Sharp or Dull Implanters: What Is Established and What Is Not

Ask two experienced surgeons whether a sharp or a dull implanter places grafts better and you will get two confident answers. We went looking for the study behind them. There isn't one: no published work compares sharp implanters with dull implanters on graft survival, damage, popping, bleeding, speed or density. This article sets out what the two methods actually are, what each side claims and on what basis, and which claims cannot be made at all.

What the two methods are

A sharp implanter makes the recipient site and places the graft in a single movement. The loaded needle punctures the skin, the graft is released, the needle is withdrawn. The method was described by Choi and Kim in 1992 (Choi and Kim, 1992; ISHRS, 2019).

A dull, or blunt, implanter does not cut. The recipient sites are made first, with a blade or needle, and the implanter places the graft into a site that already exists. Blunt implanters were manufactured from 2012 and first published on by Speranzini in 2016 (ISHRS, 2019; Speranzini, 2016).

A third group sits alongside them: placers such as the KEEP, which have no plunger. The person placing loads the graft themselves and guides it into a pre-made incision with forceps (ISHRS, 2019).

The evidence gap, and why it is not symmetrical

We searched PubMed and Europe PMC for any head-to-head comparison. There is none. There is also no controlled study establishing that implanters of either kind beat forceps on graft survival.

One thing must be said plainly, because it would otherwise mislead: most of the dull-needle literature was published in Hair Transplant Forum International, which is not indexed in PubMed or Europe PMC. Searching those databases therefore finds the sharp-implanter literature and largely misses the dull one. That absence is an artefact of where surgeons publish, not evidence that one method performs worse.

A second thing must be said for the same reason: the large majority of the usable technical literature on sharp implanters comes from one author, who discloses patents and an ownership interest in an implanter company (Park et al., 2023). His work is the most detailed description of the method that exists, and we use it here. It is not an independent comparison.

What the sharp method offers, according to its proponents

• Site creation and placement in one step, so the angle and direction can be adjusted to the hair's curl and thickness at the moment of insertion (Park et al., 2023).
• Dense packing is described as achievable at more than 50 to 60 grafts per square centimetre without popping (Park et al., 2023). This is a clinical assertion; no measurement accompanies it.
• Depth control through needle geometry: with a wide-channel tip the graft is loaded so the epidermis protrudes slightly, and that protruding cap acts as a stopper (Park et al., 2023).

The drawbacks its proponents name: placement is exposed to bleeding, because the incision is made at the moment of insertion; the physician performs the entire procedure, so every graft passes through the surgeon's hands; tips dull with use and must be replaced; and repeated popping in inexperienced hands can cost survival (Park et al., 2023).

What the dull method offers, according to its proponents

• Placement happens after bleeding from the incision has stopped, which takes the bleeding problem out of the moment of placement. Note whose description this is: it comes from Park, an advocate of the sharp method, setting out the two-step alternative (Park et al., 2023).
• Placement into pre-made sites can be delegated to trained staff. Speranzini and Souza name delegability as one of the reasons implanters were adopted at all, though they say that of implanters in general and not of dull ones specifically (Speranzini and Souza, 2024). For the sharp method Park writes that the physician performs the entire procedure (Park et al., 2023); reading that as 'cannot be delegated' is our inference, not his words.

The drawbacks: it needs a second instrument and a separate step, and the graft still has to be loaded into a lumen, which is where loading damage happens with any implanter.

What dull needles are actually for

The clearest statement of purpose comes from the surgeon who first published on the method. Implanters for pre-made sites had been developed by Shiao shortly before. Speranzini sets out both practical and clinical reasons for moving to dull needles; the practical ones are below, and his clinical claims (smaller incisions allowing higher density, less trauma, better growth) are assertions without measurement (Speranzini, 2016):

• Delegation. Placement into pre-made sites can be handed to trained assistants, so the surgeon can rest between harvesting sessions or harvest and place at the same time. Sharp-needle placement, he notes, requires the surgeon to place every graft.
• Avoiding forceps on the follicle. FUE grafts are often stripped of tissue near the bulb, which makes them more vulnerable than FUT grafts; an implanter lets the graft be placed without gripping the follicle itself.
• Smaller incisions. This is the argument specific to dull needles: because the site is made separately, it can be smaller than the needle that enters it. He makes 0.63 mm sites for single hairs and places them with 0.74 mm dull needles, and 0.80 to 0.85 mm sites for two- and three-hair grafts placed with 0.96 mm needles.
• Cost and reuse. Dull needles can be cleaned, sterilised and reused, where sharp tips blunt during a case and get replaced.
• A shorter learning curve for staff than forceps placement. In his experience it takes days rather than months.

He is equally clear about the drawbacks: in his hands placement is slower than with sharp implanters and slower than two or three technicians working with forceps, though he notes it becomes more efficient with two staff placing at once; in some cases there is more bleeding and popping than with sharp implanters; and reused needles need careful cleaning and sterilisation.

One detail is worth knowing if you are looking at dull needles: Speranzini made his by hand, sanding the edge and point off ordinary implanter needles. He preferred KNU needles for that because they are all steel without a plastic hub, which he found could be sterilised more effectively in a longer autoclave cycle.

He also reports that since adopting the method many hairs simply do not shed, which he says rarely happened when his team placed with forceps. He reports it as an observation, without data, and the comparison is with forceps rather than with sharp implanters.

What is worth more than the sharp-or-dull question

One finding is worth more than the sharp-or-dull argument. Grafts from seven patients were deliberately injured in four ways, placed with sharp implanters and transplanted into mice. Survival fell by injury type: intact 71.4%, pared 51.4%, bulb-injured 44.3%, fractured 12.9% (Kwack et al., 2021). It is a mouse model, so the absolute percentages do not transfer to patients, and only sharp implanters were used, so the study says nothing about dull ones. What it does show is a ranking: a fractured graft is by far the most costly form of damage.

Tip size matters for the same reason. Too small and the graft is crushed on loading; too large and it sits loose and pops. Sizes are matched to the graft, a question we looked at in more detail in our article on punch size and implanter needle size: roughly 0.6 mm for eyebrow and fine single hairs, 0.6 to 0.8 mm for single hairs, 0.9 to 1.0 mm for two-hair grafts, and 1.0 to 1.2 mm for three to four hairs (Park et al., 2023).

Claims we will not make

We do not claim that sharp implanters give better graft survival, less trauma, less transection, less popping or higher density than dull implanters, or the reverse. No comparative study exists, and any number attached to such a claim comes from a series with no control group, from a single patient, or from a technique comparison in which the device was never specified.

We also do not claim that one type is "the ideal method" for women or for unshaven work, that pre-made sites close up before grafts can be placed, or that sharp needles transect existing hair in unshaven cases. These are arguments we hear from surgeons, and they may well be right, but we could not find a published source for any of them, so we present them as what they are: practitioner experience, not evidence.

And we will not repeat the claim, found on clinic pages, that this technique carries no risk at all.

What this means for choosing

Both methods are in daily use by surgeons who get good results, and the same surgeon may use more than one within a single case (Park et al., 2023). The evidence does not let anyone tell you that your method is the wrong one.

What the evidence does support is narrower and more useful: match the tip to the graft, load without crushing or fracturing, control depth, and place into a site that is the right size. Those apply to both types, and they are where the difference between a good and a poor result actually shows up.

In our range

We supply sharp implanters: the LION implanter (Hans Biomed), with its own replacement needles in four sizes; the KNU implanter, with replacement needles from 0.6 to 1.2 mm in both sharp and dull versions; and the Incuram implanter. The dull KNU needles are for the approach described above: the sites are made first, and the needle places the graft into a site that already exists, without a cutting edge. We also supply the KEEP, a placer for pre-made sites that uses no needle and no plunger.

If you are choosing between the two approaches and want to know exactly what a given needle does, ask us. We would rather check with the manufacturer than let you find out on the table.

References

• Choi YC, Kim JC. Single hair transplantation using the Choi hair transplanter. J Dermatol Surg Oncol. 1992;18(11):945-948. PMID 1430550.
• ISHRS. A 2019 Guide to Currently Accepted FUE and Implanter Terminology. Hair Transplant Forum International. 2019;29(3):98-106. DOI 10.33589/29.3.98.
• Kwack MH, Kim MK, You SH, Kim N, Park JH. Dermatol Surg. 2021;47(5):e191-e194. PMID 33165067.
• Park JH, Ho YH, Manonukul K. A Practical Guide to Hair Graft Placement Using the Sharp Implanter Method. Clin Cosmet Investig Dermatol. 2023;16:1777-1785. PMID 37456803. DOI 10.2147/CCID.S411488. (The author discloses patents and an ownership interest in an implanter company.)
• Speranzini M. FUE Graft Placement with Dull Needle Implanters into Premade Sites. Hair Transplant Forum International. 2016;26(2):49,54-56. DOI 10.33589/26.2.0049a. (Full text read.)
• Speranzini M. Graft Placement Using the Dull Needle Implanter (DNI) Technique. Hair Transplant Forum International. 2017;27(2):45-56. DOI 10.33589/27.2.0045.
• Speranzini M, Souza SEG. Advancements in Graft Placement Techniques. Facial Plast Surg. 2024;40(2):223-233. PMID 37879353. DOI 10.1055/a-2198-2782.