Inability to straighten the thumb in a 4-year-old child may be caused by congenital stenosing tenosynovitis of the flexor tendon, which requires surgical treatment.
Inability to fully straighten or flex the thumb in a 4-year-old child is mostly caused by congenital stenosing tenosynovitis of the flexor tendon of the thumb. The tendon sheath will compress the flexor tendon when the tendon sheath proliferates, causing the tendon to have limited sliding, and the inability to fully straighten or flex will occur. Conservative treatment is mostly ineffective, and surgery is usually the treatment of choice.
Surgery involves incision and partial excision of the thickened tendon sheath to free the compressed flexor tendon and restore thumb flexion and extension, and most children recover well after regular treatment.
There may be other reasons why a 4-year-old child’s thumb is not straight, so it is recommended that the child be taken to the hospital in a timely manner for a complete examination to determine the cause of the problem and receive regular treatment.