Sesamoiditis is usually treated effectively with conservative (nonoperative) care. But when pain relievers, antiinflammatory medications, a thumb splint and hand therapy do not help, then steroid injection into the sesamoid joint is advised and can be very effective. But please know that a good period of conservative care (at least six weeks and more like three months) is recommended before injection therapy.
As you probably know by now, 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.
If moderate (or more severe) pain persists after conservative treatment, then one or two steroid injections might do the trick. If that doesn’t help relieve the pain, then the sesamoid bones can be surgically removed (in a procedure called sesamoidectomy).
In a recent study on the treatment of sesamoiditis for a series of 18 patients, half the group was pain free after one steroid injection. 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.
Sesamoidectomy was reserved for patients with significant degeneration in the metacarpal (thumb) bone that is above the sesamoids. Good to excellent results with pain free function of the thumb is possible with nonoperative care. Multiple steroid injections can cause thinning of the soft tissues and is not advised.
Starting with one injection (if all other avenues of conservative care have been tried fully) is the next step. You may still have to use a thumb splint off and on when the thumb is painful and/or you have to use it excessively. A hand therapist can also show you how to modify some of your sewing activities to reduce pressure on that joint. A strengthening program might be helpful, too. Even though you use your hands and thumbs for your work, there may be some weakness associated with this problem that is causing further pain or discomfort.