The healing ability and plastic ability of fracture in children were better than adults, as such, the preferred treatment for humeral shaft fractures in children is conservative treatment[1, 9, 10]. As lack of rigid fixation at fracture sites during conservative treatment, frequent X-ray examination was in need to ensure position of fracture broken end and growth of fracture callus. But frequent X-ray examination means more radiation exposure time, children are considerably more sensitive to the carcinogenic effects of radiation than adults, and the risk of cancer increases with increasing time of radiation exposure time such as cancer of the thyroid, breast, brain and skin, as well as leukemia. Risks of radiation-related cancer are greater as patients younger, also these risks will last a lifetime[11-13]. Therefore, it is an inevitable trend of medical development to find methods of examination which would not cause additional damage in the process of diagnosis and treatment.
Ultrasonography was originally used for soft tissue examination, as its real-time imaging, multiplanar capabilities, cost-effectiveness, portability, patient comfort and absence of radiation exposure, ultrasonography was widely used in musculoskeletal system examination[14, 15]. HERREN et al[16] used ultrasound to examine 201 children with forearm fractures, the sensitivity and specificity of diagnosing fractures were higher than 99.5%. Ultrasound also was used to treat displaced radial neck fractures by our hospital, ultrasonography guidance can reduce X-ray radiation exposure and the risk of posterior interosseous nerve injury[7]. In this study we used ultrasonography and X-ray to follow up humeral shaft fracture children with conservative treatment, the DASH score did not show a statistical difference, and radiation exposure time of ultrasonography group was significantly less than the X-ray group.
It has been more than a year since COVID-19 pandemic was first reported in China at the end of 2019[17], but the epidemic has not been well controlled, the number of newly infected individuals and daily number of deaths were increased every day. As CT and X-ray were important tool for screening, preliminary diagnosis and severity assessment of COVID-19[18], the radiology department inevitably became a gathering place with infected and potentially infected patients. Although countries and hospitals presented relevant measures to prevent the spread of the epidemic in the radiology department[19-21], there was report showed radiology departments as infectious source in cross-infection of COVID-19[5].
Ultrasonography has the advantages of no trauma, simple inspection, easy to disinfect and repeatability, separate ultrasound equipment can be provided in the hospital department or clinic. Children with fractures could be reexamined by ultrasound in the hospital department or clinic, and the ultrasound probe could be quickly disinfected after the examination. Some studies have shown that proper use of ultrasound could reduce the risk of virus transmission[22, 23]. Using ultrasound to follow-up of children with fractures significantly reduces the possibility of direct or in direct contact with infected peoples and minimized the transmission risk of COVID-19.
Due to the specificity of ultrasonography for soft tissue imaging, besides fracture sites, vessels, nerves and muscles are also well demonstrated with ultrasonography. It is significant to detect the arterial resistance index (RI) by ultrasonography to predict the prognosis of fracture, according to CARUSO's study[24], when RI<0.6, it predicts good blood supply and fracture healing will be well, when RI>0.7, it predicts poor blood supply and delay fracture healing or nonunion in fracture repair. Our previous studies have shown that ultrasonography could detect callus earlier than X-ray, delay fracture healing could be found early and treated timely[25].
Radial nerve is one of the most vulnerable nerves in humeral shaft fracture[3]. Children often can’t cooperate with physical examination well when injury because of their special age, and radial nerve injury can’t be determined by physical examination, it is difficult for doctors to decide whether to operate or not. Ultrasonography has absolute advantages over X-ray in examining nerve damage, studies have shown radial nerve injury can be detected early by ultrasound, and if there is no entrapment or rupture of the radial nerve, most of the radial nerve injuries will be recovered after conservative treatment[8]. In this study, there were 4 children showed radial nerve with a circumscribed swelling by the B-ultrasound image, the nerve swelling disappeared during conservative treatment of fracture, and there were no special manifestations of nerve injury on plain films in these 4 children. With the help of ultrasound, nerve injury could be better defined, and clinicians would decide whether to have surgical treatments easier.
During the ultrasound examination, the doctor can communicate with the patient to eliminate the patient’s fear. At the same time, the patients can tell the doctor how they feel and examine the specific site to find the damage, unclear neurovascular injury can be further clarified by comparative examination of both limbs. The epiphysis as unique tissue structure of children, which isn’t well displayed on plain films, but the epiphyseal injury could be defined by ultrasound examination[26]. But ultrasound also has some disadvantages, for example, 1.It requires an experienced operator with a great knowledge of the ultrasound appearance of different soft-tissue structures; 2. Ultrasound is inferior to plain film in overall view of fracture; 3.The ultrasound probe needs to be in direct contact with the children's skin[8]. Overall, Ultrasonography could be used as an alternative to X-ray examination for humeral fractures.
Limitations
The main limitation of the study was mainly due to the characteristic of a limited sample size, and patients were followed up for a short time. Bias during the research seemed to be unavoidable.