Tibialis Posterior Tendon Dysfunction: A guide for patients

Introduction

The Tibialis Posterior Tendon (TPT) is a very important tendon within the foot and ankle. The tendon’s job is to stabilise the foot and allow the transmission of force, from the foot to the ground. This exchange allows the forward movement of the body. The TPT does not achieve this alone; there are many tendons around the foot and ankle that help walking, but the TPT is one of the more important ones. It is also one of the most common tendons to be injured. The TPT muscle starts deep in the back of the leg, but the tendon itself becomes apparent at the level of the ankle joint around the back of the leg bone (tibia) on the inside part of the leg. At the tip of the tibia malleolus, the tendon changes direction, almost a 90 degree change in direction, and moves into the foot into a bone called the navicular.

The TPT acts on both the ankle joint (downward movement of the ankle) and the foot itself (inward movement of the foot).

During the walking cycle, the tendon acts when the foot is on the ground and prevents it from rolling out too much. It stabilises the joints of the foot and makes the foot more rigid. This allows for effective transmission of force and hence movement.

Causes of Tibialis Posterior Tendon Dysfunction (TPTD)

• Accessory navicular – this accessory bone is present in about 10 per cent of the population and can be found near the navicular bone, where the TPT should insert into. The presence of this accessory bone can increase TPTD.
• Reduced blood supply – studies have shown that there is a natural reduction in the blood supply to the tendon where it changes direction around the bottom of the leg bone. This area is called the retro malleolar groove. This acute change in direction can place stress on to the tendon, which, in time, can lead to injury and change in the composition of the tendon and, due to the poor blood supply coupled with the repetitive trauma, causes further damage.
• Inflammatory arthropathies – this includes conditions such as rheumatoid and psoriatic arthritis. The synovial tissue – the tissue which makes up the structures surrounding the joints and the tendon sheaths - becomes inflamed. This, coupled with normal stress placed on the tendon, can increase the chances of a patient developing TPTD.
• Congenital flatfoot or poor biomechanics - this produces a natural flatfoot. However, this low arch profile can put increased stress on to the TPT. As the foot assumes a flatter position, the TPT needs to work harder to stabilise and realign the foot.

Often, an acute or sudden injury can also lead to dysfunction of the tendon, for example stepping off a curb badly, or during sporting activities.

TPTD is three times more likely to happen in females, usually in their forties.

Initial symptoms usually include a vague pain around the inside of the foot and ankle, which is aggravated by activity. As the dysfunction develops, patients also begin to develop pain around the outside of the ankle.

The patient often notices that the affected foot becomes flatter and rolls into the body. Climbing stairs, walking long distances and sporting activities can become difficult.

TPTD is a progressive problem, which if left untreated, can produce secondary problems, such as arthritis of the foot joints and misalignment of the ankle joint. These need more complex surgical treatment. The disease process is often graded from one to four, with four being the most severe cases.

Treatment

Treatment of TPTD is dependent on the severity of the disease process, degree of arthritic changes and associated factors, such as weight and associated disease processes, for example inflammatory arthritis.

Treatment can be divided into conservative (non-surgical) and surgical.

Both grade one and two TPTD are treated conservatively initially. If this fails, surgical management may be necessary.

Conservative treatment

Conservative management aims to reduce the forces going through the foot and prevent the foot from rolling in. This can be achieved by a weight loss reduction (if overweight), footwear improvement (running trainer type shoe) and activity modifications. Often medications, such as non-steroidal anti-inflammatories, if you are able to take them, can help ease pain and discomfort.

An air cast walker boot rests the tendon and allows the healing process to begin. This needs to be followed by an insole, which can then control the position of the foot. Sometimes, more aggressive bracing is required through a device which can control the foot and ankle.

Other treatments include eccentric stretching of the tendon. This will be explained to you by the podiatric surgeon, podiatric biomechanist or the physiotherapist.

Surgical management

Surgical management of TPTD is dependent upon the grade/severity of the condition, as well as associated factors, such as weight, arthritic changes or inflammatory conditions.

Surgery can be split into reconstructive or destructive (salvage) procedures. Reconstructive procedures aim to realign and stabilise the foot without having to fuse the major joints of the foot. Salvage procedures are used when reconstruction would not produce a satisfactory outcome; this type of surgery involves fusing the joints around the rear foot.

Following reconstructive or salvage procedures, you will need to be in a non-weight bearing cast for up to three months. Recovery can take up to a year.

Reconstructive surgery

Reconstructive surgery involves a combination of bony and soft tissue procedures.

Soft tissue procedures

Achilles tendon lengthening or gastrocnemius recession

When the foot becomes flat and rolls out from beneath the leg, the distance between the heel bone and the knee reduces and the calf muscle contracts. If this is not addressed, the foot will be held in its rolled out position. This can lead to a poor overall result.

Flexor Digitorum Longus (FDL) tendon transfer

When the TPT becomes dysfunctional, its important role of stabilising the foot reduces and this compromises the foot’s function. The TPT needs to be substituted by another tendon to help re-establish the foot’s normal function. This is done through the FDL tendon, which produces a downward motion of the lesser toes. The transferred FDL tendon is attached in its new position by a small screw and stitches (tendon anchor).

The FDL tendon is not as powerful as the TPT; if soft tissue procedures are not combined with bony procedures, the overall chance of success is significantly reduced.

Other soft tissue procedures include repair and tightening of the ligaments.

Bony procedures

A number of different bony procedures can be used in the management of TPTD. They aim to realign the foot in relation to the ground. Bony procedures can be used in isolation or in combination with other bony procedures. The procedures required to correct the deformity are based upon the position of the foot.

Bony procedures include:

Medial calcaneal displacement osteotomy (MCDO)

This involves cutting the heel bone and moving it towards the inside of the foot, where a screw is inserted to hold it in place until it is healed. This procedure alters the forces transferred from the ground to the foot.

Other bony procedures include an Evan’s osteotomy. This involves placing a bone graft in the heel bone, which lengthens the outside of the foot and helps realign the forefoot to the rearfoot.

If the arch of the foot is collapsing or further stabilisation is required, a procedure to fuse the joints or change the angle of the arch by placing a bone graft into one of the bones (the cuneiform) can realign the foot and increase the arch profile.

Joint salvage procedures

Joint salvage procedures involve fusion (arthrodesis) of one or more of the four joints at the back of the foot. Fusion of these joints can have a dramatic effect on the motion of the foot.

Joint salvage procedures are reserved for patients where previous surgical management has failed, elderly patients or where the condition is associated with osteoarthritis of the hindfoot joints producing a rigid non-reducible foot. Joint salvage procedures are generally used for TPTD associated with a rigid foot and with signs of osteoarthritis; however joint salvage procedures are also used in treating stage two of the condition, especially in older patients. Specific complications are bony non-union (when the two bones fail to fuse together), as well as malunion (bad positioning of the foot). Both these complications can be debilitating and have an effect on a patient’s daily living and quality of life, so often need further surgery. Other complications include ankle joint arthritis. There is a greater evidence of this happening following fusion of all the joints of the hindfoot (triple arthrodesis).

Following fusion of the rearfoot joints, there is a significant reduction in motion of the foot which, in some people, can have an effect on their working and social activities.

Rearfoot fusions include:

Talonavicular fusion: This is a fusion of the talus (ankle bone) and the navicular (the bone which the TPT inserts into). Fusion of this joint will significantly reduce the inward and outward motion of the foot, but not affect the up and down motion as this arises from the ankle joint. You will be provided with a specific leaflet about this procedure.

Subtalar joint fusion: This is a fusion between the calcaneus (heel bone) and the talus (ankle bone). Fusion of this joint will reduce the inward and outward motion of the foot by about one third, but does not have an effect on the ankle joint motion. You will be provided with a specific information sheet around this procedure

Calcaneocuboid joint: The calcaneocuboid joint is on the outside of the foot and lies next to the talonavicular joint. It is a fusion between the calcaneus (heel bone) and the cuboid (a square shaped bone). This fusion is often done as a supplementary procedure when fusing the talonavicular and subtalar joint, if arthritis is present or a greater degree of correction is required.

Stage four TPTD

In stage four TPTD, the problem has become so severe that the hindfoot and ankle joint are affected. The forces of the foot rolling out have been transmitted to the ankle joint and this joint has begun to tilt towards the outside of the leg. Once this has happened, the deformity needs to be addressed by fusing the ankle joint, as well as the joints of the hindfoot.

Complications

Complications of surgery can be divided into general and specific risk factors.

General risk factors include:

• blood clot (DVT): Some patients may have increased risk of developing a blood clot. This is due to the immobility associated with the non-weight bearing cast. Your DVT risk will be assessed by the podiatric surgeon and medication will be prescribed to reduce your risk of DVT
• delayed wound healing
• infection rate: two per cent
• non-compliance of patients: four per cent
• scarring
• Numbness: During the operation the nerves may become irritated; this is often a short to medium term problem and resolves in time.

Specific complications include:

• non-union of the bone: Fusion of the talonavicular joint has an increased risk of non-union,10 to 15 per cent, subtalar joint, five to 10 per cent
• malunion: suboptimal positioning of the fusion
• fixation (screws, plates etc) irritation: The fixation is used to hold the two bony surfaces together whilst they unite. On occasion the fixation can produce some irritation and requires removal.