Every muscle in the body has a specific purpose and job to do. Nothing makes that clearer than when an injury or degenerative changes of a muscle result in deformity and disability. In this article, the role of the posterior tibial tendon (PTT) in the lower leg, ankle, and foot is reviewed. Anatomy, function, and dysfunction are discussed in detail.
The posterior tibial tendon (PTT) runs behind the inside bump on the ankle (the medial malleolus), across the instep, and into the bottom of the foot. The tendon is important in supporting the arch of the foot and helps turn the foot inward during walking. Tendon pathology may begin with an acute injury from a traumatic fall, an ankle fracture or dislocation, or even laceration (cut) of the tendon.
Other factors that seem to put people at risk of PTT deficiency and even rupture include female gender, obesity, diabetes, high blood pressure, taking steroids, or previous trauma or surgery to the mid-foot.
Posterior tibial tendon dysfunction can be classified into four (progressive) stages. Stage 1 is characterized by tenosynovitis (inflammation of the tendon sheath and fluid between the sheath and the tendon). The patient reports mild pain around the ankle bone (the one on the inside of the ankle) and along the instep of the foot. There may be some mild weakness when trying to turn the foot inward (inversion).
Stage 2 represents degeneration that occurs as a result of the tenosynovitis when it doesn’t heal. The tendon loses some of its flexibility and support and starts to lengthen (or elongate). In some cases, the tendon may rupture, due to weakening of the tendon by the inflammatory process. The patient is still having painful swelling and beginning to see the effects of the weakness.
Without the strong support of this tendon, the arch of the foot starts to collapse, a condition called pes planovalgus. You would recognize this deformity as a “flat foot”. By now, the patient with stage 2 posterior tibial tendon dysfunction is experiencing quite a bit of pain when trying to raise up on the toes of that foot. In fact, he or she may be unable to perform this action.
By the time stage 3 sets in, the heel raise is impossible to do, there can be pain on both sides of the ankle, and the flat foot position has become a rigid deformity (no longer correctable). Stage 4 is marked by pain and crepitus (snapping, grinding sensation and/or sound). The foot is in a “turned out” position, which causes the soft tissue structures along the lateral (outside edge) of the foot and ankle to get pinched even more.
This classification scheme is important because it guides the surgeon when determining the best plan-of-care. Treatment depends on the severity of the PTT disorder and can include conservative (nonoperative) care or surgery. Conservative care consists of adapting shoes, using an insert called an orthotic) inside the shoe, and sometimes, immobilization in a cast or boot.
Physical therapy may be helpful in regaining alignment through postural adjustments, strengthening exercises, and manual therapy to restore tissue tensegrity (balance of tension and compression). Other nonoperative forms of treatment may include a rigid (nonflexible) ankle-foot-orthosis or AFO. Some patients will end up wearing the AFO permanently to support the foot and ankle.
What about surgery? When is that appropriate and what does the surgeon do? This is an area of considerable debate and an area for continued study. Transferring another tendon to take the place of the torn, ruptured, or degenerated PTT is one option. One of the goals of surgery is to stabilize the joint and improve alignment. Procedures to accomplish this goal can be quite complex with lengthening of some muscles, repair of damaged ligaments, and/or fusion of certain ankle bones.
The authors present their preferred (surgical) treatment of PTT for each stage (1 through 4). The exact surgical procedure is described in detail. Briefly, in stage 1, they open the area, remove any dense adhesions (scar tissue) and clean out areas of synovial tissue that has solidified or overgrown.
In stage 2, the Achilles tendon is lengthened and a tendon transfer is done when needed. All other surrounding structures are checked for damage and stability. Anything that needs repair or reconstruction is taken care of right away. Sometimes it is necessary to stitch two of the tendons (flexor digitorum longus and flexor hallucis longus) together to assist in the tendon transfer. If the hindfoot (heel and attaching Achilles tendon) are out of alignment too much, a procedure may be done to realign that area as well.
The authors’ preferred surgical treatment for stages 3 and 4 follow the steps used for stages 1 and 2 but go much deeper into the foot to provide support for the rigid flat foot deformity. As much as possible, the bones of the ankle are put back in their normal, anatomic placement and held there with screws, staples, and wires. All surgical procedures are followed by immobilization, a period of non-weight bearing, and then rehab with a physical therapist. Full recovery can take 12 weeks or more.
The authors conclude that their preferred management may not be the best or only approach but their results have been satisfactory and patients are pleased with the results. Having a thorough knowledge of posterior tibial tendon (PTT) anatomy is essential in recognizing problems that are developing and knowing ways to treat PTT disorders of the foot and ankle. Since this tendon-muscle unit is the one that turns the foot in and supports the arch of the foot, knowledge of its anatomy and treatment are important for orthopedic surgeons.