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Causes of Deformity in the Rheumatoid Thumb

Rheumatoid arthritis (RA) is a destructive inflammatory disease that impacts soft tissue. This disease commonly involves the thumb and causes deformities to the thumb through tendon rupture or tendon subluxation and the abnormal stretching of ligaments and other joint structures.

The primary cause of Ulnar Deviation of the Metacarpal Phalangeal joints (MP) of the fingers, a chronic, irreversible condition, is Rheumatoid Arthritis (RA). The MP joints are a primary site of rheumatoid deformities due to several anatomical and bio mechanical factors. Chief among the factors are:

• The shape of the metacarpal head allows for a certain degree of motion in an ulnar direction which contributes to the hands ability to create a strong grip

Osteoarthritis (OA), or the degeneration of a joint, commonly occurs at the base of the thumb. OA at this joint is diagnosed with conventional radiographs (x-rays), but often can be recognized based on symptoms. Symptoms occur predominantly with pain at the base of the thumb, especially when performing tasks that require a pinch (i.e. pulling on socks).

Anatomy of the Wrist

Causes of Swan Neck Deformity

At first glance, diagnosing Swan Neck Deformity seems like a "no brainer". You have visual confirmation of hyperextension of the proximal interphalangeal (PIP) joint and flexion of the distal interphalangeal (DIP). The finger is contorted into the shape of a swan neck. And, your patient has Rheumatoid Arthritis (RA).

Yes. Swan Neck Deformity does show up in about half of all RA patients; but, there are a surprising number of other causes, including Cerebral Palsy, Lupus, Stroke, Parkinson’s Disease (PD), Ehlers-Danlos Syndrome (EDS), Marfans, post-traumatic flexor tendon ruptures and ischemic injuries.

Wrist instability is a common injury treated by many hand therapists. The anatomy of the wrist includes eight carpal bones that, with the combined efforts of the intercarpal ligaments, allow for circumduction of the wrist joint while imparting stability anywhere within the range of motion. An injury to one or several of the ligaments can lead to wrist instability.

If you ask 10 different hand therapist how they treat mallet finger injuries, you may just get 10 variations on an answer that is ultimately some form of immobilization of the involved distal interphalangeal (DIP) joint. Systematic review of the studies on conservatively treated mallet finger injuries is not able to identify which orthosis is most optimal and what the most appropriate wear time is,

Collapse deformities of the thumb are all too common in the presence of CMC joint arthritis. The Nalebuff Type III or “intrinsic minus” thumb deformity evidenced by CMC flexion, MP extension or hyperextension and IP flexion is the most common deformity.

This becomes a highly dysfunctional posture over time due to the loss of MCP flexion, web space shortening and thenar muscle atrophy - making moving the thumb away from the palm all but impossible.

There are a variety of wrist injuries that can occur from a traumatic fall on an outstretched hand. These injuries are termed FOOSH (fall on an outstretched hand) injuries. Probably the most well-known FOOSH is a distal radius fracture, which is identified and treated first by a physician. As a health care professional, you may be seeing an increase in referrals for wrist pain from falls this time of year, now may be a good time to review the clinical signs used to find other FOOSH injuries.

As skiing enthusiasts hit the slopes this time of the year, the likelihood of the number of thumb injuries increases. An ulnar collateral ligament injury of the thumb called Skier’s Thumb represents 5-10% of all skiing injuries and has been described as the most frequent injury to the upper extremity experienced by skiers.