After confirming that the incredibly unfortunate Lorenzo Insigne did indeed tear his anterior cruciate ligament in yesterday's win over Fiorentina, Napoli sent the attacker to Rome to have his surgery. While the club has more local doctors that they normally work with, a quality orthopedic surgeon is worth travelling for.
According to the club, the surgery was performed by Professor Pier Paolo Mariani, and the operation was a "complete success". While in most operations, "success" merely means that the limb in question is still attached, in the case of a reconstructive surgery, it is a good sign that things went smoothly and that no additional damage or complications were discovered.
That last point is especially important, as there were some fears that there may have been meniscus damage in Insigne's knee, something that's difficult to confirm pre-surgery. As no reports since the surgery have mentioned his meniscus, that should serve as relief for Napoli fans; additional damage to the meniscus would have complicated and likely lengthened Insigne's recovery time, as well as made it harder for him to get back to his full talent level.
No timeline has been given yet, but these days ACL injuries typically take between six to eight months to recover from, depending on the severity of the injury and other damage sustained in the joint. That means that Lorenzo is almost certainly done for the season, and will likely be limited in the early stages of summer training with the club, and possibly the beginning of next season too.
There's also often what some call a "readjustment period" while the player not only rebuilds his playing form, but also his trust in the joint. After such a traumatic and serious injury, it takes time to recover mentally in addition to the physical toll. Many players have trouble really putting their full effort in to actions that rely in that knee for months after they get back on the field. Hopefully someone has hard-nosed and high-effort as Insigne can get through that period quickly.