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To the Editor It is with great interest that we read the article "Efficacy of Liposomal Bupivacaine and Bupivacaine Hydrochloride vs Bupivacaine Hydrochloride Alone as a Periarticular Anesthetic for Patients Undergoing Knee Replacement: A Randomized Clinical Trial." 1 We find it encouraging that this large, relatively homogeneous trial has confirmed that the traditional form of bupivacaine is comparable on multiple outcomes such as opioid use, adverse events, and long-term functional outcome. In addition to clinical outcomes, traditional bupivacaine is also shown to be significantly more cost-effective compared with the liposomal vehicle.We are intrigued by the suggestion by Hamilton et al 1 that certain subgroups may benefit from periarticular liposomal bupivacaine injections. Which subgroups might fall into this category? We wonder whether subgroups based on variation in surgical technique (ie, tourniquet application) 2 and patients' psychological factors (eg, pain catastrophizing, anxiety, depression) 3 may influence pain score and opioid consumption after knee replacement surgery.The potential implication of the differing pharmacokinetics of these 2 formulations are also of interest to us. Given the longer half-life of the liposomal bupivacaine, was longer observation required compared with traditional bupivacaine? Given that these patients were given more than double the dose of the bupivacaine hydrochloride, it seems feasible that toxicity would have been a concern. 4 Are there any data on occurrence or timing of any analgesia-related toxicity?Given the ultimate goal of opioid-free surgery, perhaps further investigation regarding higher dosages of the liposomal bupivacaine or differing mixture ratios of standard to liposomal bupivacaine may yield improvements in nonopioid postoperative pain management.

BACKGROUND AND OBJECTIVES: Anterior cervical discectomy and fusion (ACDF) is among the most common spine procedures. The Sim-Ortho virtual reality simulator platform contains a validated ACDF simulated task for performance assessment. This study aims to develop a methodology to extract three-dimensional data and reconstruct and quantitate specific simulated disc tissues to generate novel metrics to analyze performance metrics of skilled and less skilled participants. METHODS: We used open-source platforms to develop a methodology to extract three-dimensional information from ACDF simulation data. Metrics generated included, efficiency index, disc volumes removed from defined regions, and rate of tissue removal from superficial, central, and deep disc regions. A pilot study was performed to assess the utility of this methodology to assess expertise during the ACDF simulated procedure. RESULTS: The system outlined, extracts data allowing the development of a methodology which accurately reconstructs and quantitates 3-dimensional disc volumes. In the pilot study, data sets from 27 participants, divided into postresident, resident, and medical student groups, allowed assessment of multiple novel metrics, including efficiency index (surgical time spent in actively removing disc), where the postresident group spent 61.8% of their time compared with 53% and 30.2% for the resident and medical student groups, respectively (P = .01). During the annulotomy component, the postresident group removed 47.4% more disc than the resident groups and 102% more than the medical student groups (P = .03). CONCLUSION: The methodology developed in this study generates novel surgical procedural metrics from 3-dimensional data generated by virtual reality simulators and can be used to assess surgical performance.