We've already discussed some of the
information about bunions on another web page, and we discuss
some of the various
procedures available to the podiatric surgeon on
Here we'll review some of the radiological (x-ray) and clinical factors a podiatric
surgeon will consider in contemplating the type of bunion surgery a
patient may require.
Intermetatarsal Angle (Or IM
The Intermetatarsal Angle is the angle between the
first and second metatarsals (the bones behind the toes that make up the
ball of the foot). On the left you can see a good
example of a deviated first metatarsal angle, as the larger first
metatarsal has drifted away from the second.
Most bunion deformities have abnormal intermetatarsal angles, and
most surgical procedures attempt to realign this angle in some
A great number of procedures can be used by the podiatric surgeon
to correct this abnormality--the advantages and disadvantages of the
various procedures depends on other factors that need to be
Hallux Abductus Angle (or HA
The Hallux Abductus Angle refers to a deviated angle
between the first metatarsal and the big toe. A good example of an
abnormal HA angle can be seen to the right. The big toe is
clearly crooked relative to the metatarsal.
There are several procedures that may be employed to correct an
abnormal hallux abductus angle.
PASA and DASA (Joint Cartilage Alignment)
Closely associate with the Hallux Abductus Angle
(discussed above) is the alignment of the opposing joint surfaces (made
of cartilage) found on the big toe and first metatarsal. The
orientation of the cartilage on the first metatarsal is known as PASA (Proximal
Articular Set Angle) and the orientation of the cartilage on the base of the big
toe is known as DASA (Distal Articular Set Angle).
example of proper alignment of the joint surfaces can be seen on the
left. PASA and DASA are in good alignment.
Most cases involving a deviated Hallux Abductus Angle (as in the
X-ray to the right) involve a concurrent deviation of the joint surfaces
(PASA and DASA). But this is
not always the case when the bunion is progressing rapidly. In
these cases, the hallux abductus angle may be deviated, but the
orientation of the cartilage (PASA and DASA) may not have had time to
adapt to its misaligned position.
How the alignment of PASA and DASA
relate to each other will dictate whether the bunion is a structural
deformity (where adaption of the joint structures
has occurred), a positional deformity
(where the joint structures have not yet adapted) or a combined
As the first metatarsal drifts away from the second
metatarsal (as shown above with the abnormal intermetatarsal angle), the small
bones beneath the first metatarsal (called 'sesamoids') may become
This deviation is usually graded on a 7 point scale, (illustrated
on the X-ray to the right), with 7 being the most
But the sesamoid bones don't simply drift across on a flat plane
of movement. As they drift, they also tend to rotate around the
first metatarsal bone. This rotation is not appreciated on the
view to the right; it is best visualized on the X-ray views below.
To the left is an example of sesamoids in normal
alignment. Also visible on this view is the normal ridge of
bone (called a 'crista') lying above and between the
To the right, on the other hand, is an example of sesamoids that have become
deviated. The sesamoid deviation would be graded a 4 if judged on
the 7-point scale, but on the view to the right you can see that the
sesamoids have also rotated around the metatarsal.
Note that in this example the crista has been worn away and is
absent in this example, not surprising when the sesamoids are this
How much the sesamoids are deviated is
quite variable, and how much this is corrected during the bunion surgery (if it needs to be at all) varies
on a case-by-case basis.
For additional information on this
topic, please visit our web page on sesamoid
The Hallux Interphalangeus Angle (HI Angle)
Sometimes the big toe itself is crooked. Usually
this occurs in the joint between the two toe bones found in the big toe
(as seen in the example to the left). Sometimes one of the big toe
bones will be bowed within the shaft of the bone.
Several procedures have been designed to correct this
Other Factors To Be Considered
Other factors that are considered when a bunion surgery is
The relative length of the first
metatarsal. A long
first metatarsal tends to speed up the arthritic process, and the first
metatarsal may need to be shortened at the time of the bunion surgery.
A short first metatarsal may tend to cause pain beneath the second
metatarsal, and the metatarsal may need to be lengthened. There are
different surgical procedures that have been designed to address long, short
and normal metatarsal bones.
The relative elevation of the first
elevated first metatarsal tends to speed up the arthritic process in the
great toe joint, and the first metatarsal may need to be dropped at the time
of the bunion surgery. (See our web page on Hallux
Limitus and Hallux Rigidis.) A dropped first metatarsal may cause the foot
to twist in compensation, which may cause pain elsewhere. In each
case, the metatarsal relative degree of metatarsal elevation needs to be
addressed at the time of surgery.
The shape of the metatarsal head. Some metatarsal
are relatively round; some are square. Others may have irregular joint
surfaces. Each may require a different type of procedure to keep the
joint functioning as well as possible.
The flexibility of the patient. Patients with a
great deal of soft-tissue flexibility in their feet (and in their bodies in
general) may need to have a more aggressive procedure performed to prevent
the return of the bunion.
The amount of arthritis in the big toe joint.
Because the joint no longer functions well when arthritis is present, a
patient with severe arthritis may require a very different procedure than a
patient with little arthritic change. (See our web page on Arthritis.)
The age of the patient. A 28 year-old female
patient, for example, will generally have a more aggressive procedure
performed because she will need to have more long-term correction than
someone who is 78.
The health of the patient. Patients who are
healthier can usually heal from larger procedures better than patients who
are in relatively poorer health.
The lifestyle of the patient. Patients who are very
active need to have a highly-functional foot, and may need a different sort
of procedure than a patient who may be very sedentary and may simply need a
procedure that provides comfort.
The type and degree of
biomechanical abnormality that may be causing or exacerbating the bunion
problem. For a common example, see our web page on pronated feet.
The degree of pain the patient
experiences. (Pain unresponsive to conservative treatment
requires more urgent surgical intervention.)
Where the pain is felt. (Is it pain
with motion about the joint? Pain from pressure to the
enlarged bone? Other types of pain?) These factors
of osteoporosis present. (If you
wish more information about this subject, we have a web page of
information about osteoporosis.)
The types of shoes the patient
Any associated calluses, which indicates
abnormal pressure forces that must be considered. (If you wish more
information about this subject, we have a web page of information
Any other associated
deformities or pathologies. For
example, bunions are associated with Hammertoes,
and Heel Pain, Excessive
Pronation, and so forth, all of which
need to be
addressed in order to properly correct the foot.
For more information on the general topic of bunions,
please visit our web page on bunions.
Putting It All Together
Only after reviewing the
patient's complaints and medical history--and after performing a
physical examination and assessing all appropriate studies (X-rays,
blood work, for examples)--and after considering all the factors
mentioned above (and others), the podiatric physician may begin to
decide which of over 150 different surgical procedures that have been
designed is most appropriate to address the various considerations
associated with this deformity. Please visit our web page on some
of the more common surgical bunion procedures
Perhaps you can see why it's difficult
to compare your surgery to the type your friend or neighbour may have had.
You may need a very different sort of procedure than your friend
had. Your right foot may even need a very different
procedure than your left foot.
It's important for the patient to fully
understand the procedure being attempted, because the post-operative course is
very different from procedure to procedure. For example, in many
procedures, you may be able to walk immediately. In others you may be in a
non-weight-bearing cast. Some cases require the use of screws.
Others require pins. Some require nothing. So before you have any
bunion surgery, sit down with your surgeon and discuss the procedure being
considered and the post-operative course in detail.