TissueDB/Simulators/VesselBox Vessel Ligation Trainer (Hu)

The VesselBox Vessel Ligation Trainer is a low-cost open-surgery simulator developed at the University of Virginia for graduating fourth-year medical students and incoming PGY-1 surgery residents preparing for open abdominal procedures (Hu et al. 2015, Journal of Surgical Education;^[1] Hu et al. 2015, Journal of Surgical Research^[2]). The construct uses a four-sided pine box, a vessel-mounting device, and a disposable latex glove finger as the vessel substitute. A trainee performs proximal and distal vessel control, division between forceps with Mayo scissors, and tied ligation using 3-0 silk, while a surgical assistant maintains opposing forceps and releases each in turn at the trainee's prompt. The construct sits in a deep, vision-restricted compartment by design, replicating the difficulty of controlling a vascular pedicle in a confined abdominal cavity. The simulator was assessed in a peer-reviewed validation study across four skill tiers (medical students, surgical interns, residents, and faculty) with significant stratification on both checklist and OSATS Global Rating Scale metrics, and the same construct was used in a Cusum-guided adaptive curriculum that demonstrated pre/post improvement on independent cadaver post-tests. Substitute mount designs and full per-row recipe details follow.

1. Cut four pine boards to form the walls of a deep, four-sided box because Hu et al. 2015 specify a "four-sided box created from pine wood" to simulate a confined abdominal compartment.^[1] Box dimensions are not specified in either published paper — choose a depth and base width that restrict visualisation of the working field while still permitting two-handed instrument access and a vessel mount span of approximately 20–25 cm. A starting reference (TissueDB-suggested, not source-specified) is approximately 30 × 20 × 15 cm internal.
2. Fasten the four walls together using wood screws or nails, ensuring the open top permits clear instrument access and that the construct sits stable on a flat workbench surface.
3. Sand any rough edges that might catch instruments or sutures during a session.
4. Confirm the box is rigid enough to resist deformation under the tension required to tie a 3-0 silk ligation against a glove-finger vessel substitute.

Important note: the original VesselBox uses a "proprietary vessel mounting device" (Hu et al. 2015) that is not described in either published paper.^[1] The design below is a TissueDB-suggested substitute, not a replica of the published mount, and may produce different clamping force and tension. Builders seeking exact replication of the published design are encouraged to contact the corresponding author Sara K Rasmussen (skr3f@virginia.edu, University of Virginia School of Medicine) or first author Yinin Hu (yh9b@virginia.edu).

1. Cut two pine blocks to approximately 50 × 30 × 15 mm from offcuts because they will form the mounting platforms for the binder-clip clamps on either side of the box base.
2. Drill two 3 mm pilot holes through the wide face of each pine block, approximately 30 mm apart, because these holes will receive the wood screws affixing each binder-clip to its block.
3. Clamp each large binder-clip arm in a vice and drill a fine matching hole (approximately 2 mm) through each arm-shaft because the binder-clip must be screw-fastened to its pine block, not adhesive-fastened, to withstand tying tension.
4. Screw each binder-clip to its pine block using two 25 mm wood screws, one screw per arm-shaft hole into the block face.
5. Position the two clip-block assemblies on opposite walls of the box base, approximately 20–25 cm apart, with the clip jaws facing each other across the open compartment.
6. Drill two pilot holes through the bottom of each clip-block assembly into the box base, and affix each block with two more 25 mm wood screws.
7. Confirm a glove-finger pinched between the two clip jaw sets is held under steady tension during a test ligation, and that slips do not occur until intentional release.

Limitations of Substitute Design A (build-phase note): binder-clip clamping force is not equivalent to the published proprietary mount's tension. Some experimentation may be required to find the optimal glove-finger length and tension for a given trainee population. Glove fingers are held by friction at the binder-clip jaws; slips can occur during high-force ligation and require reseating between attempts.

1. Cut a finger from a fresh disposable latex surgical glove because the glove finger is the vessel substitute and must be discarded after two ligations per Hu et al. 2015.^[1]
2. Insert one open end of the glove finger between one binder-clip's jaws and release the clip jaws to grip, because the glove finger must be held under tension between the two mounts.
3. Repeat on the opposing binder-clip jaws, ensuring the glove finger spans the gap between the two mounts taut and parallel to the box base.
4. Confirm the mounting time is less than 30 seconds per mounted glove finger and that the construct permits two ligation attempts per mounted glove finger before disposal, both as specified by Hu et al. 2015.^[1]
5. Replace the used glove finger and any soiled silk ties between learners, then check the binder-clip mounts and pine box for rigidity and undamaged condition before the next session.

1. Set the Cusum acceptable failure rate at 5% and the unacceptable failure rate at 20% because Hu et al. 2015 (J Surg Res) specify these decision parameters for surgical-skill acquisition Cusum analysis on this construct.^[2]
2. Set the Type I error rate at 10% and the decision interval h₀ at 1.41 because these were the parameters used in the published Cusum-guided curriculum and produced the reported 8 to 16 practice attempts to proficiency.^[2]
3. Run the trainee through a rolling window of 8 practice attempts because Hu et al. 2015 (J Surg Res) used an 8-attempt window for proficiency assessment.^[2]
4. Score each attempt against the procedure-specific checklist and the OSATS Global Rating Scale, with camera framing limited to the simulator and the participants' forearms to blind the rater to identity and skill tier.^[1][2]
5. Plan an average session length of approximately 21.8 minutes (IQR 19.5–27.7 per Hu et al. 2015, J Surg Res) and expect 8 to 16 attempts to reach Cusum-defined proficiency.^[2]
6. Run an optional fresh human cadaver post-test at the end of curriculum (short gastric artery, mesenteric artery branch, extremity venous branch, or friable strands of breast tissue as a surrogate when no vessel is available) per the published transfer-of-skill protocol.^[2]

^[1][2][3]