Arms

The arm bone is called the humerus while the forearm bones are the radius (curved bone) and the ulna (straighter bone of the two).
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Affects of MHE on the Arms

• Osteochondromas of the arm are often readily felt but rarely cause neurologic dysfunction (Figure 2). Osteochondromas of the upper extremities frequently cause forearm deformities.  The prevalence of such deformities has been reported to be as high as 40-60%.  Disproportionate ulnar shortening with relative radial overgrowth has been frequently described and may result in radial bowing.  Subluxation or dislocation of the radial head is well-described sequelae in the context of these deformities.
• The length of forearm bones inversely correlates with the size of the exostoses.  Thus, the larger the exostoses and the greater the number of exostoses, the shorter the involved bone.  Moreover, lesions with sessile rather than pedunculated morphology have been associated with more significant shortening and deformity.  Thus, the skeletal growth disturbance observed in MHE is a local effect of benign growth. Exostoses in the forearm are known to involve both the radius and the ulna. Since movements of the forearm (pronation and supination) are dependent on the radius moving in an arc of motion around the ulna, mobility may be restricted depending upon the severity of presentation. Also the lower end radius exostoses can lead to compression of the median nerve (in a closed space at the level of the wrist called the carpal tunnel) and present with weakness, tingling and numbness in the hand. Exostoses in the carpal bones can seriously hamper the wrist motion and cause pain.
• Complete dislocation of the radial head is a serious progression of forearm deformity and can result in pain, instability, and decreased motion at the elbow.  Surgical intervention should be considered to prevent this from occurring.  When symptomatic, this can be treated in older patients with resection of the radial head. 

Diagnostic Procedures

• The orthopedist will clinically feel for exostoses along the arm, elbow and forearm, and check range of motion (“ROM”) by moving the arm in different directions. The orthopedist will also check measurements on each arm and forearm to see if there is a difference. X-rays or other imaging tests may be ordered.

Possible Treatment Options

• Indications for surgical treatment include painful lesions, an increasing radial articular angle, progressive ulnar shortening, excessive carpal slip, loss of pronation, and increased radial bowing with subluxation or dislocation of the radial head
  • Minor lesions can sometimes be observed with careful follow up.
  • Bowing and some length discrepancies and be treated with a surgical procedure called “stapling,” where surgical staples are inserted into the growth plate of the bone growing faster than the other. This will hopefully give the slower growing bone the chance to “catch up” and the forearm will straighten over time.
  • Limb Lengthening with a fixator. (See Section on Fixators)
  • Resection of the radial head
  • Excision of exostoses
  • Osteotomy
  • Epiphysiodesis
  • Non-surgical measures for treatment of soft-tissue compression, irritation or inflammation (anti-inflammatories, heat, rest, etc.)
  • Adaptive devices to aid those with shortened forearms, such as grippers, long-handled sock aides, etc. 

What Parents Should Watch Out For

• Any red flags in terms of sudden increase in size of swelling, pain, nerve compression, tingling, numbness, or weakness.
• Possibility of exostoses irritating or catching on overlying tissue, such as muscles, tendons, ligaments, or compressing nerves.

• Loss of range of motion
• Pain
• Difficulty and/or pain when raising arm(s), lifting, carrying