Essential Pearls On Treating Subtalar Coalitions
Treatment protocols for subtalar coalitions have evolved over the years and more effective solutions have emerged to help preserve rearfoot motion. In addition to providing diagnostic insights and reviewing conservative care options, these authors discuss keys to surgical procedure selection in order to achieve optimal outcomes.
There are many variables in these cases that can make each coalition different in some respects. Surgical success truly requires that surgeons be mindful of symptoms, skeletal maturity, type and size of coalition, equinus, and the presence of arthritis and/or a flatfoot.1
In the last decade, we have seen an evolution in treatment algorithms, allowing surgeons to avoid rearfoot fusions and resect coalitions along with flatfoot reconstruction. While rearfoot fusion may resolve pain and return alignment, it results in a stiff foot, which is not ideal in young patients who are afflicted with subtalar coalitions. Importantly, returning rearfoot motion with resection and restoring alignment with flatfoot reconstruction have the ability to provide pain-free function and ultimately preserve the adjacent joints from long-term deterioration.
A Guide To Key Clinical Symptoms
We can best define tarsal coalitions as an absent range of motion of the back part of the foot due to physical blockage by bone (osseous) and/or scar tissue (fibrous). Subtalar coalitions are in theory the result of failure of segmentation of primitive mesenchyme with further failure of the formation of a normal joint. The condition has an autosomal dominant inheritance pattern with an incidence ranging from 1 to 13 percent of all patients and occurs bilaterally in 50 to 80 percent of those who have a tarsal coalition.2 The most common of the tarsal coalitions are calcaneonavicular coalitions, followed by talocalcaneal (middle facet) coalitions, which make up 25 to 50 percent of all coalitions.2
Typically, the onset of symptoms for middle facet coalitions depends on skeletal maturity and usually starts in the early teenage years when the bones undergo ossification.3 This process stiffens the rearfoot, making the coalition painfully noticeable.
Symptoms generally depend on the extent of rigidity of the foot and any associated structural anomalies. Early on in life, the coalitions may present as a painful and rigid foot with pes planovalgus-associated deformity. Pain in the subtalar joint arises with weightbearing activities and especially exercise. There is also a feeling of stiffness and rigidity to the foot and ankle, perhaps even an altered pattern of gait, and most commonly a feeling of spasms in the lateral leg compartment muscle of the affected lower extremity. In adulthood, however, physicians discover most middle facet coalitions during a workup for another, usually unrelated, pedal issue. As such, middle facet coalitions can be asymptomatic.
Patients may experience pain directly at the coalition site in the lateral aspect of the hindfoot as a result of impingement of the lateral process of the talus and/or more diffuse rearfoot pain. Peroneal tendons are also likely to be symptomatic and tender to palpation. Additional symptoms may include posterior tibial tendon pain and tenderness to palpation as a result of the altered mechanics of the foot.
Rigid flat feet are a hallmark of coalitions but coalitions also occur in perfectly aligned feet. Muscle spasms, specifically peroneal spasms, are commonly associated with coalitions with flat feet. Patients may also have altered hindfoot alignment, most commonly in valgus. The subtalar range of motion may also be affected as most coalitions in the adult population present with decreased or completely absent motion in comparison to the contralateral non-affected side. This may be clearly evident by a lack of supination when patients perform the heel rise test.
The middle facet tarsal coalition is a coalition that occurs within the subtalar joint. The posterior facet is the largest and most prominent facet of the subtalar joint with the middle facet being about a quarter of the size. The size of the coalition can vary as coalitions can be small and limited to a segment of the middle facet, or be large and expansive into the posterior facet. Arthritis of the entire subtalar joint may develop as a result of restricted motion of the coalition.
Imaging And Subtalar Coalitions: What You Should Know
Diagnosis of a middle facet coalition can be tricky. The clinical exam of absent rearfoot motion often points to a coalition. Radiographs can sometimes clearly depict a coalition as a radiographic C sign. Harris Beath radiographic views can demonstrate the obliquity of the middle facet with a coalition. Lateral radiographic views may also show a talar beak sign with osteophytic changes that develop secondary to the strain placed on the talonavicular joint from the presence of a middle facet coalition and reduced or eliminated subtalar joint motion.
Computed tomography (CT) is the study of choice to evaluate the structural aspects of a coalition: location, size, type (osseous or fibrous) and heel valgus. Other findings such as calcaneofibular remodeling can be apparent on coronal views, demonstrating significant heel valgus with pseudo joint formation where the fibula abuts the calcaneus.4 Magnetic resonance imaging (MRI) also demonstrates coalitions and is very useful to demonstrating the inflammatory response of a coalition with the presence of bone edema.
Pertinent Pearls On Conservative Care
Not all subtalar coalitions require surgery. Some people have lifelong asymptomatic coalitions only to identify their presence as an incidental finding. Other people have pain that starts with bone ossification. Higher levels of activity may precipitate symptoms.
Treatment should involve a trial of conservative care despite coalitions being structural abnormalities. Patients should try rest and immobilization for several weeks. A below-knee walking boot for six to eight weeks often suffices to calm down the area. Sometimes being non-weightbearing in a cast may be prudent in severe cases. Anti-inflammatories and trigger point injections can be helpful. A peroneal nerve block may be useful in temporarily breaking a peroneal spasm and relieving pain and tenderness to the peroneal compartment.5
Physical therapy can also be key in non-operative management. Therapy focuses on range of motion of adjacent joints; modalities to reduce inflammation and pain; stretching of foot and calf muscle, especially in the presence of muscle imbalance and contractures; and deep tissue mobilization in the presence of muscle spasms.
Salient Consideratons For Surgical Procedure Selection
Ongoing recalcitrant pain is the motivating factor to proceed with surgery.
The first decision surgeons make is to determine whether the middle facet coalition is amenable to resection. Surgeons should strongly consider avoiding fusion, especially in a young population. One should perform fusion in the presence of significant rearfoot arthritis, very large coalitions and/or severe pes planus. It is important to consider that the majority of middle facet tarsal coalitions are responsive to resection. Removing the coalition has the benefit of removing the blockade and restoring motion. However, the coalition resection creates a pseudo joint, allowing the posterior facet to function, albeit stiffly.
The second decision to make is whether to perform a concomitant flatfoot correction. Obviously, well aligned feet don’t require any structural flatfoot correction. An existing surgical treatment algorithm dictates coalition resection and flatfoot reconstruction.6
The plane of flatfoot deformity dictates which flatfoot procedures one should perform. Equinus correction is the first component of the flat foot that surgeons should correct. Importantly, equinus can exist in coalition feet without flat feet. Gastrocnemius intramuscular aponeurotic recession is the lengthening of choice. When there is soleus contracture, surgeons can perform recession of the soleus aponeurosis as well. Achilles lengthening is an option as well but results in thickening of the tendon. Achilles lengthening is an option as well but results in thickening of the tendon.
Subtalar arthroereisis may be a consideration as an extra-articular correction with a talonavicular fault.7 One can treat heel valgus with a medializing calcaneal osteotomy. Surgeons can treat transverse plane deformity with an Evans calcaneal osteotomy, which one would perform after resecting the coalition. Distraction calcaneal joint arthrodesis can also be a consideration with severe shortening but requires a supple talonavicular joint. Talonavicular joint spurring is often the result of strain on the joint and typically remains undisturbed. Also consider that it may be impossible to get a perfectly aligned foot and overall improvement is acceptable so long as the rearfoot motion is present. However, each case needs individual consideration.
Rearfoot fusion is indeed indicated in some cases of middle facet coalition and should be a consideration if resection and flatfoot reconstruction are not viable. A morphologically deranged talar head may not reduce with realignment and therefore, there is an indication for talonavicular joint fusion. A large coalition accounting for more than 50 percent of the subtalar joint is an indication for subtalar fusion. End-stage arthritis (stage III) of the subtalar joint is another indication for subtalar joint fusion.
Kernbach and Blitz developed a CT staging system to grade posterior facet arthrosis with talocalcaneal arthritis.8 Stage I is normal to mild arthrosis with some sclerosis and lipping. Stage II is moderate arthrosis including joint space narrowing, osteophytes, cysts and erosions. Stage III is severe/end-stage arthritis with complete joint space loss, destruction of more than 50 percent of the posterior facet, osteophytosis and marked sclerosis.
Severe pes planus associated with a coalition is also an indication for rearfoot fusion. Talonavicular uncovering of greater than 50 percent, even in the face of a pristine joint, may be well served with isolated fusion or triple arthrodesis.
Age or skeletal maturity also plays a significant role in procedure selection. In general, earlier surgical management is preferable for symptomatic cases. Restoring rearfoot motion and improving foot alignment during growth may better allow leg and foot muscles to develop in this corrected position. Avoid rearfoot fusion, which is contraindicated when growth plates are open. One can perform medializing calcaneal osteotomies with percutaneous Steinmann pins and remove the pins once healing has occurred. An Evans calcaneal osteotomy does not interfere with growth plates.
Surgical Pearls For Coalition Resection
The incisional approach for middle facet coalition is medial, directly over the coalition. The surgeon will need to retract the posterior tibial tendon and flexor digitorum longus tendons in order to gain access to the coalition. Tagging the sheaths will make reapproximation easier on closure. Identifying the flexor hallucis longus tendon is helpful in protecting the neurovascular bundle but one should not overly retract these structures as this may result in a neuropraxia.
It is useful to delineate the entire border of the sustentaculum tali before attempting to resect the coalition. Fibrous coalitions are easier to identify and resect because one can access the plane of the coalition with an elevator. This guides the surgeon to the orientation of the resection. Osseous coalitions are much more challenging as the surgeon needs to create the plane of resection and inexperience may result in damaging the posterior facet. A wide resection is important to limit the incidence of regrowth. Take care to keep the sustentaculum tali intact, though some have advocated complete resection of this bony shelf.9 In few cases, it may be impossible to preserve the sustentaculum tali with very oblique coalitions.
Placing a lamina spreader into the resection site once the coalition is gone will additionally free up any adhesions. Motion of the subtalar joint should be unrestricted after coalition resection.
Various researchers have discussed placing an interposition material into the resection site.2,10,11 While interposition material is important, it’s more important to resect the coalition widely from top to bottom and front to back. Nonetheless, adipose tissue is the most commonly used spacer material. Other tissue types include muscle, tendon and fascia lata. Surgeons have also used particulate hyaline cartilage as an interpositional material.2 Surgeons can obtain fat locally behind the ankle and/or at the leg if they are performing a concomitant gastroc resection. Apply bone wax to the raw bony surfaces of the coalition site. Placing a drain into the surgery site is a good measure to limit adhesion formation within the resection site and along the neurovascular bundle.
Middle facet talocalcaneal coalitions are complex deformities to treat. It is necessary to consider patient age, pain, coalition size/type, the presence of arthritis and the presence of flatfoot deformity when developing a surgical plan. Preserving rearfoot motion with resection and improving alignment should be priorities. When situations arise that do not allow for resection, one can consider fusion.
Dr. Blitz is in private practice in both Midtown Manhattan, New York and Beverly Hills, Calif. He is board certified by the American Board of Foot and Ankle Surgery, and is a Fellow of the American College of Foot and Ankle Surgeons. To learn more about tarsal coalition surgery, visit www.tarsalcoalitionsurgery.com.
Dr. Aitali is a third-year podiatric medicine and surgery resident within the Department of Surgery at Cedars Sinai Medical Center in Beverly Hills, Calif.
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