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Current Concepts in Treating Posterior Tibial Tendon Dysfunction

By: Douglas H. Richie, Jr., D.P.M

Ask any experienced podiatric physician what pathologies have increased most dramatically in frequency over the past 20 years and the answer is almost always plantar heel pain syndrome and posterior tibial tendon dysfunction (PTTD). At first glance, these two conditions appear un-related. Yet, further scrutiny reveals obvious correlations. Both plantar heel pain syndrome and posterior tibial tendon dysfunction are thought to be the result of mechanical failure of the arch of the foot. Curiously, both pathologies have a strong predilection for affecting women. Currently, there are many un-answered questions regarding the predisposing factors for progressive failure of the arch of the human foot.

Notwithstanding, plantar heel pain syndrome is known to be successfully treated with relatively simple, non-operative treatments. On the other hand, posterior tibial tendon dysfunction is one of the most challenging pathologies treated by the podiatric physician. In a previous article in Podiatry Today ( “Clearing Up the Confusion about Posterior Tibial Tendon Dysfunction” December, 2001) this author reviewed current knowledge about the pathomechanics of PTTD. The present article will apply this knowledge of pathomechanics in proposing a practical clinical evaluation of patients with PTTD. From a simple classification system, appropriate decision making can be made regarding non-operative and operative interventions.

Review Of Our Understanding Of Pathomechanics

Currently, most authorities have dropped the description “Posterior Tibial Tendon Dysfunction” in favor of the term “Adult Acquired Flatfoot”. The reason is increased recognition that a rupture or attenuation of the posterior tibial tendon, cannot by itself lead to the deformity and disability seen in older adults with progressive flatfoot deformity. It is recognized that significant ligamentous rupture occurs as the flatfoot deformity progresses. These ligaments include the spring ligament, the superficial deltoid ligament, the plantar fascia and the long and short plantar ligaments. Evaluating and recognizing various levels of ligamentous rupture is critical for the clinician treating the adult acquired flatfoot (AAF).

However, clinical staging of patients with AAF continues to rely on a system proposed by Johnson and Strom in 1989, ( See Table I) before the recognition of the role of ligamentous rupture in the pathology(3). Myerson, in 1996, recognized the presence of a deltoid ligament rupture in late stage AAF and proposed adding a Stage 4 to the original classification when valgus deformity of the ankle is found(29).

Prevailing opinion recognizes of the presence of a pre-existing flatoot in nearly all patients with a symptomatic, progressive adult acquired flatfoot. Also, there is a strong correlation with obesity, hypertension and diabetes amongst patients with AAF making them poor surgical risks. As mentioned earlier, there is a strong predilection for females and the average age of onset of symptoms is 60 years.

In the adult acquired flatfoot, symptoms have an insidious onset, usually unilateral. It is recognized that patients can present with a progressive flatfoot deformity secondary to acute trauma or due to neuropathic conditions. This article will focus only on the more common idiopathic, progressive symptomatic adult acquired flatfoot.

Evaluation Of The Patient With PTTD

Patients with AAF can present to the podiatric physician initially with various levels of pain, deformity and disability. Accurate clinical examination is often obscured when there is significant pain and edema. Often, immediate treatment of the acute symptoms will be necessary before further work-up can be accomplished. In these situations, patients with AAF are treated no different than an athlete with an acute ankle sprain. The combination of PRICE ( Protection, Rest, Ice, Compression and Elevation), commonly used for athletic injuries, is just as relevant in the treatement of the patient with painful symptoms of AAF.

For the immediate treatment of the acute symptoms of tenosynovitis, tendon rupture or ligament rupture in the patient with AAF, I recommend immobilization with a walking boot . Alternatively, but not as protective, would be the use of an Unna Boot or tape-wrap of the foot and ankle. These measures can usually calm down symptoms within several weeks so that subsequent detailed examination can be conducted without the interference of significant pain or antalgic gait patterns.

Clinical Evaluation

The critical part of the clinical exam of the patient with a suspected progressive adult acquired flatfoot deformity is the static stance evaluation. In less than a minute, an experienced clinician can detect the tell-tale signs of a foot which has undergone attenuation or rupture of the posterior tibial tendon and/or key ligaments of the hindfoot. Since the majority of cases of rupture of the posterior tibial tendon present uni-lateral, comparison of the symptomatic to the asymptomatic foot allows insight into the severity of the pathology.

First, evaluate malleolar postion from a dorsal view of the foot. In most cases, an obvious asymmetry appear where the symptomatic foot will have an noticeable internally rotated position of the malleoli, demonstrated by anterior displacement of the fibular malleolus and posterior displacement of the medial malleolus. See Figure?

From this same dorsal view of the feet in static stance, compare the medial and lateral borders. In the progressive symptomatic AAF, the medial bulge of the talon-navicular joint and the lateral concavity of the calcaneal-cuboid joint will appear more extreme on the symptomatic side.

Next, evaluate the position of the rearfoot from the posterior view. Both feet will demonstrate a valgus heel, but the symptomatic foot will show various extremes of medial displacement of the distal tibia and talus, relative to the calcaneus and forefoot. This medial displacement of the rearfoot will cause an apparent tibial varum deforminty. These finding are consistent with closed chain pronation-subluxation of the midtarsal joint.

From this posterior view, the alignment of the tibia relative to the calcaneus (rearfoot angle, can be measured. This rearfoot angle should be measured in a relaxed postion and in a corrected, neutral position of the subtalar joint. This provides an assessment of the relative flexibility of the disorder. Flexibility and reduceability of the deformity can be important parameters in the choice of surgical procedures or in the selection of appropriate ankle foot orthosis correction.

While the patient is standing, ask them to perform the single heel rise test: While holding one foot off the floor, raise up on the ball of the other foot, lifting the heel off the floor. When the posterior tibial tendon is weak or ruptured, the midtarsal joint will be significantly unstable. The normal rigid lever of the entire arch of the foot is now shortened into two segments intersecting at the midfoot. The force of the calf muscles will cause a plantar flexion moment to the midtarsal joint rather than the metarsal phalangeal joints. A shortened lever distal to the insertion of the achilles will prohibit lifting of the heel off the ground, despite full strength of the gastroc-soleus.

The off-weight bearing exam (open chain) should include all standard biomechanical protocols including range of motion and muscle testing. Comparisions should be made between the symptomatic and asymptomatic foot.

Testing for strength of the posterior tibial muscle/tendon can be mis-leading due to recruitment of the anterior tibial muscle. Therefore, the patient’s ankle should be in a plantarflexed and everted position to minimize contribution of the anterior tibial muscle to invert the foot. The examiner should push against the plantar-medial portion of the 1st metatarsal head while the patient is instructed to invert the foot from a plantarflexed, and everted ankle position (see Figure 3).

While the patient is non-weight bearing, an evaluation of heel cord tighness must be performed with the knee flexed and extended. This is an important pre-surgical criteria and also determines the need for an ambitious stretching program during the non-operative treatment period. Almost all authorities agree that the heel cord is the single most deforming force in the progression of the adult acquired flatfoot deformity.

Another subtle, yet effective measure of activity of the posterior tibial muscle is the Supination Lag test described by Abboudi and Kupcha(7). In this test, the patient is seated on the edge of the exam table with both feet hanging in the air in a plantarflexed ankle position. The patient is instructed to “bring the soles of the feet together” in the direction of supination of the subtalar joints. In the case of an attenuation or rupture of the posterior tibial tendon, the affected foot will “lag behind” the normal foot and show a loss of inversion curvature on the dorsum of the foot (See Figure 4).

Tests For Ligamentous Integrity

Crucial to the clinical exam of the patient with AAF is the assessment of ligamentous integrity in the hindfoot. As the flatfoot deformity progresses, there is potential for attenuation or rupture of the spring ligament, the superficial and deep deltoid ligaments, the plantar fascia as well as the long and short plantar ligaments. Currently, there are no reliable clinical tests for determining loss of integrity of any of these specific structures. However, we do know that the ligaments of the hindfoot are responsible for movement transfer between the foot and the leg. Specifically, inversion of the foot is coupled to external rotation of the leg. When the major hindfoot ligaments are ruptured, this coupling is lost and the foot literally becomes mechanically disconnected from the leg.

A test for mechanical coupling between the foot and the leg is the Hubscher maneuver or the Jack test. In a weight bearing position, the patients hallux is passively dorsiflexed to end range of motion. Thru activation of the windlass mechanism and dependent upon ligamentous integrity oft the hindfoot, the dorsiflexion movement of the hallux causes plantar flexion of the first ray, supination of the subtalar joint and external rotation of the tibia. When the plantar fascia, spring ligament and superficial deltoid ligaments have been attenuated, passive dorsiflexion of the hallus results in no movement transfer between the foot and the leg, i.e. the tibia will not be observed to externally rotate. (See Figures?)

A second test, presumed to be linked to rupture of the posterior tibial tendon as well as the plantar ligaments is the First Metatarsal Rise test described by Hintermann (6). In this test, the patient is fully weight bearing on both feet and the examiner inverts the heel of the symptomatic foot in a varus direction. When there is a “dysfunction of the posterior tibial tendon”, the first metatarsal is noted to rise off the ground as the heel is brought into inversion. In the normal foot, supination of the rearfoot raises the height of the medial arch and the forefoot will remain plantigrade, due to tensioning of the intact plantar ligaments. With absent or lax plantar arch ligaments, inversion of the heel causes no arch raise and the forefoot simply inverts with the rearfoot as one unit.

Others may argue that the First Metatarsal Rise test identifies a forefoot suppinatus deformity which almost always accompanies a moderate to severe AAF. Prolonged ambulation on a valgus heel requires the forefoot to invert to remain plantigrade Prolonged inversion of the forefoot, caused by ground reaction forces against an everting rearfoot will cause attenuation and adaptation of the ligaments supporting the medial column of the foot. When the foot is brought into a corrected position, i.e. out of calcaneal eversion, this adapted forefoot inverted deformity (suppinatus) becomes immediately apparent. Regardless of explanation, the First Metatarsal Rise test can identify ligamentous attenuation and resultant forefoot deformity which must be considered when planning surgical interventions. What is critical again in this test is a determination of reduceability of deformity. The examiner should press down on the first metatarsal to determine if the suppinatus can be fully corrected. Recognition of a non-reduceable varus deformity of the forefoot is critical in planning surgical procedures for the correction of the adult acquired flatfoot.

Diagnostic Testing

Radiographic evaluation of the AAF requires weight bearing AP and lateral views of the foot, as well as weight bearing AP views of the ankle. Comparison views of the contralateral foot are helpful, but significant differences may not be obvious. Radiographic criteria for working up the adult acquired flatfoot deformity have been well described in the literature and will not be repeated in this article. (20-22,29)

The AP ankle view can determine severe stages of AAF with valgus tilt of the talus in the ankle mortise as well as impingement between the calcaneus and the fibula. Ocassionally, a stress fracture of the fibula will result from this chronic valgus force of the calcaneus.

Further diagnostic testing involving ultrasound and magnetic resonance imaging may be of questionable value in the intial evaluation of the patient with symptomatic AAF. Determining the extent of rupture or tendinopathy may not necessarily dictate variations in the treatment regimen. Clinical testing as described above may be just as helpful in directing the initial treatment program. In most cases, the treatment approach will be non-operative. When these measures fail, further testing with ultrasound and MRI can then be very helpful in making surgical decisions.

Ultrasound has been recently shown to be more sensitive and specific for diagnosing longitudinal tears of the posterior tibial tendon than MRI (28). Advantages of ultrasound include convenience of office based exams and ability to conduct the exam in a static and dynamic condition.

The Next Step: Choosing The Right Non-Operative Intervention

After evaluating and staging the severity of pathology, a practitioner must make a careful decision about choice of treatment. In the majority of cases, a non-operative intervention would be the choice for initial management of symptoms and disability. Since most surgical interventions for any stage of AAF are significant in scope and potential disability, the use of non-operative measures are almost always preferred considering the multiple medical problems commonly seen in the patient population with AAF.(5)

The compilation of clinical findings in the tests described above will allow a practitioner to classify the deformity into one of four stages, based upon the widely accepted Johnson and Strom classification. This classification originally had only a few clinical guidelines to determine staging. The following description is proposed to more clearly differentiate levels of pathology and deformity.

In Stage I AAF, there has not been noticeable structural change in the foot, and the patient can still heel rise without difficulty. The primary symptoms are tenosynovitis of the posterior tibial tendon. Short term immobilization (2-6 weeks) with a rigid walking boot or pneumatic walking boot will usually calm down symptoms. Then, most patients can be maintained in a rigid functional foot orthosis with stable footwear. Numerous orthotic enhancements have been suggested to control the severe pronation forces seen in patients with any stage of AAF. Most podiatric orthotic labs have a so called “PTTD Package” orthotic design which would include a deep heel cup, medial heel skive and medial and lateral flanges designed to control severe pronation.

In Stage II AAF, there has been attenuation of the posterior tibial tendon, accompanied by visible change in foot structure alignment with loss of one or more critical ligaments in the hindfoot. However, the hallmark of this deformity is the fact that it is still flexible and reduceable. Key findings in the clinical exam of patients with Stage II AAF include:

    1. Difficulty, or inability to independently heel raise
    2. Inversion strength of the posterior tibial tendon will be at least one grade weaker than contralateral side.
    3. Rearfoot can be manually inverted to a vertical position in stance, but first metatarsal will rise off of the ground ( positive First Metatarsal Rise test)
    4. First metatarsal rise can be reduced, i.e. Forefoot Suppinatus can be reduced, producing a neutral forefoot to rearfoot relationship. This reduction will be observed in both the weight bearing and non-weight bearing assessment.
    5. The Hubscher maneuver will detect loss of ligamentous integrity. Activation of the windlass causes no movement transfer to the tibia.
    6. Absence of degenerative changes in rearfoot complex, no valgus tilt of ankle mortise on standing radiographs

These tests confirm rupture of the posterior tibial tendon as well as loss of ligamentous integrity of the rearfoot. This loss of ligamentous integrity found in Stage II AAF will inhibit the efficacy of standard podiatric foot orthotic therapy. Hintermann has shown that the foot becomes mechanically disconnected from the leg when the spring ligament, the deltoid and the subtalar interosseous ligaments are severed. Foot orthotics rely on ligament integrity to re-direct ground reaction forces to the ankle and leg. Thus, three point force systems applied above and below the ankle-rearfoot complex, as provided by ankle-foot-orthoses (AFO’s) are necessary for successful treatment of intermediate to advanced stages of AAF.

The podiatric ankle foot orthosis ( Richie Brace®) was introduced in 1996. Since that time, over 20,000 patients with AAF have been treated with this type of device. A podiatric ankle foot orthosis differs from a traditional AFO by including a balanced functional foot orthotic footplate. In addition, the podiatric ankle foot orthosis has limb uprights oriented to control ankle rotations in the transverse and frontal planes---as opposed to posterior shell AFO’s designed to control dropfoot and other sagittal plane conditions.

Podiatric ankle foot orthoses are fabricated on corrected models, created from negative casts taken of the patient’s foot and lower leg. The traditional neutral suspension casting technique is recommended in order to capture contours of the heel, as well as the medial and lateral arches. In addition, the forefoot suppinatus deformity must be manually reduced to assure optimal functioning of the First Ray. See Figure--

As with any orthotic therapy, appropriate footwear prescription is critical. Running shoes with motion control characteristics such as medial posting, reinforced heel cup and stiff shank construction are recommended. Alternatively, high top leather oxford orthopedic footwear with adjunctive pedorthic modifications (medial sole wedge and flare) can be extremely effective in augmenting orthotic therapy for AAF. (See picture)

Physical therapy can be an important adjunctive treatment of Stage II AAF. Strength deficits and loss of range of motion can be significantly improved with 4 to 8 weeks of supervised, hands-on therapy. In addition, older patients with AAF demonstrate significant loss of balance and proprioception which can also be improved with rehabilitation.

In Stage III AAF, the deformity becomes rigid and arthritic changes become visible on radiographs. The clinical exam findings include the following:

    1. Patient cannot independently heel rise
    2. Supination Lag test positive
    3. First Metatarsal Rise test positive, and varus deformity is non-reduceable
    4. Rearfoot cannot be brought to vertical in stance
    5. Radiographs demonstrate arthritic changes in calcaneal-cuboid joint, subtalar joint and/or talo-navicular joint
    6. Calcaneus can be seen impinging on the fibula on A-P Ankle x-ray

Whether the patient demonstrates the above Stage III or Stage IV findins, the non-operative approach should be more aggressive in terms of restricting ankle and rearfoot motion. Here, a gauntlet style AFO ( Arizona AFO®) is best indicated. This combination of a polypropylene and leather device can maintain foot-ankle-leg alignment similar to a well molded cast.

In a recently published study ( Augustin, et.al : “Non operative treatment of adult acquired flatfoot with the Arizona brace.” Foot and Ankle Clinics N America 8 (2003) 491-502), impressive outcomes were reported in the treatment of twenty patients with various stages of AAF. Ninety percent of the patients in various stages of AAF reported statistically significant improvement of symptoms.

The long term results of AFO therapy in patients with stage II and III AAF have not been reported. Anecdotally, we have received many reports from practitioners stating that up to 30% of patients with stage II AAF will only require an AFO for 6 to 12 months, and then remain asymptomatic without the AFO for months or years thereafter as long as they wear traditional foot orthoses and proper shoes.

What If Non-Operative Treatment Fails?

Despite the success reported with ankle foot orthoses to treat intermediate and late stage AAF, a percentage of patients will become surgical candidates. Continued symptoms after 3 months of immobilization and after 3 more months of AFO therapy could validate the need for surgery. Furthermore, documented progression of the deformity both clinically and radiographically would warrant consideration of surgery.

Over the past ten years, there appears to be a trend towards unification of opinion about the surgical approach to patients with AAF. Ten years ago, it would not be unusual to hear experts advocate arthrodesis of one or more joints of the hindfoot as the procedure of choice for the treatment of Stage II AAF. Perhaps this was a response to the disappointing results of the solitary Flexor Digitorum Longus tendond transfer procedure which had gained popularity in the 80’s.(14)

Today, there appears to be a reluctance to fuse any major joint of the rearfoot in the treatment of Stage II AAF. A survey of 104 academic orthopaedic foot and ankle surgeons , regarding their preferred surgical approach to flexible Stage II AAF, was published last year (30 ). Only 12% of the respondents stated they would use an arthrodesis procedure of any of the major hindfoot joint. Eighty eight percent favored other bony procedures including the medializing calcaneal osteotomy, a calcaneal lengthening osteotomy or a medial column stabilization involving arthrodesis of the navicular cuneiform joint or the first metatarsal-medial cuneiform joint. Most preferred a combination of procedures including a medializing calcaneal osteotomy with a posterior tibial tendon augmentation.

With this trend in mind, it is easy to apply our clinical examination system to the selection of general categories of surgical procedures. We have identified tests for the early Grade I AAF foot with no structural change or tendon rupture. The surgical consideration should focus on debridement of the posterior tibal tendon when conservative care fails.

Our tests to determine reduceability of deformity can also differentiate those patients needing arthrodesis and those who do not. Generally, the reduceable Stage II AAF can be approached with calcaneal osteotomy (medializing or lateral column lengthening) and/ or medial column stabilization with posterior tibal tendon augmentation as well as spring ligament repair.

Arthrodesis of one or more joints of the hindfoot are favored in Stage III AAF where rigidity and arthritis are key findings. O’Malley has shown that the talo-navicular fusion most accurately reduced deformity in experimental adult acquired flatfoot models.(22) Wulker has confirmed that a talo-navicular fusion acts almost like a triple arthorodesis in eliminating motion in the remaining joints of the hindfoot.(31) However, many would consider the effect of such a rigid fusion on an older patient population and the deleterious effects of force transmitted to the ankle and knee.(18,24).

Conclusion

Much has been learned from significant research conducted over the past ten years in studying the pathomechanics of the adult acquired flatfoot. There appears to be more agreement today among practitioners regarding operative and non-operative strategies for treatment of this challenging disorder. Selection of treatment interventions requires careful evaluation of the patient and determination of the extent of pathology. Several simple clinical examination techniques have been presented which will help determine which stage of deformity a patient may be in. Accurate staging is critical in determining which treatment intervention is most appropriate.