Expandable Interbody Fusion Cages: An Editorial on the Surgeon's Perspective on Recent Technological Advances and Their Biomechanical Implications

Abstract

Background: Expandable cages have gone through several iterations since they first appeared on the market in the early 2000s. Their development was prompted by some common problems associated with static interbody cages, including migration, expulsion, dural or neural traction injury, and pseudarthrosis.Objective: To summarize current technological advances from earlier expandable lumbar interbody fusion devices to implants with vertical and medial-to-lateral expansion mechanisms.Methods: The authors review the currently available expandable cage designs, the incremental technological advances, and how these devices impact minimally invasive surgery interbody procedures and clinical outcomes. The strategic concepts intended to improve the minimally invasive application of expandable interbody fusion implants are reviewed from a surgeon's perspective in a clinical context to discuss how their use may improve patient outcomes.Conclusions: The geometrical configuration, effective stiffness of composite multi-material cage designs may impact the bone-implant contact area with the endplates. Hybridization strategies of expandable cage technology with modern minimally invasive and endoscopic spinal surgery techniques are presented by outlining their advantages and disadvantages.

Comparison of Transforaminal Lumbar Interbody Fusion in the Ambulatory Surgery Center and Traditional Hospital Settings, Part 1: Multi-Center Assessment of Surgical Safety

“…There is a limited but growing body of clinical evidence supporting the clinical utility of minimally-invasive TLIF using a standalone expandable cage for the treatment of lumbar spinal disorders [ 7 , 22 , 23 ]. This is due, in large part, to the lack of FDA-approved implants for this indication with the VariLift ® cage having this rare distinction [ 12 ].…”

“…The continued expansion in the range of spinal surgeries undertaken in the ASC has mirrored technical developments that support increasingly less invasive operative approaches that minimize the size of the surgical “footprint” [ 5 , 6 ]. Lumbar fusion procedures such as transforaminal lumbar interbody fusion (TLIF) have enjoyed increasing clinical adoption in the ASC that correlates with significant advances in minimally-invasive approaches and technologies, such as the use of stand-alone expandable cages [ 7 ]. Indeed, Heemskerk et al [ 8 ] recently reported that patients treated with minimally-invasive TLIF have similar two-year clinical outcomes as patient having open TLIF.…”

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

“…Interbody fusion cages were introduced to improve fusion rates and restore lumbar lordosis, intervertebral disc height, and foraminal height ( 25 - 29 ). Initial designs of interbody fusion cages, also known as static cages, were offered in multiple different sizes and shapes to account for variability in patients’ anatomy ( 29 ).…”

Expandable vs Static Interbody Devices for Lateral Lumbar Interbody Fusion

“…[4][5][6] Interbody devices for anterior column support were first introduced as autografts in 1936. 7 They were historically designed to improve fusion between vertebral end plates, recreate lumbar lordosis, and restore intervertebral and foraminal height. Currently, structural devices are used in lieu of bone autograft spacers.…”

“…Initial structural devices were static in design; however, expandable devices are now available in an attempt to provide more individuality with correction of spinal alignment and potentially improve radiographic and clinical outcomes. 7 Insertion of expandable devices at minimal height allows for reduced impaction force and preservation of the end plate, thus theoretically mitigating the risk of end plate violation and device subsidence. In addition, insertion in a compressed state allows for less soft tissue disruption possibly reducing risk of lumbar plexus injury and postoperative thigh pain.…”