Over-shortening of the first metatarsal can lead to serious problems. The patient may be thrilled that the bunion is gone (i.e. bump gone and toe straight), but the resultant pain under the second metatarsal head can be challenging to treat. Typically, the first and third metatarsal should be about the same length with the second metatarsal slightly longer. When the first metatarsal is the same length as the fourth metatarsal, there is a likelihood of lesser metatarsalgia. Over-shortening may be a result of osteopenia, inadequate fixation of the osteotomy, a poorly executed osteotomy or the patient started out with a short first metatarsal prior to surgery. Of course, it may be a combination of many factors. Certain osteotomy types, such as the Mitchell procedure, are known to cause excessive shortening.
In my experience, delayed union and non-unions are relatively rare even with a Lapidus procedure. Certainly, risks for this complication are higher in smokers, patients with diabetes and those with vitamin D deficiency.
Malunion of a distal metatarsal osteotomy occurs on occasion. It typically involves excessive dorsiflexion or plantarflexion. In both cases, a non-purchasing toe may develop. Malunions typically occur after the patient starts to walk altwhough a poorly executed osteotomy and fixation can certainly be the cause.
When a patient presents to the office with a failed bunion surgery, the most important elements of evaluation should include: what failed (loss of correction, malunion, shortening, stiff joint, etc.) and why? Certainly, the “why” is your best educated guess after examining the patient and looking at before and after X-rays. Often, we do not have the luxury of preoperative X-rays. Sometimes, I will take an X-ray of the contralateral foot to get an idea of what the normal anatomy looks like.
When I have to repair a sagittal plane malunion of the first metatarsal, my go-to procedure is usually the sagittal Z osteotomy. It affords correction in the sagittal plane where I can raise or lower the first metatarsal head. In addition, I can lengthen the bone at the same time if necessary. Rarely would I need to shorten the bone but I can do that if necessary.
If I need to fix the malunion in the transverse plane and alter length, I will consider a Mau/Ludloff oblique-type osteotomy. These osteotomies are not very stable and require immobilization but are very versatile. You can shorten, lengthen, translate and swivel. Not many osteotomies allow one to manipulate the bone in that many directions.
A challenging scenario involves patients who are happy with their bunionectomy but have developed lesser metatarsalgia. If the great toe joint is moving well, the patient is happy with the results and the joint is congruent, I find it difficult to address the first metatarsal surgically. I learned never to destroy normal anatomy but rather fix the abnormal anatomic segment. So the “textbook” answer would be to lengthen the first metatarsal versus shortening the second metatarsal.
My experience with lengthening the first metatarsal is that it is fraught with complications and leads to stiffening of the great toe joint. Therefore, I tend to shorten the “relatively long” second and third metatarsal (if necessary). Shortening lesser metatarsals leads to other problems such as floating toes due to the lack of flexor power. Certainly, we try to minimize this with postoperative splinting and physical therapy. I make it a priority to explain to patients that pain will resolve under the second metatarsal head but the toe may float. They need to be aware of that. The last thing that you want to hear from your patient after surgery is that, “You never told me ...” (see the sidebar “What To Include In Patient Consent Forms” at right).