Test and Treatment for Sesamoiditis

True or false? Chronic sesamoiditis can be treated effectively with conservative (nonoperative) care. A sampling of the published studies on this condition suggests "no" -- steroid injections, physical therapy, splints, and pain relievers do not relieve the painful symptoms of chronic sesamoiditis. But in this report of 18 patients, hand surgeons from Singapore present a differing opinion.

Sesamoiditis refers to an inflammatory process affecting the sesamoid bones of the thumb. The sesamoid bones are two pea-sized bones embedded in the volar plate of the thumb. The volar plate is actually a very thick ligament that prevents hyperextension of the joint. The volar plate also reinforces the joint capsule and gives the joint greater stability.

Even though they are small in size, the sesamoids play an important role in how the thumb moves. These tiny bones are part of the pulley system that allows for thumb movement. Two different tendons (adductor pollicis, flexor pollicis brevis) insert into each of these little bones. Together, these tendons across the sesamoid bones pull to create thumb adduction (moving the thumb toward the hand) and thumb flexion (bending the tip of the thumb).

The sesamoid bones lift the tendons and their attached muscles away from the joint to increase the mechanical advantage needed for smooth thumb motion. If the sesamoids are injured or starting to degenerate, they can be a source of severe pain and disability.

Normally, as the thumb bends, the sesamoid bones "track" or move up and down against the head of the thumb metacarpal (bone that forms the tip of the thumb). If the sesamoids do not track evenly on the center of the metacarpal head, the cartilage starts to wear unevenly and break down. That's when inflammation develops around the sesamoid bones with eventual bone-on-bone pain from chronic sesamoiditis.

The 18 patients studied in this case series were men and women between the ages of 17 and 57. One-third of the group had a history of trauma (e.g., direct crush of the sesamoid bones, fall onto the thumb).

Everyone had a positive sesamoid provocation test (SPT). This test is done in two steps. First, the examiner holds the thumb in a flexed position and applies resistance to the patient's effort to bend the tip of the thumb. Then the thumb is held in an extended position and resistance is applied to the tip of the thumb again. A positive test for sesamoiditis is no pain with the first test and much more pain when the second test is done. This test is helpful because most of the time, X-rays are normal.

Treatment for these patients followed a flow-chart (called an algorithm) starting with one steroid injection into the sesamoid joints. Each patient was put on pain relievers and given a thumb splint for six weeks. The splint held the thumb joint in a neutral position but still allowed the tip of the thumb to move.

Six weeks later, they were re-evaluated and treated further if pain continued. Mild pain was treated with activity modification and continued use of pain medications and splint as needed. Moderate (or more severe) pain was treated with a second steroid injection. If that didn't help relieve the pain, then the sesamoid bones were surgically removed (in a procedure called sesamoidectomy).

Follow-up with each patient showed these results: half the group was pain free after one steroid injection and five more patients achieved the same results after the second steroid injection. That's a total of 13 out of 18 patients who were successfully treated with just steroid injections.

Everyone else had the sesamoidectomy procedure. During the surgery, the hand surgeon could see significant degeneration in the metacarpal (thumb) bone that is above the sesamoids. One person in the group ended up having the thumb joint fused when all treatment failed to end his pain.

The author concluded that surgery to remove the sesamoid bones and repair the muscle insertions isn't always necessary for chronic sesamoiditis. Good to excellent results with pain free function of the thumb is possible with nonoperative care. They use the sesamoid provocation test (SPT) to confirm the diagnosis.

The best candidates for this treatment approach are patients with no prior trauma to the thumb and who have sedentary (low-demand) jobs. Early diagnosis of the problem before it becomes chronic may also help create successful treatment with conservative care. They recommend surgery (sesamoidectomy) should always be considered a last resort after trying all other nonoperative approaches first.

Reference: 

Andrew Y. H. Chin, MD, et al. Long-Term Results Using a Treatment Algorithm for Chronic Sesamoiditis of the Thumb Metacarpophalangeal Joint. In The Journal of Hand Surgery. February 2013. Vol. 38A. No. 2. Pp. 316-321.

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