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The plantar fascia is a crucial structure in the foot. It is also often painful. Scarring in the plantar fascia near its attachment in the heel is the most common cause of heel pain and is also sometimes referred to as “heel spur syndrome”. When non-operative care for this condition fails to heal it, surgery is sometimes recommended. Although alternatives do exist, surgery on the plantar fascia is usually a cutting or release of the plantar fascia either open (meaning through an incision 1-2 inches in length) or endoscopically (meaning through smaller ¼ inch incisions using a fiber optic camera for visualization). This is called plantar fasciotomy. Although most people recover well after this procedure, there are many potential pitfalls related to the lengthening of the plantar fascia.
Now let’s look at one function of the plantar fascia, protection of the joints and bones. All of the body weight is transferred from the forefoot to the ankle through the bones and ligaments of the foot. Unlike the ankle, knee and hip where the body weight force is applied perpendicular to the joints and bones, in the arch the force of the body weight is at an angle to the joints that is nearly parallel to the joint. If strong ligaments were not present, the arch would collapse. These ligaments help to convert forces that run parallel (shearing forces) to the joint into forces that are perpendicular (compressive forces) to the joint. Compressive forces are tolerated by the joint cartilage and bones much better than shearing forces. The ligaments therefore protect the joints from wearing out or arthritis and the bones from stress fractures.
There are ligaments that are closer to the joint and farther from the joint. The ones closer to the joint are called capsular ligaments since they are essentially a part of the joint capsule. The distribution of the body weight force across the joint is in proportion to the distance from the ligament. This means that if the main stabilizing ligament is close to the joint, then the force across the portion of the joint (figure 1) close to the ligament is low but the force on the side of the joint opposite the ligament is high. This would be the case in a foot that had undergone a complete plantar fasciotomy, an operation that cuts the plantar fascia.
In the foot with an intact plantar fascia, the stabilizing ligament is the plantar fascia (figure 2), which is much farther from the joint. The difference between the compression from the top to the bottom is not as great. This minimizes the shear and protects the joint and bones from damage.
This helps to explain the common problem of joint pain and stress fracture after plantar fasciotomy. Sometimes, the remaining ligaments and muscles are sufficient to do the job. Other times, the joints and bones adapt to the new pressure distribution and the pain resolves, but this symptom can become quite troublesome, even disabling. No studies have looked at the long-term incidence of arthritis after plantar fasciotomy, but it would not be surprising to find that it would be increased. It has been shown that the arch flattens after plantar fasciotomy. While plantar fasciotomy is a useful last resort in the treatment of plantar fasciitis, it is a potentially dangerous procedure and should be considered only after all non-operative methods have been thoroughly explored.
-Brett Fink, MD, Indiana Orthopedic Center, Indianapolis, IN, (317) 588-2663, co-author of The Whole Foot Book, A Complete Program for Taking Care of Your Feet.
Posted in Medical Tips and Pearls, Plantar fasciitis
Tags: feet, foot, foot pain, heel pain, heel spurs, plantar fascia, Plantar fasciitis
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