How to determine the bone mineral density of the distal humerus with radiographic tools?

INTRODUCTION: The aim of this study was to investigate three methods of prediction of the bone quality of the distal humerus: dual-energy X-ray absorptiometry (DEXA), Ct-Scan and plain radiographs. MATERIALS AND METHODS: The bone mineral density (BMD) of 21 cadaveric distal humerus was determined using DEXA at two levels. Then a CT-scan and anteroposterior radiographs were taken. The cancellous density was estimated with the CT-scan. The cortico-medullar index (CMI) was calculated as cortical thickness divided by total bone thickness on AP views. RESULTS: A significant positive correlation was found between the BMD of the epiphysis and the CMI of r = 0.61. The mean BMD of the distal humerus was 0.559 g/cm(2). Male specimens showed a significantly higher BMD than females. The mean CMI of diaphysis was 1.431 and the mean BMD of the metaphysis region was 0.444 g/cm(2). DISCUSSION: More than a direct evaluation of the bone density with a CT-scan, the CMI of the distal humerus diaphysis is a predictor of the bone quality of the distal humerus. This should be of great help for the surgeon's decision making in case of fracture of the distal humerus, as open Reduction and Internal Fixation (ORIF) of fractures of the distal humerus can lead to failure due to poor bone quality. LEVEL OF EVIDENCE: Basic Science Study, Anatomic Cadaver Study.

Usefulness and reliability of two- and three-dimensional computed tomography in patients older than 65 years with distal humerus fractures.

BACKGROUND: Distal humerus fractures are difficult to characterise and to classify according to the AO system. In this multicentre study, our objectives were to assess the usefulness of computed tomography (CT) and to measure intra-observer and inter-observer reliability according to observer experience. MATERIALS AND METHODS: An online survey of professional practice was performed using a questionnaire based on a clinical case. Participants were asked to determine the AO classification using radiographs then to reappraise their answers after the addition of CT images. For the reliability study, 16 observers in five centres evaluated radiographs and CT scans of 26 distal humerus fractures. They used the radiographs to determine the AO classification and assess the main fracture characteristics then reappraised their findings after adding the CT images. The radiographs and 2D CT images were read twice at an interval of 2 weeks, and during the second reading, 3D CT images were available also. At least 1 month later, the same observers performed similar readings 2 weeks apart (radiographs and 2D CT images at the first reading and addition of 3D CT images at the second reading). RESULTS: Correct fracture classification was achieved in 95% of cases with the CT images compared to only 73% with the radiographs. CT led to diagnostic and therapeutic changes in 90% and 25% of cases, respectively. Inter-observer reliability was poor for both AO classification and fracture characteristics, not only with the radiographs and 2D CT images, but also with the added 3D CT images. In contrast, intra-observer reliability improved after the addition of 3D CT images. Assessment accuracy was influenced by image quality and geographic origin of the observer but not by observer experience. CONCLUSION: CT improves diagnostic accuracy and, in some cases, changes the surgical strategy. In our study of a large number of observers, CT did not improve inter-observer agreement about the study variables. Intra-observer agreement was improved by 3D CT but not by 2D CT. Accuracy was not influenced by years of observer experience but was dependent on image quality, proficiency with computer-based tools and, above all, image observation and interpretation. LEVEL OF EVIDENCE: Level III.