Ambispective study of fusion and subsidence in degenerated L4-5/L5-S1 discs treated with oblique lumbar interbody fusion/anterior lumbar interbody fusion using 3D-printed titanium open arch cages.

BACKGROUND: Anterior lumbar interbody fusion (ALIF) is a common surgical procedure for treating degenerative discs in the lumbar spine. The popularity of ALIF continues to rise due to favorable reported outcomes, leading to the introduction of the oblique lumbar interbody fusion (OLIF) approach, which yields similar outcomes with less morbidity. Designs of cages are also evolving to improve fusion rate and optimize clinical outcomes. This study aims to evaluate the performance and safety of SPIRA cages (Camber Spine Technologies, King of Prussia, PA, USA), which are designed and constructed using a novel patented three-dimensional (3D)-printed titanium open-arch architecture design.

METHODS: This was a single center, ambispective study of consecutive patients previously treated with lumbar open-arch cages at L4-5 and/or L5-S1, with or without supplemental fixation. Prospective lumbar computed tomography (CT) scan at minimum 12 months postoperatively was used to define the primary study objectives, interbody fusion, and implant subsidence. The secondary objectives were to evaluate safety from the retrospective medical data, including adverse events (AEs) related to the device or procedure and any consequential follow-up operations/revisions. Study inclusion criteria selected patients with intractable back and/or leg pain having clinical and radiological evidence of lumbar degenerative disc at L4-5 and/or L5-S1 who failed 6 months of conservative treatment and had OLIF or ALIF surgeries from an oblique approach. The patients were at least 18 years of age and were able to provide informed consent to participate per study protocol.

RESULTS: A total of 33 subjects with 39 L4-5 and/or L5-S1 levels were included in the study. The cohort had a mean age of 57 years, a mean body mass index (BMI) of 32 kg/m2, and they were 60.6% female. All of the subjects had at least one comorbidity, and 78.8% (26/33) of subjects presented with two or more. Considering levels treated, L4-5 and L5-S1 were 43.6% (17/39) and 56.4% (22/39), respectively. The mean follow-up was 30 months. The interbody fusion rate was 97.44% and the occurrence of implant subsidence was 12.82% in the treated levels. There were no device-related complications reported, and a third of subjects experienced probable or direct procedure-related complications. The revision rate at the index level was 9.0%.

CONCLUSIONS: Surgeons have many options when selecting an interbody cage for treating a degenerative disc. While surgical technique is fundamental to interbody fusion efficacy and safety, the cage design has been shown to influence these factors since the cage design itself can promote bone growth and reduce the risk of subsidence. The current study reporting fusion and subsidence rates for the open-arch designed cages supports this novel design's efficacy and safety. The results of this study support the efficacy of the open-arch cage design, which has focused on promoting interbody fusion and minimizing subsidence while maintaining implant safety.