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Partial Occlusion Device - A Novel 3D-Printed Tool for Microsurgical Anastomosis Revision

This study introduces a novel 3D-printed Partial Occlusion Device (POD) that serves as a stable, reusable, and fiber-free alternative to cotton-tip applicators for microsurgical anastomosis revision, demonstrating comparable efficacy and safety while offering surgeons improved stability and control in a rat femoral artery model.

Original authors: Yuzhu Huang, Abraham Joshua Johnson, Jonas Zhao, Shahabeddin Yazdanpanah, Elan Shukhmakher, Omer Bilal, Hui Zhang, Tina Moon, Sophia Jao, Stephen Fox, Sharon C. Usip, Jennifer Baccon, Fayez F. Safadi

Published 2026-07-02

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Yuzhu Huang, Abraham Joshua Johnson, Jonas Zhao, Shahabeddin Yazdanpanah, Elan Shukhmakher, Omer Bilal, Hui Zhang, Tina Moon, Sophia Jao, Stephen Fox, Sharon C. Usip, Jennifer Baccon, Fayez F. Safadi, Yelena Akelina

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you are a tiny surgeon working on a microscopic water pipe (a blood vessel) that is only as wide as a human hair. Your job is to sew the two cut ends of the pipe back together perfectly. But sometimes, the first attempt leaks a little. To fix it, you need to stop the water flow just enough to see the leak and sew it up, without crushing the pipe or getting your workspace messy.

This paper introduces a new, 3D-printed tool called the Partial Occlusion Device (POD) designed to help with this exact problem. Here is the story of how it works, why it was made, and what the researchers found, explained simply.

The Problem: The "Fluffy Stick" Dilemma

For years, surgeons in training have used a standard cotton-tip applicator (like a Q-tip) to fix these leaks. They press the soft cotton tip against the vessel to stop the blood flow temporarily.

However, the researchers pointed out two big problems with using a Q-tip:

It's Wobbly: The round, fluffy tip is unstable. It's like trying to build a Lego tower on a rolling ball; the tool can slip or roll away, making it hard to work precisely.
It Leaves a Mess: Cotton fibers can shed and fall into the tiny surgical area. Imagine trying to fix a watch while someone is sprinkling sawdust on it. These tiny fibers could theoretically cause blockages or inflammation inside the body.

The Solution: The "3D-Printed Wedge"

To fix these issues, the team at Columbia University designed the POD. Think of it as a custom-made, 3D-printed "wedge" or "step-stool" made of smooth, hard plastic resin.

The Shape: Instead of a round ball, it has a flat bottom so it sits perfectly still on the table without rolling.
The Steps: The top of the device has three little "saddles" or steps of different heights. Surgeons can slide the vessel onto a lower step for a gentle squeeze or a higher step for a tighter squeeze, giving them precise control.
The Handle: It has a grooved handle that fits perfectly into standard surgical tweezers, allowing the surgeon to place and remove it with steady, controlled movements.
The Material: It is made of smooth resin, so it never sheds "dust" or fibers into the wound.

The Experiment: A Rat Race

To see if this new tool worked, the researchers set up a training scenario using rats. They cut the femoral artery (a major leg artery) and sewed it back together. Then, they intentionally made it leak to force a "revision" (a fix).

They split the surgeries into two groups:

Group A: Used the new POD tool.
Group B: Used the traditional cotton-tip applicator.

What They Found

The researchers looked at three main things: how long it took to fix, whether the pipe stayed open, and what the tissue looked like under a microscope.

1. Speed and Success

Time: Both tools took about the same amount of time to fix the leak (roughly 3 to 4 minutes). The new tool didn't slow anyone down.
Success Rate: The cotton-tip group had a 100% success rate (all pipes stayed open). The POD group had a 90.9% success rate. While the cotton-tip group did slightly better, the difference wasn't statistically huge, and the few failures in the POD group were likely due to other factors, not the tool itself.

2. The Surgeons' Feelings
The surgeons who used the POD said they liked it much better. They reported that:

It was more stable (didn't roll around).
It gave them better visibility (no cotton fuzz blocking the view).
It gave them more control over the vessel.
Only a couple of surgeons preferred the old cotton tip because they sometimes needed to lift the vessel higher than the POD's steps allowed.

3. The "Damage" Check (Microscope View)
After the surgery, they looked at the tissue under a microscope to see if the tools hurt the blood vessels.

Both tools caused some minor irritation (inflammation) and cell loss, which is expected when you squeeze a tiny vessel.
Crucially: There was no significant difference in the amount of damage between the two groups.
However, when looking closely at the type of damage, the cotton-tip vessels seemed to have more "clumped" inflammation (like a pile-up of cells), while the POD vessels had more spread-out, sparse inflammation. This suggests the cotton might be slightly more irritating, even if the scores looked similar.

The Bottom Line

The paper concludes that the POD is a practical, reusable alternative to the old cotton swab.

Think of it like upgrading from a wobbly, messy broom to a sleek, solid squeegee. It doesn't necessarily clean the floor faster, but it's much more stable, doesn't leave behind debris, and gives the user better control. The researchers believe this tool could make microsurgery training safer and more efficient by removing the risk of fiber contamination and providing a steady platform for delicate work.

Important Note: The study was done on rats in a lab setting. The authors state that while the results are promising, more studies are needed to see how it works in different situations and with different surgeons before it becomes a standard tool in hospitals.

Technical Summary: Partial Occlusion Device (POD) for Microsurgical Anastomosis Revision

Problem Statement
Achieving reliable vascular anastomosis is fundamental to microsurgery, yet revisions are frequently necessitated by leakage at suture sites due to the fragility and small diameter of vessels. Historically, proximal vessel clamping was used to facilitate revision, but this carries risks of thrombosis and vessel injury. Consequently, cotton-tip applicators (Q-tips) became the standard for partial occlusion, allowing surgeons to elevate vessels and clear the field of view without clamps. However, the paper identifies two critical limitations of this standard technique:

Instability: The rounded tips of cotton applicators create an unstable operating surface that can roll, requiring continuous manual stabilization.
Contamination: The shedding of cotton fibers into the operative field poses a risk of particulate contamination, potentially leading to embolic events, granulomas, and inflammatory responses.

Methodology
The study introduces and evaluates a novel Partial Occlusion Device (POD), a 3D-printed tool designed to replicate the occlusion function of cotton swabs while mitigating their limitations.

Device Design and Fabrication:
- The POD was designed using computer-aided design (CAD) software to feature a curved anterior surface conforming to vessel contours, minimizing focal pressure.
- It includes a flat-bottomed base to prevent rolling and a grooved handle for engagement with standard microsurgical clamp appliers, ensuring stable placement and removal.
- The superior surface features three saddles of varying heights to allow graded vessel elevation and incremental adjustment of occlusion.
- The device was fabricated via stereolithography (SLA) 3D printing using biocompatible BioMed White Resin on a Form 2 printer, followed by washing, drying, and post-curing to ensure mechanical strength and biocompatibility.
Experimental Model:
- The study utilized a rat femoral artery end-to-end anastomosis revision model using male Sprague-Dawley rats.
- Procedure: After initial anastomosis and reperfusion, revisions were performed for persistent leakage. The POD was positioned beneath the anastomosis to achieve partial occlusion, allowing for additional suturing.
- Comparison: The POD group ( $n=22$ ) was compared against a control group using traditional cotton-tip applicators ( $n=13$ ).
- Outcome Measures: Metrics included revision time, vessel patency (assessed at 20 and 40 minutes via the lift test), and surgeon-reported usability.
- Histological Analysis: Tissue samples were harvested, fixed, and stained with H&E. A board-certified pathologist evaluated vessel segments (intima, media, adventitia) for endothelial cell loss, inflammation, necrosis, and clotting using a scoring system adapted from Naides et al. (2018).

Key Contributions

Novel Instrumentation: The development of a reusable, 3D-printed POD that eliminates the risk of fiber shedding associated with cotton applicators.
Enhanced Stability: The flat-bottomed design provides a stable platform that does not require continuous manual support, improving surgeon control.
Comparative Validation: The study provides empirical data comparing the POD against the current standard of care (cotton swabs) regarding operative time, patency rates, and histological impact.

Results

Operative Time: There was no statistically significant difference in revision times between the two groups. The mean time for cotton-tip applicators was $3.81 \pm 2.50$ minutes, compared to $4.00 \pm 2.15$ minutes for the POD ( $p = 0.5382$ ).
Vessel Patency:
- Cotton-tip group: 100% patency (13/13) at 40 minutes.
- POD group: 90.9% patency (20/22) at 40 minutes. Two failures occurred: one within 20 minutes post-revision and one prior to 40 minutes due to intraoperative mortality.
Surgeon Feedback: Twelve surgeons reported that the POD improved maneuverability, visualization, and control while eliminating fiber interference. Two surgeons preferred cotton tips for cases requiring greater vessel elevation.
Histopathology:
- Both groups exhibited endothelial cell loss and inflammation compared to control vessels, but no necrosis was observed in any group.
- Quantitative scoring showed no statistically significant differences between POD and cotton-tip groups in intimal ( $p=1.0$ ), medial ( $p=0.50$ ), or adventitial ( $p=0.52$ ) injury scores.
- Qualitative Observation: While scores were similar, qualitative assessment suggested that cotton-tip treated vessels exhibited a higher density of inflammatory cells compared to the sparse, circumferentially distributed cells in POD-treated vessels.

Significance and Claims
The paper posits that the POD is a practical, reusable alternative to cotton-tip applicators that addresses specific limitations of current microsurgical training and practice. The authors claim the device offers distinct functional advantages:

Safety: By eliminating cotton fiber shedding, the POD reduces the risk of particulate contamination and associated inflammatory or embolic complications.
Efficiency and Stability: The design improves intraoperative stability and visibility without increasing operative time.
Feasibility: With comparable patency rates and operative times to the standard technique, the POD demonstrates feasibility for integration into existing microsurgical workflows.

The authors conclude that while the POD performs comparably to current techniques, its ability to provide a stable, fiber-free environment represents a promising advancement. They note that variability in patency outcomes and the need for greater vessel elevation in some cases warrant further investigation, larger studies, and device optimization before broader clinical translation.