Flatfoot disorder, commonly referred to as Posterior Tibial Tendon Dysfunction (PTTD), has recently become more popularly known as AAFD, or Adult Acquired Flatfoot Deformity. It is generally accepted that flatfoot deformity is the result of posterior tibial tendon disease, but after its onset, patients develop a variety of foot and ankle deformities. The pathologic changes are not limited to the posterior tibial tendon, but also include changes in the arch of the foot and lesions in the ligaments that support the arch. Severe flatfoot syndrome can cause severe foot deformities and trigger painful weakness in the foot.
The posterior tibial tendon is one of the deepest muscles in the posterior fascial compartment of the lower leg and is located between the long toe flexors and long bunion flexors. It starts behind the interosseous membrane and adjacent to the tibial and fibular surfaces, with the main stops at the navicular tuberosity, the lower part of the navicular cuneiform joint and below the medial cuneus, in addition to the middle cuneus and lateral cuneus and the dice bone, and three other branches ending at the base of the middle three metatarsals. There is also a posterior end at the anterior margin of the talonavicular process of the heel bone. About 9% to 23% have seed bones within the posterior tibial tendon. The main function is inversion, plantarflexion of the foot, and support of the medial column of the foot when walking.
1.Etiology and pathology
There are no obvious causative factors for PTTD. The patient has no clear history of trauma, and the onset is a gradual process of tendon degeneration. The posterior tibial tendon has an ischemic zone between the medial ankle and the navicular tuberosity. The onset of the disease is usually followed by tendinopathy and subsequent progressive deformity after the patient is flat-footed. the onset is more common in women between 50 and 60 years of age.
The posterior tibialis and posterior tibialis tendons are the second strongest tendons of the lower leg. The tendon degenerates, elongates, and progressively loses inversion strength and loses the power to lock the hindfoot in gait without locking. Without normal inversion strength, medial ligament stress increases, as does the adjacent spring ligament complex. Repeated stresses strain the ligaments and cause loss of function, resulting in a flat foot. If the ligament is damaged to begin with, then the stress on the posterior tibial tendon is significantly increased. Whichever condition occurs first will result in arch collapse.
After the flat foot appears, the heel bone is turned out and the Achilles tendon is weakened to compensate for the inversion. When the heel is overturned, the Achilles tendon becomes an external turning force. In this case, the strongest tendon in the lower leg will promote the progression of the deformity. When there is an overturning of the heel bone, the Achilles tendon becomes an external turning force. In this case, the most powerful force in the calf becomes the force that causes the deformity. After heel ectropion, contracture of the gastrocnemius muscle occurs. Its tension should be noted during the examination, because the contracture of the gastrocnemius muscle occurs and requires surgical release. Ligamentous strains and strains can occur in any part of the arch, including the first metatarsal cuneiform joint and the navicular cuneiform joint.
Staging of PTTD
Stage I, degeneration and tearing of the tendon, but no deformity of the foot
Stage II, tendon degeneration with soft, reversible deformity of the foot
A (early stage) heel exostosis, mild to moderate arch subsidence
B (late stage) arch subsidence, midfoot valgus at the talonavicular joint
Stage III, fixed deformity, not passively repositionable
Stage IV, due to strain on the deltoid ligament, the talus is tilted and turned out, reaching the position of the medial ankle
2.History, clinical manifestation and physical examination
The staging can be performed by the physical examination. Most patients with stage I and II have a history of posterior medial hindfoot pain, which is located in the posterior tibial tendon, at the distal, medial walk of the medial ankle. The pain is located in the posterior tibial tendon, in the distal, medial course of the medial ankle. The patient may not be able to complete the heel lift test. The unipedal heel lift test is the simplest and most sensitive. The foot can be seen to turn inward during the heel lift when viewed from behind the patient. In some patients, the patient complains of pain and weakness, but can complete the heel lift test without inversion.
In addition, a positive sign of heel valgus can be seen when the patient is viewed from the posterior aspect of the heel bone. In addition, “polydactyly” can be seen, which is caused by forefoot abduction. To identify whether the foot deformity is a stiff deformity, there is also the “wood block test”, in which the patient steps on a 2 cm high wood block on the outside of the forefoot, and if the heel exostosis disappears and the polydactyly sign disappears, then the patient is in stage II and the deformity is still a reversible lesion.
As the disease progresses, the medial pain and pressure can disappear. Patients may have a period of symptom relief or may notice weakness in the foot and softening of the arch. As the deformity progresses, the pain and pressure from bone impingement progresses laterally to the tip of the fibula and the lateral subtalar joint. MRI may show tendonitis, longitudinal tears or complete ruptures.
The examination of posterior tibial tendon insufficiency also includes an examination of the gastrocnemius muscle. The patient is seated with the hind foot in a neutral position, and the dorsiflexion of the ankle is passively moved in knee extension (gastrocnemius and hallux valgus) versus flexion (hallux valgus). Most patients have a simple contracture of the gastrocnemius muscle. Achilles tendon lengthening can be performed for either type of contracture.
3.Treatment
Stage I Indications and contraindications for surgery
Stage I patients with painful tenosynovitis and partial tears of the tendon for more than 3 months may be considered for surgery when conservative treatment has failed. Emergency surgery should be performed for complete rupture of the posterior tibial tendon. Conservative treatment includes: foot support with AFO immobilization for 6 weeks or longer to reduce patient discomfort. Long-term treatment with UCBL, or a brace such as Arizona, is also available. The patient is asked to review the deformity periodically to observe for recurrence, with or without pain. It is important to explain to the patient that the development of the deformity will require complex surgical treatment and that postoperative function is poor.
Consider surgical treatment when the patient has progressive pain and deformity. There is only partial tearing and elongation in the tendon and some inversion ability, causing persistent pain at the tendon. Surgery involves displacement of the flexor digitorum longus tendon and either augmentation or replacement of the torn posterior tibial tendon. If less than 75% of the degeneration is visible in the cross-section of the tendon, the degenerated tissue can be excised, thus preserving the integrity of the tendon. However, it is most common for a patient to have complete degeneration of the tendon within a segment, necessitating removal of the entire degenerated tendon. The elasticity of the posterior tibial tendon can be checked intraoperatively. If the elasticity is not diminished the long toe flexor tendon can be sutured to the posterior tibial tendon at the level above the ankle joint. If the patient has a flat foot, an internal heel displacement osteotomy is feasible during the tendon displacement procedure to reduce the postoperative stress of the posterior tibial tendon displacement and to avoid further deformity development. The osteotomy improves the inversion activity of the Achilles tendon by improving the static structure of the arch and the inversion of the heel lift.
When evaluating patients with stage I posterior tibial tendon insufficiency, MRI can help determine the degree of tendon degeneration, and some patients may not have tears and degeneration, but only tendinitis. Conservative treatment may be considered at this time, with tenosynovectomy if necessary.
Surgical treatment
A medial incision is made between the medial ankle and the navicular bone to expose the tendon and explore the medial and lateral aspects of the tendon. The degenerated and torn portion is commonly found at the height of the medial ankle, so the incision is made higher than the medial ankle to explore the proximal end. The flexor support band should be preserved for 1 to 2 cm. Below the posterior tibial tendon and medial to the navicular joint is the flexor digitorum longus tendon. In some cases, the flexor digitorum longus tendon is connected to the flexor digitorum longus tendon and forms a Henry’s node at the base of the foot; if this node is not present on intraoperative exploration, the two tendons should be sutured.
Postoperative care
The non-weight-bearing cast is immobilized for 4 to 6 weeks and is replaced by a removable cast at 6 weeks for gradual weight-bearing exercises. 10 to 12 weeks for weight-bearing activities with a shoe or brace. For 4 months after surgery, only light inversion strength exercises were performed, and then strength exercises were performed after 4 months when the tendon had fully recovered.
Prognosis and results
Medial pain in patients with stage I posterior tibial tendon insufficiency is treated well. If the bone alignment of the foot is corrected, there is usually no progression of deformity. Because the strength and flexibility of the tibial tendon is not fully restored in most patients, most patients are unable to perform physical activities with running and jumping after recovery. Some patients may be able to return to physical activities such as running. Patients can also regain better inversion strength if they perform specialized rehabilitation exercises after the tendon has fully healed 4 to 5 months postoperatively.
Complications
Inadequate or excessive osteotomies may occur. Intraoperative judgment is required to avoid this. It is also important to avoid excessive tension or laxity of the tendon during surgery. At the end of the procedure, the foot should be placed in a neutral position and aligned normally. Bone from the lateral heel can be implanted in the navicular bone for early healing after tendon displacement.
Stage II Indications and contraindications for surgery
Patients in this stage are most suitable for surgical treatment. The rate of progression of the deformity and functional insufficiency varies from person to person. If progression continues, surgical treatment can be complicated and postoperative patient satisfaction decreases. Patients who are contraindicated to surgery or who do not want to undergo surgery may have an Arizona brace made. Patients are also advised that non-surgical treatment will not control progression and that they should be followed up regularly.
The surgical approach is controversial. In early stage II lesions with moderate anterior rotation of the arch, mild or moderate heel inversion, and mild talar navicular subluxation, surgical osteotomy and tendon transposition of the heel can correct the lesion. However, careful examination is required to note any laxity of the 1st metatarsal cuneiform joint or contracture of the Achilles tendon. If there is laxity, a fusion of the 1st metatarsal cuneiform joint may be performed to eliminate instability.
The treatment of patients with severe valgus and sunken talonavicular joint resulting in severe arch subsidence is controversial. Most surgeons perform lateral column lengthening of the heel. A subset of surgeons perform orthopedic surgery less frequently. Instead, they perform talar navicular and subtalar joint fusion. The goal of treatment is to correct the deformity of the foot and to maximize the preservation of function. Lateral column lengthening can be performed through the heel dice joint, and proximal lateral column lengthening of the heel (Evan procedure) heals better and is easier to perform. There is a possibility of postoperative heel dice arthritis so some surgeons also perform fusion of the heel dice joint. Current studies have shown that patients rarely require re-fusion after Evan surgery.
Postoperative care
Patients should not be weight-bearing for 8 weeks after lateral column lengthening for either the Evan procedure or the heel dice fusion. After heel lengthening, patients can be replaced in a cast from 8 to 10 weeks. Wear a boot-shaped brace for mobility. Patients with fused heel dice joints are casted for 12 weeks, and weight bearing can be started at 8 weeks. Mild triple joint activity is started after removal of the cast. Internal and external rotation exercises, as well as toe strength exercises are performed.
Prognosis and outcome
Patients with stage II had better triple joint motion after surgery, without complete inversion strength, but with relatively intact retention of foot strength. The foot has mild stiffness and weakness or medial or lateral weakness of the foot, but does not produce symptoms. Late stage II patients have poor foot motion and inversion strength, but with appropriate correction, the results are acceptable. Postoperatively, patients often feel discomfort in the lateral aspect of the foot. There is some discomfort during recreational physical activity. Most patients have good foot function and can walk or exercise. The goal of treatment for these patients is minimal joint stiffness and optimal alignment. In addition to complications in stage I patients, stage II patients have a high likelihood of under- and over-orthosis. Bone nonunion is also more common with heel dice joint fusion and lateral column lengthening. Bone nonunion can continue with braking, but bone graft failure and orthopedic failure may occur. The loss of motion after heel dice fusion is not as great as with inferior talofibular and talofibular fusions. However, the impact is greater than with Evan’s heel lengthening.
Stage III Indications and contraindications for surgery
Patients with significant deformity but no pain can be treated conservatively with the Arizona brace. Patients with unrealistic hopes should also be included as a contraindication to surgery. Patients with talofibular and subtalar fusions are unlikely to be able to run after surgery, and physical exercise for walking activities is difficult to accomplish. Uneven surfaces and prolonged walking can cause discomfort for patients after talofibular or triple fusion. If such a fusion is to be performed, a remedial plan is necessary to maintain the patient’s ambulation.
If the patient’s foot deformity is completely rigid, there is no good inversion of the foot even after anesthesia. In this case, it is necessary to correct the deformity after fusion of the foot. The number of fusion joints depends on which deformities are to be corrected. The most critical is the correction of the talofibular joint, which largely determines the position of the triple joint fusion.
For postoperative care, weight-bearing is prohibited for 8 weeks, the position of the foot and bone healing are checked by X-ray, and partial weight-bearing is started for another 4 weeks when conditions permit, and the cast is removed at 12 weeks. Braking boots were in place for 4 weeks before switching to regular shoes.
Prognosis
Pain is significantly reduced in stage III patients after triple joint fusion. Some patients have very good postoperative activity, although playing sports can still be limited. This includes limited running.
Complications
Complications of hindfoot fusion include non-union and deformity healing. The correct surgical approach can reduce the incidence of complications. The position of the heel and forefoot should be carefully examined by the naked eye during surgery, and the position of the joint can be examined by X-ray or fluoroscopy. The deformity should not be allowed to remain when fusing in situ. The talus is well positioned in the ankle cavity preoperatively, but due to increased stress on the triangular ligament and ligamentous strain after triple joint fusion, the talus can become exostotic. This condition may result in fusion failure. Preoperatively, if the talus is already found to be tilted, then caution should be exercised in performing triple joint fusion. Intraoperatively, attention should be paid to the alignment of the talus with the foot. Postoperatively, the patient can use a brace but a splint cannot prevent the development of the deformity.
Stage IV Indications and contraindications for surgery
Surgical treatment options for stage IV patients are limited, and most patients cannot correct the talar tilt in the ankle cavity after surgery. Therefore, post-operative fixation with a brace or AFO is preferred. After triple joint fusion in patients with severe talar tilt within the ankle cavity, progressive deformity at the ankle level is very large, and as the deformity progresses, most develop arthritis. The most effective treatment for arthritis and ankle deformity is to perform an ankle fusion in patients with limited postoperative mobility, and therefore such procedures are performed only in patients who already have minimal mobility. In a small number of patients with active deformity but also significant talus valgus deformity within the ankle cavity, surgical treatment of such patients is feasible with non-fusion correction, but surgery cannot control the progression of the deformity within the ankle cavity. Triangular ligament reconstruction is also possible, and short-term surgical results are fair.
Postoperative
The increased moment of lower extremity movement after ankle fusion may result in bone nonunion. Therefore, the patient should refrain from weight-bearing during the postoperative period until the bone heals. A boot-shaped brace is worn for approximately 8 weeks, and since the patient cannot move the ankle, an athletic shoe or a rocker-soled shoe with an insole is worn to improve mobility.
Prognosis
Postoperatively, the patient has limited mobility. However, the patient can hobble after surgery, but the patient cannot walk too much, up to a few blocks. Functionally the patient will function similarly to a better below-knee amputee after surgery. If the patient has an intact deltoid ligament, an ankle replacement is possible.