A saddle bone deformity, also known as a metatarsal cuneiform exostosis, is a build up of bone that forms on the top of the arch.  The formation of a saddle bone deformity occurs secondary to hypermobility in the 1st metatarsal cuneiform joint. 

Saddle bone deformities become painful when trying to fit into enclosed shoes.  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.

Treatment of Saddle Bone Deformities

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.

Hypermobility - excess motion in a joint or series of joints

Saddle bone - the name is derived from the location of the deformity.  A saddle bone deformity is located on the crest of the arch where it 'saddles' the arch.

Saddle bone deformities occur at the base of the first metatarsal.  Although saddle bone deformities are the result of motion of the entire 1st metatarsal cuneiform joint, the symptoms of this condition are usually specific to the dorsal aspect of the joint.  Lipping or spurring of the dorsal joint become evident over time.

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.

Saddle bone deformities are often asymptomatic.  Most patients describe only limited pain while barefoot.  But when enclosed shoes are used, a saddle bone deformity is often difficult to fit into the shoe.  Compression of the deep peroneal nerve often results in referred pain to the 1st and 2nd toes.  Pain is described as a dull ache and relieved by taking off the shoes.

Nerve entrapments 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 following images 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.

Entrapment of the common peroneal nerve in the leg.

Fracture.

Ganglionic cyst.

• Tarsal Tunnel Syndrome

• Charcot Joint

• Arthritis Of The Foot and Ankle

• Shoe Fitting

• Pronation

This article was written by Jeffrey A. Oster, DPM and was last edited on 6/27/07. No additional references are available for this condition.