The effect of expandable versus static lordotic interbody implants in minimally invasive spine surgery: patient reported outcomes, sagittal alignment, and restoration of disc height and foraminal height

Abstract

Background Pain and disability due to age-related spinal disorders are increasing due to a more active population placing greater demands on their musculoskeletal system. For patients requiring surgery, spinal fusion is typically indicated. Interbody fusion cages improve fusion rates and restore lordosis, disc height, and foraminal height. Static cages are offered in multiple conformations to account for anatomic variability; however, they have issues related to implant subsidence and loss of lordosis. Expandable cages were developed to address these drawbacks. Methods Patients treated with either static or expandable transforaminal lumbar interbody fusion devices (ProLift ® Expandable Spacer System) for the treatment of spondylolisthesis, degenerative disc disease, spinal stenosis, disc herniation, or degenerative scoliosis at L4-L5 or L5-S1 were chosen from retrospective data. Outcomes included radiographic and spinopelvic changes, patient-reported outcomes, and incidence of non-union and revision surgery. Results One hundred patients were included (Static: 50; Expandable: 50). Demographics between groups were similar, with some differences in comorbidities and spinal disease diagnosis. Radiographically, changes in disc height, foraminal height, and lordosis were significantly improved in the Expandable group up to 2 years (P<0.001). Improvements in patient reported outcomes were more favorable in the Expandable group. Conclusions In patients who underwent transforaminal lumbar spinal fusion via minimally invasive surgery, the Expandable device group demonstrated significantly improved radiographic and patient reported outcomes compared to a static cage over 2 years.

Comparing expandable and static interbody cages in lumbar interbody fusion

“…Kucharzyk reported lower nonunion rates in the expandable compared to static group (6% vs. 12%) and lower revisions surgery rates (4% vs. 8%) which was statistically insignificant. Even with the variable rates of subsidence previously noted, fusion rates have been reported to be similar between groups ( 13 ). The meta-analysis by Alvi et al found fusion rates to be 75% in expandable and 90% in static (P=0.3) and noted that the type of bone graft affects fusion which was not well documented in many of the studies ( 7 ).…”

“…Kucharzyk et al reported that improvement in both ODI and VAS back pain to be significantly more favorable in the expandable cage group at all study visits up to two years and the VAS leg pain to be improved in expandable cage group only at 2 years ( 13 ). Massie et al reviewed 44 patients undergoing MIS TLIF for spondylolisthesis and found correction of segmental angle and sagittal vertical axis at the 90-day visits ( 18 ).…”

“…With pleasure, we further discuss the paper by Kucharzyk et al “The effect of expandable versus static lordotic interbody implants in minimally invasive spine surgery: PROs, sagittal alignment and restoration of disc height and foraminal height” ( 13 ). In their retrospective review of 100 patients across multiple lumbar pathologies (degenerative disc disease, spondylolisthesis, spinal stenosis, disc herniation, and degenerative scoliosis) the authors aimed to investigate multiple outcome metrics clinically and radiographically over a two-year postoperative period following MIS-TLIF with either a static polyether-ether-ketone (PEEK) spacer or an expandable interbody spacer.…”

“…The study by Kucharzyk et al brings forward additional evidence regarding the utility and benefits of expandable versus static interbody cages when used in the MIS TLIF technique ( 13 ). Many previous investigations have contradictory results for each cohort making it difficult for surgeons to guide their surgical decisions.…”

“…Pain generators come from compression of the intervertebral space, vertebral endplates, facet joints, and nerve roots. The study by Kucharzyk finds significant improvements between preoperative and postoperative radiographic changes favoring expandable cages over static cages that are maintained throughout 2-year follow up, but literature supporting significantly improved radiographic changes favoring one cage type has not been as clearly delineated ( 13 ). Armocida et al reported in a retrospective study of 65 patients (40 static, 25 expandable) over 1 year found there to be no significant changes between each groups’ SL, ADH, PDH ( 6 ).…”