Use Of 3d Printed Ribcage Models To Investigate Ideal Intrathoracic Ratio For Robotic Left Internal Thoracic Artery Harvesting
Sarah Chen, Jorge Catrip, Bob Kiaii.
University of California, Davis, Sacramento, CA, USA.
BACKGROUND: Patient selection is crucial when considering eligibility for robotic coronary surgery in order to minimize complications and conversions. For robotic left internal thoracic artery (LITA) harvesting in particular, careful measurement of intrathoracic anatomy is critical to ensure adequate exposure to access the length of the LITA. To achieve this, an anteroposterior (AP) distance to transverse distance ratio of greater than 0.45 is generally favored, as a ratio of less than 0.45 is thought to increase risk of compromising instrument maneuverability. This study aims to investigate the limits of the AP to transverse ratio using 3D printed models.
METHODS: Life-sized left hemi-ribcage models were created based on a CT scan of an average adult-sized chest. The control ribcage model had an AP to transverse ratio of 0.55, from which derivative ribcage models were created with ratios of 0.45, 0.40, and 0.35. These models were 3D printed using a fused deposition modeling 3D printer. The printed models were then used for simulation using a da Vinci (Intuitive, Sunnyvale, CA, USA) robotic trainer to mimic LITA harvesting. For the simulation, the camera port was placed in the fourth or fifth intercostal space (ICS), and the working ports in the second/third and the sixth/seventh ICS.
RESULTS: There were no issues with instrument maneuverability or LITA access in the ribcage models with AP to transverse ratios of 0.55 and 0.45. For the 0.40 ratio model, there were initially challenges with instrument collision, which were eventually alleviated with port placement adjustment.
CONCLUSIONS: This study demonstrates the use of customized 3D printed models to help define the limits of intrathoracic anatomy conducive to robotic LITA take down. The study suggests that robotic LITA harvesting may be possible in a chest wall space with an AP to transverse ratio of less than 0.45—and as low as 0.40 and potentially even lower—as long as port placements are sufficiently precise. This type of study using 3D printed models can be further developed to investigate the extremes of chest wall measurements to determine compatibility with robotic cardiac procedures, which may ultimately expand the patient population eligible for robotic cardiac surgery.
LEGEND: Ribcage models for simulation; (A) digital models, with varying anterior posterior (AP) to transverse ratios, from left to right 0.35, 0.40, 0.45, and 0.55; (B) physical 3D printed models; (C) view of robotic left internal thoracic artery harvest simulation inside 3D printed ribcage model. 
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