Surgeon Upper Extremity Kinematics During Error and Error-Free Retropubic Trocar Passage.

INTRODUCTION AND HYPOTHESIS: Surgeon kinematics play a significant role in the prevention of patient injury. We hypothesized that elbow extension and ulnar wrist deviation are associated with bladder injury during simulated midurethral sling (MUS) procedures. METHODS: We used motion capture technology to measure surgeons' flexion/extension, abduction/adduction, and internal/external rotation angular time series for shoulder, elbow, and wrist joints. Starting and ending angles, minimum and maximum angles, and range of motion (ROM) were extracted from each time series. We created anatomical multibody models and applied linear mixed modeling to compare kinematics between trials with versus without bladder penetration and attending versus resident surgeons. A total of 32 trials would provide 90% power to detect a difference. RESULTS: Out of 85 passes, 62 were posterior to the suprapubic bone and 20 penetrated the bladder. Trials with versus without bladder penetration were associated with more initial wrist dorsiflexion (-27.32 vs -9.03°, p = 0.01), less final elbow flexion (39.49 vs 60.81, p = 0.03), and greater ROM in both the wrist (27.48 vs 14.01, p = 0.02), and elbow (20.45 vs 12.87, p = 0.04). Wrist deviation and arm pronation were not associated with bladder penetration. Compared with attendings, residents had more ROM in elbow flexion (14.61 vs 8.35°, p < 0.01), but less ROM in wrist dorsiflexion (13.31 vs 20.33, p = 0.02) and arm pronation (4.75 vs 38.46, p < 0.01). CONCLUSIONS: Bladder penetration during MUS is associated with wrist dorsiflexion and elbow flexion but not internal wrist deviation and arm supination. Attending surgeons exerted control with the wrist and forearm, surgical trainees with the elbow. Our findings have direct implications for MUS teaching.

Surgeon estimation of retropubic trocar position in blind 3D space.

INTRODUCTION AND HYPOTHESIS: Retropubic midurethral sling surgery involves the blind passage of trocars near vital organs. We quantified the proximity of surgeons' mental representation of trocar position relative to actual position using a pelvis simulation platform. We hypothesized that novice surgeons, compared with experts, would estimate the trocar's location to be further from the actual location. METHODS: Novice and expert surgeons performed bilateral retropubic trocar passes of a Gynecare TVT trocar (#810041B-#810,051) on the simulation platform. We measured the trocar tip's position using a motion capture system, and recorded vocalizations when they perceived contacting the bone and crossing three landmark-oriented planes. We calculated differences (∆Bone, ∆Turn, ∆Top, ∆Pop) between vocalization times and when the trocar crossed the corresponding plane. We performed Mann-Whitney and Chi-squared tests to investigate differences between novices and experts and Levene's test to assess equality of variances for subject-level variation. RESULTS: A total of 34 trials, including 22 expert and 12 novice trials, were performed by six participants. ∆Bone was significantly smaller among novice surgeons (1.27 vs 2.81 s, p=0.013). There were no significant differences in the remaining three deltas or in vocalizing early versus late. Levene's test revealed no significant differences in within-subject variability for any of the four deltas. Novices passed the trocar anterior to the pubic bone on three passes. CONCLUSIONS: Novices were similar to expert surgeons in their estimation of the trocar's location and may have relied more heavily on anticipatory mechanisms to compensate for lack of experience. Teaching surgeons should make sure the novice surgeon trocar pass starts posterior to the bone.

Cognitive models for mentally visualizing a sharp instrument in a blind procedure.

Purpose: Our objective was to understand the cognitive strategies used by surgeons to mentally visualize navigation of a surgical instrument through blind space. Methods: We conducted semi-structured interviews with 15 expert and novice surgeons following simulated retropubic trocar passage on 3D-printed models of pelvises segmented from preop MRIs. Midurethral sling surgery involves blind passage of a trocar among the urethra, bladder, iliac vessels, and bowel while relying primarily on haptic feedback from the suprapubic bone (SPB) for guidance. Our conceptual foundation was based on Lahav's study on blind people's mental mapping of spaces using haptic cues. Participants detailed how they mentally pictured the trocar's location relative to vital anatomy. We coded all responses and used constant comparative analysis to generate themes, confirmed with member checking. Results: Expert and novice participants utilized multiple cognitive strategies combined with haptic feedback to accomplish safe trocar passage. Some used a step-by-step route strategy, visualizing sequential 2D axial images of anatomy adjacent to the SPB. Others used a map strategy, forming global 3D pictures. Although these mental pictures vanished when they were "lost," a safe zone could be reestablished by touching the SPB. Experts were more likely to relate their body position to the trocar path and rely on minor variations in resistance. Novices were more inclined toward backtracking of the trocar. Conclusions: Our findings may be extended to any blind surgical procedure. Teaching visualization strategies and incorporating tactile feedback can be used intraoperatively to help learners navigate their instrument safely around vital organs.

Retropubic trocar modified with a load cell to verify contact with pubic bone.

BACKGROUND: Vital injuries during midurethral sling surgery are avoided by maintaining constant trocar contact with bone, and yet this is challenging for a teaching surgeon to monitor during this blind procedure. We modified a retropubic trocar with a load cell to distinguish on-bone and off-bone movement and tested it on a midurethral sling surgery 3-dimensional surgery simulator. METHODS: Two experts and 3 novice surgeons performed retropubic trocar passage on the physical pelvic floor model using the modified trocar. Biofidelity was assessed comparing expert performance on a Thiel-embalmed cadaver and the physical model. The test-retest was assessed comparing performance on the physical pelvic model 2 weeks apart. The force variables were analyzed with paired and independent t tests. We performed post hoc analyses comparing the experts to novices on the physical model. RESULTS: The root-mean-squared force was similar between the cadaver and model (24.3 vs 21.1 pounds, P = .62), suggesting biofidelity. Root-mean-squared force was also similar between the test and retest (14.0 vs 19.1 pounds, P =. 30). The expert surgeons exhibited a larger maximum force amplitude (51.2 vs 22.7 pounds, P = .03), shorter time to maximum force (2.7 vs 9.5 seconds, P = .03) and larger maximum rate of force development (171.5 vs 54.0 pounds/second, P = .01). CONCLUSION: This study suggested high test-retest reliability and adequate biofidelity of the modified trocar used on our midurethral sling surgery 3-dimensional surgery simulator. This innovative trocar can be used both in simulation and in the operating room to help the novice surgeons stay on the bone and to help the attending surgeon monitor safe surgery.