DHI graft survival rates range from 90% to 95% when performed by a skilled surgeon using the Choi Implanter Pen with proper technique. The primary factors that determine whether a transplanted follicle lives or dies are out-of-body time, temperature control, hydration, gentle handling, and the surgeon's implantation precision.
This article is for informational purposes only and does not constitute medical advice.
How the Choi Implanter Pen Affects Graft Survival
The defining feature of DHI (Direct Hair Implantation) is the Choi Implanter Pen, a hollow needle device that allows simultaneous channel creation and graft placement. This single-step process offers a structural advantage for graft survival compared to traditional FUE.
Reduced Out-of-Body Time
In standard FUE, extracted grafts sit in a holding solution while the surgeon creates hundreds or thousands of recipient channels with a blade. This storage period can last 2 to 6 hours depending on session size. During this time, grafts are separated from their blood supply and vulnerable to cellular damage.
With DHI, each graft is loaded directly into the Choi pen after extraction and implanted within minutes. This shorter out-of-body window reduces ischemic injury, the damage caused when cells are deprived of oxygen and nutrients.
| Method | Typical Out-of-Body Time | Impact on Survival |
|---|---|---|
| Standard FUE | 2-6 hours | Grafts stored in solution, moderate ischemic risk |
| DHI with Choi Pen | 5-15 minutes per graft | Minimal ischemic exposure |
| FUE with rapid cycling | 1-3 hours | Improved over standard, but longer than DHI |
Research shows that graft viability drops measurably after 4 hours outside the body, even in optimal storage conditions. DHI avoids this risk entirely for most grafts.
Precise Depth and Angle Control
The Choi pen allows the surgeon to control implantation depth (typically 1-2mm) and angle (10-45 degrees depending on location) with each placement. Consistent depth ensures the follicle sits at the correct level in the dermis where it can establish blood supply. Too shallow, and the graft dries out. Too deep, and the follicle can become buried or form cysts.
Temperature Control and Graft Storage
Even with DHI's faster implantation cycle, grafts still spend time outside the body during the extraction phase. Temperature management during this window is critical.
Optimal Storage Conditions
Grafts waiting to be loaded into the Choi pen should be kept in a chilled holding solution between 4 and 10 degrees Celsius. Common storage solutions include:
- Hypothermosol: A commercially designed biopreservation medium shown to extend graft viability
- Chilled saline: The most common and cost-effective option, adequate for short storage periods
- Platelet-rich plasma (PRP): Some clinics add PRP to the storage solution, though evidence of benefit is mixed
- ATP-containing solutions: Newer formulations that supply cellular energy during storage
The holding solution should be kept on ice or in a temperature-controlled container throughout the procedure. Room temperature saline degrades graft quality within 1 to 2 hours.
Operating Room Temperature
The ambient temperature of the operating room also affects graft survival. Clinics that maintain cooler room temperatures (18-20 degrees Celsius) create a more favorable environment for exposed grafts. Overhead surgical lights generate heat that can dry out grafts sitting on the preparation tray.
Gentle Handling Throughout the Process
Physical trauma during extraction and loading is the second major cause of graft loss after ischemia. Each follicular unit contains 1 to 4 individual hairs surrounded by a protective tissue sheath. Damaging this sheath during any step reduces survival probability.
Extraction Technique
The surgeon uses a 0.7 to 1.0mm micro-punch to score around each follicular unit before extracting it with fine forceps. Common handling errors that reduce survival include:
- Transection: Cutting through the follicle during punch rotation, severing the hair bulb
- Crushing: Applying too much pressure with forceps during extraction
- Desiccation: Allowing grafts to dry on the extraction tray before storage
- Repeated manipulation: Touching or repositioning grafts multiple times
Experienced DHI surgeons maintain transection rates below 5%. Less experienced practitioners may transect 10-15% of grafts, directly reducing the number of viable follicles available for implantation.
Loading the Choi Pen
Loading a graft into the Choi Implanter Pen requires a trained technician to position the follicular unit inside the hollow needle without bending, twisting, or compressing it. This step demands steady hands and consistent technique across hundreds or thousands of repetitions during a single session.
Clinics that use multiple Choi pens simultaneously (rotating between 6-10 pre-loaded pens) can reduce the time each graft spends loaded in the device, further protecting viability.
Surgeon Technique and Experience
The surgeon's skill level is arguably the most important variable in DHI graft survival. Two surgeons working with the same tools, same patient, and same grafts can produce survival rates that differ by 10-15 percentage points.
What Separates High-Survival Surgeons
- Implantation speed: Faster, more fluid placement means less time per graft outside the body
- Consistent depth: Uniform implantation depth across the entire recipient area
- Appropriate density: Knowing the vascular capacity of the recipient tissue and not over-packing
- Session size management: Staying within the 3,500 graft maximum for a single DHI session to maintain quality throughout
- Team coordination: Working with experienced technicians who handle extraction and pen loading efficiently
The Density vs. Survival Trade-Off
DHI allows dense packing of up to 80-90 grafts per square centimeter in the frontal zone. However, packing grafts too tightly reduces blood supply available to each follicle. The tissue between implantation sites swells, compressing neighboring grafts and reducing oxygen delivery.
Most experienced DHI surgeons target 40-60 grafts per cm2 as the optimal balance between visual density and graft survival. Pushing beyond 60-70 grafts per cm2 can increase the risk of poor survival in the densely packed areas.
Patient Factors That Influence Survival
Not all survival factors are under the surgeon's control. Patient health and behavior before and after the procedure also play a role.
Pre-Procedure Factors
| Factor | Impact on Survival | Recommendation |
|---|---|---|
| Smoking | Reduces blood flow to scalp by 20-30% | Stop at least 2 weeks before |
| Blood thinners | Increase bleeding, making implantation difficult | Discontinue per surgeon's instructions |
| Scalp inflammation | Compromised tissue reduces graft take | Treat any dermatitis or psoriasis first |
| Donor hair quality | Thin, miniaturized donor hair survives at lower rates | Surgeon should assess before proceeding |
Post-Procedure Factors
The first 7 to 10 days after DHI are the critical window for graft anchoring. During this period, newly placed follicles establish vascular connections with surrounding tissue. Actions that disrupt this process include:
- Touching, scratching, or rubbing the recipient area
- Sleeping face-down on the transplanted zone
- Strenuous exercise that increases scalp blood pressure
- Exposure to direct sunlight or extreme heat
- Swimming in chlorinated or salt water
Following your surgeon's post-operative care instructions precisely during this window directly impacts how many grafts survive long-term.
Measuring Your Graft Survival
You cannot assess graft survival during the first 3 months. Shock loss at weeks 2-4 causes most transplanted hairs to shed, which is normal and not an indicator of graft failure. New growth begins emerging around months 3-4.
At your 12-month follow-up, your surgeon can measure hair density in the transplanted areas and compare it against the number of grafts placed. A density measurement above 85-90% of the implanted graft count indicates strong survival.
For a full overview of the DHI procedure and what makes it distinct from other transplant methods, see our DHI overview guide. To understand the month-by-month progression of growth, read the DHI results timeline.
Ready to find out if DHI is right for your hair loss pattern? Get a free AI hair analysis at myhairline.ai/analyze for a personalized assessment of your graft needs and expected outcomes.
FAQ
What is the graft survival rate for DHI?
DHI graft survival rates typically range from 90% to 95% when performed by an experienced surgeon using proper Choi Implanter Pen technique. This means that for every 100 grafts implanted, 90 to 95 follicular units will establish blood supply and produce new hair. The remaining 5-10% of grafts are lost due to unavoidable cellular stress during extraction and reimplantation.
Does the Choi pen improve graft survival compared to standard FUE?
The Choi Implanter Pen can improve graft survival by reducing the out-of-body time for each graft. In standard FUE, grafts are extracted, stored in a holding solution, and then placed into pre-made incisions in a separate step. With DHI, the graft is loaded into the Choi pen and implanted almost immediately, reducing exposure to air, temperature changes, and dehydration.
How long does it take to know if DHI grafts survived?
You will not know your final graft survival rate until 12 to 18 months after the DHI procedure. Initial shedding at weeks 2-4 (shock loss) is normal and does not indicate graft failure. New growth begins at months 3-4, and density continues to increase through month 12. A follow-up with your surgeon at 12 months can assess actual survival based on density measurements.