Beyond bar configuration: redefining pectus excavatum repair from deformity correction to complete chest wall remodeling

Introduction

Over the past two decades, minimally invasive repair of pectus excavatum (MIRPE) has undergone a fundamental paradigm shift (1). Historically centered on single-bar placement to alleviate cardiopulmonary compression (2) and cosmetic distress, the procedure has evolved into a comprehensive strategy aimed at total chest wall remodeling. To achieve complete morphological correction while maximizing surgical safety, the surgical repertoire has expanded dramatically. Advanced multi-bar constructs are now deployed, ranging from parallel, cross, and XI configurations (3) to complex quadruple-bar repairs (4). Concurrently, technical advances have enhanced procedural safety by including sternal elevation (e.g., the crane technique), and mediastinal dissection, adjunctive procedures (to address costal flaring and focal protrusions) (3), and novel stabilization strategies (like bridge fixators and hammock stitches to prevent bar displacement and intercostal muscle stripping) (3).

Despite the technological advancements and accumulating global experience, expert consensus regarding the optimal reconstructive strategy remains elusive. Marked practice variation persists, driven in part by heterogeneous patient demographics spanning pediatric, adolescent, adult, and revision cohorts. This divergence is exemplified by contrasting philosophies among leading centers: while some centers maintain that refined stabilization techniques allow single-bar repairs to suffice in up to 50% of cases (1), others routinely advocate for standard double- or triple-bar constructs to distribute load across the anterior chest wall (3). While single-bar repairs carry the potential risks of incomplete correction and focal pressure concentration, multi-bar constructs potentially introduce trade-offs regarding operative time, cost, surgical trauma, and complexity during subsequent hardware removal (1).

In a recent systematic review and meta-analysis published in the Journal of Thoracic Disease, D’Ambrosio and colleagues (5) provided valuable insights into this ongoing debate by evaluating multi-bar MIRPE practice. Analyzing 1,021 patients across 449 cross-bar and 572 parallel-bar repairs, the authors evaluated key perioperative and efficacy outcomes. No differences were observed in operative times, length of hospital stay, and reported rates of specific complications (pleural effusion and pneumothorax) between the two approaches. While cross-bar repair yielded a statistically significant but clinically minor improvement in postoperative Haller Index (mean difference =−0.10), the overall certainty of evidence across outcomes was low to very low with moderate-to-serious risk of bias (5). Importantly, the greatest strength of D’Ambrosio and colleagues’ study may not lie in determining whether parallel- or cross-bar configurations are superior, but in clarifying why this question remains difficult to answer.

Comparing techniques, or comparing patients?

D’Ambrosio and colleagues provide a commendable synthesis of a clinically relevant topic, offering needed structure to the literature on multi-bar MIRPE. However, as the authors appropriately point out in their discussion, the clinical dilemma is rarely as simple as choosing one bar configuration over another. It is a matter of tailoring a reconstructive construct to an individual patient’s anatomy. The fundamental issue is that the currently available literature does not truly compare two interchangeable surgical techniques, but rather two distinct patient cohorts. Asking whether a cross-bar configuration is superior to a parallel-bar configuration assumes that surgeons choose between them under identical clinical conditions. In practice, however, cross-bar configurations are typically reserved for older patients, and those with complex deformities or deformities of the lower sternum and adjacent costal margins, including asymmetric and more rigid chest walls. Consequently, a substantial degree of confounding by indication is inherent in the published evidence. In addition, surgeon experience plays a role in both configuration selection and clinical outcomes. Because cross-bar repairs were only recently approved in several regions, surgical teams may still be in their early learning curves compared to their long-standing experience with parallel bars. Rather than evaluating equivalent interventions in comparable patient cohorts, the literature compares relatively straightforward deformities treated with familiar parallel-bar configurations versus complex deformities managed with novel cross-bar constructs. Thus, bar configuration may primarily serve as a surrogate marker of deformity complexity and morphology, while also reflecting differences in surgeon experience, rather than an independent determinant of surgical outcome.

Morphological blind spots

A deeper paradox within current pectus literature emerges around the recommendation that surgical techniques should be tailored to chest wall morphology (5). While this principle is intuitively correct and widely supported, morphology itself is rarely objectively defined across clinical studies. Current characterization remains largely reliant on the Haller index. This index is knowingly limited to a rudimentary, two-dimensional description of a complex three-dimensional deformity. It fails to capture morphological features such as asymmetry, sternal rotation, deformity width, location of the deepest point, and lateral chest wall involvement. Yet these are precisely the characteristics that drive a surgeon’s decision to select a specific reconstructive strategy. In clinical practice, these complex anatomical variations are better represented by distinct morphological subtypes, such as cup-shaped, saucer-shaped, and trench-like deformities (6). These variations underline a clear clinical reality: different subtypes require different surgical strategies. There is simply no one-size-fits-all approach. However, consensus on how to objectively define and classify these subtypes remains lacking. Because current classifications rely primarily on visual inspection and imaging, they have inherent limitations and exhibit substantial inter- and intra-observer variability (7,8). In other words, anatomical variables remain unstandardized, and often entirely uncaptured, across the available evidence base. This observation extends beyond the current meta-analysis; it reflects a broader challenge within the field of pectus surgery. As long as current primary metrics fail to adequately characterize three-dimensional morphology, comparative studies evaluating surgical techniques will continue to suffer from the same limitations. Ultimately, the primary value of this synthesis lies not in determining whether parallel or cross bars are superior, but in demonstrating that the field currently lacks the morphological framework required to ask the right question.

Addressing this limitation requires a comprehensive evaluation of the entire thorax, instead of evaluating only the point of maximal depression (9). To achieve this, three-dimensional computed tomography reconstruction or three-dimensional surface imaging (10) may serve as the cornerstone of preoperative planning. Critical anatomical variables can help provide a more objective framework to support this shift, including: chest asymmetry, sternal shape [including the retrosternal angle for banana sternum (11)], sternal rotation, the cephalocaudal extent of the deformity [e.g., titanic index (12)], bilateral inferior costal depression, costal flaring, platythorax, and posture.

The future: precision pectus surgery

The transition to objective evaluation of the entire thorax can be propelled by emerging technologies, such as artificial intelligence-assisted planning to enable patient-specific bar design, and digital twins.

The clinical value of dynamic, biomechanical digital twins will particularly be evident in anatomically challenging cases, where conventional planning methods fail to capture patient-specific variability (13). By replicating an individual patient’s unique thoracic anatomy and biomechanical properties, such as chest wall rigidity, digital twins could enable surgeons to rehearse complex procedures and test different surgical scenarios under varying conditions prior to skin incision. In practice, this technology could enable virtual simulation of forces from different bar configurations, allowing AI-assisted planning to predict the optimal number, shape, and placement of bars. This predictive capability could achieve ideal chest wall correction while minimizing both chest wall tension and surgical complications. Ultimately, integrating digital twin technology throughout all surgical stages has the potential to enhance precision and safety (14), and may shift pectus surgery from an intuitive craft to a predictable, personalized science. Achieving this translation over the next decade will require close inter- and multidisciplinary collaboration to bridge the gap between digital modeling and the operating room (14). Ultimately, this collaborative effort will allow us to reframe the debate from “Parallel versus cross: which is superior?” to “Which patient characteristics and chest wall morphology require which reconstructive strategy?”. Viewed from this perspective, the evolution of pectus surgery can be divided in three phases: first, the historical transition from single- to multiple-bar repairs; second, the current discussion surrounding parallel versus cross-bar configurations; and finally, the next frontier in pectus surgery is not determining which configuration is best, but defining for whom it is best.

D’Ambrosio and colleagues should be commended for their valuable efforts in synthesizing a complex and highly heterogeneous body of literature on parallel- versus cross-bar configurations. Their study highlights the critical need for a deeper, more objective understanding of chest wall morphology to guide surgical decision-making. However, until we exceed the limitations of two-dimensional metrics like the Haller index, comparing these surgical techniques head-to-head will remain highly susceptible to confounding. Therefore, the primary focus of the pectus community should now shift toward establishing standardized, three-dimensional morphological classification. By embracing these advancements and fostering multidisciplinary collaboration, we can move closer to an era of personalized, anatomy-driven pectus surgery.

Supplementary

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Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.