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RO The visible hair misleads. A hair shaft leaves the skin at one angle, but the follicle beneath it does not run in a straight line from that exit point — it curves, and often changes direction within the first few millimetres. A punch aligned with the hair you can see will therefore cut across the part you cannot. This is the single commonest mechanical cause of transection.
The angle is not one number for a whole head. It shifts across the donor area and with hair type:
| Where | How the angle behaves |
|---|---|
| Mid-occipital | Most consistent direction; the easiest region to read |
| Nape and lower margin | Sharpest, most acute exit; the hair here is also the finest |
| Parietal and temporal edges | Direction shifts and sweeps, so the angle changes over short distances |
| Curly or tightly coiled hair | The follicle curves markedly below the surface; the exit angle is least reliable of all |
What a mismatch costs. The punch shaves or severs the follicle instead of enclosing it. A transected graft may still be implanted and may still be counted, but it grows thinly or not at all — which is why a graft number alone says little about a result.
Angle and punch size are one decision, not two. A smaller punch leaves less room for angular error. Choosing a narrower diameter without the angular accuracy to match trades a smaller donor scar for a higher transection rate.
The problem is the same whether extraction is manual or motorised. The device changes the speed, not the anatomy.
Related terms
For how extraction is performed step by step, see the FUE technique. For why curly and Afro-textured hair changes the approach, see Afro-type hair transplant.
