Excision of Talocalcaneal Coalition

DEFINITION

A talocalcaneal coalition is an abnormal connection between the talus and the calcaneus that limits subtalar motion.

As is the case for calcaneonavicular coalitions, which are described in the prior chapter, talocalcaneal coalitions typically result in a rigid flatfoot that is sometimes painful.

ANATOMY

Talocalcaneal coalitions occur within the subtalar joint, most commonly involving the middle facet.9 These connections can be bony, cartilaginous, or fibrous and can involve any amount of the joint.

The size of the coalition is described with respect to the percentage of the entire subtalar joint that is coalesced.9

PATHOGENESIS

Like calcaneonavicular coalitions, the cause of talocalcaneal coalitions remains unknown, but they may be the result of failure of segmentation during fetal development.1

Although they are presumed to be congenital in nature, symptoms typically do not appear until early adolescence, ages 12 to 16 years.7, 10

It is unclear why some coalitions become painful. One theory suggests the possibility of altered talar joint kinematics placing additional stress on adjacent joints. Another is the development of microfractures or stress

fractures through the coalition over time, rendering them painful.1

NATURAL HISTORY

Most talocalcaneal coalitions are asymptomatic.6

They may result in the development of a rigid flatfoot, characterized by valgus alignment of the heel, abduction of the forefoot, loss of the arch, and failure of the arch to reconstitute on toe-rise or when non-weight bearing.

Pain secondary to talocalcaneal coalitions usually develops between 12 and 16 years of age.7, 10

PATIENT HISTORY AND PHYSICAL FINDINGS

Patients typically describe pain in the foot that is activity related; it is exacerbated by walking on uneven surfaces and relieved by rest.

This pain may be generalized to the midfoot and hindfoot or can be specifically localized to the medial aspect of the hindfoot and ankle.

Patients may also complain of lateral pain at the tip of the fibula.

There may be a history of progressively worsening out-toeing or loss of the arch.

The clinician should observe the patient's gait for an antalgic pattern and torsional alignment, with specific attention to foot position during stance.

The patient's foot alignment is examined; the heel may be in valgus alignment with the forefoot abducted.

The rigidity of the flatfoot is observed. Flexible flatfoot has a restoration of the arch on toe-rise; rigid flatfoot has no arch restoration. A rigid flatfoot is a sign of decreased subtalar motion and may indicate a tarsal coalition.

The physician should test for subtalar motion. The test is not specific for talocalcaneal coalition but is indicative of some process within the subtalar joint.

The physician should palpate over the medial aspect of the hindfoot, just plantar to the medial malleolus, in the region of the sustentaculum tali. Tenderness in this region may be indicative of a middle facet talocalcaneal coalition.

IMAGING AND OTHER DIAGNOSTIC STUDIES

Plain radiographs should be obtained in an attempt to identify the coalition and assess foot alignment. These should include anteroposterior (AP), lateral, oblique, and Harris axial views (FIG 1A,B).

A talocalcaneal coalition is best seen on the Harris axial view, but it may be difficult to obtain the exact orientation to adequately visualize the middle facet.

On the lateral view, there may be a continuous C-shaped line along the talar dome and into the posterior facet (C-sign).8

On the AP and oblique view, one may identify other concurrent coalitions.

Standing AP and lateral radiographs and a Saltzman hindfoot alignment view can be useful for assessing foot alignment, especially hindfoot valgus.

A computed tomography (CT) or magnetic resonance imaging (MRI) scan is mandatory to clearly visualize the coalition and determine the percentage of the subtalar joint that is involved (FIG 1C).9

An MRI may be useful if the diagnosis is equivocal and a cartilaginous or fibrous coalition is suspected.

DIFFERENTIAL DIAGNOSIS

Flexible flatfoot Subtalar arthritis

Other tarsal coalition (calcaneonavicular or less common ones)

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FIG 1 • A. The oblique radiograph confirms the absence of a concurrent calcaneonavicular tarsal coalition.

B. On the lateral radiograph, a C-sign is visible as a confluent line around the posterior margin of the talar body and the posterior aspect of the calcaneus just beneath the posterior facet of the subtalar joint. This sign is often associated with a talocalcaneal tarsal coalition. C. CT scanning can be used to visualize the coalition and determine the percentage of the subtalar joint that is involved.

Tumor or infection involving the subtalar joint Idiopathic rigid flatfoot

NONOPERATIVE MANAGEMENT

Nonoperative management is indicated for all patients with talocalcaneal coalition at first presentation. Painless coalitions need no treatment.

The initial treatment for painful talocalcaneal coalitions is activity modification, anti-inflammatory medication, or immobilization in a short-leg walking cast.

SURGICAL MANAGEMENT

The indication for surgical management is persistence of pain despite nonoperative management. The main goals of treatment are, primarily, elimination of pain and restoration of function.

Restoration of subtalar motion is a secondary goal.

Restoration of arch height is unlikely following excision of a talocalcaneal coalition.

Preoperative Planning

All imaging studies are reviewed.

An examination of subtalar motion may be performed under anesthesia to compare to the motion obtained after excision of the coalition.

Positioning

The patient is positioned supine on the operating table.

Generally, the leg assumes an external rotation posture at rest so that the medial ankle and hindfoot are easily accessible. If this is not the case, then a small bump can be placed beneath the opposite hip.

A tourniquet is placed on the upper thigh or an Esmarch tourniquet may be used just proximal to the ankle.

Approach

The approach involves identification of the entire coalition with delineation of the normal cartilage on either side.

The bone representing the coalition is exposed, and subcutaneous fat or a portion of the flexor hallucis longus is interposed.

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TECHNIQUES

• Incision and Dissection

The procedure can be done under tourniquet control, if desired.

A straight horizontal incision is made along the medial aspect of the hindfoot centered over the sustentaculum tali.

The incision should extend from the location of the neurovascular bundle to the prominence of the navicular tuberosity (TECH FIG 1A). For harvesting of fat graft from the retrocalcaneal space, it is sometimes useful to extend the incision more posteriorly.

If any fibers of the abductor hallucis are encountered, they are retracted plantarly. The tibialis posterior tendon is identified dorsally (TECH FIG 1B).

TECH FIG 1 • A. Incision marked on the skin. B. The posterior tibial tendon (superior) and flexor digitorum longus tendon (inferior). C. The neurovascular bundle is seen directly posterior to the posterior tibial

tendon.

The flexor digitorum longus tendon is identified and its sheath is opened along the length of the incision (TECH FIG 1C).

The neurovascular bundle is identified just posterior to the flexor digitorum longus.

The flexor hallucis longus tendon sheath can be opened if it is to be used as interposition material. If autologous fat graft is to be used, then this step is unnecessary.

The Achilles tendon is then identified at the most posterior aspect of the wound.

At this point, all of the critical anatomic structures have been identified and the coalition can now be exposed.

• Exposure of the Talocalcaneal Coalition

   

  The talocalcaneal coalition lies just dorsal to the sustentaculum tali and deep to the sheath of the flexor digitorum longus.

   

  While retracting the flexor digitorum longus tendon plantarly, palpate the sustentaculum tali.

   

  The coalition lies deep to the medial portion of the sheath of the flexor digitorum longus and periosteum.

   

  The medial aspect of the flexor digitorum longus sheath, along with the periosteum just deep to it, should be incised slightly dorsal to the prominence of the sustentaculum tali, taking care to maintain an adequate layer to be used later for closure (TECH FIG 2A,B).

   

  Because the normal joint in this area is now obscured by the coalition, it is often difficult to determine the appropriate level for bone resection without first identifying some normal joint space.

   

  If this is the case, the dissection may be carried posteriorly and anteriorly to identify the posterior and anterior facets of the subtalar joint, respectively, so that the normal articular cartilage in these areas can be identified.

   

  The posterior facet can be identified by retracting the neurovascular bundle posteriorly and dissecting deep to it.

   

  The anterior facet is identified just proximal to the talonavicular joint and plantar to the talar neck.

   

  Occasionally, a stripe of cartilage can be identified traversing through the center of the coalition. In these cases, resection may proceed directly to this level.

   

  Next, while retracting the flexor digitorum longus plantarly and the tibialis posterior dorsally, the bone is resected between the two previously identified areas of normal articular cartilage.

   

  This can be accomplished with a high-speed burr, rongeurs, and curettes (TECH FIG 2C).

   

  Resection of bone is continued until normal articular cartilage is encountered deep within the wound, lateral to the coalition as well as anterior and posterior to it (TECH FIG 2D-F).

   

  Careful attention to the preoperative imaging studies (namely CT scan and possibly MRI) will aid in estimating how far lateral the dissection should continue.

   

  Take care to resect bone from known to unknown areas, as it is possible to drift dorsal or plantar into the body of the talus or calcaneus, consequently missing the coalition.

   

  Once the entire coalition has been resected, the foot should be inverted and everted, demonstrating an improvement in subtalar motion.

   

  It should be possible at this point to see clear space from the posterior facet to the anterior facet with supple motion through the joint.

   

  Apply a thin layer of bone wax to the exposed bony surfaces to minimize bleeding and theoretically decrease the risk of recurrence of the coalition.

   

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  TECH FIG 2 • A,B. The medial aspect of the sheath of the flexor digitorum longus and the periosteum overlying the talus are incised. C. The posterior facet is visualized (just posterior to the curette) and the coalition is entered with a curette. D-F. The coalition has been removed and there is a visible gap between the talus (superior) and calcaneus (inferior). Just beyond the excised bone, normal articular cartilage can be seen.

   

   

   

• Interposition of Fat Graft

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  Next, to retrieve fat graft, the neurovascular bundle is retracted anteriorly, exposing the retrocalcaneal fat between the Achilles tendon and the calcaneus (TECH FIG 3A).

   

  If there is insufficient fat in this area, fat autograft can be harvested from the buttock instead.

   

   

   

  TECH FIG 3 • A. Retrocalcaneal fat is exposed between the Achilles tendon and the neurovascular bundle and harvested for the graft. B-D. The graft is inserted into the area of the resected coalition, and the periosteum is closed over the graft.

   

   

  A piece of fat about 1 cm in diameter is excised from the area.

   

  This fat is interposed into the space from where the coalition was resected (TECH FIG 3B,C).

   

  The layer of tissue composed of periosteum and flexor digitorum longus sheath is then repaired over this fat with absorbable sutures helping to secure it in place (TECH FIG 3D).

   

   

• Interposition of a Portion of the Flexor Hallucis Longus Tendon (Alternative Technique) As an alternative to autologous fat graft, half of the flexor hallucis longus tendon may be interposed.3, 6 After completely resecting the coalition and confirming adequate motion of the subtalar joint, the flexor

  hallucis longus tendon is exposed by opening its sheath just inferior to the sustentaculum tali, if this has not

  been done during the surgical approach.

   

   

  The flexor hallucis longus lies in a groove directly inferior to the sustentaculum tali. The flexor hallucis is then split longitudinally but left in continuity along its length.

   

  The superior half of the tendon is then placed in the gap that has been created where the coalition was resected.

   

  Care is taken to ensure that the length of tendon that is split is sufficiently long so that the motion of the flexor hallucis longus is not restricted.

   

  This is accomplished by moving the interphalangeal joint of the great toe through a range of motion and confirming that motion is not restricted.

   

  The periosteum from the talus is then sutured to the periosteum from the sustentaculum to prevent the tendon from slipping out of place.

• Wound Closure

The tourniquet is released and hemostasis is obtained.

The tendon sheaths of the flexor digitorum and tibialis posterior are closed with fine absorbable sutures. Subcutaneous tissue and skin are closed in standard fashion.

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PEARLS AND PITFALLS

Indications ▪ The preoperative CT scan should be carefully assessed for the extent of the

coalition and the presence of subtalar arthritis. Excision of the coalition is contraindicated if greater than 50% of the joint surface is coalesced or in the presence of subtalar arthritis.

• Hindfoot alignment is determined clinically and radiographically to assess for hindfoot valgus. Excessive valgus has been associated with poor outcomes.

Approach

• The incision should be long enough to allow adequate identification of normal

  subtalar joint.

• The periosteum and medial sheath of the flexor digitorum longus are preserved to secure the graft.

Excision

of coalition

• The surgeon should identify normal articular cartilage posterior and anterior to the

  coalition so that the level of resection can be identified.

• Bone is resected from the area where the normal joint can be seen toward the center of the coalition.

• It is possible to resect bone into the body of the talus or calcaneus, missing the coalition, if careful attention is not paid to the level of resection.

Closure

• The periosteum and medial sheath of the flexor digitorum longus tendon are repaired

to prevent extrusion of the graft.

POSTOPERATIVE CARE

A splint or short-leg cast is applied.

The foot is immobilized and the patient should remain non-weight bearing for 2 to 3 weeks to allow for wound healing and consolidation of the graft.

After that, progressive weight bearing and gentle range-of-motion exercises are initiated, focusing on restoring subtalar motion.

OUTCOMES

Most series report better than 85% good to excellent results.3, 6, 7, 9

Poor results, characterized by persistent pain, have generally been associated with coalitions of more than 50% of the joint surface, subtalar arthritis, or severe valgus alignment of the heel in excess of 21 degrees.4,

9, 11

There may be a role for deformity correction in cases of severe planovalgus with ongoing pain despite complete resection of the coalition or, in some cases concurrently, at the same time as coalition excision.5

A long-term study of functional outcomes in patients with tarsal coalitions found those with talocalcaneal coalitions entailing over 50% surface area and those with more than 16 degrees of hindfoot valgus did as well as those with less than 50% surface area and less than 16 degrees of valgus. Also, outcomes were

both favorable and comparable between talocalcaneal and calcaneonavicular coalitions.2

COMPLICATIONS

Failure to adequately resect the coalition Recurrence of the coalition

Residual pain or stiffness due to preexisting subtalar arthritis or severe malalignment

REFERENCES

1. Harris RI, Beath T. Etiology of peroneal spastic flat foot. J Bone Joint Surg Br 1948;30:624-634.

    

    

2. Khoshbin A, Law PW, Caspi L, et al. Long-term functional outcomes of resected tarsal coalitions. Foot Ankle Int 2013;34:1370-1375.

    

    

3. Kumar ST, Guille JT, Lee MS, et al. Osseous and non-osseous coalition of the middle facet of the talocalcaneal joint. J Bone Joint Surg Am 1992;74:529-535.

    

    

4. Luhmann SJ, Schoenecker PL. Symptomatic talocalcaneal coalition resection: indications and results. J Pediatr Orthop 1998;18: 748-754.

    

    

5. Mosca VS, Bevan WP. Talocalcaneal tarsal coalitions and the calcaneal lengthening osteotomy: the role of deformity correction. J Bone Joint Surg Am 2012;94:1584-1594.

    

    

6. Olney BW, Asher MA. Excision of symptomatic coalition of the middle facet of the talocalcaneal joint. J Bone Joint Surg Am 1987;69: 539-544.

    

    

7. Raikin S, Cooperman DR, Thompson GH. Interposition of the split flexor hallucis longus tendon after resection of a coalition of the middle facet of the talocalcaneal joint. J Bone Joint Surg Am 1999;81: 11-19.

    

    

8. Sakellariou A, Sallomi D, Janzen DL, et al. Talocalcaneal coalition: diagnosis with the C-sign on lateral radiographs of the ankle. J Bone Joint Surg Br 2000;82:574-578.

    

    

9. Scranton PE Jr. Treatment of symptomatic talocalcaneal coalition. J Bone Joint Surg Am 1987;69:533-539.

    

    

10. Stormont DM, Peterson HA. The relative incidence of tarsal coalition. Clin Orthop Relat Res 1983;(181):28-36.

     

     

11. Wilde PH, Torode IP, Dickens DR, et al. Resection for symptomatic talocalcaneal coalition. J Bone Joint Surg Br 1994;76(5): 797-801.