Ankle fractures constitute 9% of all fractures and have an incidence of approximately 187 per 100,000 persons per year in Norway. A posterior malleolar fragment (PMF), located on the lower backside of the tibia, is present in up to 46% of Weber B. Weber B fractures are the most common type of fractures of the fibula, located at the height of the syndesmosis. Patients with a PMF were recently shown to have significantly lower patient-reported outcome measures (PROM) than the general population. For this reason, the indication and choice of intervention for these fractures have been the object of increased interest over the recent years. It is one of the most debated areas within ankle fracture surgery. Traditionally, these PMFs have been treated with closed reduction, without direct manipulation of the PMF, anteroposterior screw fixation, or even no-fixation of the smaller fragments. A more novel posterior approach to the ankle for open reduction and internal fixation is increasingly popular and has led to fixation of smaller and medium-sized PMFs. Studies suggest fracture reduction is better with a posterior approach. However, there is no consensus as to what the best treatment is. There are no available randomized controlled studies examining PROM in patients after surgery with fixation versus no fixation for the PMF.

Through a multicenter prospective randomized controlled trial initiated from Haukeland University Hospital, patients will be recruited and randomized to receive treatment with or without fixation of the PMF. Patients will be recruited at six study hospitals from all Regional Health Trusts in Norway. Treatment today is often based on local tradition and retrospective, ambiguous literature. As there is no clear evidence supporting the choice to fixate, or not fixate, the posterior malleolus fracture. The current study can contribute new knowledge and thereby contribute to an evidence-based approach to treating these patients.

Mason and Molly type 2A and 2B fractures will be included in the study.

Ankle fractures constitute 9% of all fractures and have an incidence of approximately 187 per 100,000 persons per year in Norway. Weber B fractures are the most common type of fracture of the fibula. A posterior malleolar fragment (PMF) is present in up to 46% of Weber B and Weber C fractures. Patients with a PMF were recently shown to have significantly lower patient-reported outcome measures (PROM) than the general population. Clinical outcome for ankle fractures with a PMF is known to be poor from several studies. For this reason, the indication and choice of intervention for these fractures have been the object of increased interest over the recent years. It is one of the most debated areas within ankle fracture surgery. Traditionally, PMFs have been treated with closed reduction, without direct manipulation of the PMF, and anteroposterior screw fixation, or even no-fixation of the smaller fragments. A more novel posterior approach to the ankle for open reduction and internal fixation is increasingly popular and has led to fixation of smaller and medium-sized PMFs.

The reason for focusing on the posterior approach is new knowledge that intraarticular step-off in the tibiotalar joint and malreduced syndesmosis is associated with poor outcomes. Studies suggest fracture reduction is better with a posterior approach. However, there is no consensus as to what the best treatment is. Pilskog et. al. published a retrospective study in Nov. 2020 where patients without fixation reported similar PROM to patients with fixation. Most studies are retrospective and with a variable number of patients without a reasonable conclusion as to what is best practice. A few prospective studies are published. But there are no available randomized controlled studies examining PROM in patients after surgery with fixation versus no fixation for the PMF.

Through a multicenter, prospective, randomized controlled trial initiated from Haukeland University Hospital, patients with Weber B fracture and associated PMF (with or without a medial malleolus fracture) will be recruited and randomized to receive treatment with or without fixation of the PMF. Patients will be recruited at seven study hospitals from all Regional Health Trusts in Norway.

Mason and Molly type 2A and 2B fractures will be included in the study. Type 2 fractures are medium-sized fractures of the posterior malleolus which involve the fibular incisura. The fractures are classified as type 2A if only the posterior malleolus is fractured and as type 2B if there are two posterior fragments of the tibia in which the medial fragment extends to and involves the medial malleolus.

The lack of consensus on best practice is of great concern as patients of all ages are affected. In a retrospective study examining the patient-reported outcome of 130 patients with a PMF, 75% were aged 67 or younger. Such an injury, therefore, affects patients with many active years left in both their working life and daily activities. Interviews with the patient representative and with patients at the outpatient clinic reveal a long time for rehabilitation, over 16-18 months until 100% working ability. The patients also talk about the need to change working tasks due to reduced range of motion and pain. The study will not only answer the best way to treat the PMFs, but also give insights into the impact on the patient's life through the use of sick leave, treatment of the ankle syndesmosis, and complication rates. The aim is to give the patients the best possible treatment for better recovery and function.

The main aim of the study is to compare PROM in patients who had fixation of the PMF with patients without PMF fixation with the intention to define what is the best surgical approach and treatment of the fractures in question.

The null hypothesis (H0): There is no difference in mean patient-reported outcome (Self-reported Foot and Ankle Score, SEFAS) in patients treated with fixation of the PMF and patients treated without fixation of the PMF.

The intention is to deliver treatment recommendations based on the study results. The results will thus have direct consequences for both patients and orthopedic surgeons.

Additional aims:

• Publish treatment recommendations for ankle fractures including a PMF
• Sub-analysis of patients with and without syndesmotic injury
• Publish complication rates in the different treatment groups
• Health economic impact of ankle fractures
• Report rate of posttraumatic osteoarthritis after 2 and 5 years

The primary outcome is the summary score of Self-reported Foot and Ankle Score (SEFAS) at 2 years.

Project methodology:

Patients will be prospectively recruited from all six participating hospitals. An estimated 275 patients with ankle fractures per year will be eligible for inclusion. The investigators aim to include 208 patients over two years. Data are collected and stored by using Viedoc as the electronic case report form (eCRF). Patients will be treated according to randomization and data will be collected at each study site, stored via Viedoc, and sent to Haukeland University Hospital for analysis. Randomization is performed using Viedoc without interference from the surgeon on call. The last follow-up will be 5 years postoperative. Local coordinators at each hospital will manage inclusion and ensure correct treatment according to protocol.

The primary outcome of the mean difference between groups will be analyzed with an analysis of covariance (ANCOVA) with SEFAS at two years with baseline as covariate. Change in SEFAS over time (3 months - 1 year - 2 years - 5 years) will be analyzed with linear mixed effect models. The use of ANCOVA with adjusting for PROM at baseline (inclusion) is unique in orthopedic trauma studies as most studies report solely 1- or 2- year results with differences in mean values between groups. Adjusting for baseline will strengthen the analysis.

The Student t-test for continuous variables and chi-squared test for categorical variables will be used.

A power of 90% with a priori significance level of 0.05 requires 86 patients in each arm of randomization. A difference between groups of five points is considered to be a clinically relevant difference. Accounting for 20% lost to follow-up or dropout, 104 patients will be included in each group. The total number of patients will be 208.

NorCRIN will be used as a national monitoring service via Viedoc and Anne Mathilde Henden Kvamme.

Helse Bergen HF, Haukeland University Hospital, will be the coordinator of the project. All four regional health trusts in Norway are involved in this project. There will be responsible local coordinators for the study at the seven sites represented. The local coordinators are responsible for developing and coordinating the study and communicating with the project leaders and main coordinators.

Ethical considerations None of the surgical methods can be considered experimental as they are in conventional use at the study clinics and several other level 1 trauma centers. Participation in the study will not cause any delay in treatment compared to conventional care, nor will patients have any extra expenses related to follow-up evaluation. Patients having any concerns throughout the study period will be offered an extra follow-up by one of the participating surgeons.

As there is no clear evidence supporting the choice to fixate, or not fixate, the posterior malleolus fracture, the study can contribute new knowledge thereby contributing to a more evidence-based approach to treating these patients.

The project is approved by the Helse Bergen Data Protection Officer and Regional Committees for Medical and Health Research Ethics (REC). REC ref.nr: 255548. Patients will have to give their written, informed consent prior to inclusion in the study.

Inclusion Criteria:

• Posterior malleolar (PM) fracture, of Mason & Molly type 2A/2B, associated with Weber B lateral malleolar fracture, with or without medial malleolar fracture

• Posterior malleoli >=2 mm displaced (on CT in axial, sagital or coronal plane)

• Patients informed, written consent

• Age 18-65 years

• For inclusion axial CT images are examined

  • Measurements are performed 5 millimeters (mm) cranial to the tibia plafond
  • Posterior malleolus fractures involving less than 40% of the fibular notch are included.

Exclusion Criteria:

• Non-compliant patient, i.e.: dementia, alcohol- or substance abuse
• ASA-4 patients
• Known congenital bone decease
• Pathological fractures
• Immunocompromised patients
• Tourists or patients on a short-term work/study permit
• Previous injury or condition of the ipsilateral ankle or ipsilateral lower extremity with a resulting dysfunction
• Poor controlled diabetes
• Patients with known arterial insufficiency
• Open fractures
• Severely traumatized patients (ISS>16)
• Patient declines to participate in study