A Closer Look At Central Metatarsal Osteotomies
- Volume 24 - Issue 6 - June 2011
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Sharing insights from the literature as well as their own clinical experience, these authors discuss anatomical considerations, biomechanical principles and patient factors that go into central metatarsal osteotomies. They also offer proactive tips on reducing the risk of complications such as dorsal contractures and floating toes.
Podiatric surgeons typically perform lesser metatarsal surgery to address local or global metatarsal deformities. The majority of the deformities are length and/or sagittal plane deviations. The anatomic declination of the metatarsals makes the delineation difficult as length affects the sagittal plane position. Structural metatarsal deformities can include elongated, shortened, elevated or depressed metatarsals. Occasionally, these deformities can translate into pain, which can be secondary to the local metatarsal deformity or referred from an adjacent metatarsal.
Metatarsalgia is one of the most common pedal complaints. Metatarsalgia has a multifactorial etiology, which can range from structural metatarsal deformities to local or systemic disease. For the purposes of this article, we will focus on the structural deformities.
Researchers have shown that conservative treatment can be of benefit for metatarsalgia.1 These modalities include but are not limited to shoe modification (padding, metatarsal bar), orthotics, nonsteroidal anti-inflammatory drugs (NSAIDs) and palliative care. One should attempt conservative care for three to six months prior to considering operative treatment. The majority of cases respond well to these treatment modalities.
The biomechanics of metatarsalgia are secondary to load transmission through the metatarsal heads. There is usually abnormal load or pressure on one or more of the metatarsal heads, and this causes overload and subsequent pain. In normal stance, this pressure should be evenly distributed on all five metatarsal heads. The first metatarsal head supports twice as much force as any of the lesser metatarsals.2 The pressure transfer during the gait cycle tends to focus on the metatarsal heads for 30 to 55 percent of the gait cycle.2,3 The second and third metatarsals are relatively locked into position through their articulation at the Lisfranc’s joint. This explains why first ray pathology (hallux valgus, first ray hypermobility, Morton’s foot) can lend itself to central metatarsalgia.
In terms of evaluating metatarsal length and sagittal plane deviation, weightbearing radiographs are still considered the best method. The AP and sesamoid axial views are the most important. As we noted earlier, all of the metatarsal heads should purchase the ground in normal stance. The axial view can depict this scenario. The AP view is best to access the length pattern and the parabola.
Some uncertainty still exists in regard to determining the “normal” length pattern.4 Most believe the first and second metatarsals are equally the longest, and they are followed by the third, fourth and fifth metatarsals. Maestro demonstrated this in his study using the “Maestro Line,” a line from the center of the fibular sesamoid perpendicular to the longitudinal bisection of the second metatarsal.5 According to Maestro, this line should pass through the fourth metatarsal head.