父母有绿卡，去年在美呆了1年，10月底回中国，本来计划今年四月底回美，机票都买好了，结果父亲最近不小心摔倒，导致骨折手术，遵医嘱可能需要修养半年，到今年下半年才能返美。不知道这样对他们的绿卡是否有影响？
-They must return to US before their stay in China reaches one year! Just bring the doctor/hospital diagnosis for his injury and treatment, and explain it to the IO at the port of entry if asked.
特此请教8老师和各位大侠，看看这种情况应该如何处理，多谢！！
