Addressing Hallux Valgus In The Metatarsus Adductus Foot Type

When patients with metatarsus adductus develop bunions, surgery can be particularly challenging. This author explores keys to bunionectomy procedure selection and offers several pertinent case studies.

Metatarsus adductus is a congenital foot deformity characterized by a uniplanar deformity in which the metatarsals are angulated at the Lisfranc joint, causing adduction of the forefoot in relation to the midfoot and hindfoot.¹ The occurrence of metatarsus adductus is reportedly one to two cases per 1,000 people.^2,3 Metatarsus adductus is the most common congenital foot deformity in the newborn with a male predilection as high as 80 percent.^2,3 Fetal constraint is the most common cited etiologic factor with compression of the forefoot with the legs crossed across the body.²

One can quickly identify obvious congenital deformities such as calcaneovalgus and talipes equinovarus (clubfoot) at birth, and treat these deformities appropriately. Since there are no standard foot screening methods or protocols in regard to newborns for minor deformities such as metatarsus adductus, these go untreated and will surface as problems later in life. As clinicians, we see metatarsus adductus in older children and adults on a regular basis, confirming the lack of recognition at infancy.    

The metatarsus adductus foot type is associated with a number of clinical challenges for the podiatrist. Some of the common pathologies include Jones fractures, pain due to the prominence of the fifth metatarsal base, premature non-traumatic arthrosis of the second and third tarsometatarsal joints, lateral column foot pain, and severe bunion deformities. When metatarsus adductus is present in the high arched foot, pathologies worsen and treatment is even more challenging. These feet are associated with lateral ankle instability, chronic peroneal tendinopathies, dorsal tarsometatarsal joint exostoses with or without peroneal nerve irritation, and chronic dorsolateral foot pain (lateral column overload).

For this article, I will focus on the management of hallux valgus in the metatarsus adductus foot type. The real challenge occurs when a patient wants surgery for the bunion deformity. Clinically, the bunion deformity always looks worse than the X-ray. Often, there is not much of an increased intermetatarsal angle due to the varus deformity of all of the metatarsals.

Why You Should Rule Out Some Bunionectomy Options

When a patient presents to the office with the chief complaint of a bunion and there is a recognized significant metatarsus adductus in the diagnostic workup, the physician should carefully assess surgery options. Unless there is severe dysfunction of the foot, I do not recommend panmetatarsal osteotomies.  

However, your typical “go-to” bunionectomy may not be the best option either. For example, if you typically perform an Austin bunionectomy or equivalent (distal metaphyseal osteotomy), that will likely yield a poor outcome with failure to correct the deformity and/or rapid recurrence of the deformity. Decision-making and procedural selection become more intense. The surgeon must clearly communicate expectations of the surgery to the patient as the typical result of “bump gone, toe straight” is unlikely.

We are familiar with evaluating the intermetatarsal angle on an anteroposterior view of an X-ray. If you in part determine your procedure based on that criterion, remember to calculate the true intermetatarsal angle, which is the intermetatarsal angle plus (metatarsus adductus angle – 15 degrees). For example, if the intermetatarsal angle measures 8 degrees and the metatarsus adductus angle measures 25 degrees, then the true intermetatarsal angle is 18 degrees: 8+(25–15)=18. An Austin bunionectomy may be appropriate for an 8-degree intermetatarsal angle. However, a bunion deformity with an 18- degree intermetatarsal angle will typically need another type of correction.

Pertinent Considerations For Addressing Large Bunion Deformities With Underlying Metatarsus Adductus

The following list will include some insights and pearls to remember when addressing large bunion deformities with underlying metatarsus adductus deformity.

1. In regard to expectations, always discuss with patients the two deformities (metatarsus adductus and hallux valgus) that you are addressing or treating. Explain to your patients that their anatomy limits the amount of “straightening” of the first metatarsal bone. Even though pain should resolve and the foot will clinically look better, there will still be a residual bunion and the toe will not be straight. I typically show patients that all of their toes deviate laterally due to the medial drift of the metatarsal bones. Remember, the toes move in the opposite direction of the metatarsals.

2. Avoid distal metatarsal osteotomies. I am always more aggressive in correction by doing a base wedge osteotomy or Lapidus. This is the case in juvenile hallux valgus and with underlying metatarsus adductus. You will sometimes need to overcorrect your bunion slightly. You are less likely to get a varus deformity in the metatarsus foot type with a slightly negative intermetatarsal angle than in the rectus foot type.

3. Consider an Akin. It is difficult to get a straight toe after completing the metatarsal work. Clinically, an Akin helps with appearance.

4. Consider a second and third metatarsal osteotomy if the deformity is mostly of the medial three metatarsals, which is quite common. After shifting the second and third metatarsals laterally, now you have more room to get the first metatarsal over. You can then do a Lapidus, scarf or base wedge osteotomy.

5. Consider a first metatarsophalangeal joint (MPJ) fusion when there is an element of degenerative joint disease or if you are considering a panmetatarsal head resection in a severe case of laterally windswept toes. You can be assured that when the fusion is complete, the toe is not going to drift laterally and you will not lose correction. A first MPJ fusion should always be on your radar screen for a “jumbo” bunion deformity. We have all seen recurrence of a bunion with a Lapidus due to splaying at the intercuneiform joint but you will be hard pressed to find recurrence of a bunion after a first MPJ fusion. In the older patient with advanced longstanding deformity, remember to consider a first MPJ fusion.

6. Pick your battles. Let’s face it: we are surgeons and we fix things. There is nothing wrong in being honest with your patients and telling them that unless they can’t live with it, they should live with it. As you know, most patients think a bunionectomy is a simple procedure in which you shave the bump and call it a day. After a thorough review of what would need to happen to fix the problem appropriately, the best answer may be wearing wider shoes and using pads/cushions. If you and the patient are both up to the challenge and investment of time and energy, then it is fine to do the surgery. Otherwise, there is no harm in treating the bunion conservatively. I tell my patients all day long that bunions won’t kill you, they just make you suffer a little.

Case Study One: Why The Closing Base Wedge Osteotomy Was The Best Choice For An Athletic Teen

A 14-year-old girl, who was active with cheerleading and volleyball, presented with the chief complaint of a painful bunion deformity. An evaluation of her AP X-ray reveals moderate metatarsus adductus with a bunion deformity (see left photo above).

I knew an Austin bunionectomy would not hold up in the long run. I chose to do a closing base wedge osteotomy. When you look at the postoperative X-ray, you will notice a slight overcorrection of the intermetatarsal angle (see right photo above). In order to get a congruous joint, you will need to do that at times.

Case Study Two: Attaining A Congruous Joint With A Lapidus Bunionectomy

A 24-year-old female presented to my office wanting her bunion fixed. Her pain was on the “bump” and she had trouble wearing dress shoes that were necessary for her work. X-rays revealed a metatarsus adductus with a moderate bunion deformity (see left photo above).

Again, this is a case in which an Austin bunionectomy is not going to give you the correction that you need. I chose to do a Lapidus bunionectomy. Again, notice slight overcorrection of the intermetatarsal angle (see right photo above). By doing this, I was able to get a congruous joint, which should give long-lasting correction.

Case Study Three: When There Is Severe Metatarsus Adductus And Midfoot Arthrosis

A 56-year-old female presented to me with a severe deformity of her left foot. She was having trouble wearing conventional shoes and was wearing mostly slipper type shoes. She stood all day sorting mail in a United States Postal Service mailroom. X-rays revealed severe metatarsus adductus deformity with midfoot arthrosis.  

This is one of those very challenging cases in which one has to consider major reconstruction. I chose to lateralize the second and third metatarsals, and then do a Lapidus bunionectomy. Certainly, you could consider a panmetatarsal head resection with first MPJ fusion. However, she did not have any metatarsalgia pain and surprisingly did not have any midfoot pain where she had arthrosis of the tarsometatarsal joints. Radiographic evidence of arthritis in this area of the foot is a common finding for this foot type.

Case Study Four: Meeting The Expectations Of A Patient With A Painful Bunion And Windswept Toes

A 74-year-old male presented with a painful bunion pain in his left foot (see left photo). He had trouble wearing shoes and clinically, his big toe joint was stiff.

I chose to address his second and third toes that were severely windswept like the great toe by shortening and lateralizing the metatarsal heads followed by a first MPJ fusion (see right photo). He still has some residual deformity but expectations were that he would be able to wear shoes without pain and that is what I delivered.

In Summary

As podiatrists, we know the first MPJ better than any other anatomic part of the foot. We feel that we can do bunionectomies blindfolded. Ninety-five percent of the time, we do our “go-to” bunionectomy and life is good. However, when the “jumbo” bunion presents with metatarsus adductus, we have to slow down, take a break and figure out a game plan. It is not going to be easy for you or the patient as there is typically more of a reconstruction in mind with a period of non-weightbearing.  

Remember to have a heart-to-heart talk with the patient regarding the complexity of the case and hash out the realistic expectations. There is nothing wrong with not doing surgery if that is what your patient decides. In general, one will need to be more aggressive in correction by addressing the proximal aspect of the metatarsal. Consider a first MPJ fusion in older patients with longstanding deformity. Think about a second and third metatarsal osteotomy to give you some “elbow room” when realigning your first metatarsal. Finally, don’t be afraid to overcorrect the intermetatarsal angle slightly.

Dr. Fishco is board-certified in foot surgery and reconstructive rearfoot and ankle surgery by the American Board of Podiatric Surgery. He is a Fellow of the American College of Foot and Ankle Surgeons, and a faculty member of the Podiatry Institute. Dr. Fishco is in private practice in Phoenix.

Editor’s note: For further reading, see “When Bunion Surgery Fails” in the October 2013 issue of Podiatry Today, “Managing Pediatric Metatarsus Adductus: Should You Treat It?” in the April 2008 issue, or the DPM Blog “Managing The Tricky Metatarsus Adductus Foot” by Dr. Fishco at https://tinyurl.com/p3naohc . To access the archives, visit www.podiatrytoday.com.

References

1.     Dawoodi AI, Perera A. Radiological assessment of metatarsus adductus. Foot Ankle Surg. 2012; 18(1):1-8.
2.     Graham J. Smith’s Recognizable Patterns of Human Deformation, Third Edition, Chapter 4, Elsevier, St. Louis, 2007.
3.     Williams CM, James AM, Tran T. Metatarsus adductus: development of a non-surgical treatment pathway. J Paediatr Chil Health. 2013; 49(9):E428-33.