Effect of mixed reality glasses combined with mannequin training on lumbar puncture simulated performance in medical interns: a pilot randomized controlled trial

Lumbar puncture is a core procedural skill that medical interns must master, yet its training has long been hampered by the invisibility of internal anatomy and the abstract nature of needle trajectory. Conventional mannequin training offers a safe practice environment but is limited in developing learners’ three-dimensional spatial cognition. Mixed reality (MR) technology can overlay a virtual three-dimensional bony image onto the real world, potentially addressing the spatial-cognition challenge inherent to “blind” procedural skills. This pilot randomized controlled trial (RCT) was designed to provide preliminary evidence on whether MR glasses combined with mannequin training improve lumbar puncture skills in medical interns compared with mannequin-only training. This single-centre, parallel-group, assessor-blind pilot RCT enrolled 30 clinical interns with no prior lumbar puncture experience, randomized 1:1 to a simulation-only group (SM, n = 15) or a mixed-reality-plus-simulation group (MR, n = 15). Both groups received a standardized didactic lecture, an initial mannequin practice, and a baseline skills assessment. In the second practice session, the SM group completed two additional conventional mannequin practices, while the MR group completed two practices assisted by a static holographic lumbar spine overlay (Microsoft HoloLens); total practice duration was 1.5 h in both groups. After the intervention, performance was evaluated with a self-developed lumbar puncture skill assessment scale (100 points, 6 dimensions), scored independently by two blinded neurosurgeons. The principal outcome was the post-intervention total lumbar puncture skill score, analysed with analysis of covariance (ANCOVA) using baseline score as a covariate. Because the trial was not prospectively registered, the principal outcome and the ANCOVA approach were designated after data verification revealed a substantial baseline imbalance and are reported as post hoc rather than prospectively prespecified. The core-puncture procedure subscale was designated as a key secondary outcome. At baseline, the SM group scored higher than the MR group (62.67 ± 1.80 vs. 59.73 ± 2.05, t = 4.16, P < 0.001), so the principal analysis adjusted for baseline using ANCOVA. After the intervention, the MR group achieved a significantly higher total score than the SM group (97.93 ± 2.40 vs. 84.67 ± 4.70; adjusted between-group difference 17.29 points, 95% CI 14.74–19.85; F(1,27) = 192.82, P < 0.001, partial η²=0.88). For the core-puncture subscale, the baseline×group interaction was significant ( P = 0.047; non-parallel slopes), so the effect is reported as the simple effect of group at the mean baseline score (5.79 points, 95% CI 2.48–9.10; P = 0.001) rather than a single pooled adjusted difference. A sensitivity analysis excluding the core-puncture subscale also showed a significant group difference (simple effect 7.35 points, 95% CI 6.63–8.06, P < 0.001; interaction P = 0.002); this indicates the total-score difference was not solely driven by the core-puncture dimension, but because this outcome also showed non-parallel slopes the estimate is descriptive rather than a definitive adjusted inference. Because pronounced ceiling effects in the MR group mechanically inflate standardized effect sizes, all effect sizes are interpreted together with the absolute score differences and their confidence intervals. In the MR group, 93.3% of interns agreed or strongly agreed that the MR glasses enhanced their confidence and accuracy; these data are reported only as acceptability. In this small single-centre randomized study, MR-assisted mannequin training was associated with higher immediate post-training performance on a simulated lumbar puncture task than mannequin-only practice. Larger studies with validated outcome measures, delayed retention testing, and assessment of transfer to clinical practice are needed. This exploratory pilot trial was not prospectively registered.