On June 16, 2023, a search was conducted using PubMed, MEDLINE, EBSCOhost, and Google Scholar to find studies that assessed the learning curve for RA- and CN-THA that were published between January 1, 2000, and June 16, 2023. The Boolean operators “AND” or “OR” were combined with the following keywords and Medical Subject Headings (Mesh): (“Arthroplasty, Replacement, Hip”[Mesh] OR “Arthroplasty, Replacement”[Mesh] OR “total hip arthroplasty” OR “THA”) AND (“Robotics”[Mesh] OR “robotic*” OR “Surgery, Computer-Assisted”[Mesh] OR “Robotic Surgical Procedures”[Mesh] OR “robotic arm” OR “computer navigated”) AND (“Learning Curve”[Mesh] OR “learning” OR “curve” OR “train*” OR “skill*” OR “development” OR “education” OR “proficiency”).

Eligible articles included studies that had (1) full-text manuscripts in English and (2) evaluated the learning curve in adopting CN-THA. The following articles were excluded from the analysis: (1) case reports, (2) reviews, (3) duplicate articles, (4) gray literature (preprint server articles, posters, and abstracts), and (5) articles not written in English.

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed in conducting this review (PROSPERO registration: CRD42023394031, June 27, 2023). After deleting duplicates, 655 articles were returned by the query. Each unique article retrieved via the search term was evaluated for eligibility by two independent reviewers (PAS, JRP). To reach consensus, any differences were consulted with a third reviewer (CJH). Forty-eight papers were eligible for a full-text evaluation after title and abstract screening, with nine meeting all criteria for inclusion in the present analysis. No further studies were found when the reference lists for each article were reviewed (Fig. 1).

This PRISMA diagram depicts the selection process for article information

Using the MINORS tool, two independent reviewers (PAS, JRP) evaluated the bias risk [26]. Using 12 criteria regarding the rigor of the study design, outcomes assessed, and follow-up, this verified grading method assigns comparative studies a score between 0 and 24, with higher scores denoting higher quality research. Grading disagreements were settled by reaching a consensus with a third reviewer (CJH). The average MINORS score was 21.3 ± 1.2.

Two methods were used to evaluate the learning curve: (1) temporally evaluating a surgeon’s performance over their initial versus later CN-THA cases and (2) comparatively comparing initial CN-THA case outcomes versus outcomes achieved via other THA approaches (namely M-THA). Outcomes of interest included operative time, accuracy of acetabular component placement, radiographic accuracy (LLD and offset), functional outcomes, radiation exposure, and postoperative adverse events. No studies included in the review compared complication profiles during the learning curve. The accuracy of acetabular component placement was assessed with anteversion and inclination (i.e., average values, target value deviations, and safe zone outliers). As the included studies had substantial methodologic heterogeneity, a meta-analysis was not conducted; rather, we conducted a narrative synthesis by presenting and synthesizing key findings. When available, we reported quantitative data for positive findings and qualitative data for negative findings. Likewise, due to substantial heterogeneity in the comparison cohorts among studies, we were unable to visually represent the acetabular component placement accuracy metrics via Bland-Altman plots for both the temporal and comparative assessments of the CN-THA learning curve.

Included in the final analysis were a total of nine studies assessing 847 THAs [21,22,23,24,25, 27,28,29,30] (Table 1). Six studies assessed the learning curve temporally [21, 23, 25, 27,28,29] and six assessed the curve comparatively [22,23,24, 28,29,30]. Patient characteristics, follow-up timeframes, THA approach, type of acetabular implant, and computer-navigated platform utilized varied among articles (Table 1).