Departments of Radiology and Orthopaedic Surgery
University of Washington
Introduction
Hallux valgus is a common foot disorder of several etiologies, which
can lead to significant foot pain and deformity. Little has been published
in the radiographic literature about the pre- and postoperative radiographic
findings of this very common and very treatable cause of foot pain.
Definition
The term hallux valgus denotes deviation of the great toe toward the
fibular border of the foot. Hallux valgus is not synonymous with bunion,
which is derived from the same root as "bun" or "bunch",
and means an area of swelling. In connection with the foot, bunion usually
refers to the prominent medial portion of the first metatarsal head and
especially to the bursa or a bursa plus osteophyte over it, when this exists.
A bursa and/or osteophyte may or may not accompany hallux valgus.
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normal foot in which the normal intermetatarsal angle
measures about 5 - 10 degrees |
foot with metatarsus primus varus, in which the intermetatarsal
angle measures about 20 degrees |
Pathogenesis
The etiology of hallux valgus is somewhat controversial. Some cases are
congenital, perhaps secondary to a sloping surface of the first tarsometatarsal
joint. When this joint is hypermobile, with or without the normal angle,
it is often referred to as an "atavistic" tarsometatarsal joint.
Other cases are almost certainly due to environmental factors, such as poorly
fitting footwear. The fashionable shoes worn by many women are more constraining
than the shoes worn by men and are felt by many authors to be the etiologic
factor in most cases of hallux valgus. This would help to explain the 10:1
ratio of females to males seen with this disorder.
25 year old female with normal feet and no shoes.
Same patient as figure above, but now in shoes with 3 inch
heels. The intermetatarsal angle has widened in both feet, and a functional
hallux valgus has developed, due to her constricting shoes.
Radiographic Findings
Hallux valgus is often associated with abnormalities in two planes. In
such cases, the first metatarsal head is not only deviated medially, but
also dorsally. As the first metatarsal splays dorsally, greater stress is
placed on the central metatarsals, especially the second, leading to hyperostosis
and occasionally stress fractures.
Normal foot
Foot with metatarsus primus varus. Dorsal splaying of both
the first and fifth metatarsal heads is noted. Keratosis (dark pink) is
seen in the skin adjacent to these heads, due to pressure against the
shoe.
The central metatarsal heads now bear more of the weight, leading to
plantar
keratosis and hyperostosis.
Normally, the 1st and 2nd metatarsals are parallel to each
other, and their superior surfaces appear within 1 - 2 mm of each other,
as shown here.
Some patients with metatarsus primus varus demonstrate not
only medial angulation of the first metatarsal head, but also dorsal angulation
as well. Here the first metatarsal is elevated several mm above the second
metatarsal head.
Two large sesamoid bones are present beneath the first metatarsophalangeal
joint within the tendons of the flexor hallucis brevis. With the development
of hallux valgus, the 1st metatarsal head migrates medially and dorsally.
The fibular sesamoid frequently rotates slightly dorsally, and is seen on
the AP film in profile.
This patient has a marked hallux valgus deformity in both
feet. As the first toe migrates more and more to valgus, it presses against
the second toe, and may aggravate dorsal clawing of the second toe, which
is usually initiated by overload of the second metatarsal and synovitis
of the metatarsophalangeal joint. Also note the relative hyperostosis of
the second metatarsal shafts compared to the third and fourth, as well as
dorsal rotation of the fibular sesamoids.
This patient exhibits soft tissue swelling medial to her first
metatarsal head, indicative of bursitis and synovial thickening. Also noted
is dystrophic calcification in this bursa. Such changes could also be seen
in tophaceous gout.
Preoperative film showing hallux valgus and clawtoe deformities
of the second and third toes. Medial subluxation of the head off the sesamoids
is shown, as well as marked hyperostosis of the second metatarsal shaft.
Same patient status post Lapidus procedure. With osteotomy
of the 1st metatarsal, the 1st metatarsal head has been realigned in a more
lateral and plantar location over the sesamoids. The 1st tarsometatarsal
joint has been fused. Kirschner wires are seen in the 2nd and 3rd toes after
osteotomy for clawtoe deformities.
Broken screw following Lapidus procedure. Cancellous screws,
especially the thinner ones, usually break at the junction of the shank
and the threaded portion. Therefore, this probably represents at least a
delayed union if not a nonunion. However, if correct position is maintained,
as in this case, and the surgical site is painless, it may be considered
a satisfactory result.
This patient has undergone bilateral osteotomy of the medial
1st metatarsal heads ("bunionectomy"). Unlike the Lapidus procedure,
this procedure does not correct the underlying splaying of the 1st metatarsal,
and can lead to instability of the first metatarsophalangeal joint. In this
case, the hallux valgus has been overcorrected, and the patient now has
a bilateral hallux varus. Bilateral osteotomies are noted in the 5th metatarsals
for correction of "bunionette" deformities.
CONCLUSIONS
- Hallux valgus is a very common and very treatable cause of foot pain.
- Hallux valgus cannot be adequately assessed unless weight-bearing views
are performed in the AP and lateral positions.
- With experience, the radiologist can make valuable observations in
both the pre- and postoperative films in patients with hallux valgus.
References
- Coughlin MJ. Hallux valgus: causes, evaluation, and treatment. Postgrad
Med 1984;75:174-178.
- Frede TE, Lee KJ. Compensatory hypertrophy of bone following surgery
on the foot. Radiology 1983;146:347-348.
- Inman VT. Hallux valgus: a review of etiologic factors. Orthop Clin North Am 1974;5:59-66.
- Kelikian H. The hallux. In: Jahss MH, ed., Disorders of the foot. Philadelphia: WB Saunders, 1982:539-621.
- Kilcoyne RF, Farrar E. Injuries and deformities of the foot. In: Handbook of radiologic orthopaedic terminology. Chicago: Year Book, 1986:123-137.
- Weissman BNW, Sledge CB. The foot. In: Orthopedic radiology. Philadelphia: WB Saunders, 1986:625-670.
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