Decortication as an underreported determinant of fusion success in adult spinal deformity

A recent review on biologic fusion augments in adult spinal deformity (ASD) provides a comprehensive synthesis of contemporary grafting strategies and appropriately frames pseudarthrosis as a biological failure of angiogenesis and bone remodeling (1). The discussion of osteogenic, osteoconductive, and osteoinductive mechanisms is thorough and clinically relevant. Notably, however, within the section describing the authors’ preferred technique, it is stated that “the most important component of the fusion process is adequate decortication” (1). This statement, although presented briefly, raises an important methodological consideration for the interpretation of osteobiologic research in ASD. The biological rationale for decortication is well established. Cortical disruption exposes cancellous bone, promotes vascular ingrowth, and initiates the inflammatory cascade necessary for new bone formation. As cited in the review, experimental models demonstrate decreased tissue neoformation in the absence of decortication (2). More recent systematic evaluation of murine posterolateral fusion models confirms that decortication is a defining feature of successful fusion paradigms and is consistently incorporated in models achieving higher fusion rates (2). Contemporary technical investigations similarly emphasize that effective facet decortication is associated with improved fusion biology and seek to optimize methods of achieving adequate cortical breach even through percutaneous approaches (3). Thus, the importance of decortication itself is not novel. The novel issue arises from its implications. If adequate decortication is indeed the most important determinant of fusion success, as the authors state (1), then variation in fusion-bed preparation may represent an underrecognized confounder in comparative studies of biologic augments. In most ASD series, detailed reporting focuses on graft type, recombinant human bone morphogenetic protein-2 (rhBMP-2) dosage, interbody use, pelvic fixation, and number of fused levels. However, the extent, method, and anatomical completeness of decortication are rarely standardized or described. This omission is particularly relevant in long-segment deformity constructs, where biological demands are amplified and the lumbosacral junction is known to be a region of elevated nonunion risk. Recent higher-level ASD evidence underscores the need to distinguish structural augmentation from biological optimization. Cavagnaro et al. performed a systematic review and meta-analysis evaluating whether L5/S1 interbody fusion is necessary in long-segment constructs for adult degenerative scoliosis and found no clear reduction in pseudarthrosis with routine addition of interbody support (4). Similarly, Park et al., in a computed tomography (CT)-based 2-year follow-up study, reported a 15.6% rate of L5–S1 nonunion despite the use of anterior column support combined with iliac screw fixation (5). These findings indicate that additional structural or mechanical strategies alone do not uniformly eliminate pseudarthrosis risk. If enhanced fixation and interbody augmentation do not fully resolve nonunion, attention must logically return to the biological environment at the fusion interface. The reviewed article itself emphasizes meticulous exposure of the L5 transverse process, sacral ala, and inner iliac wing to create a graft “pocket” (1), highlighting the potential centrality of fusion-bed preparation at the lumbosacral junction. The new contribution of this correspondence is therefore methodological rather than conceptual. The established importance of decortication is not disputed. Rather, the concern is that decortication quality and extent are seldom treated as reportable variables in ASD research. If fusion-bed preparation varies across surgeons and institutions—and is not quantified—then comparisons among biologic agents may be biologically inequivalent. Differences attributed to rhBMP-2, demineralized bone matrix (DBM), or other augments could partially reflect variation in cortical breach, cancellous exposure, or regional graft containment. How can biologic efficacy be reliably compared if the biological substrate itself is not standardized? Furthermore, variability in decortication may help explain inconsistencies across trials evaluating similar biologic agents. When fusion rates differ substantially between studies using comparable graft materials, the explanation is often sought in dosage, carrier, or patient factors. Yet could differences in the biological activation of the fusion bed itself account for a meaningful portion of this variability? Without documentation of cortical disruption techniques or anatomical extent, it remains difficult to exclude this possibility. In this context, decortication should perhaps be considered analogous to a “dose-modifying” variable for osteobiologics—one that conditions the local environment in which these agents operate. Incorporation of minimal reporting parameters for fusion-bed preparation may strengthen future ASD studies. Such parameters could include: (I) method of decortication (burr, osteotome, curette); (II) anatomical extent (transverse processes, facet joints, sacral ala, iliac wing); (III) region-specific preparation at L5/S1; and (IV) distinction between primary and revision fusion beds. Even semi-quantitative descriptors would improve reproducibility and interpretability. Standardized reporting would not impose significant burden, yet it may substantially enhance cross-study comparability. Recognizing decortication as a measurable determinant—rather than a background assumption—may help reconcile variability in reported fusion rates across osteobiologic studies. Given that pseudarthrosis is fundamentally a biological failure of angiogenesis and bone formation (1), the surgical step that initiates vascular access to cancellous bone should be considered integral to outcome interpretation. In this light, the review’s acknowledgment that adequate decortication is the most important component of fusion may represent more than technical commentary—it may signal a necessary recalibration of how osteobiologic efficacy is evaluated. Reframing decortication as a reportable biological variable does not diminish the importance of graft innovation; rather, it situates biologic augmentation within its essential surgical context. Such refinement may ultimately strengthen both research methodology and clinical translation in ASD surgery.

Acknowledgments

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Footnote

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Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://asj.amegroups.com/article/view/10.21037/asj-2026-1-0015/coif). The authors have no conflicts of interest to declare.

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