The goal of this prospective, randomized study is to learn about the effects of two different surgical techniques for treating unstable chest wall injuries in adults. The main questions it aims to answer are:

Does fixing two fractures per rib lead to better healing than fixing one fracture per rib in patients with unstable chest injuries? Does the choice of surgical method affect lung function, pain, other symptoms, risk of pneumonia, or the risk of complications?

Participants will:

• Undergo surgery using either the standard method (fixing one fracture per rib) or an alternative method (fixing two fractures per rib), both using a muscle-sparing technique.
• Be followed up at 1, 3, and 12 months after surgery.
• Have CT scans at 3 months (and at 12 months if healing is incomplete) to assess bone healing.
• Be evaluated for lung function, pain, symptoms, and complications.

This study aims to provide new knowledge about which surgical method is best for unstable chest wall injuries, helping to improve treatment and recovery for these patients.

Surgical treatment of chest wall injuries is an area that has attracted increased interest in the research community. It is known that rib fractures, especially unstable injuries-so-called "flail chest"-lead to pain, increased risk of pneumonia, and in some cases, the need for ventilator support and intensive care. Surgical treatment has been shown to reduce the risk of these complications. There are several described surgical methods, including large, open surgery with or without simultaneous thoracotomy, and muscle-sparing open surgery that aims to minimize damage to surrounding tissue. Thoracoscopy is used both as the main fixation method and as an adjunct to open surgery to check for intrathoracic injuries and to clear the thoracic cavity of blood. There is also a described method where a working space is created between the chest wall and the overlying tissue, and surgery is performed using thoracoscopic techniques.

There are only a few studies comparing different surgical methods. It has been shown that a muscle-sparing method resulted in shorter stays in the intensive care unit and hospital, as well as less need for ventilator support. It has also been observed that a thoracoscopic technique led to shorter hospital stays than open surgery. Muscle-sparing surgery enables stabilization of the unstable chest wall segment through one or more smaller incisions where muscle fibers are preserved during fixation. It is not clearly established how many fractures should be fixed. It has been shown that a muscle-sparing technique is advantageous compared to a method with larger incisions and thoracotomy, even if fewer ribs are fixed in the muscle-sparing method. A retrospective study from 2014 showed that the more dorsal fracture row dislocates over time if only the anterior fractures are fixed. However, it is unclear whether this has any clinical significance in the long term. We have not found any prospective study comparing fixation of both fractures in an unstable chest wall segment with fixation of only one of the fractures.

The purpose of this study is to investigate whether fixation of both fractures in an unstable chest wall segment leads to better healing than fixation of only one of the fractures. We also want to examine whether lung function improves when more fractures are fixed, whether it leads to less pain for the patient, and what symptoms related to chest wall injuries patients experience in the long term.

The project is designed as a prospective, randomized study where we compare our current muscle-sparing surgical method with fixation of only one fracture in an unstable chest wall segment with a muscle-sparing method where at least two fractures on each rib (including cartilage) in an unstable segment are fixed.

Patients are asked to participate in the study. Upon consent, patients are randomized to surgery according to clinical routine with fixation of one of the fractures on each rib in the unstable segment or surgery of two or more fractures on each rib in the unstable segment. For the unstable segment to be considered fixed, no more than two fractures on consecutive ribs may be left unfixed. Both surgical methods are performed with minimally invasive muscle-sparing technique via one or more incisions. Randomization between the two groups will be 1:1 using sealed, opaque envelopes prepared by a person independent of the study and based on a digital randomization table.

CT scans of included patients are reviewed for the presence, location, and extent of fractures on the sternum, cartilage, and ribs, as well as the presence of pneumothorax and/or hemothorax, lung contusion, and lung laceration. Injuries are graded according to AIS, presence of flail segment, ISS, and NISS. Fractures are assessed for displacement. The surgeon decides on the indication for surgery according to current guidelines (flail segment) and documents which fractures are planned to be fixed.

Demographic data collected for included patients: age, sex, height, weight, BMI, smoking status, comorbidities (COPD, asthma, pulmonary emphysema, diabetes mellitus).

The following data are collected during the hospital stay: number and length of incisions, knife time, time in hospital, time in intensive care unit and on ventilator, incidence of pneumonia, degree of pain measured with visual analogue scale (VAS), opioid equivalents, and a graphical representation on postoperative days 1, 2, and 3.

The following data are collected at follow-up visits at 1, 3, and 12 months: Radiological healing is examined with CT after 3 months. If complete radiological healing of the chest wall is lacking, a new CT is performed after 12 months. Presence of chest wall deformity and synostosis between ribs is noted. At all visits, lung function is studied with spirometry, chronic complications such as implant dysfunction and osteomyelitis, as well as pain with VAS, opioid equivalents, and a graphical representation. Patients also complete a standardized questionnaire about their symptoms.

Prospective, randomized methodological studies for fixation of rib fractures are currently lacking. It is important for method development to study the outcomes of different surgical techniques, and increased understanding of their advantages and disadvantages can greatly benefit future patients with rib fractures where surgery is indicated. The surgical technique used can affect recovery time, postoperative pain, function, and quality of life.

Inclusion Criteria:

• Patients scheduled for surgery of acute (≤7 days after trauma) unstable injuries in the chest wall at the Department of Surgery, Sahlgrenska University Hospital
• Both parts of the unstable segment must be accessible for surgery.

Exclusion Criteria:

• Patients with injuries resulting from CPR
• Patients with severe head injury (Head AIS>3)
• Patients with spinal injury
• Patients with neurological or musculoskeletal disease affecting chest wall mobility.