Effects of Experience and a Reference Tool in Laparoscopic Length Measurements

Sara L Zettervall, MD, Hope T Jackson, MD, Ezra Teitelbaum, MD, Matt Holzner, BS, Jason Weissler, BS, Amdur L Richard, PhD, Khashayar Vaziri, MD, FACS. Department of Surgery, George Washington University School of Medicine and Health Sciences, Washington, DC. Department of Surgery Feinberg School of Medicine, Northwestern University, Chicago, IL..

INTRODUCTION: Various gastrointestinal operations necessitate the measurement of a specific length of small intestine; however, the accuracy of surgeons, and surgeons-in-training, performing these measurements laparoscopically is unknown. In this study, we evaluated the accuracy and precision of laparoscopic length measurements performed by surgical attendings, residents, and medical students using a box-trainer model with and without a measuring tool.

METHODS AND PROCEDURES: Surgical attendings and residents who perform laparoscopy, and medical students were studied. To simulate measurement of the small intestine, a 500cm length of rope was placed within a laparoscopic box-trainer and affixed at one end. Study subjects completed two length measurements (LM). For LM#1, they were asked to measure 150cm from the affixed rope end using two laparoscopic graspers. The actual length measured and time required was recorded. For LM#2, subjects repeated the task with the aid of a 10cm suture to act as a reference. Measurement accuracy was tested by comparing mean measurement lengths between training level groups using an independent t-test. Measurement precision was tested by comparing the mean deviation of measurements from 150cm. Within-subject change was evaluated using a paired t-test.

RESULTS: 40 attendings, 40 residents, and 50 medical students were studied. For LM#1, in terms of measurement accuracy, there were no differences in mean length measured between training level groups (attendings: 144 ±45cm vs. residents 128 ±42cm vs. students: 145 ±51cm, p=ns for each comparison). However, residents were the only group to significantly underestimate the true 150cm length (95% CI: 114cm–141cm). In terms of precision, there were no differences in the mean deviation from 150cm between groups (attendings: 34 ±30cm vs. residents 38 ±28cm vs. students: 40 ±32cm, p=ns for each comparison). Attendings performed LM#1 faster than both residents and students, and residents performed faster than students (mean 66 ±33 seconds vs. 89 ± 46s vs. 121 ±48s, p<.05 respectively). When LM#1 and LM#2 were compared, attendings’ mean measurement length did not change (144 ±45cm vs. 136 ±16cm, p=ns) but their mean deviation from 150cm decreased (i.e. precision improved) (34 ±30cm vs. 18 ±12cm, p<.01). Residents’ mean measurement length increased at a trend level (128 ±42cm vs. 141 ±18cm, p=.08) and their deviation from 150cm decreased (mean 38 ±28cm vs. 16 ±12cm, p<.001). Students’ mean measurement length did not change, but their deviation from 150cm similarly decreased (40 ±32cm vs. 22 ±21cm, p=.001). For LM#2, there were again no differences in mean measurement length and deviation from 150cm between groups. Attendings performed the measurement faster than both residents and students in LM#2 (p<.01 for both comparisons).

CONCLUSIONS: In this study, there were no differences in the accuracy or precision of simulated laparoscopic small intestine length measurements between surgical attendings, residents, and students. More experienced operators required less time for completion of the task. Use of a measuring tool improved precision of measurements regardless of experience level.

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