MDCT of the Elbow in Pediatric Patients with Posttraumatic Elbow Effusions

Transcription

1 Chapman et al. MDCT of the Pediatric Elbow Pediatric Imaging Original Research C M E D E N T U R I C L I M G I N G JR 2006; 187: X/06/ merican Roentgen Ray Society Y O Vernon Chapman 1,2 Brian Grottkau 3 Maurice lbright 3 hmed Elaini 3 Elkan Halpern 3 Diego Jaramillo 4 F Chapman V, Grottkau B, lbright M, Elaini, Halpern E, Jaramillo D Keywords: elbow, fracture, MDCT, pediatric, trauma DOI: /JR Received pril 8, 2005; accepted after revision July 10, The Children s Hospital of Denver, 7136 S Hudson Ct., Centennial, CO ddress correspondence to V. Chapman (vernon.chapman@riaco.com). 2 Massachusetts General Hospital for Children, Boston, M. 3 Radiology Imaging ssociates, Englewood, CO. 4 Children s Hospital of Philadelphia, Philadelphia, P. MDCT of the Elbow in Pediatric Patients with Posttraumatic Elbow Effusions OBJECTIVE. The purpose of this study was to determine the performance characteristics of MDCT in the detection of fractures in children with posttraumatic elbow effusions and to assess the effect of MDCT findings on clinical management. SUBJECTS ND METHODS. Unenhanced MDCT of the elbow was prospectively performed without sedation on 31 children 20 months to 16 years old who had posttraumatic elbow effusions. Two blinded reviewers independently and in consensus characterized all MDCT scans as positive or negative for the presence of fracture. Level of interobserver agreement was determined with the kappa statistic. Sensitivity, specificity, positive predictive value, and negative predictive value of MDCT for fracture detection were determined for the consensus MDCT interpretations with follow-up radiographs as the reference standard. Patients were treated with casts and instructed to return in 2 3 weeks for clinical and radiographic follow-up unless a change in management was indicated on the basis of MDCT findings. The frequency of alteration of management was determined. RESULTS. Both reviewers detected fractures in 15 (48%) of the patients individually and in 16 (52%) of the patients by consensus. Interobserver agreement for fracture detection with MDCT was excellent (κ = 0.85). The sensitivity, specificity, positive predictive value, and negative predictive value of MDCT in the detection of fractures were 92%, 79%, 79%, and 92%, respectively. Four (13%) of the children had changes in management based on the MDCT findings. CONCLUSION. MDCT is a sensitive means of evaluating for radiographically occult fractures in children with posttraumatic elbow effusions. It has a high negative predictive value and a high level of interobserver agreement. MDCT findings may lead to alteration of treatment of children with nondisplaced lateral condylar and radial head fractures. ccurate diagnosis of injuries to the elbow of a child can be difficult for orthopedists and radiologists, because radiographs can be normal or show only secondary findings in children with fractures. common secondary finding after elbow trauma is a joint effusion with a fat pad sign, which is elevation of the normal anterior fat pad or visualization of the posterior fat pad on a lateral radiograph of the elbow [1]. In the setting of acute trauma, studies of case series of the use of MRI and follow-up radiographs have shown fractures in 17 76% of children with only the presence of a fat pad sign on initial elbow radiographs [2 5]. Sonography and arthrography are useful in examining children with posttraumatic elbow effusions but can be painful and invasive [6, 7]. lthough it has proven effective in examinations of these patients [3, 8], MRI is time-consuming and requires sedation of younger patients. In the past, CT also required sedation, limiting its use in pediatric imaging. However, with the development of multidetector technology, CT examinations take seconds to perform, eliminating the need for sedation in most cases. In addition, MDCT studies can be reformatted and evaluated in multiple planes, reducing the manipulation necessary for optimal imaging of the area of interest. The sensitivity of MDCT surpasses that of plain radiography in the evaluation of trauma to the face, spine, and bony pelvis [9 12]. Its use in the evaluation of acute extremity trauma is less well studied [13]. To our knowledge, the role of MDCT in evaluation of the elbows of children with posttraumatic effusions has not been studied. The purpose of this study was to pro- 812 JR:187, September 2006

2 MDCT of the Pediatric Elbow spectively determine the performance characteristics of MDCT in the detection of radiographically occult fractures in pediatric patients with posttraumatic elbow effusions and to assess the effect of MDCT findings on clinical management. Subjects and Methods Patients We prospectively performed unenhanced MDCT of the elbow on 31 children, 12 girls and 19 boys. The patients ages ranged from 20 months to 16 years, with an average age of 7.2 years. Patients were included in the study if there was evidence of posttraumatic elbow effusion as determined by the presence of the fat pad sign on a lateral radiograph of the elbow and if frontal and lateral radiographs obtained immediately after the trauma did not show a fracture. ll patients C were examined and underwent scanning within 48 hours of injury. None of the patients had previous significant musculoskeletal abnormalities. The institutional review board at our hospital approved this study, and informed consent was obtained from the parents of all children participating in the study. MDCT Technique Scans were obtained with a 16-MDCT scanner (LightSpeed 16; GE Healthcare) without sedation or administration of IV contrast material. Scanning was performed with the patient in the prone position with the affected arm held above the head in approximately 90 degrees of flexion. Frontal and lateral localizer radiographs were obtained with the minimum technique allowed by the scanner (80 kvp, 10 m). Coverage included the distal part of the humerus and the proximal B D Fig year-old boy with left elbow pain after falling down stairs., Lateral radiograph of elbow shows fat pad sign with elevation of anterior and posterior fat pads (arrows). No fracture was identified on frontal or lateral radiographs of elbow. B, xial MDCT image through level of distal humerus confirms presence of joint effusion (arrows). C and D, Sagittal (C) and coronal (D) reformatted images show nondisplaced supracondylar fracture (arrow). portions of the radius and ulna for a total of approximately 80 mm. MDCT scan parameters were as follows: 100 kvp, z-axis automatic tube current modulation (noise index, 20; minimum, 25 m; maximum, 200 m), rotation speed, 0.5 s/rotation; table speed, mm/rotation; beam pitch, 1.375:1; detector configuration, mm. Reconstructions included slice thickness of 2.5 mm, image spacing of 2.5 mm, full reconstruction mode, and bone reconstruction algorithm as well as slice thickness of 1.25 mm, image spacing of 1.0 mm, full reconstruction mode, and standard reconstruction algorithm. Sagittal and coronal reformations were obtained from the latter reconstructions. Follow-up Radiographs Frontal and lateral radiographs of the elbow were obtained 2 3 weeks after the initial evaluation. JR:187, September

3 Chapman et al. Image nalysis Two reviewers interpreted all of the images in this study. One reviewer was a fourth-year radiology resident, and the other was a senior pediatric musculoskeletal radiologist. Both reviewers were blinded to clinical and demographic data. ll MDCT studies and follow-up radiographs were reviewed on a PCS workstation (Impax RS K review station, GF Technical Imaging Systems). MDCT studies were reviewed with bone (window level, 500 H; window width, 3,000 H) and soft-tissue (window level, 40 H; window width, 400 H) settings. The two reviewers first examined MDCT images independently. They characterized MDCT scans as either positive or negative for the presence of fracture. n MDCT scan was considered positive only if there was direct evidence of fracture (cortical discontinuity or bone deformity). Indirect evidence of fracture (joint effusion or soft-tissue swelling) was not considered sufficient for characterization of a scan as positive. Reviewers recorded the site of the fracture as supracondylar, lateral condylar, medial epicondylar, radial head, radial neck, or proximal ulnar. Both reviewers in consensus then reviewed B Fig. 2 3-year-old girl with left elbow pain after wrestling., Lateral radiograph of elbow shows fat pad sign with elevation of anterior and posterior fat pads (arrows). No fracture was identified on frontal or lateral radiographs of elbow. B, Coronal reformatted MDCT image shows fracture (arrow) of lateral condylar of distal humerus with less than 2-mm displacement of fracture fragments. Patient was treated nonoperatively, and fracture healed without complication. MDCT images. Together the reviewers characterized each MDCT scan as either positive or negative and recorded the site of fracture. Follow-up radiographs were interpreted by both reviewers in consensus and categorized as positive or negative on the basis of presence or absence of healing (periosteal reaction or sclerosis). Reviewers were blinded to the findings of the MDCT studies. Patient Treatment The consensus interpretation of the MDCT study was communicated to the referring pediatric B C Fig year-old boy with left elbow pain after falling off bicycle., Lateral radiograph of elbow shows fat pad sign with elevation of anterior and posterior fat pads (arrows). No fracture was identified on frontal or lateral radiographs of elbow. B and C, xial (B) and coronal (C) reformatted MDCT images show nondisplaced fracture (arrow) of radial head. 814 JR:187, September 2006

4 MDCT of the Pediatric Elbow orthopedist at the time of initial evaluation. ll patients were treated with an elbow cast in 90 degrees of flexion and instructed to return in 2 3 weeks for clinical and radiographic follow-up, unless the orthopedist believed the patient would benefit from a change in management. Such changes in management were recorded. Statistical nalysis The sensitivity, specificity, positive predictive value, and negative predictive value of elbow MDCT in fracture detection were determined for the individual and consensus interpretations of the follow-up radiographs, which were used as the reference standard. The 95% CI was calculated for sensitivity, specificity, positive predictive value, and negative predictive value of the consensus interpretations. Interobserver variability for the interpretation of all MDCT studies was determined with the kappa statistic. The percentage of patients with changes in management as a result of the MDCT findings was determined. B Fig. 4 7-year-old girl with left elbow pain after falling out of chair., Lateral radiograph of elbow shows fat pad sign with elevation of anterior and posterior fat pads (arrows). No fracture was identified on frontal or lateral radiographs of elbow. B, Sagittal reformatted MDCT image shows nondisplaced Salter type 2 fracture (arrow) of radial neck. Follow-up radiographs obtained 2 weeks after injury showed no evidence of healing fracture. Results Both reviewers identified fractures in 15 (48%) of the 31 children and had identical interpretations in 14 cases. Fractures identifiedby both reviewers included five supracondylar (Fig. 1), three radial neck, two lateral condylar (Fig. 2), two radial head (Fig. 3), and two proximal ulnar fractures. Each reviewer identified an additional supracondylar fracture not identified by the other reviewer. In consensus, both reviewers identified frac- B C Fig. 5 3-year-old boy with right elbow swelling after fall., Lateral radiograph of elbow shows fat pad sign with elevation of anterior and posterior fat pads (arrows). No fracture was identified on frontal or lateral radiographs of elbow. B and C, xial (B) and coronal oblique (C) reformatted MDCT images show nondisplaced fracture (arrows) of proximal ulna. Follow-up radiographs obtained 3 weeks after injury showed no evidence of healing fracture. JR:187, September

5 Chapman et al. tures in 16 (52%) of the children. Interobserver agreement for detection of fracture with MDCT was excellent with a kappa value of 0.85 (95% CI, ). Twenty-six patients underwent follow-up radiography. Of the five patients with no radiographic follow-up, one patient with MDCT evidence of a proximal ulnar fracture had sustained multiple trauma, was transferred to another hospital, and was lost to follow-up. One patient with evidence of a radial head fracture on MDCT had the cast removed at a 1- week follow-up visit and did not return for the scheduled clinical and radiographic follow-up 2 weeks later. Three patients with no evidence of fracture on MDCT had normal findings at clinical examinations 2 3 weeks after trauma and did not undergo repeated radiography. In consensus, both reviewers found evidence of fracture healing on follow-up radiographs of 12 (46%) of the 26 patients. The reviewers independently and in consensus identified 10 of these fractures on MDCT, including five supracondylar, two radial neck, and two lateral condylar fractures and one radial head fracture. One reviewer identified an additional supracondylar fracture that exhibited evidence of healing on follow-up radiographs. Both reviewers identified no fracture on MDCT scans of a patient found to have evidence of a healing lateral condylar fracture. mong the 14 patients with no evidence of healing on follow-up radiographs, both reviewers identified an additional two fractures with MDCT, including a radial neck fracture (Fig. 4) and a proximal ulnar fracture (Fig. 5), and one reviewer identified an additional supracondylar fracture. With follow-up radiographs as the reference standard, the sensitivity of MDCT for fracture detection was 83% and 92% for the individual reviewers and 92% (95% CI, %) for both reviewers in consensus. The specificity was 79% and 86% for the individual reviewers and 79% (95% CI, 49 95%) for both reviewers in consensus. The positive predictive value was 77% and 85% for the individual reviewers and 79% (95% CI, 49 95%) for both reviewers in consensus. The negative predictive value was 85% and 92% for the individual reviewers and 92% (95% CI, %) for both reviewers in consensus. Four (13%) of the patients had alterations in management based on the MDCT findings. Two patients with radial head fractures had the cast removed after 1 week to allow early mobilization and prevent restricted range of motion. Two children with nondisplaced lateral condylar fractures were treated nonoperatively with weekly follow-up radiographs for close monitoring for delayed displacement. Discussion The results of our study suggest that MDCT is a sensitive (92%) and specific (79%) means of evaluating for radiographically occult fractures of the elbow in children and has a high negative predictive value (92%). MDCT depicted occult injuries in 52% of children with joint effusion and normal radiographs. Excellent interobserver agreement (κ = 0.85) suggests that MDCT is reproducible, and the short examination time and lack of need for sedation suggest that it is practical. There has been controversy regarding the prevalence of fractures in cases in which a child sustains acute elbow trauma and radiographs show only a fat pad sign but no identifiable fracture. The variability appears to stem from the reference standard used to determine the presence of occult injuries. For example, using follow-up radiographs as a standard, Donnelly et al. [2] found that only 17% of posttraumatic effusions were associated with fractures, whereas studies in which MRI was used as a standard have shown that more than one half of patients have bone injury [3, 4]. Consequently, the specificity (79%) and positive predictive value (79%) observed in our study likely reflect the use of a reference standard, follow-up radiographs, that is less accurate than MDCT. Specifically, three fractures a supracondylar fracture, a radial neck fracture (Fig. 4), and a proximal ulnar fracture (Fig. 5) were identified on MDCT, and there was no evidence of healing on the follow-up radiographs. In our experience, MDCT of the elbow in children is a relatively easy and painless examination. ll of the patients in the current study, which included two 4-year-olds, one 2-yearold, and a 20-month-old, underwent scanning without incident. This success was likely due to the minimal manipulation necessary to perform MDCT and the relative speed with which the examination is performed. In contrast, a series of radiographs necessitates positioning the injured elbow as many as four times, an often time-consuming process that is painful for the child. Furthermore, MDCT can be performed with no image degradation when the elbow is in a cast [14]. The additional views that may be needed after a radiographic series are not necessary with MDCT, because the data can be reformatted in any plane or examined on a 3D workstation to help solve diagnostic dilemmas. MDCT of the elbow performed with an automated tube current modulation technique entails a much lower radiation dose than a fixed tube current technique [14]. Furthermore, when properly performed, the radiation dose from MDCT of the elbow is limited to the elbow and does not include the closest critical organs, the corneas. It is difficult to assess the extent to which added information about fractures obtained with MDCT affects management or improves outcome. Examples of changes in management in the current study include early mobilization of two radial head fractures to prevent restricted range of motion and more frequent radiographic follow-up of two nondisplaced lateral condylar fractures for close monitoring for delayed displacement. The latter of these examples is particularly noteworthy because some orthopedic surgeons pin all lateral condylar fractures and would consider prospective knowledge of the presence of this type of fracture particularly useful. Limitations of the current study were the relatively small sample size, which led to the wide confidence intervals observed, and the use of only frontal and lateral radiographs for the initial evaluation of fractures. rguably, inclusion of at least one oblique view may have decreased the false-negative rate of the initial radiographs and ultimately affected the sensitivity, specificity, positive predictive value, and negative predictive values observed for MDCT. n additional potential limitation is the cost-effectiveness of elbow MDCT in children with posttraumatic effusions, particularly given the relative costs of MDCT and radiography. factor limiting routine use of MDCT in children with posttraumatic elbow effusions is the false-negative results observed in this study. lthough MDCT was very sensitive in the detection of fractures and has a high negative predictive value, both reviewers did not identify a lateral condylar fracture, and one reviewer did not identify a supracondylar fracture with evidence of healing on followup radiographs. This observation suggests that the combination of conservative management and radiographic follow-up is appropriate for most patients and that MDCT may be most useful in cases in which radiographs are normal but there is clinical suspicion of a lateral condylar or radial head fracture. In conclusion, MDCT of the elbow is a sensitive means of evaluating for radiographically occult fractures in children with only 816 JR:187, September 2006

6 MDCT of the Pediatric Elbow joint effusion on initial radiographs of the elbow after acute trauma. MDCT has a high negative predictive value and a high level of interobserver agreement among radiologists of varied experience. MDCT findings may lead to changes in management for a subset of these patients, including those with nondisplaced fractures of the lateral humeral condyle and radial head. References 1. Goswami G. The fat pad sign. Radiology 2002; 222: Donnelly L, Klostermeier T, Klosterman L. Traumatic elbow effusions in pediatric patients: are occult fractures the rule? JR 1998; 171: Beltran J, Rosenberg Z, Kawelblum M, et al. Pediatric elbow fractures: MRI evaluation. Skeletal Radiol 1994; 23: Griffith J, Roebuck D, Cheng J, et al. cute elbow trauma in children: spectrum of injury revealed by MR imaging not apparent on radiographs. JR 2001; 176: Skaggs D, Mirzayan R. The posterior fat pad sign in association with occult fractures of the elbow in children. J Bone Joint Surg m 1999; 81: Blane CE, Kling TF Jr, ndrews JC, DiPietro M, Hensinger RN. rthrography in the posttraumatic elbow in children. JR 1984; 143: Davidson RS, Markowitz RI, Dormans J, Drummond DS. Ultrasonographic evaluation of the elbow in infants and young children after suspected trauma. J Bone Joint Surg m 1994; 76: Badelon O, Bensahel H, Mazda K. Lateral humeral condylar fractures in children: a report of 47 cases. J Pediatr Orthop 1988; 8: Rhea J, Rao P, Novelline R. Helical CT and threedimensional CT of facial and orbital injury. Radiol Clin North m 1999; 37: Sheridan R, Peralta R, Rhea J, Ptak T, Novelline R. Reformatted visceral protocol helical computed tomographic scanning allows conventional radiographs of the thoracic and lumbar spine to be eliminated in the evaluation of blunt trauma patients. J Trauma 2003; 55: Guillamondegui O, Pryor J, Gracias V, Gupta R, Reilly P, Schwab C. Pelvic radiography in blunt trauma resuscitation: a diminishing role. J Trauma 2002; 53: Haapamaki VV, Kiuru MJ, Koskinen SK. Multidetector computed tomography diagnosis of adult elbow fractures. cta Radiol 2004; 45: Pretorius E, Fishman E. Volume-rendered three-dimensional spiral CT: musculoskeletal applications. RadioGraphics 1999; 19: Blickman JG, Dunlop RW, Sanzone CF, et al. Is CT useful in the traumatized pediatric elbow? Pediatr Radiol 1990; 20: JR:187, September