In Reply: Delineating Neurosurgery Resident Development: Insights From a Ten-Year National ACGME Milestones and Learning Trajectories

We thank the authors for their insightful commentary1 on our article, “Delineating Neurosurgery Resident Development: Insights from a 10-Year National Accreditation Council for Graduate Medical Education (ACGME) Milestones and Learning Trajectories”.2 Their observations resonate with longstanding themes in competency-based medical education, including the influence of assessor effects, heterogeneous faculty development, and variability in Clinical Competency Committee processes.3-7 Recent large-scale studies in multiple specialties reinforce that Milestone ratings—despite potential biases—demonstrate meaningful signals that link with important outcomes in early physician practice. For instance, Han and colleagues examined 9340 trainees across many fields and found that residents with Milestones below the recommended “proficient” threshold in professionalism (P) and interpersonal and communication skills had significantly higher odds of patient complaints in the first year of independent practice. Although this odds ratio was modest (1.2), it nevertheless points to a tangible link between educational outcomes (measured using Milestones performance) and post-training outcomes.8 Similarly, among those training in general surgery, Smith et al9 demonstrated that vascular surgery trainees' Milestones performance near graduation were associated with complication rates after endovascular aortic aneurysm repair, indicating that even incremental changes in Milestone ratings may translate into clinically meaningful differences. Parallel research by Hauer et al and by Bienstock et al10,11 in internal medicine and obstetrics/gynecology, respectively, found moderate but consistent associations between Milestone ratings and standardized assessments. Collectively, these findings underscore that educational outcomes measured using Milestones can serve as a significant predictive measure, albeit with variability in the strength of association across specialties and subcompetencies. Although these results validate the fundamental purpose of the Milestones framework, the literature also highlights persistent challenges. The lack of assessor training and assessment structure may lead to inconsistent evaluations, as can “grade inflation” in certain programs.12,13 Reliance on a single data point (construct underrepresentation) risks misclassification and threats to validity, making repeated measures over time essential to derive stable performance trajectories. Furthermore, multiple authors note that existing assessments may insufficiently capture “softer” domains such as professionalism, interpersonal skills, self-regulated learning, and adaptability, which are central to lifelong learning. Equally pressing are equity concerns: studies show that residents from underrepresented or marginalized backgrounds may be disproportionately affected by subtle biases in Milestones assessments.14,15 Targeted faculty development and clearer rating criteria are necessary to limit these inequities and increase transparency. The neurosurgical training context introduces additional complexity. Our analysis of neurosurgery residents revealed five distinct developmental clusters, confirming the heterogeneity in developmental progression among trainees. One subgroup began at a low baseline yet eventually exceeded independence benchmarks, illustrating the adaptability of neurosurgical curricula and reinforcing the principle that early identification of at-risk learners paired with structured interventions—such as simulation-based skill training or dedicated mentorship—can favorably alter trajectories. Another subgroup plateaued during midresidency, suggesting that postgraduate year 2 to postgraduate year 3 constitutes a high-leverage period for remediation and enhanced feedback, as corroborated by other specialties.2 We concur with the call of letter writers for more practical guidance on how best to implement these targeted interventions in real-world neurosurgical programs. Although simulation-based training and individualized learning plans are known to be effective, further prospective studies could bolster the evidence that these strategies measurably decrease complications, accelerate competency, and address reported plateaus in progress. Dedicated faculty development on the principles of Clinical Competency Committee best practices would also be essential to ensure that Milestones ratings remain consistent and free from intrinsic or systemic biases, which is a particular concern in high-stakes fields such as neurosurgery. We likewise echo recommendations for longitudinal and multi-institutional research. By merging large Milestones data sets with long-term follow-up data—such as board certification, clinical performance indices, malpractice incidents, and patient experience measures—we can establish more comprehensive models of how different educational pathways influence eventual practice outcomes. Such studies will require overcoming multiple data-sharing hurdles across programs, institutions, and boards, but the promise of more robust correlations between training performance and patient-level outcomes justifies these efforts. In conclusion, although our study affirms the value of Milestones as an organizing framework for neurosurgical resident assessment, these findings—together with the studies cited—reveal important directions for improvement. We strongly endorse the calls of letter writers to heighten the fidelity of Milestones data through faculty development, address equity issues by enhancing assessment operational protocols and analyzing disaggregated outcomes, and extend sustained and continuous studies beyond graduation to link Milestones to meaningful patient care measures. With consistent, rigorous implementation and ongoing refinement, the Milestones assessment framework can evolve into a powerful, equitable, and truly predictive tool for developing the next generation of neurosurgical leaders and ultimately improved health care for patients and the public.