Developing A Surgical Strategy For Metatarsalgia In The Cavus Foot
Metatarsalgia is one of the most common conditions that we treat on a daily basis. I am sure we all treat this the same way. After ruling out a neuroma, one typically treats metatarsalgia with shoe gear modifications such as stiff soled shoes and accommodative padding. Treatment ultimately leads towards an orthotic device with appropriate modifications such as metatarsal pads and cutouts. If there is significant equinus, then a heel cord stretching protocol may be part of the treatment plan.
Sometimes surgery is necessary to address metatarsalgia and what I want to discuss is metatarsalgia in the challenging cavus foot type. I personally believe that the cavus foot and the cavovarus foot (underlying metatarsus adductus with pes cavus) is the one of the most difficult foot types to manage. Patients with this foot type typically have lateral column pain dorsally and sometimes along the styloid process (which is typically very prominent) and in the sub-fifth metatarsal head area. Moreover, these patients generally develop lateral ankle problems including peroneal tendinopathies. In a nutshell, these patients overload the lateral column, which can be menacing for the foot and ankle.
In school we learned that the cavus foot type hits the ground like a tripod. There are high ground reactive forces to the heel and under the first and fifth metatarsal heads. When assessing for metatarsalgia in this foot type, it is critical to evaluate the hindfoot for varus conditions as well as the position of the first metatarsal as it is typically plantarflexed in relation to the lesser metatarsals.
In the non-cavus foot, metatarsalgia is generally due to a dysfunctional first ray, hammertoes and/or aberrant metatarsal lengths. In surgical treatment for these conditions, I am typically performing a bunionectomy with hammertoe repair and possible metatarsal osteotomy to establish a harmonious metatarsal parabola.
In the cavus foot, however, I am more likely going to be doing a calcaneal osteotomy and dorsiflexory wedge osteotomy of the first metatarsal. Hammertoe surgery may be necessary as well, but I have found that hammertoe surgery alone generally does not help resolve the metatarsalgia complaints.
I have learned a couple of things about the cavus foot and metatarsalgia serendipitously. The first thing involves the effect of the peroneus longus tendon. As you know, the peroneus longus tendon stabilizes the first ray and one of its roles is to plantarflex the metatarsal. A common problem associated with the pes cavus foot type is peroneal tendon disorders such as tendinosis, split tears and ruptures. In cases where I have had to resect the peroneus longus tendon at the cubital tunnel due to severe hypertrophy and partial tears, patients have told me that their pain in the ball of the foot has resolved.
The second observation that I have made is that following calcaneal osteotomies such as a Dwyer or Keck and Kelly type osteotomy for chronic posterior heel pain, metatarsalgia oftentimes resolves as well. Removing the hindfoot varus influence on the forefoot can be powerful.
When evaluating the cavus foot for possible surgery to address metatarsalgia I make a mental checklist of four things:
1. Which metatarsal head(s) is painful and/or has callus?
2. Is the first ray plantarflexed and is it rigid?
3. Is there calcaneal varus? (always perform the Coleman block test)
4. Are there hammertoes?
With these questions answered, you can formulate a surgical strategy. I have learned that digital stabilization (metatarsophalangeal joint release with fusion of the proximal interphalangeal joint) does help reduce retrograde buckling, making the ball of the foot less prominent. However, if the metatarsalgia is localized under a metatarsal head or two, then this surgery alone will be ineffective. If, however, the metatarsalgia is diffuse under the entire ball of the foot and there is not a significant plantarflexed first ray (forefoot valgus) then this may be beneficial as an isolated procedure.
When I see the patient with sub-fourth and sub-fifth metatarsal pain, I am more likely to address the foot more globally. If the first ray is very flexible, then a Jones tenosuspension may be appropriate. If the first ray is rigid, then I am going to do a dorsiflexory wedge osteotomy.
If there is calcaneal varus, I typically perform a modified Dwyer, which includes removing a laterally based wedge (as described by Dwyer) but I will also transpose the tuberosity laterally and proximally. I will fixate that with two screws as is typical with a medial calcaneal transpositional osteotomy for pes valgus surgery.
Although the surgery may seem radical for metatarsalgia, it is effective for the patient who cannot get comfortable with orthotics and shoe gear modification. Moreover, simple metatarsal condylectomies and osteotomies may not be sufficient to resolve the problem.