DHI (Direct Hair Implantation) is a hair transplant technique that uses the Choi Implanter Pen to extract individual hair follicles and implant them directly into the scalp without creating pre-made channels. This single-step implantation process reduces graft handling time and gives the surgeon precise control over the angle, depth, and direction of each transplanted hair.
This article is for informational purposes only and does not constitute medical advice.
How DHI Works: The Core Mechanism
The defining feature of DHI is the Choi Implanter Pen, a pen-shaped instrument with a hollow needle at its tip. The device allows a surgeon to load a single hair follicle into the needle and then press the plunger to simultaneously create a tiny channel in the scalp and deposit the graft into that channel in one motion.
This contrasts with the two-step process used in traditional FUE, where the surgeon first creates hundreds or thousands of recipient channels (slits) with a blade, then goes back and places each graft into an open channel.
The Choi Implanter Pen
The Choi Implanter Pen was developed at Kyungpook National University in South Korea. It consists of:
- A hollow needle (0.5-1.0mm diameter): Sized to match the follicular unit being implanted. Single-hair grafts use a smaller needle than multi-hair grafts.
- A plunger mechanism: Pushes the loaded graft through the needle and into the scalp at a controlled depth.
- An ergonomic pen body: Allows the surgeon to hold and angle the device precisely.
During a DHI procedure, a team of technicians continuously loads follicular units into multiple Choi pens (typically 6-8 pens in rotation). This relay system keeps the surgeon working continuously, implanting one graft after another without pausing to load each pen individually.
Step-by-Step Overview
- Extraction: Individual follicular units are harvested from the donor area (typically the back and sides of the head) using a micro-punch tool, identical to the FUE extraction method
- Loading: Each extracted graft is carefully loaded into the hollow needle of a Choi Implanter Pen by a trained technician
- Implantation: The surgeon positions the pen at the desired angle and depth on the recipient area, presses the plunger, and the needle creates a channel while simultaneously depositing the graft
- Repeat: The surgeon takes a freshly loaded pen from a technician and implants the next graft, continuing in a systematic pattern across the treatment area
DHI vs. Traditional FUE: Key Differences
While DHI is technically a variation of FUE (both extract individual follicular units), the implantation process creates meaningful differences in outcomes and procedure characteristics.
Implantation Method
| Feature | Traditional FUE | DHI |
|---|---|---|
| Channel creation | Pre-made slits with blade or needle | Created by Choi pen during implantation |
| Graft placement | Manually inserted into open channels with forceps | Deposited directly via pen plunger |
| Steps in implantation | Two (create channel, then place graft) | One (simultaneous) |
| Graft time outside body | Longer (channels made first, then grafts placed) | Shorter (implanted immediately after loading) |
Clinical Differences
| Aspect | Traditional FUE | DHI |
|---|---|---|
| Maximum grafts per session | Up to 4,000-5,000 | Up to 3,500 |
| Procedure duration | 4-8 hours | 6-10 hours (longer per graft) |
| Donor scarring | Tiny dot scars | Tiny dot scars (identical) |
| Recipient scarring | Minimal | Minimal (slightly smaller sites) |
| Recovery time | 7-10 days | 7-10 days |
| Graft survival rate | 90-95% | 90-95% |
| Shaving required | Usually full or partial shave | Often possible without full shave |
| Cost | Standard FUE pricing | 10-20% higher than FUE |
Where DHI Has an Advantage
DHI offers specific advantages in certain clinical situations:
- Hairline design: The pen allows the surgeon to control the exact angle and direction of each graft in real time, which is valuable for creating a natural-looking hairline where single hairs need to point in slightly different directions
- Unshaved procedures: Because the implantation tool is a pen rather than forceps placed into open slits, DHI can be performed without shaving the recipient area. Existing hair is parted, and grafts are implanted between native hairs.
- Density work between existing hair: When adding density to thinning areas that still have native hair, the Choi pen allows precise placement without disturbing surrounding follicles
- Reduced graft handling: Each graft goes from the extraction punch to the Choi pen to the scalp with minimal manipulation, potentially reducing trauma
Where Traditional FUE Has an Advantage
- Larger sessions: FUE can handle more grafts per session (up to 4,000-5,000 vs 3,500 for DHI)
- Speed: The two-step process is faster per graft because channel creation can be done rapidly in bulk
- Cost: FUE is typically 10-20% less expensive because the procedure requires less time and fewer specialized instruments
- Surgeon availability: More surgeons are trained in traditional FUE than in DHI
DHI Graft Survival and Results
DHI achieves graft survival rates of 90 to 95%, matching traditional FUE. The reduced time that grafts spend outside the body during DHI may contribute to survival, though clinical studies have not demonstrated a statistically significant difference between DHI and FUE survival rates when both are performed by experienced surgeons.
Growth Timeline
| Timeframe | What Happens |
|---|---|
| Week 2-4 | Transplanted hairs shed (shock loss, completely normal) |
| Month 3-4 | New growth begins from transplanted follicles |
| Month 6-8 | Noticeable density improvement |
| Month 12-18 | Final results with full thickness and coverage |
Results are permanent because the transplanted follicles come from the DHT-resistant donor area at the back of the head. These follicles retain their genetic resistance to pattern hair loss after transplantation.
Who Performs DHI?
DHI requires specific training beyond standard hair transplant education. The surgeon must be proficient with the Choi Implanter Pen, and the clinic needs trained technicians who can efficiently load grafts into the pens. Not all hair transplant surgeons offer DHI, so patients seeking this method should confirm the surgeon's DHI-specific experience and ask about the number of DHI procedures they have performed.
Some clinics market DHI as a branded or proprietary technique. The underlying technology (Choi Implanter Pen, direct implantation) is the same across clinics. The difference in outcomes comes from the surgeon's skill and the quality of the medical team, not from proprietary methods.
Is DHI Right for You?
DHI is best suited for patients who:
- Need precision hairline work with controlled graft angles
- Want the procedure done without shaving the recipient area
- Require density work between existing native hairs
- Are planning sessions of up to 3,500 grafts
For larger restoration needs (4,000+ grafts), traditional FUE or FUT may be more practical. For a broader comparison of transplant methods, see our FUE vs FUT comparison. To understand pricing across different techniques, visit the hair transplant cost guide.
FAQ
What is DHI hair transplant?
DHI (Direct Hair Implantation) is a hair transplant technique that uses a specialized Choi Implanter Pen to extract individual follicular units from the donor area and implant them directly into the recipient zone. Unlike traditional FUE, DHI combines channel creation and graft placement into a single step, eliminating the need for pre-made recipient incisions.
How does DHI differ from FUE?
The key difference is the implantation method. In FUE, the surgeon first creates recipient channels with a blade or needle, then places grafts into those channels separately. In DHI, the Choi Implanter Pen creates the channel and inserts the graft simultaneously. This reduces the time grafts spend outside the body and allows more precise control over implantation angle and depth.
How many grafts can be done in a DHI session?
A single DHI session typically handles up to 3,500 grafts. Because each graft is individually loaded into the Choi pen and implanted one at a time, the procedure takes longer per graft than traditional FUE. Larger sessions of 3,000-3,500 grafts may require two consecutive days. Surgeons often use a team of technicians with multiple Choi pens to increase efficiency.
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