Letter to the Editor: Learning curve considerations in lateral-approach total ankle replacement

Abstract

This letter comments on a retrospective cohort study published in World Journal of Orthopedics by Liszka et al, examining the learning curve of lateral-approach total ankle replacement (TAR) using the Zimmer™ system. The study provides a multidimensional evaluation of surgeon performance by integrating patient-reported outcome measures, operative efficiency, and complication profiles. Notably, improvements in pain and function, assessed using the Manchester-Oxford Foot Questionnaire and the European Foot and Ankle Society score, were consistent from the earliest cases, suggesting early stabilization of patient-reported outcomes despite increasing surgical experience. In contrast, operative time and complication rates improved progressively and plateaued after approximately 25-30 cases, reflecting maturation of technical proficiency. This article highlight key methodological strengths, including single-surgeon consistency, validated outcome measures, and structured learning-curve analysis, while also addressing limitations related to retrospective design, attrition, procedural heterogeneity, and generalizability. The concentration of infection-related complications in patients with inflammatory arthritis underscores the importance of careful patient selection and preoperative optimization, particularly during the early learning phase. Overall, the in-press study contributes meaningful insights into the learning dynamics of lateral-approach TAR and informs surgical training, credentialing, and future prospective investigation.

Key Words: Total ankle replacement; Learning curve; Lateral approach; Patient-reported outcome measures; Surgical complications

Core Tip: This letter highlight that in lateral-approach total ankle replacement, patient-reported pain and functional outcomes can stabilize early in a surgeon’s experience, while operative efficiency and complication rates continue to improve with increasing case volume. By integrating validated outcome measures with technical and safety metrics, the in-press study demonstrates that the learning curve of this complex procedure is multidimensional rather than linear. Careful patient selection and preoperative optimization-particularly in patients with inflammatory arthritis-remain critical during the early learning phase, and structured training pathways may facilitate safer adoption of the lateral approach.

TO THE EDITOR

The expanding role of total ankle replacement (TAR) in the management of end-stage ankle arthritis has renewed interest in understanding procedure-specific learning curves, particularly for technically demanding approaches[1,2]. Among these, the lateral approach-while offering excellent visualization and alignment control-has historically raised concerns regarding operative complexity and complication risk during early adoption[1,2]. The in-press retrospective cohort study commented on here provides a timely and nuanced exploration of these issues by examining the learning dynamics of lateral-approach TAR using the Zimmer™ system.

A major strength of the study is its multidimensional evaluation of surgeon performance, integrating patient-reported outcome measures (PROMs), operative efficiency, and complication profiles rather than relying on a single surrogate of proficiency. Such an approach is particularly appropriate in TAR, where success is ultimately defined by pain relief and functional restoration, not operative speed alone. The use of validated PROMs-the Manchester-Oxford Foot Questionnaire and the European Foot and Ankle Society score-adds methodological robustness and enhances the clinical relevance of the findings. While these instruments provide robust early indicators of patient-perceived success, the possibility of ceiling effects in PROMs should be acknowledged. Such effects may partly explain why PROMs appear to stabilize early in the learning curve, despite continued improvements in technical performance and complication profiles.

Notably, the study demonstrates that improvements in pain and function were achieved consistently from the earliest cases, with no significant variation in functional gains across chronological quartiles. This observation challenges the assumption that early-phase TAR necessarily compromises patient-reported outcomes and suggests that, with careful case selection and standardized technique, acceptable functional results can be attained even during the initial learning phase. Such findings are reassuring for surgeons transitioning to the lateral approach and support its safe introduction within structured practice environments. Cautions should be exercised comparing available evidence in real-world practice[3].

In contrast, operative time and complication rates showed a more traditional learning curve, with progressive improvement and stabilization after approximately 25-30 cases. This divergence between early stabilization of PROMs and delayed maturation of technical efficiency underscores the multifaceted nature of surgical learning. The study’s pragmatic division of experience phases based on operative time provides a clinically intuitive framework that is readily interpretable and relevant to surgical training and credentialing discussions. However, this threshold should not be interpreted as universal; it likely reflects a composite influence of procedure complexity, implant-specific instrumentation, and individual surgeon experience, with important implications for training pathways and credentialing standards.

I read with great interest the recent article by Liszka et al[4] published in World Journal of Orthopedics. Their decision to analyze complications in a structured manner-distinguishing reoperations from conservatively managed events and applying internationally accepted infection criteria-further strengthens the validity of the safety analysis[4]. Of particular interest is the observation that infection-related complications clustered in patients with inflammatory arthritis. While the study is not powered to establish causality, this finding highlights the critical importance of patient selection and preoperative optimization, especially during the early phase of the learning curve, and reinforces principles already well recognized in complex joint arthroplasty. This observation should be interpreted as an association rather than a causal relationship, as confounding factors such as immunomodulatory therapy, disease severity, and comorbidity burden may contribute and warrant cautious extrapolation to broader patient populations.

Several limitations, inherent to the study design, deserve consideration. The retrospective nature of the analysis introduces potential selection and information biases, while attrition due to incomplete follow-up reduces the final sample size. Additionally, although the single-surgeon design enhances internal consistency and allows clearer attribution of learning effects, it limits generalizability across surgeons with differing backgrounds, volumes, and institutional support. The heterogeneity introduced by concomitant and secondary procedures, while reflective of real-world practice, also complicates interpretation of outcomes attributable solely to TAR or surgeon experience. Furthermore, learning curves derived from high-volume specialist centers may not directly translate to lower-volume clinical environments, where differences in case exposure, team experience, and institutional infrastructure may significantly influence outcomes.

Another important consideration is the absence of a standardized postoperative rehabilitation protocol, which may have influenced functional recovery and introduces an additional layer of variability. Future prospective studies incorporating protocolized rehabilitation and risk-adjusted analytical methods, such as cumulative sum or time-to-event analyses, may further refine understanding of TAR learning dynamics.

CONCLUSION

Despite these limitations, the in-press study makes a meaningful contribution to the evolving TAR literature by demonstrating that patient-reported outcomes can stabilize early, even as technical proficiency continues to mature. By clearly delineating the distinct trajectories of functional recovery and operative performance, the authors provide valuable insights for surgeons, training programs, and institutions considering adoption of the lateral approach. Ultimately, this work advances the conversation on how learning curves in TAR should be interpreted-not as barriers to adoption, but as frameworks for safer implementation, targeted training, and future prospective investigation. Taken together, these considerations clarify the scope, applicability, and interpretive boundaries of the findings, strengthening their relevance for surgical education, credentialing, and real-world clinical implementation.