Correct Diagnosis is the First Step in Recovery from Peroneal Tendon Injuries

In this review article on ankle sprains, three doctors of osteopathy (musculoskeletal medicine) look at the normal and abnormal ankle anatomy that might contribute to chronic lateral ankle pain. Lateral refers to the outside of the ankle (away from the other leg). The main focus of this review is the peroneal tendon.

The peroneal tendon is located along the lateral side of the leg coming down from near the knee to the base of the big toe under the foot and the base of the little toe. The peroneal muscle is actually made up of two separate bundles: peroneus longus and peroneus brevis. That's why it can attach to two different bones on opposite sides of the foot.

These two muscles with their tendons work together to stabilize the ankle, especially the lateral side of the ankle. Their main functions are to evert (turn out), pronate (flatten), and plantarflex (point) the foot and ankle.

Other soft tissue structures around these two tendons that are affected when the ankle is sprained include the fascia (connective tissue) and protective sheath (covering) that covers and blends these muscle/tendon units together.

The authors discuss unusual variations in ankle anatomy that might contribute to chronic ankle sprains. For example, sometimes there are extra bony bumps, extra bones, or a slightly displaced muscle belly. Some people have an additional muscle such as the peroneus quartus, peroneus digiti quinti, or peronealcalcaneus. In others, the tendon is angled more than is considered within normal limits. Any of these added anatomical features change the dynamics of how the foot works and can contribute to problems.

With MRIs now, it's possible to see soft tissue anatomy that bone X-rays just don't show. Cadaver studies have also revealed new information. We realize now that a fair number of people (up to 20 per cent or one in five) have at least one of these anatomical variations. Even small changes such as a more prominent bone, flat groove for the tendon, or oddly shaped bone can result in peroneal injuries.

The authors suggest that peroneal tendon disorders occur much more often than is realized. That's why anyone with chronic lateral ankle sprain should be examined carefully for peroneal tendon involvement. The way to do this is to take a thorough patient history, order imaging studies (when deemed appropriate), and exam the foot and ankle by comparing it to the other (uninjured) side.

The history will reveal signs and symptoms that might point to ankle instability. For example, an ankle that rolls easily when walking on slightly uneven ground (or for no apparent reason) might be a sign of lateral instability. Ankle popping, excess ankle and/or foot range-of-motion, ankle swelling, and pain with certain resisted movements are indicators of possible tendon and ligament instability.

CT scans, ultrasonography, and MRIs help show swelling, fractures, tendon injuries, and tendon subluxation or dislocation. Scars or thickening on the tendon can indicate a poorly healed injury that puts the person at risk for re-injury. MRIs can give useful information about the integrity of the peroneal muscle complex.

The type of damage observed with advanced imaging techniques helps in the diagnosis. Fluid all the way around a tendon indicates the presence of an inflammatory condition called tenosynovitis. Recognizable changes in the MRI signal and intensity alert the radiologist to the possibility of a tendon tear.

Putting the patient history together with signs and symptoms and results of imaging studies helps the physician finalize the diagnosis. Repetitive or prolonged activity, recent injury or trauma, recent participation in competitive sports events are common histories given in tendon tears.

Once the area of pathology has been located and the underlying cause identified, then the physician turns his or her attention to planning the best treatment. Acute injuries with pain, swelling, and bruising are still treated conservatively with R.I.C.E. (Rest, Ice, Compression, Elevation). Recent evidence has shown that a short-leg cast may actually result in faster healing for moderate to severe ankle sprains than using a splint or elastic wrap to support the lower leg and ankle.

Surgery is considered when the injury is chronic -- either the person sprains the ankle over and over or symptoms of pain, weakness, and swelling just never go away. Anyone who has completed a three- to six-month course of physical therapy but the ankle is still unstable is also a potential candidate for surgery.

The type of surgery done depends on what's going on inside the ankle. Is the tendon partially torn or fully ruptured? Are both tendons involved? Are there any other injuries in the foot, ankle, or leg? The surgeon also takes into consideration the age and activity level of the patient. Young athletes may need a different approach from an older, more sedentary adult.

Torn tendons can be repaired or reconstructed with a tendon transfer. Excess or protruding bone can be shaved down, frayed tissue can be shaved or smoothed away, and tight or swollen tendon sheaths can be released or removed. The authors describe their surgical techniques for tendon repairs (e.g., debridement, tendon repair, excision, tubularization, tenodesis).

The surgeon evaluates the patient's ankle/foot movement, movement, and biomechanics. Surgery may need to address variations in anatomy leading to ankle subluxation (partial dislocation) and dislocation. Muscle/tendon imbalances can be corrected surgically. Young, active athletes who want to get back into sports activities are more likely to consider surgery without trying rehab first.

Individuals who suffer peroneal tendon tears without apparent cause (no trauma, no sports injuries) may have other predisposing conditions. Diabetes, hyperparathyroidism, rheumatoid arthritis, and psoriasis can put patients at an increased risk of tendon injury and ankle instability. Steroid injections for chronic inflammation can also thin and weaken the very soft tissue structures they are trying to treat. The result can be a tendon tear or rupture.

Sometimes the groove in the bone that holds the tendon in place is too shallow. The peroneal tendon may pop out of the groove. The surgeon may have to make the groove deeper, put the tendon back in place, and repair the connective tissue that was holding the tendon in place back together. This piece of reinforcing fibrous band is called the superior peroneal retinaculum (SPR). Again, the authors provide drawings and descriptions of the tendon rerouting techniques they prefer.

After surgery comes the inevitable rehabilitation. Splinting or casting, limited weight bearing, and physical therapy are part of the post-operative plan. Physical therapy focuses on helping the patient regain motion, strength, and mobility.

Eventually sports specific activities may be added to prepare the patient for a return to full form. Full sports activities are allowed at different times depending on the type of injury, type of surgery, and level of activity.

High-demand patients with significant loss of function and who want to be involved in athletic activities may be out of the game for three months or more. All of this depends on an accurate diagnosis, which brings us back to the start of this article. The authors contend right from the start that knowing the ankle/foot anatomy, mechanism of injuries, and choosing the right treatment is the most important part of recovery from peroneal tendon disorders.

Reference: 

Terrence M. Philbin, DO, et al. Peroneal Tendon Injuries. In Journal of the American Academy of Orthopaedic Surgeons. May 2009. Vol. 17. No. 5. Pp. 306-317.

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