Disorders of the Subtalar Joint, Including Subtalar Sprains and Tarsal Coalitions

Clinical Presentation

The typical injury that leads to instability of the subtalar joint is a severe supination or supination-inversion force applied to the hindfoot. This results in a progressive injury to the talonavicular ligament and talonavicular capsule, followed by injury to the calcaneofibular and lateral talocalcaneal ligaments. The presenting complaint often is a sensation of giving way of the ankle. The patient may report pain localized to the region of the sinus tarsi. Athletic activities can exacerbate the symptoms, resulting in a dependence on bracing or taping. Uneven surfaces may cause pain and a feeling of instability.

It is difficult to differentiate lateral ankle instability from subtalar instability on the basis of patient history. A thorough clinical and radiographic workup can help define the source of the athlete’s complaints, but the differentiation still can be elusive.

Physical Examination

The most notable finding on physical examination is increased inversion of the subtalar joint. This should be compared with the presumably uninjured opposite limb. The increased inversion can result from subtalar instability or a combination of subtalar and ankle instability. It is not possible to detect the location of increased inversion by examination. In addition to increased inversion of the hindfoot, an increased translation of the calcaneus in the medial direction has been noted by Thermann et al. In their test, a valgus stress was applied to the calcaneus, followed by an abrupt internal rotation stress. Stress radiographs showed a medial shift of the calcaneus in relation to the talus or an opening of the talocalcaneal angle in patients with subtalar instability.

Following an acute injury, there may be swelling, bruising, and tenderness laterally. In the more chronic setting, increased inversion and lateral tenderness are more likely. It is easier to detect instability clinically in the chronic setting because the athlete will be less apt to guard because of pain.

Radiographic Evaluation

The initial radiographic workup of the patient with subtalar instability involves a weight-bearing anterior-posterior (AP), lateral, and mortise view of the affected ankle, as well as weight-bearing AP, lateral, and oblique radiographs of the affected foot to rule out evidence of bony pathology.

Plain radiographs often are negative, and further investigation must be carried out to arrive at the diagnosis. There have been multiple investigations into the use of stress radiographs in the workup of subtalar instability ( Fig. 17.3 ). In a series of three patients, Brantigan et al. were able to radiographically demonstrate subtalar instability. They attributed the instability to an injured CFL. Heilman et al. sequentially sectioned ligaments in cadaver limbs and then obtained lateral and Broden’s radiographs. They found that sectioning of the calcaneofibular joint caused a 5-mm opening of the subtalar joint. With subsequent sectioning of the interosseous ligament, the joint opened up to 7 mm.

The utility of stress radiographs has been called into question by multiple authors. Harper reported a wide range of subtalar tilt with stress radiographs in his group of asymptomatic patients. Louwerens et al. examined 33 patients with chronic ankle instability and 10 control patients who were asymptomatic. Broden’s views were checked under fluoroscopy and they detected no difference between symptomatic and asymptomatic feet with regard to subtalar tilt or medial shift. Van Hellemondt et al. examined both stress radiographs and stress computed tomography (CT) scans in 15 patients with unilateral chronic ankle instability with suspected subtalar instability. Although three of the symptomatic feet and one of the asymptomatic feet had increased subtalar tilt on plain films, there was no significant difference between the symptomatic and asymptomatic sides. None of the patients had increased subtalar tilt on the stress CT scans. The authors therefore doubted that a Broden’s stress examination reveals the true amount of subtalar tilt. Frost and Amendola reviewed the collective literature on both talar tilt and anterior drawer stress radiographs for ankle instability and found no normative values and little agreement between studies. Nevertheless, a markedly positive stress radiograph remains the only definitive means to demonstrate the presence of subtalar instability.

It is most accurate to state that a positive stress radiograph, either in a clinic or operating room setting, is a necessary but not sufficient condition to clearly make the diagnosis of isolated subtalar instability. The false-positive rate is high, and the radiographic findings must be correlated with the physical examination and history.

Nonoperative Treatment

In an acute injury, the standard treatment regimen for lateral ankle sprains will suffice for subtalar ligamentous injuries as well. Rest, ice, compression, and elevation (RICE) are part of a good protocol, as well as immobilization and physical therapy, when needed. The same can be said for management of chronic subtalar instability. The routine nonoperative regimen used for chronic lateral ankle instability is initiated. This may include proprioceptive training, peroneal strengthening, and bracing or strapping. With bracing, it is important to understand the delicate balance in providing an athlete with enough support without impeding his or her performance. Taping by an athletic trainer before participation can be effective. Wilkerson examined a modification of the standard method of ankle taping with the incorporation of a “subtalar sling.” He found that addition of the sling enhances the protective function of taping but cautioned that it may impede performance of certain activities.

Surgical Treatment

Patients with residual symptomatic instability despite an adequate program of nonoperative management will require a surgical stabilization of their subtalar joint. If both ankle and subtalar instability exist and require surgery, both problems should be corrected at the time of surgery. Surgical stabilization involves direct ligament repair or lateral tendinosis procedures to substitute for the irreparable ligaments.

Many techniques have been described to concurrently stabilize the ankle and subtalar joint ( Fig. 17.4, A through C ). Many require some form of extraarticular tendon transfer to provide stability. Kato and Pisani described techniques focused on the subtalar joint involving intraarticular ligament reconstruction of the interosseous ligament between the calcaneus and talus.

A less invasive technique that, according to Clanton and Berson and Gould et al., provides a good treatment for subtalar instability is the Brostrom-Gould reconstruction technique for lateral ankle instability ( Fig. 17.4, D and E ). With the reconstruction of the CFL and anterior talofibular ligament (ATFL) buttressed by the inferior extensor retinaculum, subtalar stability is effectively restored. There is no significant drawback to its routine inclusion in lateral ankle ligament reconstruction; doing so may obviate any concern over subtle subtalar instability in many cases. When the extensor retinaculum and the fibular periosteum are sufficient to hold suture, the Gould modification of the Brostrom procedure should be performed.

No clear criteria exist to guide the use of allograft or autograft reconstruction of the lateral ankle ligaments. In patients with a previous failed reconstruction, documented history of Ehlers-Danlos syndrome, or failed contralateral reconstruction, augmentation of the repair is warranted. The technique originally described by Colville utilizes a split peroneus brevis tendon to recapitulate the ATFL and CFL in an anatomic fashion. Rather than split a normal native tendon, O’Neil and Guyton recently described a method of reconstruction utilizing a combination of semitendinosis allograft and a braided suture construct to provide both new tissue and early strength to difficult cases with poor soft-tissue envelopes.

The use of the braided suture anchored with interference screws has also recently been described for lateral ankle ligament reconstruction. The primary utility of the suture construct is immediate strength of the ATFL portion of the reconstruction to allow early mobilization. That same rigidity can create the hazard of limited subtalar motion if it is used across the path of the CFL. While routine use of the suture construct across the ATFL reconstruction may have significant benefit for early mobilization, extension across the subtalar joint is not necessary in most cases.

Clinical Presentation

The typical complaint is pain over the lateral and anterolateral ankle and hindfoot centered in the region of the sinus tarsi. The patient may report a sensation of mild hindfoot instability. It has been estimated that as many as 70% of patients with sinus tarsi syndrome have had a previous inversion injury to the hindfoot.

Excessive motion of the subtalar joint may result in temporary impingement against the fibula in the athlete participating in a cutting activity. The symptoms in these cases are transient and localized to the sinus tarsi or lateral calcaneus. The diagnosis of this entity is based primarily upon the same criteria as for subtalar instability. As in subfibular impingement, edema in the distal fibula or lateral calcaneus may be present on MRI.