LHCF is an intra-articular fracture. The integrity of the articular cartilage is an essential factor in predicting the stability of the fracture. In our study, both ultrasound and arthrography assess the highly consistent of the preoperative integrity of the articular cartilage status. Compared with arthrography, ultrasound was efficient in determining the integrity of the articular cartilage with noninvasive, no ionizing radiation, and more convenient. Ultrasound can be used as a complementary tool with arthrography to predict the integrity of the articular cartilage status of patients with minimally displaced LHCF.
The recent Song's and Weiss's classification are based on the integrity of the articular cartilage surface. Because the distal humeral epiphysis is not ossified, the cartilage of the distal humerus could not be detected by radiography. Therefore, there is a controversy between the integrity of the articular cartilage status and the classification of the radiograph. Ultrasound is a reliable, non-ionizing radiation, low-cost, noninvasive technique that does not require sedation or general anesthesia, especially for pediatric elbow examination[12–15, 18]. Previous study had shown that transverse ultrasound could be used to detect whether the fracture was complete or incomplete. Vocke-Hell et al found that ultrasound could show 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, it is determined to be a complete LHCF. If the hypoechoic articular cartilage hinge is smooth and continuous, it is judged to be incomplete LHCF. Our study showed that the ability of arthrography to predict the integrity of the articular surface involvement was powerful, and ultrasound had high diagnostic value in predicting the integrity of the articular surface in the patients. The obtained results confirmed that both ultrasound and arthrography were effective imaging modalities for predicting the integrity of the articular surface status, but the former has less invasive and no radiative exposure.
In our study, even if the displacement of the fracture was ≥ 2 mm, 64.1% of minimally displaced LHCF were intact articular surface. Similar to the previous reports[3, 6, 8, 19], the fractures displaced < 4 mm on radiographs were more likely to be intact articular surface. However, no fractures with ≥ 4 mm of displacement were performed arthrography in Weiss’s data. Song et al found that all patients with incongruent articular surface fractures displaced > 2 mm on radiographs. But, the integrity of the cartilage hinge status of Song’s data was mainly determined on the basis of the internal oblique radiograph. Although there was a statistically significant correlation between arthrography assessments and fracture displacement, this correlation was not found on ultrasound. It is difficult to assess the relationship between the displacement of the fracture and the integrity of the cartilage hinge status. Especially, there were only three patients with > 4 mm of fracture displacement in this series. We could not find the relationship between fractures with > 4 mm of displacement and the integrity of the articular surface from our data. However, this 4 mm cut-off was not a clinical criterion prospectively used for assessment of the incongruity articular surface. In addition, compared with the displacement of the fracture, the routine use of ultrasound was more effective in the evaluation of the cartilage hinge status before the initial treatment of these fractures.
There were three patients predicted to have controversial integrity of the articular surface between ultrasound and arthrography. Ultrasound can observe the hypoechoic layer of the hyaline articular cartilage in the distal humeral epiphysis. The fracture line is directly found by the hyperechoic gap and disrupted of the hypoechoic layer on the anterior articular surface. Arthrography is a reference standard for predicting the integrity of the articular cartilage surface[3, 11, 20]. However, arthrography indirectly detects the integrity of the articular surface of the distal humerus through contrast medium tracking. For the complex three-dimensional articular cartilage fractures, it is difficult to judge by arthrography. In addition, radiation exposure exists in arthrography, which requires sedation or anesthesia, and false-negative results. On the basis of Pennock data, they considered arthrography is unclear to confirm the congruency of the articular surface. Although this study has not been further confirmed those differences, on the base of our data, we believe that ultrasound can provide more accurate information to determine the integrity of the articular cartilage.
In our study, CRPP was achieved in all patients, and no major complications occurred. As previously reported in the literature, it is controversial whether minimally displaced LHCF was treated with ORIF or CRPP. The displaced LHCF with displacement > 1 mm has been treated with ORIF to avoid re-displacement and non-union, enabling direct visualization of the articular surface to confirm anatomical reduction[21, 22]. Because the articular surface was intact in most cases with a displacement of ༜4 mm confirmed by arthrography, those fractures were recently treated safely used CRPP, and no major complications were reported[3, 19, 23]. Song et al[17, 24] expanded the indications of CRPP to all fracture with incongruent articular surface or fracture displacement > 2 mm with a close reduction success rate of 73% (46/63). Even in case NO.24 (Fig. 1) was displaced 5 mm on internal oblique radiographs. Intact articular cartilage was confirmed by ultrasound. Based on the existence of cartilage hinges, the fracture can easily be achieved close reduced like a door hinge switch by overstretching and valgus of the elbow joint. Therefore, we recommend that CRPP is introduced in the treatment of LHCF with minimal displacement, especially in the case with an intact articular surface.
There are some limitations to our study. First, although this was the largest study on this topic published up to now, the sample size is still small. Our results clearly show that ultrasound and arthrography were consistent in predicting the integrity of cartilage hinges of patients with min-displaced LHCF in children. We believed that our results could be generalizable to other clinicians with focused ultrasound. Second, an inherent limitation of this study was that arthrography refers to the diagnostic criteria of ultrasound in predicting the integrity of the cartilage hinge and the stability of the fracture. In fact, whether arthrography itself meets the diagnostic criteria has not yet been reported. We performed arthrography for all fractures as a standard. Howerver, it is not known whether there was a potential complete fracture. Recently, we have begun trying to use preoperative MRI and ultrasound to better assess the integrity of the articular surface of the fracture in further research.