 1 and 2 show overall study and patient characteristics, respectively.…”

Nitinol Spinal Vertebrae: A Favorable New Substitute

“…Moreover, the cage has let osteoblasts to grow. However, because of the little contact of the cage with the grafted bone, the results have not been as proper as expected before [12].…”

“…No adverse reaction detected [79] Suitable for controlling bone modeling [79] Rings They can transfer more compression forces to the cage [80] Suitable for neck regions [80] Staples Suitable for idiopathic scoliosis treatment, osteotomies and lumbar curve treatments [81,82] Cages Frequent as lumbar interbody in surgeries [9] Better restoring vertebral height than kyphoplasty [27] Self-assembled and being similar to disc [9] Let osteoblasts grow [12] Screws suitable for vertebral fusion surgeries [76] Nitinol screws along with Nitinol rods have more flexibility and maintain the spinal movements [76] Stents…”

“…If there is no interaction between implant and the body tissue, implantation rejection may occur. With Nitinol usage, due to good interaction, decrease in the risk of failure has lowered [12]. A comparison of Nitinol with Ti rods applied to 70 patients to improve their degradative lumbar scoliosis showed better spinal deformation correction by the former [7].…”

“…During the past five decades, metallic orthopaedic devices have been used for spinal shape correction in scoliosis disease [7,[11][12][13][14]. Despite good strength, Young's moduli of metals are higher than bone.…”