The Bascom approach to pilonidal disease emphasizes keeping the incision away from the midline and not excising any excess tissue.
With an abscess, I and D from a vertical incision 1-2 cm lateral to the midline.
For an excision, excise just the pits with the tip of an 11 blade, excising just a tiny rim of tissue around each pit. Then, make an incision as above and clean out the hair and granulation tissue underneath the midline from this lateral incision.
Apparently, the natural forces in the pilonidal area pulled the midline apart so midline wounds take longer to heal.
Have the patient keep the area hair free forever by having it shaved or using depilatory creams.