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The ankle fracture is one of the most common fractures in adult patients and is a heterogeneous group of fractures. From the fully stable fracture on the most distal part of thefibula to severely unstable and even dislocated ankles. Patients with ankle fractures often report a good result after treatment, but a small group have persistent problems.The purpose of the dissertation is to investigate classification, epidemiology, complications, and results in order to improve knowledge and management of ankle fractures.This dissertation is mainly based on data from the Swedish Fracture Register (SFR).

In Study I the accuracy of the AO/OTA classification, version 2007, of ankle fractures in the SFR was examined. Entry of data into the SFR is mainly performed by the attending doctors at the accident and emergency departments, often with varying experience of fracture classification. Classification of fractures can in some cases bedifficult even for experienced orthopaedic surgeons. This is because the fractures to be categorized can be seen being on a spectrum and there will always be cases which is on the border between different categories. We created a reference group that classified several randomly selected ankle fractures from the SFR based on X-rays from treatingorthopedic departments. The assessment that was then agreed upon was considered to be the gold standard classification and could in turn be compared to the classification found in the SFR. The agreement between the classification in the SFR and the classification of the reference group was 88% for AO/OTA type level and 74% for AO/OTAgroup level. This corresponded to a kappa value of 0.77 and 0.66 respectively. The findings were equivalent to or higher than in previous studies.

In study II the aim was to examine the incidence of ankle fractures in Norrbotten county, as well as the relationship between AO/OTA-classes of ankle fractures with age, gender and low-energy trauma. Ankle fractures are increasing in an ageing population but are not generally seen as a fragility fracture. All ankle fractures treated at a hospital in the county were retrospectively identified, X-rays were inspected and classified, and the medical record reviewed. The study found 1,756 ankle fractures corresponding to an incidence of 179 per 100,000 person-years. Females had an increasing incidence with age while among males the incidence was more evenly distributed. The type B fractures showed a slightly higher proportion of low-energy trauma and increased substantially with age. In contrast were the A21-subgroup and type C ankle fractures which had a lower mean age and proportion of women.

Study III investigated the association between the incidence of venous thromboembolic event (VTE) and the use of low-molecular-weight heparin (LMWH) prophylaxis following an ankle fracture, as well as factors affecting the risk of VTE. VTE is a well-known complication after ankle fracture and especially after ankle fracture surgery. The use of LMWH prophylaxis is debated. Data on ankle fracture treatment from the Swedish Fracture Register was linked to data for VTE diagnosis and LMWH prescription from the Swedish National Patient Register and the Swedish Prescribed Drug Register. Cases of diagnosed VTE were identified among 222 of 14,954 ankle fractures. Orthopaedic departments with higher-than-average use of LMWH prophylaxis among non-operatively treated ankle fractures had a lower incidence of VTE (OR 0.60, 95% CI, 0.39-0.92). Among patients treated operatively at departments with guidelines for routine use of LMWH prophylaxis there was an incidence of VTE of 1.6%, compared to 2,7% at departments without routine use of LMWH prophylaxis (OR 0.56, 95% CI, 0.37-0.86). During the first two weeks following injury, there was only one case of VTE in 5,332 patients with prescribed LMWH, compared to 39 cases of VTE among 9,622 patients without prescription.

Study IV examined the variations in the length of sick leave in ankle fracture patients. Even though most patients with an ankle fracture report a satisfactory outcome there are still a number of patients with persistent pain and functional impairment. The aim of the study was to analyse how treatment, different types of ankle fracture and patients-related factors were associated with the length of sick leave by combining data from the SFR and Swedish Social Insurance Agency (SSIA). Fifty-three per cent of patients registered with an ankle fracture in the SFR had a period of paid sick leave from the SSIA. There was an association between the length of the sick leave and the severity of the fracture. A correlation was also seen between the length of the sick leave and a worse patient-reported outcome.