The purpose of this project is to investigate whether the use of the new robot-assisted technique in surgery for large and medium-sized ventral midline hernias has brought tangible benefits to patients in terms of Textbook outcome, length of stay, complications and recurrence, compared to open technique and conventional laparoscopic technique. In addition, the investigators will assess the health economic aspects of the different techniques.

In the Stockholm Region, ventral hernia surgeries are performed at Södersjukhuset, Danderyds Hospital, Södertälje Hospital, Norrtälje Hospital, St Göran Hospital, Ersta Hospital and Karolinska Hospital. The hospitals differ in terms of admission areas, profile areas and access to surgical robots for hernia surgery. Since the introduction of robot-assisted surgery in Stockholm around 2017-2018, Södersjukhuset and Danderyd Hospital have used this technology to varying extents for ventral hernia, while the other hospitals have only offered open and conventional laparoscopic surgery. There is no established distribution of hernia patients in the region and no joint treatment conferences. The patients have therefore been distributed primarily depending on place of residence and referral patterns between the hospitals, which has also influenced the choice of method. Similar hernia patients have thus been offered different surgical treatments depending on which hospital in Stockholm the patient was treated at.

The robotic platform involves significant investment costs and costs for robotic instruments. Several studies also indicate that the surgical time is often longer, which can also increase costs. However, the promising results with shorter hospital stay and fewer complications could outweigh the increased surgical costs that have been demonstrated in several studies. The investigators will compare the costs of robot-assisted ventral hernia surgery in the operating room, in the hospital and after discharge with the corresponding costs for open and conventional laparoscopic surgery. Cost-effectiveness analyses will be performed.

Inclusion Criteria:

• Large and medium-sized midline hernias (EHS classification W2-W3)

Exclusion Criteria:

• Hernia operations combined with bowel procedures

All patients registered in the Swedish Abdominal Hernia Registry and operated on at Södersjukhuset, Ersta Hospital, Danderyd Hospital, or Södertälje Hospital