A saddle bone deformity, also known as a metatarsal cuneiform exostosis, is a prominence of bone that forms on the top of the foot above of the arch. A saddle bone deformity occurs as a result of hypermobility in the 1st metatarsal cuneiform joint. Bone is deposited at the periphery of the metatarsal cuneiform joint in an attempt to limit hypermobility. Therefore, what we call a saddle bone is actually a problem that involves the entire metatarsal cuneiform joint. The onset of a saddle bone deformity is between the ages of 25 to 60 years of age. Saddle bone deformities show a gradual onset and may be painful with direct pressure to the saddle bone by shoes. Saddle bone deformities are found equally in men and women.
Saddle bone deformities are not usually painful in and of themselves. The primary problem with a saddle bone deformity is trying to find shoes that will accommodate the bump on the top of the
foot. Also, saddle bone deformities tend to develop immediately beneath the deep peroneal nerve. Painful nerve compression of the deep peroneal nerve can result when pressure is applied to the nerve and underlying saddle bone deformity by the laces and the tongue of a shoe.
The primary location of the nerve entrapment can be located by a test called a Tinel's sign. A Tinel's sign is said to be positive when the location of the entrapment is tapped with two fingers and tingles occur. The tingling can be localized to the area of entrapment or extend distally into the toes. A positive Tinel's sign is often found in conjunction with a saddle bone deformity due to compression and irritation of the deep peroneal nerve.
The images to the left show the normal path of the deep peroneal nerve (green line) and the location of an entrapment found in saddle bone deformities. A positive Tinel's sign would result by tapping with the two fingers on the top of the foot.
Causes and contributing factors
Formation of a saddle bone deformity occurs secondary to hypermobility of the 1st metatarsal cuneiform joint. Hypermobility of any joint can lead to destruction of the joint over time. In an effort to prevent that destruction, spurring occurs around the periphery of the joint. Spurring is an attempt by the joint to limit hypermobility. In the case of a saddle bone deformity, this spurring is most evident on the dorsal (top) aspect of the arch. In advanced cases, spurring will become evident on the medial and plantar aspects of the metatarsal cuneiform joint. Contributing factors to the formation of the saddle bone include generalized hypermobility. Contributing factors that cause pain found with a saddle bone include tight shoes, particularly shoes that lace across the saddle bone, compressing the deep peroneal nerve.
The differential diagnosis of a saddle bone deformity includes;
Conservative treatment of a saddle bone deformity includes avoidance of direct pressure to the bump (exostosis). Open shoes, such as flip-flops or low cut dress shoes can help to limit direct pressure to the saddle bone deformity. Padding can be used to protect the saddle bone from compression by the shoe. The images at left show how to use a tongue pad to create a small pocket on the underside (tongue) of the shoe. This pocket places pressure to the medial and lateral sides of the saddle bone.
Surgical correction of a saddle bone deformity requires resection of the dorsal exostosis. By removing the exostosis, compression of the deep peroneal nerve is relieved and patients can return to enclosed shoes. Resection of a saddle bone is a procedure that takes approximately an hour to complete. This procedure can be performed in a hospital or surgery center using general anesthetic or local anesthesia and sedation. Patients are able to bear weight on the foot immediately following surgery. Return to normal activities take approximately 4-6 weeks.
When to contact your doctor
Saddle bone deformities are often asymptomatic. Please contact your podiatrist or orthopedist for additional treatment suggestions is your saddle bone becomes symptomatic.
References are pending.
Author(s) and date
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Cite this article as: Oster, Jeffrey. Saddle Bone Deformity. http://www.myfootshop.com/article/saddle-bone-deformity
Most recent article update: September 12, 2017.
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