To determine whether olecranon fractures have osteoporotic features such as age-dependent, low bone attenuation and low-energy trauma as a cause of injury.
Elbow computed tomography (CT) and medical record review were performed in 114 patients (53 males and 61 females) with acute olecranon fractures. The mean age was 57 years. Bone attenuation was measured on the central part of the olecranon on sagittal CT images avoiding the fracture, and on the distal humerus (distal metaphysis and medial and lateral condyles) on coronal CT images. We compared bone attenuation and causes of injury (high or low energy trauma) between younger (<50 years) and older (≥50 years) patients in each gender. Multiple regression analysis was performed to determine the effect of age and gender on bone attenuation.
Mean bone attenuation in older male and female patients was significantly lower than in younger patients, except at the medial condyle in men. The proportion of low-energy trauma in older male patients was significantly higher than in younger male patients. In female patients, low-energy trauma was predominant in both younger and older patients. Age and female gender had significantly negative effects on bone attenuation.
This study demonstrated that olecranon fractures have osteoporotic features, including age-dependent low bone attenuation and low-energy trauma as the predominant cause of injury. Our results suggest that osteoporosis evaluation should be considered for patients aged 50 years or more with olecranon fractures.
Osteoporosis, a serious systemic disease, is associated with increased morbidity, mortality, and economic cost.[
Although fractures around the elbow are common,[
This study was approved by the Institutional Review Board of our hospital. We reviewed consecutive patients with acute olecranon fracture between March 2004 and February 2016 who were treated at our institution, an urban tertiary referral hospital. The inclusion criteria were: 1) acute olecranon fracture; 2) age of 20 years or more; and 3) available computed tomography (CT) scan of the elbow and medical record that documented the causes of injury. Exclusion criteria were: 1) avulsion fracture; 2) interval of more than 1 week between injury and CT examination; 3) CT scan taken at other hospitals; 4) rheumatoid arthritis, previous elbow trauma history, or any other conditions that could affect bone quality around the elbow.
A total of 114 patients who met the inclusion criteria were analyzed, including 53 males and 61 females. Their mean age was 57 years with standard deviation (SD) of 20 years. The causes of injury were categorized into high-energy trauma and low-energy trauma. Motorcycle accidents, car traffic accidents, fall from a height over a standing height, and sports accidents such as skiing were considered as high-energy trauma whereas slips and falls from a height less than a standing height were considered as low-energy trauma.[
Elbow CT examinations were performed using Brilliance iCT (Philips Healthcare, Cleveland, OH, USA) at 120 or 140 kVP with patient in supine position. CT images were obtained and measurements were performed using picture archiving and communication system (PACS). Bone attenuation was measured by placing a circular region of interest (ROI) on sagittal images of the olecranon and at the distal humerus (distal metaphysis and medial and lateral condyles) on coronal images where each region appeared to be the largest (
Patients were divided into two age groups. The older age group consisted of patients who were 50 years of age or older. The younger age group consisted of those who were less than 50 years old. We chose this age as a cut-off value because several previous studies have used the age of 50 as the cut-off value for osteoporosis evaluation. In addition, it has been reported that bone mineral density (BMD) remains fairly constant until about 50 years of age.[
The effects of age and gender on bone attenuation of the olecranon and the distal humerus were analyzed for all patients by multiple linear regression analysis. Independent variables were age and gender. Dependent variables were bone attenuations of the olecranon, lateral condyle, medial condyle, or the center of the distal humerus. In addition, the relationships between bone attenuation of the olecranon and age in both genders were assessed by spearman's correlation coefficient.
To determine the statistical power, primary outcome variable was bone attenuation on the olecranon. To determine a difference of 87 HU (50% of the mean bone attenuation) between two groups with a pooled SD of 82 HU (for an effect size of 1), a power analysis indicated that a sample size of 18 patients in each group would provide 80% statistical power to detect this effect size between groups (α=0.05, β=0.2) using t-test. Thus, the number of patients in each group of this study satisfied the statistical power. All statistical analyses were performed using the SPSS version 23.0 (SPSS Inc., Chicago, IL, USA). Statistical significance was considered when P-value was less than 0.05.
Mean bone attenuations of the olecranon, the lateral condyle of the distal humerus, the medial condyle, and the center were 174 (SD, 82), 130 (SD, 90), 117 (SD, 95), and 140 (SD, 69) HU, respectively. In male patients, the mean bone attenuation of the older age group was significantly lower than that of the younger age group in the olecranon (
In male patients, the proportion of olecranon fractures caused by low-energy trauma in the older age group was significantly higher than that in the younger age group (
Multiple linear regression analysis revealed that age and female gender independently had negative effect on bone attenuation (
Intraclass correlation coefficient (ICC) values for intra- and inter- observer reliability are shown in
Several studies have suggested that fractures of the vertebrae, hip, proximal humerus, and distal radius are major osteoporotic fractures. Fractures of the femur diaphysis, ankle, and rib also have features of osteoporotic fracture.[
We used elbow CT as a surrogate examination of BMD at the olecranon and the distal humerus. Several studies have demonstrated that the average bone attenuation on CT of the spine is correlated with BMD on dual energy X-ray absorptiometry (DXA).[
This study has several limitations. First, the number of patients was not large. In addition, patients included in this study were all Koreans recruited from a tertiary referral hospital. Therefore, the population in this study may not represent the general characteristic of all patients with olecranon fracture. However, evaluation with a single CT scanner made the measurement of bone attenuation reliable in this study. Second, this study did not involve control group. Elbow CT examinations could not be performed for age- and sex-matched patients without olecranon fracture because of radiation exposure. In addition, patients who had elbow CT scan without fracture had a certain condition that could affect bone quality such as rheumatoid arthritis. Third, analysis of bone attenuation involved only cancellous bone. However, both cancellous and cortical bones are important for mechanical strength. High-resolution peripheral quantitative CT that can quantify cortical porosity
In conclusion, our results demonstrate that olecranon fractures have features of osteoporotic fracture, including age-dependent low bone attenuation in both genders and low-energy trauma as predominant cause of injury in men aged 50 years or more and in women regardless of younger or older. Our results suggest that patients aged 50 years or more with olecranon fracture should be evaluated for osteoporosis and fracture risks for secondary prevention of subsequent fractures.
This study was in part supported by a research fund (2015-R1D1A1A01058562) from National Research Foundation of Korea.
No potential conflict of interest relevant to this article was reported.
The data is presented as number or mean±standard deviation.
HU, Hounsfield units.
CI, confidence interval.
ICC, intraclass correlation coefficient; CI, confidence interval.