The “slit” means three dimensions puncture wounds or tunnels created by a physician in the skin and subcutaneous tissue in the recipient area for the purpose of insertion of donor hair follicles.
The process of hair transplant is started with slit-making over the recipient area.
Characteristics of a Slit
Dimension of slit—Depth, Width, Shape
Angle
Direction
1. Sagittal-Along direction of hair growth
2. Coronal—perpendicular to the direction of hair growth
Pattern
1. Brick pattern (offset)
2. Row pattern -one behind another
Instruments for slit making are hypodermic needles of various sizes, rectangular blade, angled blade, blade handle, custom made blade
DIMENSIONS OF SLIT
The depth and width of the slit are important from two points of view. The depth and width shall mimic the dimensions of a graft. If slits are bigger than graft, there will be popping of graft and linear damage to the recipient bed will be more leading to more vascular trauma, which may, in turn, affect graft survival. If slits are smaller than graft size, there will be difficulty in placing them. The forceful insertion will cause crushing or trauma to the graft, which will affect the hair growth. So the slit depth and size shall be adequate for each graft. It is advisable to make different sizes of the slit for 1FU,2FUs,3FUs graft to reduce linear damage to the recipient bed.
A-coronal slits B-Sagittal slits
A shows the coronal slits, which are perpendicular to the direction of the hair. the black lines show slits and yellow arrow shows the direction of hair growth. B shows the sagittal slits which are parallel to the direction of hair growth.
Instruments For Slit Creation
Instruments for slit making are a handle to hold a blade or a needle, and a sharp device for creating a slit in the skin, which can be a hypodermic needles of size No18,19,20 and 21. needle or a blade. the blades cutting edge can be angled or rectangle. the blades commonly used are custom made comes in different size from 0.7. mm to 1.2 mm. Some surgeons used cut to size persona shaving blades.
A-Chisel Blade Handle B- Angled Blades C- Needles
Slits Creation For Different Zones of Scalp
There are three major zones of the scalp. The table shows all the zones and subzones of the scalp with direction, angle of slits, and size of the follicular unit to be implanted in these zones.
Frontal Zone -Anterior hairline including frontal tuft and Temporal triangle
Mid-scalp and parietal fringe
Table -showing the area(zones) of scalp and direction of slits
SCALP ZONE | ANGLE | FUS | Average Density G/Sqcm | DIRECTION | CAUTIONS |
Anterior hairline zone | 10 to 15 degree | 1 FUS 2 FUS | 35 to 45 | Centre-forward, lateral side-laterally | Micro and macro irregularities shall be created |
Forelock, rest of frontal zone | 10 to 20 degree | 2 FUS 3,4 FUS | Forelock 45 Remaining 25 to 30 | Forward | Follow existing hair |
Temporal zone | 3 to 5 degree | 1 FUS | 15 to 20 | Upper-downward anteriorly lower-downward posteriorly | Follow existing hair, when using a needle, bend it. if blade keep handle close to skin |
Parietal fringe | 10 to 15 degree | 1 FUS, 2 FUS | 20 to 25 | Down word anteriorly | Follow existing hair |
Mid-scalp | 25 to 35 degree | 2,3,4 FUS | 20 to 30 | Central anteriorly lateral side-slightly laterally | Follow existing hair |
Vertex transition | 25 to 35 degree | 2,3,4 FU | 20 to 30 | Central-anteriorly Lateral side—slightly radially | Follow existing hair |
Vertex whorl | 10 to 15 degree | 1 FU 2 FU | 15 to 20 | Make whorl | Follow existing whorl Draw whorl and do |
Occipital fringe | 5 to 10 degree | 2 FU, 3 FU | 20 to 25 | down word | Follow existing hair |