As wound care doctors we understand the multiple reasons why a person can develop a chronic wound. Many of these reasons include diabetes, polyneuropathy, lack of circulation, problems in the venous system, pressure, malignancy etc. (and many others).  Specifically in the foot, when you have a patient with a wound part of the first assessment is to figure out “what is causing the wound?”. There are not only systemic diseases that can cause a wound in the foot but also bony misalignments, tendon imbalances or biomechanical abnormalities that add up to these diseases that make the situation worse. In order to heal we have to consider “what  local factors can I identify that are detrimental to this wound?”. Here are some factors to always consider depending on the location of the wound.

Explaining basic biomechanics to a patient can make a world of a difference not only so they can understand the reasons they have a foot ulcer, but that they understand why they might reopen and ultimately in case they need surgical correction of the foot deformities if conservative treatment fails.  In a later article I will explain the surgical procedures to correct this ulcers.

Big toe (hallux) Interphalangeal ulcer-Patients with this kind of ulcer many times have a small round bone (interphalangeal sesamoid) right underneath the ulcer. You will not see the bone through the ulcer as it is embedded dorsal to the flexor tendon (this is why is so important to know anatomically the plantar layers of the foot!). Another reason to have an ulcer in this location is a rigid big toe. When you try to perform range of motion of the first metatarsophalangeal joint (joint where bunion occur) you feel a restriction of motion or lack of the toe going up or down. This lack of mobility causes the toe to move up excessively on the neighbor joint (interphalangeal joint) as a means of compensation and therefore forming a wound at the bottom of the base of the toe.

Big toe metatarsophalangeal joint ulcer– Usually you see this ulcer with patients that have a high arched foot. Also this ulcer may be caused by an “over pull” of the peroneus longus (it inserts at the base of the first metatarsal). This tendon when it pulls takes the first metatarsal bone down causing more plantar pressure at the area where its head is and causing skin breakdown under the joint.  One way to know if this is your patients case is by making them plantarflex ( pointing the foot down) . If there if significant pressure/prominence under the first and send metatarsals that means the peroneus longus tendon is very strong.

Distal tuft ulcerations (Ulcers at the tip of toes)– usually are there secondary to excessive clawing of the toes due to the long tendon below the toe. When the tendon pulls too much the toe will claw or contract putting a lot of pressure at the end tip of the toe.

Lesser metatarsal ulcers (ulcers at the ball of the foot) – You need to consider Ankle equinus (lack of dorsiflexion in the ankle) always when you have any lesser metatarsal ulcers. If your foot cannot go up (dorsiflexion) enough because of excessive pull from the Achilles tendon then the foot will have excessive ground forces on the ball of the foot during walking.  Another reason to have an ulcer underneath, for example,  the third metatarsal head (central long bone)of the foot it might perhaps be because of an excessive long bone compared to the metatarsals right next to it. That means, that bone while in the phase of propulsion during walking is getting the majority of pressure from the ground. Another reason is that if you have a pathology on the first metatarsal phalangeal joint (like lack of range of motion, hypermobile joint or a short first metatarsal) you can get a transfer lesion on the second metatarsal head that ultimately ulcerated. A chronically dislocated second metatarsal phalangeal joint (like when you see a bunion with a second toe overriding the first toe) can give you an ulcer right underneath that joint.

Fifth metatarsal head ulcers (ulcer on the bottom of the side of the foot)- This ulcer is caused by a fixed or rigid varus hindfoot. This means, if your heel bone is fixed in an inverted or “rolling in” position the lateral long bone will get more pressure causing skin breakdown. If to this, you add equinus (excessive pull from the Achilles tendon) the forces to the fifth metatarsal head increase dramatically.

Midfoot ulcers (medial or lateral foot ulcers) – Always think about the possibility of a Charcot neuropathic foot. Lateral midfoot ulcers tend to be secondary to a drop of the cuboid bone. This are more devastating than the medial ulcers. The medial ulcers are due to a collapse of the medial longitudinal arch or a specific bone.

This are a few examples of biomechanical and structural problems that end up in skin breakdown. If you add systemic disease such as the devastating diabetes with peripheral neuropathy and lack of oxygenated blood flow to skin, the end result is a very hard to heal wound.  Keeping in mind this list might help you address a fixable reason to a chronic wound.

Article contributed by Coral J. Villanueva DPM, CWS