Improving Results After Bunion Surgery
Bunions. They are more than just ugly toes. The medical term is hallux valgus. Hallux refers to the big toe. Valgus describes the awkward angle that forms as the base of the metatarsal bone drifts away from the rest of the foot. Surgery for the deformity is more than just for cosmetic reasons. Hallux valgus can be very painful and disabling.

In this study, surgeons from Japan take a look at how often hallux valgus comes back after surgery based on one risk factor: the position of the sesamoid bones. The sesamoids are two tiny, pea-sized bones that sit just under the main joint of the big toe. They are embedded in the soft tissues and play an important role in how the foot and big toe work. If the sesamoid bones are not properly realigned after bunion surgery (called a bunionectomy), will the patient have a recurrence of the problem? That's the question this study attempted to answer.

They compared two groups of women: one group with normal feet, the other group with diagnosed hallux valgus. The women with the bunions had surgery to restore normal alignment of the bones. The medical term for a bunionectomy procedure is proximal metatarsal osteotomy. More specifically, the surgeon cut through the involved soft tissues and joint capsule of the first toe. The bump that had started to form around the angled joint was removed. A wedge-or pie-shaped piece of bone was removed from the metatarsal bone. That step helps restore the straight alignment of the bones forming the joint at the base of the big toe.

The adductor hallucis tendon and the transverse metatarsal ligament were also cut. Any other steps necessary to restore normal alignment and function of the big toe were also completed. Each patient was evaluated on an individual basis as to what else was needed surgically. In some cases, bone spurs along the bottom of the bone called callosities were removed to give the patient some additional pain relief. Sometimes it was necessary to shorten the second and/or third metatarsals (toe bones).

But when it was all said and done, the surgeons took a second look to see what the results were with a special focus on the position of the sesamoid bones. They used X-rays to determine angles of the bones forming the first joint. The position of the sesamoid bones was also charted in relation to a line drawn down the center of the first metatarsal. They measured how far away the sesamoid bones were from this line. Then they watched the patients over time to look for recurrence of the deformity. Follow-up was between one and 10 years.

The sesamoid bones are supposed to be right under the big toe so that when you rise up on your toes, the bones form a separate point of support and stability for the joint. For such tiny bones, they have a powerful function. With is one sesamoid bone on each side of the base of the big toe, they act as a fulcrum point for the toe flexors. That gives these muscles extra leverage and power. The sesamoids also help absorb pressure under the foot during standing and walking. And they ease friction in the soft tissues under the toe joint when the big toe moves.

So you can see why the position of these little bones is important after a metatarsal osteotomy. Now let's see how important their location is after surgery. Because the sesamoids are embedded in the soft tissues, they can't always be moved exactly underneath the joint where they belong. The tendons and ligaments have a way of tethering (anchoring) the sesamoids. If the sesamoids remain too far away from the base of the big toe joint, it's referred to as incomplete reduction of the sesamoids. The soft tissues start to pull again and after a while, the same deformity returns.

How often does this happen? Some studies report that recurrence happens anywhere between four and 11 per cent of the time when everything lines up well after the first surgery. This is the first study to examine the recurrence rate when the sesamoids are not completely realigned (reduced) under the base of the big toe joint. About 25 per cent of the patients did not get an optimal reduction of the sesamoid bones as measured at the end of the first month postop.

This figure increased to 35 per cent later in the follow-up. They also found that the more the sesamoid bones were displaced from their normal, neutral position under the big toe joint, the more likely it was that the foot would develop a hallux valgus angle again. And once the bones started to shift, the deformity got worse over time. So some joints that looked pretty good one month after surgery didn't maintain their good alignment 12 months later. And the reason for the displacement was the lack of proper alignment of the sesamoid bones at the time of the first operation.

What's the take home message here? Incomplete reduction of the sesamoid bones sets some patients up for recurrence of their bunions. Yet, complete reduction of the sesamoid bones is possible with improved surgical technique. And it's necessary in order to improve the final results.

Surgeons performing a proximal metatarsal osteotomy for hallux valgus must pay attention to the position of the sesamoid bones before completing the procedure. If these two little bones are not completely reduced (placed back in their normal, neutral position under the joint of the big toe), then the surgery must be modified until they are in the necessary alignment. The surgeon may have to release other soft tissue structures, including the capsule (fibrous soft tissue) surrounding the joint. X-rays must be taken to confirm proper alignment before closing up the surgical incision.
Ryuzo Okuda, MD, et al. Postoperative Incomplete Reduction of the Sesamoids as a Risk Factor for Recurrence of Hallux Valgus. In The Journal of Bone & Joint Surgery. July 2009. Vol. 91-A. No. 7. Pp. 1637-1645.