Vertical vs Horizontal Lip Injection Techniques – What the Evidence Really Shows

I analysed a cadaver study that gets cited frequently as definitive proof that vertical injections carry more risk than horizontal techniques when treating lips, and the methodology reveals some significant limitations that change how we should interpret the findings. The paper has become central to the safety debate, with practitioners on both sides using it to justify their preferred approach, so examining what the researchers actually tested becomes essential for making informed decisions.

The Ghannam/Cotofana cadaver study

The study “Treating the Lips and its Anatomical Correlate in Respect to Vascular Compromise” by Sahar Ghannam (with Sebastian Cotofana on the author list) is available free on PubMed, and reading the full paper yourself will help you form your own conclusions about what the data actually supports.

The authors tested their techniques on three cadavers averaging 85 years old, two female, one male, with a BMI of 26. The arteries were injected with red latex prior to the procedure, making them stand out more clearly during dissection and creating resistance to needle penetration. This differs considerably from living tissue where arteries are softer and more compliant.

Cross-sectional analysis examined just one point of reference after each procedure to determine how close the product had been placed to the vessel.

What was actually tested

The first technique tested is common to every injector: a linear thread running along the vermilion border. The diagrams included with the treatment plans show quite clearly that needle placement went into the vermilion part of the lip, into the pink area running parallel with the lip while staying superficial.

The authors use “contouring” to mean superficial injections and “volumizing” for deeper placement, and this distinction becomes crucial when examining their conclusions. Dissection after this superficial injection showed no close relationship to the artery, compatible with standard lip anatomy where the orbicularis oris muscle protects the artery in about 80% of cases, with filler lying a couple of millimeters above it.

The oblique angle injection came next, entering at roughly 45 degrees to the lip but angled down towards the wet-dry border. This technique fits somewhere between true vertical and what most practitioners imagine vertical injection to be. Examining the diagram closely reveals the entry point sits two to three millimeters above the pink-white border into the white part of the lip, even though the description states “entering the vermilion border.”

That entry point becomes significant based on how we understand anatomical structure. Cross-sectional analysis found filler very close to the artery, deeming this a high-risk procedure.

A true vertical injection with superior entry point followed, where the needle enters the white lip then passes down into the lip body before product placement. Dissection revealed a close relationship with the artery.

Contradictory cannula results

A horizontal cannula insertion from the corner of the lip showed confusing results. The arteries looked further away than expected from the schematic on one side, while the opposite side showed close proximity to the artery. This inconsistency becomes important when drawing conclusions about technique safety.

The lower lip vertical injection showed some arterial proximity, but the image revealed a critical study flaw. The cadaver specimen differs dramatically from the young model used in the treatment plan, and this difference matters considerably when you realize how much lip anatomy changes with age and how that affects injection angles.

One unusual technique entered the white part of the lower lip about a centimeter back from the border, crossed through the layers into the pink part, and showed filler close to the artery. A lower lip cannula also showed close arterial relationship during dissection.

The study’s actual conclusion about risk

The paper states that based on cadaveric findings, 58% of volumizing procedures related to potential intra-arterial injection because product was injected deep inside the lip body. Procedures aiming for contouring (superficial placement) can be regarded as safer because product was positioned in the subcutaneous plane, separated from arteries by the orbicularis oris muscle.

This conclusion reveals that depth creates the risk, not the angle of entry.

Why we cannot conclude vertical is riskier than horizontal

This paper doesn’t actually test vertical versus horizontal injection techniques. The study tested subtly different injection techniques that the authors use, without controlling for the specific question of angle comparison. Too many other variables changed, making it impossible to draw certain conclusions about horizontal versus vertical safety.

Contradictory evidence appears within the paper itself. The cannular injections showed higher arterial proximity than some needle injections despite being obviously horizontal, demonstrating that you can still position filler close to the artery with horizontal technique depending on depth and entry point. Most practitioners would accept this sometimes occurs.

The most important variable that changed is needle entry point. Proper comparison requires all other factors to remain constant. The vertical injections used more superior entry points (further back), necessarily passing through the orbicularis oris when going deeper. Some practitioners inject this way, but vertical injections more commonly enter the vermilion rather than the white lip, which makes a world of difference regarding technique safety and risk.

The cadaver problem

The reason so many injections entered the white lip might stem from using cadavers, which differ anatomically from the patients we actually treat. Deciding whether data applies to our patients requires asking whether study subjects resemble our patient population.

This study used 85-year-olds (one male, two female), but 85-year-old lips differ extremely from the lips we typically treat with volumizing techniques. The treatment design picture shows a young female, very different from what you’d draw on a cadaver because you literally couldn’t draw a vertical injection on most of these specimens, their lips were too atrophied.

That atrophy changes the injection angle. Entry point placement into the pink lip becomes harder because the pink lip involutes so severely. They’re entering the white lip then passing the needle down at a very different angle compared to injecting a young, slightly fuller lip. That angle potentially matters more than whether you’re vertical or horizontal.

As the angle gets steeper, you’re pointing more into the retro-orbicularis oris space where the artery tends to lie. In someone with very small or atrophied lips, you’ll end up much closer to the artery because you’re forced to inject through the orbicularis oris muscle since there’s no space to inject into the pink part of the lip.

When vertical injections might carry more risk

A vertical injection probably is riskier than a horizontal injection in someone with a very small or involuted lip, but that probably isn’t the typical patient being treated with this technique. The technically perfect version of this technique more likely gets applied to patients with enough space in their vermilion to allow entry, with the needle passing potentially either parallel to or further away from that retro-orbicularis oris space where the artery tends to lie.

Additional study weaknesses

Cross sections examined only one point of reference, and the cannular results themselves showed differences on either side depending on where they cut the lip to examine. Moving along the lip could have produced completely different results, which doesn’t help draw conclusions about technique safety.

Massive variation exists between cadavers (as you’d expect), but three specimens isn’t enough to determine average arterial position. There’s an element of luck about where injection goes relative to the artery in any given specimen.

This technical test doesn’t reflect what actually happens in clinics where you’d vary technique according to who you see. They decided to test a particular technique on a patient type they would never have actually used that technique on in real life, since doing a vertical injection on someone with a horizontal lip wouldn’t be intuitive to most practitioners.

What we can extract from this research

The real risk involves proximity to the retro-orbicularis oris space, which varies according to injection technique but may be influenced more by whether the lip is small or atrophied. Picture a bigger or fuller lip protruding out as it would in youth, you’re actually working in a little anterior pocket that’s further away from that space than in a much more atrophied or small-lipped case.

This research changed how we might think about different size lips and made it clear that older patients might be at risk with the wrong technique, though most practitioners aren’t using vertical techniques in those older patients anyway.

My mental model still suggests you can put filler in a risky spot with both horizontal or vertical injections because depth matters most. If you’re injecting underneath orbicularis oris, that’s the danger zone. Injecting horizontally means spending more time in that danger zone than injecting vertically.

The angle of approach changes arterial risk more than the simple categorization of vertical versus horizontal. Picture a small atrophied lip in an older person, the angle you would have to take (as these authors had to take in the study) sits much more at right angles to the face than in a younger lip where you tend to enter from the top of the vermilion border pointing downwards.

This changes the entire interpretation of procedural risk. In one case you’re angling away from the artery, while in the other case you’re angling directly towards that space where the artery tends to lie.

The limitations of cadaver research

Cadaver studies aren’t the gold standard for this type of research. Living tissue with imaging would better study these different techniques, though obviously that would be much harder to conduct. Techniques should also be designed for the individual in front of you, taking into account each person’s anatomy, since nobody would use just one technique for everyone.

Using only one technique for all patients probably means you haven’t optimized how to deal with each individual’s unique anatomy and aesthetic goals. This specialty resists digital standardization or black-and-white protocols because so many subtle variables exist, it’s actually quite analog. Small changes in depth, position, entry point, and patient selection make huge differences in terms of risk.

Every injector and every patient is unique. Even in this study there’s a clear significant difference between the cadavers, making it hard to get reliable evidence since thousands of case studies would be required, all preferentially using the same injector or at least a really standardized injection technique.

Ready to master your lip filler strategy and increase your lip prices? Join our exclusive free training where we explore 3D lip anatomy and learn from Dr Tim how to attract high value lip patients. Register for the next free webinar here >

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