Sunday, October 20, 2019

Nerve Injury after Trauma

The blog is mostly about kids born with differences in the arms (and occasionally legs).  However, my practice also includes kids with sports injuries and other traumas.  I will occasionally post interesting findings on these topics as well.  This is a child with a nerve that is not working correctly after an elbow fracture.  Specifically, this child sustained a fracture of the humerus (supracondylar humerus fracture) as shown here.



This patient was treated with a closed reduction (bones put back in place without making a skin incision) and pins were placed to keep the bones stable as healing started. 

Supracondylar humerus fracture after fixation


It is important to understand the patient's physical examination prior to surgery- this patient had a median nerve palsy.  That is, the median nerve was stretched and not functioning perfectly.  There were signs of the muscles/ tendons not working and signs the feeling in the fingers was not normal. 

This is not expected to improve during surgery and typically the nerve recovers over months after the surgery.  We typically watch and wait as the nerve recovers. 

This patient is now 8 weeks after surgery.  The bone is healed.  Elbow motion is almost normal.  BUT, the median nerve is not working perfectly- specifically, the FPL and FDP to index fingers are not strong as she demonstrates in this amazing video.




Also, this picture helps with an understanding of the change in feeling- see the skin changes on the index finger.  The other helpful finding on examination is the lack of sweat on the index finger- without the nerve working well, the finger is dry.

Skin changes with median nerve palsy

To be clear- this patient has a median nerve palsy (bruising).  This injury affect muscle and feeling.  Sometimes, there can be a AIN (anterior interosseous nerve) palsy which only affects the muscles (specifically, the FPL, the FDP to index and middle, and the pronator quadratus).  Patients with an AIN palsy have normal feeling.  Or, if the whole median nerve is affected, there are changes to the muscle and to the nerve that affect feeling. Anatomically, the AIN is part of the median nerve at the elbow and then, typically around 5 cam past the joint, the median nerve branches the AIN as a separate nerve.  The AIN is susceptible to injury because it sits in the back of the nerve, closest to the bone and, in this case, closest to the fracture.

At this point, we will watch and expect the nerve to get better over the next few months.  Very rarely, the nerve will not perfectly recover and further assessment with nerve studies can be helpful to understand the nerve's recovery.



Charles A. Goldfarb, MD              
My Bio at Washington University     
email: congenitalhand@wustl.edu

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