Interbody Fusion: Are We Posing the Right Questions or Simply Caught up in Abilene Paradox?

Lumbar interbody fusion techniques, comprising PLIF, TLIF, LLIF, OLIF, and ALIF have gained considerable acceptance in the surgical management of degenerative disorders of the lumbar spine.[1,2] Despite initially being proposed for spondylolisthesis, some of these methods (both open and minimally invasive) have become workhorse approaches for a variety of indications, including refractory low back pain. The primary aim remains the removal of the pathological disc, decompression of the involved nerve root, restoration of the disc space height, and lumbar lordosis using spacers and bone grafts, providing a stable biomechanical fusion. The efficacy of artificial cages is often debated in comparison to iliac crest graft, local bone grafts, bone grafts along with Bone Morphogenetic Protein (BMP), and bone graft expanders for lumbar interbody fusion procedures.[3] The proponents of spacer or cage usually claim immediate anterior interbody support, better restoration of lumbar lordosis, and preservation or augmentation of disc space height till the time of bony fusion. At the same time, concerns have been raised related to the cost, lower fusion rate, retropulsion or migration of the cage, risk of injury to the nerve root, dural sac, and endplates. Comparative studies on PLIF often favoured the use of cages over local bone grafts. Abdul et al. noted better restoration of disc space height and pain scores using cages with similar fusion rates of 86%.[4] Yu et al. observed a superior Oswestry Disability Index (ODI), disc space height, lumbar lordosis, and bony fusion with cages when compared to local bone grafts mixed with allograft.[5] However, studies on TLIF had varied findings compared to PLIF. Lv et al. noted comparable outcomes with morselized local grafts and cages in 180 patients followed for a mean period of 35 months.[6] They emphasize that continued impaction of the graft fragments into the disc space facilitated close apposition between the pieces and the graft bed, thereby achieving satisfactory biomechanical integrity, good fusion, and symptomatic improvement. The disc height to the vertebral body ratio was equally preserved with similar fusion rates (94%). Similarly, Govindasamy et al. in 30 patients of low-grade listhesis, noted local bone grafts to be equally efficient in maintaining disc space and foraminal heights as cages, with no significant difference in the time to achieve bony fusion.[7] Zhong et al. analyzed the outcome findings of TLIF between the young and elderly.[8] They advocated cages in young patients for long term maintenance of the intervertebral space and foraminal heights, while recommending bone grafts among the elderly for earlier bony fusion. In the study by Chandra et al.,[1] most outcome parameters were similar between minimally invasive transforaminal (TLIF) and oblique lumbar interbody fusion (OLIF). While OLIF had longer duration of surgery, it resulted in earlier recovery probably due to better lordotic correction. In this era of minimally invasive and endoscopic spinal procedures,[2,9] it may not be feasible to get a sufficient volume of local grafts to fill the disc space, especially when laminectomy is either not needed or previously undergone. Moreover, the choice of size and angulation required in the restoration of the lumbar lordosis with a prefabricated cage will not be available with local bone fragments. Most studies have tried to compare and analyse which surgical corridor (PLIF, TLIF, etc.)?, which fusion technique (open or minimally invasive)?, how fusion occurs?, which interbody device?, which type of graft?, whether to use BMP? and which pedicle screw system? is better for lumbar spine fusion than the rest.[2,3,10] But there are hardly a few studies that pose the question of whether fusion is needed at all.[11] Maybe we need to start confirming the diagnosis of degenerative disc disease by ruling out other causes, elicit differences in the chief complaints between low backache, radicular pain, neurogenic claudication, and then analyse the impact of surgical procedures on both disability and pain.[4,5,12-14] Fusion procedures are undoubtedly helpful for patients of listhesis with refractory low backache. But others may benefit most from decompression alone,[11] while the apparent benefit of fusion procedures is probably due to the associated direct or indirect neural decompression. Hopefully, we will ask the right questions rather than assuming what everyone would prefer and get caught in the web of Abilene Paradox.[15]