Posterior tibial tendon insufficiency (also called posterior tibial tendon dysfunction or adult acquired flatfoot) has been named literally after failure of the posterior tibial tendon. However, the condition is caused not only by the progressive failure of the posterior tibial tendon; it is also failure of associated ligaments and joints on the inner side of the ankle and foot. This results in collapse of the arch of the foot, along with the deformity which most often becomes the debilitating problem in its later stages. While at the beginning the common symptom is pain over the tendon in the inner part of the hindfoot and midfoot, later on it is the deformity that can threaten a person?s ability to walk. Just as the tendon degenerates and loses its function, other soft tissue on the same inner side of the foot – namely the ligaments – degenerate and fail. Ligaments are responsible for holding bones in place, and when they fail, bones shift to places where they shouldn?t; deformity is the result. The deformity causes malalignment, leading to more stress and failure of the ligaments.
Rheumatoid arthritis This type of arthritis attacks the cartilage in the foot, leading to pain and flat feet. It is caused by auto-immune disease, where the body?s immune system attacks its own tissues. Diabetes. Having diabetes can cause nerve damage and affect the feeling in your feet and cause arch collapse. Bones can also fracture but some patients may not feel any pain due to the nerve damage. Obesity and/or hypertension (high blood pressure) This increases your risk of tendon damage and resulting flat foot.
The symptom most often associated with AAF is PTTD, but it is important to see this only as a single step along a broader continuum. The most important function of the PT tendon is to work in synergy with the peroneus longus to stabilize the midtarsal joint (MTJ). When the PT muscle contracts and acts concentrically, it inverts the foot, thereby raising the medial arch. When stretched under tension, acting eccentrically, its function can be seen as a pronation retarder. The integrity of the PT tendon and muscle is crucial to the proper function of the foot, but it is far from the lone actor in maintaining the arch. There is a vital codependence on a host of other muscles and ligaments that when disrupted leads to an almost predictable loss in foot architecture and subsequent pathology.
Clinicians need to recognize the early stage of this syndrome which includes pain, swelling, tendonitis and disability. The musculoskeletal portion of the clinical exam can help determine the stage of the disease. It is important to palpate the posterior tibial tendon and test its muscle strength. This is tested by asking patient to plantarflex and invert the foot. Joint range of motion is should be assessed as well. Stiffness of the joints may indicate longstanding disease causing a rigid deformity. A weightbearing examination should be performed as well. A complete absence of the medial longitudinal arch is often seen. In later stages the head of the talus bone projects outward to the point of a large “lump” in the arch. Observing the patient’s feet from behind shows a significant valgus rotation of the heel. From behind, the “too many toes” sign may be seen as well. This is when there is abducution of the forefoot in the transverse plane allowing the toes to be seen from behind. Dysfunction of the posterior tibial tendon can be assessed by asking the patient to stand on his/her toes on the affected foot. If they are unable to, this indicates the disease is in a more advanced stage with the tendon possibly completely ruptured.
Non surgical Treatment
In the early stages, simple pre-fabricated orthotics can help improve the heel position to reduce the mechanical load which is contributing to the symptoms. In advanced stages or long term orthotic use, a plaster of paris or foam box cast can be taken and specific bespoke orthotics manufactured. If the condition develops further a AFO (ankle foot orthotic) may be necessary for greater control. In more advanced stages of symptomatic Adult Acquired flat feet, where the conservative methods of treatment have failed there are various forms of surgery available depending upon the root cause of the issue and severity.
Surgery should only be done if the pain does not get better after a few months of conservative treatment. The type of surgery depends on the stage of the PTTD disease. It it also dictated by where tendonitis is located and how much the tendon is damaged. Surgical reconstruction can be extremely complex. Some of the common surgeries include. Tenosynovectomy, removing the inflamed tendon sheath around the PTT. Tendon Transfer, to augment the function of the diseased posterior tibial tendon with a neighbouring tendon. Calcaneo-osteotomy, sometimes the heel bone needs to be corrected to get a better heel bone alignment. Fusion of the Joints, if osteoarthritis of the foot has set in, fusion of the joints may be necessary.