Forearm deformity Tumor

Bony Outgrowth, osteochondroma

Bone growths in children come in many different forms.  In the upper extremity, there are relatively few growths on the surface of the bones; one of these is the solitary osteochondroma.  The solitary osteochondroma is, as its name implies, a single bony and cartilage growth.  It differs from multiple hereditary exostoses, or osteochondromatosis, which is an inherited condition in which the child has many of these tumors.  Multiple hereditary osteochondromatosis (or multiple hereditary exostoses– MHE) is a topic for a later post (hopefully not too much later).  These are almost always benign growths.
The solitary osteochondroma may appear anywhere but, to focus on the upper extremity, grows from the shoulder blade (scapula), humerus, radius/ ulna, or fingers (phalanges) most commonly.  These osteochondromas typically arise from the growth plate but can also arise from cartilage of the joint.  The osteochondroma is most often painless but may also be painful, especially when pressure is applied to the lump.  There is more likely to be associated pain if it is applying pressure near a nerve or if the bump is particularly close to the skin.  One of the biggest issues is bone deformity related to the growth of the osteochondroma.  This is especially problematic in the forearm (or lower leg) as irregular growth of one bone will affect the growth of the other in the same segment.  The most common situation is when an osteochondroma of the ulna limits the growth of the ulna due to its relationship to the growth plate near the end of the ulna.  If the ulna growth does not keep up with the radius growth, the radius may deform and the radial head will, in certain situations, dislocate at the elbow joint. 
Patients with an isolated osteochondroma present to the orthopaedic surgeon for one of a couple of reasons. First, there may be a painless bump and the patient and family may be curious about it.  If so, it may be observed for growth and possible deformity- xrays are typically taken on an every 6 month or yearly basis depending on the age of the child and the period of growth.  We have to be especially careful to watch for developing deformity during periods of rapid bone growth. 
Second, painful or otherwise worrisome osteochondromasare typically removed but those decisions are to be made after discussion of the pros and cons of such surgeries.  Rarely, a previously painless osteochondroma may become painful; this is a reason to be wary as it could indicate a change in the nature of the benign growth and often warrants an MRI or surgical excision.  
Finally, the bumps may cause the above- mentioned deformity.  The most difficult part of our task is to identify those growths and deformities which are concerning and which may worsen and limit motion or cause increasing functional issues.  If so identified, surgery to excise the osteochondromaand possible cut and realign the bone is considered.

The following images are from an adolescent with a painful (with pressure) and enlarging solitary osteochondroma of the radius.  The size and discomfort led to a decision for surgical removal.  There was no bony deformity aside from the bump.  There were no other osteochondromas and no family history. 

Osteochondroma on ulna.  It is easiest to see on the right picture.

Osteochondroma on the ulna from the side view (lateral).  Not the prominence on the bone.

Osteochondroma at the time of surgery.  This bump was removed.

Charles A. Goldfarb
My Bio at Washington University

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