RÉSUMÉ
3D-printing technology has revolutionized spinal implant manufacturing, particularly in developing personalized and custom-fit titanium interbody fusion cages. These cages are pivotal in supporting inter-vertebral stability, promoting bone growth, and restoring spinal alignment. This article reviews the latest advancements in 3D-printed titanium interbody fusion cages, emphasizing their relevance in modern personalized surgical spine care protocols applied to common clinical scenarios. Furthermore, the authors review the various printing and post-printing processing technologies and discuss how engineering and design are deployed to tailor each type of implant to its patient-specific clinical application, highlighting how anatomical and biomechanical considerations impact their development and manufacturing processes to achieve optimum osteoinductive and osteoconductive properties. The article further examines the benefits of 3D printing, such as customizable geometry and porosity, that enhance osteointegration and mechanical compatibility, offering a leap forward in patient-specific solutions. The comparative analysis provided by the authors underscores the unique challenges and solutions in designing cervical, and lumbar spine implants, including load-bearing requirements and bioactivity with surrounding bony tissue to promote cell attachment. Additionally, the authors discuss the clinical outcomes associated with these implants, including the implications of improvements in surgical precision on patient outcomes. Lastly, they address strategies to overcome implementation challenges in healthcare facilities, which often resist new technology acquisitions due to perceived cost overruns and preconceived notions that hinder potential savings by providing customized surgical implants with the potential for lower complication and revision rates. This comprehensive review aims to provide insights into how modern 3D-printed titanium interbody fusion cages are made, explain quality standards, and how they may impact personalized surgical spine care.
RÉSUMÉ
OBJECTIVE: Advances in surface architecture and technology have made interbody fusion devices more bioactive, with the hope of facilitating the fusion process more successfully. The advent of these increasingly bioactive implants may reduce reliance on more expensive biologics that have previously been used to achieve high fusion rates. METHODS: A retrospective review of prospectively collected data (August 2018-December 2019) was conducted of consecutively performed anterior lumbar interbody fusions in which an acid-etched, nanosurface-modulated, titanium interbody device packed only with corticocancellous allograft chips and local blood was used. Minimum follow-up was 1 year, and inclusion required available imaging and outcome metrics preoperatively and at 1 year. Fusion and subsidence were assessed via CT scans and/or dynamic radiographs. Health-related quality-of-life measures (Oswestry Disability Index [ODI], visual analog scale [VAS] back/leg) were collected pre- and postoperatively. RESULTS: In total, 55 patients met inclusion criteria (1 year of follow-up, available imaging, and outcome metrics). A total of 69 lumbar levels were treated in these 55 patients. The mean age was 67 ± 12.1 years, with 47% female patients. Roughly one-third (35%) had previous spine surgery, and approximately one-tenth (9.1%) had prior spinal fusion. A total of 20.6% were treated at multiple levels (mean levels per patient 1.2, minimum 1, maximum 3). The mean preoperative patient-reported outcomes were as follows: ODI 39.71 ± 18.15, VAS back 6.49 ± 2.19, and VAS leg 5.41 ± 2.71. One year after surgery, the mean improvements in patient-reported outcomes (vs preoperative scores) were as follows: ODI -22.9 ± 13.08 (p < 0.001), VAS back -3.75 ± 2.03 (p < 0.001), VAS leg -3.73 ± 2.32 (p < 0.001). All levels achieved fusion at 1 year postoperatively based on CT scans (65/69 levels) or dynamic radiographs (4/69 levels, change in score < 5% on flexion-extension radiographs). Four of the 65 levels were assigned to the grade 3 category according to a CT-based grading system, meaning cranial and caudal endplate bone apposition to the implant on both surfaces with no clear intervertebral bone connection through or around the implant. Sixty-one of 65 were found to have contiguous intervertebral bone bridging and thus were assigned to grade 1 (n = 54) or grade 2 (n = 7). Low-grade graft subsidence (Marchi grade 0 or I) occurred in 9 levels (13.0%) and high-grade subsidence (Marchi grade II or III) in 4 levels (5.8%). No patients required reoperation at the level of anterior lumbar interbody fusion and no radiographic or clinical evidence of pedicle screw loosening or failure was observed. CONCLUSIONS: The combination of advances in materials science and surface technology as demonstrated with a nanotechnology titanium cage resulted in the ability to obtain lumbar interbody fusion with allograft chips and local blood alone. Achieving high fusion rates with low-cost biologics/allograft provides for an attractive pathway toward reducing the cost of reconstructive spine care, and a potential incremental benefit for healthcare economics.
RÉSUMÉ
PURPOSE OF REVIEW: To summarize the history of titanium implants in spine fusion surgery and its evolution over time. RECENT FINDINGS: Titanium interbody cages used in spine fusion surgery have evolved from solid metal blocks to porous structures with varying shapes and sizes in order to provide stability while minimizing adverse side effects. Advancements in technology, especially 3D printing, have allowed for the creation of highly customizable spinal implants to fit patient specific needs. Recent evidence suggests that customizing shape and density of the implants may improve patient outcomes compared to current industry standards. Future work is warranted to determine the practical feasibility and long-term clinical outcomes of patients using 3D printed spine fusion implants. Outcomes in spine fusion surgery have improved greatly due to technological advancements. 3D printed spinal implants, in particular, may improve outcomes in patients undergoing spine fusion surgery when compared to current industry standards. Long term follow up and direct comparison between implant characteristics is required for the adoption of 3D printed implants as the standard of care.
RÉSUMÉ
OBJECTIVE: Intervertebral devices are increasingly utilized for fusion in the lumbar spine, along with a variety of bone graft materials. These various grafting materials often have substantial cost burdens for the surgical procedure, although they are necessary to overcome the limitations in healing capacity for many traditional interbody devices. The use of bioactive interbody fusion devices, which have demonstrable stimulatory capacity for the surrounding osteoblasts and osteoprogenitor cells and allow for osseointegration, may reduce this heavy reliance on osteobiologics for achieving interbody fusion. The objective of this study was to evaluate the rate of successful interbody fusion with a bioactive lateral lumbar interbody titanium implant with limited volume and low-cost graft material. METHODS: The authors conducted a retrospective study (May 2017 to October 2018) of consecutively performed lateral lumbar interbody fusions with a bioactive 3D-printed porous titanium interbody device. Each interbody device was filled with 2-3 cm3/cage of a commercially available ceramic bone extender (ß-tricalcium phosphate-hydroxyapatite) and combined with posterior pedicle screw fixation. No other biological agents or grafts were utilized. Demographic, clinical, and radiographic variables were captured. Fusion success was the primary endpoint of the study, with graft subsidence, fixation failure, and patient-reported outcomes (Oswestry Disability Index [ODI] and visual analog scale [VAS]-back and -leg pain scores) collected as secondary endpoints. The authors utilized a CT-based fusion classification system that accounted for both intervertebral through-growth (bone bridging) and ingrowth (integration of bone at the endplate-implant interface). RESULTS: In total, 136 lumbar levels were treated in 90 patients. The mean age was 69 years, and 63% of the included patients were female. Half (50.0%) had undergone previous spinal surgery, and a third (33.7%) had undergone prior lumbar fusion. A third (33.7%) were treated at multiple levels (mean levels per patient 1.51). One year after surgery, the mean improvements in patient-reported outcomes (vs preoperative scores) were -17.8 for ODI (p < 0.0001), -3.1 for VAS-back pain (p < 0.0001), and -2.9 for VAS-leg pain (p < 0.0001). Bone bridging and/or appositional integrity was achieved in 99.3% of patients, including 97.8% who had complete bone bridging. No fixation loosening or implant failure was observed at any segment. Low-grade graft subsidence (Marchi grade ≤ I) occurred in 3 levels (2.2%), and intraoperative endplate violation occurred twice (1.5%). High-grade subsidence was not found. No implant failure or revision surgery for pseudarthrosis/subsidence was necessary. CONCLUSIONS: The use of bioactive titanium interbody devices with a large surface footprint appears to result in a very high rate of effective fusion, despite the use of a small volume of low-cost biological material. This potential change in the osteobiologics required to achieve high fusion rates may have a substantially beneficial impact on the economic burden inherent to spinal fusion.
RÉSUMÉ
BACKGROUND: Interbody fusion by open discectomy is the usual treatment for degenerative disk disease but requires a relatively long recovery period. The transforaminal posterolateral approach is a well-known standard in endoscopic spine surgery that allows direct access to the disk with progressive tissue dilation. The aim of this study was to assess the feasibility of percutaneous transforaminal interbody fusion (pTLIF) with insertion of an expandable or a standard rigid interbody implant for patients with degenerative disk disease with or without spondylolisthesis and for revision surgery. METHODS: Between 2009 and 2014, the pTLIF procedure was performed in 30 patients. Ten patients underwent insertion of a rigid implant (group A) and the remaining 20 underwent insertion of an expandable titanium interbody implant as the initial procedure (n = 10) (group B) or after failed back surgery (n = 10) (group C). Patient outcomes were scored with visual analogic scale (VAS), Oswestry disability index (ODI) and modified Macnab criteria. RESULTS: The mean follow-up period was 38 (17) (range 11 to 67) months. The outcome was excellent in 18, good in 10 and fair in 2. No poor results and no major complications were reported. No differences in VAS and ODI scores according to the study group were found. Median postoperative time until hospital discharge was 26 hours (20 to 68 hours). Postoperative values for VAS and ODI scores improved significantly (p<0.05) compared to preoperative data in all study groups. CONCLUSIONS: These preliminary results have shown the feasibility and efficacy of the pTLIF procedure using a posterolateral approach for the treatment of degenerative disk disease with or without spondylolisthesis up to grade 2 and in revision surgery. No significant differences in outcome were observed between an expandable and a rigid cage. Median postoperative time until hospital discharge was faster compared to standard TLIF (26 hours vs. 9.3 days).