Subjects
From March 1, 2012 until January 13, 2017, patients aged ≥40 years presenting with acute distal radius fracture at the Department of Orthopedic Surgery at District General Hospital of Førde (Sogn og Fjordane County) were included in a case control study. The study was primarily designed to explore the prevalence of celiac disease in patients with peripheral fractures compared to community-based controls. The original study has previously been described [13]. Fracture patients who fulfilled the inclusion criteria and consented to participate were referred for DXA scan and consideration of secondary fracture prevention (n = 516). Two hundred eighty-nine patients agreed to participate, giving an inclusion rate of 56%. We included both patients with low energy fractures (equivalent to fall from standing height or lower) and fractures due to traumas with higher energy. Five patients suffered multiple simultaneous fractures (one with bilateral radius fractures, one with an additional humerus fracture, one with an additional ankle fracture, and two with additional vertebral compression fractures).
Procedures and measurements
The radiographic distal radius series comprised standard anteroposterior and lateral radiographs. In 68% of cases (197 of 289 patients) a supplementary CT scan was available. The same radiologist classified the fractures as extra articular (type A), partly articular (type B) or complete articular (type C) according to the Müller AO-system (AO) [14, 15]. Types B and C were considered more complex than type A. In addition, the multifragmentary fractures (types A3, C2 and C3) combined were compared to the other AO fracture types. Five of the distal radius fractures could not be classified because the radiographic images had been performed elsewhere.
The BMD measurements were performed by DXA technology (Lunar Prodigy Rtg 5603, manufacture year 2000, GE Healthcare), with a daily quality assurance of +/− 2%. BMD was reported as g/cm2 and T-scores by standard definition. Osteoporosis is defined as T-score ≤ − 2.5 in the femoral neck, total hip or lumbar spine. Osteopenia (low bone mineral density) is defined as T-score between − 1.0 and − 2.5 [16]. History of previous fractures, comorbidities, medications, and lifestyle factors were registered. The original documents from the orthopedic surgeons and examining rheumatologist were reviewed to classify the injury as due to a low energy trauma or not. Height and weight were measured as part of the DXA procedure. BMI was calculated and categorized into underweight (BMI < 18.5), normal weight (BMI 18.5–24.99), overweight (BMI 25–29.99) and obesity (BMI ≥ 30). Blood tests were analyzed to detect common causes of secondary osteoporosis [13].
Statistical analyses
We performed descriptive statistics for age, sex, BMI, number of patients with osteoporosis, osteopenia, and overweight in the distal radius fracture subgroups. Data between subgroups were compared using chi square or Fisher’s exact test for categorical data and two-sample t-test or Mann-Whitney U test for continuous data. To assess risk factors associated with the complexity of fractures, we estimated odds ratios (ORs) with 95% confidence intervals (CIs) using unconditional logistic regression models. Complexity of fractures was defined as more radiological complex fractures (AO type B + C) as opposed to less complex fractures (AO type A). Relevant risk factors for complexity of fracture included osteoporosis, osteopenia, age > 65 years, male sex, BMI, and current and previous smoking. In all analyses, the association between the risk factor and the complexity of fractures was first examined crudely and then with adjustment for the other risk factors under study. All p-values were two-sided and values below 0.05 were considered statistically significant. All calculations were performed using R version 3.6.2 (team).