Ulnocarpal Abutment Syndrome

Ulnocarpal abutment syndrome is a common degenerative condition that causes ulnar-sided wrist pain (on the little finger side of your wrist). It is also known as ulnocarpal impaction syndrome. The ulna and radius are forearm bones that connect your wrist (or carpus) to your elbow. Ulnocarpal abutment syndrome is most often seen in people with a relatively long or prominent ulna when compared to the radius. The condition can sometimes follow a wrist fracture (break) but not always.

Ulno- refers to the ulna bone and ‘ulnar’ relates to the little finger side of your wrist. Carpal refers to the small bones of the wrist (carpus is the Greek word for wrist).

There are other causes of wrist pain and a thorough assessment will help to identify the cause.

Do you experience pain alongside the little finger side of your wrist? Does the pain worsen when moving your hand from side to side?

  • Ulnocarpal abutment syndrome is caused by increased or excessive loads being transmitted through the ulnar side of the wrist, which can cause progressive degeneration (wear and tear) between the ulna, triangular fibrocartilage complex (TFCC) and bones of the wrist (including the lunate and triquetrum). When lifting, the ulna transmits around 20% of the load to your arm, with the remainder passing through the radius. With excessive prominence or length of the ulna, the force transferred through the ulnar side of the wrist will increase. Just a millimeter or two makes a big difference to the forces transferred, with a 2mm increase in ulna length relative to the radius increasing the force from 20% to 40%. The condition can lead to cartilage wear (arthritis) as the bones impact against each other (and rarely ligament injury).

  • A relatively prominent or long ulna can be a normal variant of wrist anatomy. The TFCC acts as a cushion or shock absorber between the ulna and small bones of the wrist and with increasing age the TFCC can thin and tear to permit bone-on-bone impaction and pain. Scans like MRI will commonly demonstrate signs of ulnocarpal abutment in older adults but most will have no symptoms.

    Ulnocarpal abutment syndrome can also develop after wrist or forearm fractures (breaks), especially when the radius heals in a shortened position. It can sometimes follow injury or operations at the elbow.

  • Some of the potential symptoms of ulnocarpal abutment syndrome are listed below.

    Typically present:

    • Pain on the ulnar side of the wrist (little finger side).

    • Pain worsened with side-to-side wrist movements (especially moving the wrist towards the little finger side, termed ulnar deviation) or lifting or with rotation of the wrist or forearm.

    • Weakness of grip or unreliable grip.

    Sometimes present:

    • Wrist swelling at the site of your pain.

  • It is important to correctly diagnose ulnocarpal abutment syndrome and exclude other causes of pain on the ulnar side of the wrist, such as ECU tendonitis or arthritis. The diagnosis is usually made on the history (your symptoms) and clinical examination. Plain radiographs (X-rays) are useful to assess the relative lengths of the ulna and radius bones. An MRI scan is also useful and will highlight any associated inflammation or degenerative TFCC tears.

    • Non-surgical treatment options include painkillers, avoidance of painful activities, wrist splintage, physiotherapy (mostly functional advice and splintage) and steroid injection (e.g. cortisone).

    • Surgical treatment options aim to offload the ulnar side of the wrist. So-called ‘joint-leveling’ procedures shorten the relatively long ulna by either (1) excising a wafer of bone at the wrist (called the wafer procedure), or, (2) cutting the ulna in the mid-forearm to shorten and fix with metalwork (called ulna shortening osteotomy). On occasions, keyhole (arthroscopic) surgery can be performed to debride (excise) any loose or inflamed tissue or degenerative TFCC tear and sometimes perform a wafer excision.

    Matthew offers all of the above treatments. He can refer you for physiotherapy if required.

    Surgery for ulnocarpal abutment syndrome is usually performed under general or regional anaesthesia. Click here for an overview of the different types of anaesthesia and the general risks of hand surgery. The additional and specific risks associated with surgery for ulnocarpal abutment syndrome will be discussed if surgery is an option, but includes continuing or new pain and stiffness.