Hallux Valgus: Is Hypermobility A Cause Or Effect?
While this author concedes there is no universal definition of hypermobility and a lack of evidence-based medicine to support hypermobility as a cause or effect of hallux valgus, he cites some research and clinical experience that suggest hypermobility as a possible factor in bunion formation.
By Gary M. Rothenberg, DPM, FACFAS
Does hypermobility cause bunions or did the bunion result in hypermobility? The question is admittedly difficult to answer, mostly because we cannot universally agree on a definition of hypermobility.
Morton first introduced the concept of hypermobility of the first ray in 1928.1 He postulated that hypermobility of the first ray led to a multitude of foot problems but was the first to admit that there was no reliable method to quantify the magnitude of first ray hypermobility.
This historic dilemma continued in the subsequent decade when Lapidus introduced the tarsometatarsal fusion in 1934 as a surgical treatment for hallux valgus with associated hypermobility.2 Lapidus believed strongly in hypermobility as a cause of hallux valgus and felt this procedure stabilized and corrected the anatomic deviation.
The Lapidus bunionectomy fell out of favor for many reasons, most notably complications including delayed unions and nonunions. Through the decades, we have modified and improved our understanding of foot biomechanics, and there have been technological advances in fixation options and surgical techniques. These developments have led us to revisit the indications for the Lapidus procedure for correction of hallux valgus deformity. While many reports dealing with correction of bunion deformities implicate first ray hypermobility as a cause, there is little evidence-based medicine to support hypermobility as either a cause or an effect of hallux valgus.
Many of us who perform the Lapidus procedure stick to its original indications: larger intermetatarsal half-angles of greater than 15 degrees; obliquity of the first metatarsocuneiform joint; and as a salvage procedure for previously failed correction and hypermobility. However, inherent in our thought processes must be concern for satisfactory long-term outcomes. If the patient is younger and more active, why not fuse that joint in the hopes of a potentially lower recurrence rate?
What The Research Reveals About Hypermobility
Many of our orthopedic colleagues have repeatedly debated hypermobility as a cause of bunions. Coughlin, Myerson and other foot and ankle orthopedists have provided studies supporting the implication of hypermobility causing hallux valgus and the use of the first metatarsal joint fusion as a surgical treatment option for symptomatic hallux valgus.3-6
In an effort to quantify hypermobility objectively, Klaue and co-workers describe the application of a noninvasive metal caliper to the foot.7 The device is a modified ankle-foot orthosis with an external micrometer to quantify first ray mobility. The authors found measurable, reproducible values for normal and hypermobile first rays. They have concluded that hypermobility is often associated with the development of hallux valgus deformity. Admittedly, the studies have been mostly conducted on cadavers and the device is still not widely utilized or available in the podiatric community.
The radiograph examination can provide objective information regarding the presence of hypermobility. Once again, dating back to Morton’s 1928 publication on hypermobility, he proposed the most notable evidence of the problem to be a hypertrophy of the second metatarsal diaphysis seen on an AP radiograph.1 Several authors have subsequently debated this issue without arriving at a strong conclusion.8
Roukis and Landsman expand on the concept that throughout time, practitioners have tried to come up with a definition for hypermobility but have been unsuccessful.9 They point out that the problem begins with the way that various authors have attempted to conduct evidence-based medicine to answer this question.