Nondisplaced elbow fractures: A commonly occurring and difficult diagnosis.

PURPOSE: Determine the sensitivity and specificity of radiography in identifying nondisplaced elbow fractures after trauma. Our hypothesis is that nondisplaced fractures occur commonly following impact injuries and are difficult to diagnose with plain film imaging. METHODS: An in vitro double-blinded study of 16 cadaver arms was designed, simulating axial forearm trauma. Following injury, anteroposterior and lateral radiographs were obtained. Each specimen was dissected, and the injury described. A musculoskeletal radiologist, blinded to dissection results, examined the radiographs. RESULTS: Dissection revealed 39 fractures of 96 sites examined. A total of 14 fractures were nondisplaced, 7 involving the coronoid process. Radiographs identified 27 fractures. Of the 12 missed fractures, 11 were nondisplaced. Radiographic diagnosis of nondisplaced elbow fractures demonstrated a 21% sensitivity, 95% specificity, 50% positive predictive value, and 83% negative predictive value. CONCLUSIONS: Radiography for nondisplaced elbow fractures demonstrated limited success. Additional imaging studies may be required in suspected elbow injuries with initial negative radiographs.

Forearm interosseous membrane trauma: MRI diagnostic criteria and injury patterns.

OBJECTIVE: Define criteria for interosseous membrane (IOM) injury diagnosis using MRI, and characterize patterns of IOM disruption following forearm trauma. Our hypothesis is that most IOM injuries occur along the ulnar insertion, and MRI should be obtained following forearm trauma to assess IOM competency. DESIGN: Sixteen cadaver forearms were subjected to longitudinal impact trauma. Prior to and following injury, MR images were examined by a board-certified musculoskeletal radiologist using pre-defined criteria for determining IOM integrity. Each specimen was dissected and the viability/pattern of injury examined. The MRI and dissection results were compared using a double-blinded methodology. RESULTS: Eight of the 16 specimens demonstrated IOM trauma. Seven specimens demonstrated complete IOM disruption from the ulnar insertion, and one revealed a mid-substance tear with intact origin and insertion. The dorsal oblique bundle was disrupted in four specimens. MRI analysis identified IOM injury in seven of the eight forearms. The injury location was correctly identified in six specimens when compared to dissection observations. MRI determination of IOM injury demonstrated a positive predictive value of 100%, a negative predictive value of 89%, a sensitivity of 87.5% and a specificity of 100%. CONCLUSION: Our findings demonstrate the accuracy of MRI in identifying IOM disruption, and its ability to localize specific injuries in a clinically relevant model of forearm trauma. The injury patterns demonstrated most lesions occurred along the IOM's ulnar insertion, and in half of the injured specimens there was concomitant dorsal oblique bundle disruption.

Forearm and elbow injury: the influence of rotational position.

BACKGROUND: The purpose of this study was to develop an axial loading forearm fracture model and to determine the influence of forearm rotation on the fracture pattern. METHODS: Twenty-six cadaveric arms were thawed in saline solution. Pressure-sensitive film was sealed and was placed through a lateral arthrotomy into the radiocapitellar joint. The arm was potted at the proximal part of the humerus with the elbow in extension. Rotational range of motion was measured with use of a goniometer starting from a supinated position (0 degrees ). Specimens were placed in a vertical position at various angles of forearm rotation, and a 27-kg mass was raised to 90 cm and was dropped onto the distal part of the radius. The pressure film was removed and was analyzed to determine the radiocapitellar joint contact area following impact. Each arm was dissected, and the injury pattern was assessed. RESULTS: Both-bone forearm fractures (proximal radial fractures with concomitant distal ulnar fractures) occurred at 5 degrees +/- 2.6 degrees of rotation, isolated radial head fractures occurred at 44.4 degrees +/- 5.2 degrees of rotation, and Essex-Lopresti fractures (radial head fractures with tearing of the interosseous membrane) occurred at 70 degrees +/- 25.2 degrees of rotation. The distribution of Essex-Lopresti and radial head fractures was significantly different at a cutpoint of 54 degrees of forearm rotation (p = 0.009), and the distribution of radial head fractures and both-bone forearm fractures was significantly different at a cutpoint of 10 degrees of forearm rotation (p = 0.001). The percent contact area of the radial head varied with the injury pattern (p = 0.029). Marginal radial head fractures occurred at 46.7 degrees +/- 6.6 degrees of rotation with a contact area of 30.9% +/- 8.6%, while comminuted radial head fractures occurred at 74.4 degrees +/- 27.2 degrees of rotation with a contact area of 53.9% +/- 8.3%. CONCLUSION: The amount of forearm rotation at the time of axial load impact directly influenced the injury pattern. Furthermore, the radial head contact area and the fracture severity increased in pronation compared with supination.