LHCF is an intra-articular fracture. The integrity of the articular cartilage is an essential factor in predicting the stability of a fracture. In the present study, both ultrasound and arthrography were used to assess the preoperative integrity of the articular cartilage status, and the results were highly consistent. Compared with arthrography, ultrasound was more efficient in determining the integrity of the articular cartilage noninvasively, without ionizing radiation, and ultrasound was more convenient to use. Ultrasound can be used as a complementary tool with arthrography to predict the integrity of the articular cartilage status in patients with minimally displaced LHCFs.
The classification systems recently proposed by Song and Weiss are based on the integrity of the articular cartilage surface. Because the distal humeral epiphysis is not ossified, the cartilage of the distal humerus cannot be detected by radiography. Therefore, there is controversy regarding the relationship between the integrity of the articular cartilage status and the results determined by the radiography. Ultrasound is a reliable, ionizing radiation-free, low-cost, noninvasive technique that does not require sedation or general anaesthesia, especially for paediatric elbow examinations[10, 11, 13, 16]. A previous study showed that transverse ultrasound could be used to detect whether a fracture was complete or incomplete. Vocke-Hell et al found that ultrasound can show whether the fracture line extends through the articular cartilage in the transversal view. If the hypoechoic cartilage hinge is disrupted and the hyperechoic fracture line extends to the distal humeral articular cartilage, the fracture is determined to be a complete LHCF. If the hypoechoic articular cartilage hinge is smooth and continuous, it is judged to be an incomplete LHCF. The present study showed that the ability of arthrography to predict the integrity of articular surface involvement is powerful, and ultrasound has a high diagnostic value in predicting the integrity of articular surface in patients. The obtained results confirmed that both ultrasound and arthrography are effective imaging modalities for predicting the integrity of the articular surface, but the former method is less invasive and does not lead to radiation exposure.
In the present study, even when the displacement of the fracture was ≥ 2 mm, 64.1% of the minimally displaced LHCFs had intact articular surfaces. Consistent with the findings of previous studies[2, 5, 7, 17], fractures displaced by < 4 mm on radiographs were more likely to have intact articular surfaces. However, no fractures with ≥ 4 mm of displacement were assessed by arthrography in Weiss’s study. Song et al found that all patients with incongruent articular surfaces had fractures displaced by >2 mm, as measured by radiography. However, in Song’s study, the integrity of the cartilage hinge was mainly determined on the basis of the internal oblique radiograph. Although there was a statistically significant correlation between the arthrography assessments and fracture displacement, this correlation was not found in the ultrasound assessments. It is difficult to assess the relationship between the displacement of the fracture and the integrity of the cartilage hinge. In particular, there were only three patients with >4 mm of fracture displacement in this study. We did not find a relationship between fractures with >4 mm of displacement and the integrity of the articular surface in our study. However, this 4 mm cut-off value was not a clinical criterion prospectively used for the assessment of the incongruity of the articular surface. In addition, compared with the assessment of the displacement of the fracture, the routine use of ultrasound was more effective in evaluating the cartilage hinge status before the initial treatment of these fractures.
Three patients were predicted to have different statuses of articular surface integrity according to the ultrasound and arthrography assessments. Ultrasound can be used to observe the hypoechoic layer of the hyaline articular cartilage in the distal humeral epiphysis. The fracture line is directly identified by the hyperechoic gap and the disrupted hypoechoic layer on the anterior articular surface. Arthrography is a reference standard for predicting the integrity of the articular cartilage surface[2, 18]. However, arthrography indirectly detects the integrity of the articular surface of the distal humerus through contrast medium tracking. It is difficult to assess complex three-dimensional articular cartilage fractures by arthrography. In addition, arthrography leads to radiation exposure, which requires sedation or anaesthesia, and false-negative results have been reported. Pennock suggested that arthrography findings are unclear and cannot be used to confirm the congruency of the articular surface. Although this study did not confirm these differences, on the basis of our data, we believe that ultrasound can provide more accurate information to determine the integrity of the articular cartilage.
In the present study, CRPP was performed in all patients, and no major complications occurred. As previously reported in the literature, whether minimally displaced LHCFs should be treated with ORIF or CRPP is controversial. Displaced LHCFs with displacements > 1 mm were treated with ORIF to avoid re-displacement and non-union, enabling direct visualization of the articular surface to confirm anatomical reduction. Because the articular surface was intact in most cases displaced by <4 mm, as confirmed by arthrography, these fractures were recently treated safely using CRPP, and no major complications were reported[2, 17]. Song et al[15, 21] expanded the indications of CRPP to all fractures with incongruent articular surfaces or fracture displacements > 2 mm, with a closed reduction success rate of 73% (46/63). In particular, in patient number 24 (Fig 1), the displacement was measured to be 5 mm on the internal oblique radiographs. The articular cartilage was confirmed to be intact by ultrasound. Elbow fractures can easily be reduced without surgery by inducing overstretching and a valgus angle of the elbow joint because the elbow has an intact cartilage hinges. Therefore, we recommend that CRPP is included in the treatment of LHCFs with minimal displacement, especially in patients with an intact articular surface.
Our study has some limitations. First, although this is the largest study on this topic published to date, the sample size is still small. Our results clearly show that ultrasound and arthrography yielded consistent results in predicting the integrity of cartilage hinges of children with min-displaced LHCFs. We believe that our results can be generalizable to cases treated by other clinicians with focused ultrasound. Second, an inherent limitation of this study is that arthrography was related with the diagnostic criteria of ultrasound in predicting the integrity of the cartilage hinge and the stability of fractures. In fact, whether arthrography itself meets the diagnostic criteria has not yet been reported. Howerver, we performed arthrography for all fractures according to the standard procedure. Recently, to research this issue further, we began using preoperative MRI and ultrasound to better assess the integrity of the articular surface of fractures.