Current Concepts in the Surgical Management of Tarsal Coalitions

A congenital tarsal coalition is simply defined as a condition where 2 or more tarsal bones are abnormally united (Figure 1). Tarsal coalitions often progress to symptomatic conditions that limit both hindfoot and midfoot motion. They are also often associated with tonic spasm of the peroneal musculature. When tarsal coalitions become symptomatic, initial conservative measures should include rest, immobilization, anti-inflammatory medications, and physical therapy modalities. Conservative treatment often fails to alleviate a patient’s symptom complex, and when it does, surgical intervention becomes a consideration. The surgical management of tarsal coalitions remains a primary decision between resection of the tarsal coalition or arthrodesis of the joints involved with the coalition.

Examining the Criteria for Surgical Planning

The criteria by which one decides on the best surgical option for a particular patient with a tarsal coalition has varied and evolved over the years. The author published a manuscript that outlined the logical, known criteria at the time (1991) for assisting a surgeon in planning between coalition resection and joint fusion.¹ These deciding factors included the patient’s age or osseous maturity, the relationship of the bones forming the coalition (ie, the articular involvement), and the degree and severity of any secondary arthritic and/or adaptive changes present within the joints surrounding or involved with the tarsal coalition.¹ The argument for using patient age as a consideration is based upon the premise that a patient who has not yet reached full osseous developmental maturity will have a greater potential for adaptation, improved recovery, and a better outcome following resection of a tarsal coalition. In other words, younger patients, particularly children and adolescents, will do better following resection approaches than adults.  

The second criterion for consideration is the articular involvement of the coalition. The 2 most common tarsal coalitions are the talocalcaneal coalition and the calcaneonavicular coalition. The talocalcaneal coalition, along with other tarsal coalitions such as talonavicular, calcaneocuboid, etc., are present within otherwise normal joints and can be deemed “intraarticular coalitions” or coalitions occurring within a joint space. Conversely, the calcaneonavicular coalition, along with other coalitions such as a cubonavicular coalition, can be considered “extraarticular coalitions” as they occur outside a normal joint space. Reasonably then, with other factors being equal, one would expect a resection surgical approach to be more successful for an “extraarticular coalition” than an “intraarticular coalition,” as one is not destroying a portion of a normal joint when removing the “extraarticular coalition.”

Finally, since tarsal coalitions by their simple presence restrict normal hindfoot and midfoot motion, surrounding joints often compensate for this decreased motion. These surrounding joints often have greater demands for motion placed upon them and develop secondary adaptive and/or arthritic changes with time. Examples of such compensatory changes would be the dorsal talonavicular joint beaking often seen with a talocalcaneal coalition, or a ball-and-socket ankle joint which may result from any tarsal coalition. The presence of these secondary arthritic and/or adaptive changes is generally considered to decrease the likelihood of a successful surgical outcome with coalition resection. Debating and clinically documenting whether the secondary changes are adaptive or arthritic is important, as arthritic changes are a much more negative prognostic indicator for outcome following coalition resection. 

Incorporating New Thinking

When I authored my paper in 1991 regarding these surgical criteria, I coined the term “Articular Classification System” to describe their combined use in deciding whether to perform surgical resection of a tarsal coalition or surgical arthrodesis of the involved joints (Figure 2).¹ I believe this classification system for tarsal coalitions is more helpful in deciding the best surgical approach than prior described classifications. Since the publication of the “Articular Classification System” manuscript, several additional conditions have been documented in the literature as possible important criteria to be considered in the surgical decision-making process.² These criteria are primarily important for talocalcaneal coalitions and are less important for calcaneonavicular coalitions. These criteria include the size of the tarsal coalition, the morphologic shape of the tarsal coalition, and the degree of heel valgus that is present. Arbitrarily, many surgeons have argued  that surgical resection of any “intraarticular coalition” is less likely to be successful if more than 50% of the joint is involved.² It makes sense that joints more extensively damaged and/or mechanically distorted by the presence of a tarsal coalition would be less likely to have success with resection, as there is less joint remaining after the resection.

However, the exact amount (ie, percentage) of joint involvement by the coalition that precludes a successful coalition resection remains open to debate.

For example, I would argue that many younger patients who have not yet reached bone growth maturity can still have a talocalcaneal coalition resection attempt even when more than 50% of the joint is involved with the coalition. Obviously, the patient and/or their parents must be educated that failure of the resection is more likely in such circumstances. The shape or morphology of a talocalcaneal coalition may also be a factor in the outcome of its resection. With the continued improvement of advanced imaging techniques, particularly in 3-dimensions, there is increasing study and documentation of the different configurations of talocalcaneal coalitions. Although most talocalcaneal coalitions express themselves in the middle facet (~70%), it is now well-known that talocalcaneal coalitions can present in the posteromedial aspect of the joint or in the posterior facet.² Talocalcaneal coalition shapes that involve less of the joint, are smaller in size, are incomplete, and are more superficial (ie, easier to resect) would seemingly offer better outcomes with surgical resection.²

Finally, many investigators have concluded that the success of a tarsal coalition resection may be at least partially dependent on the degree of heel valgus present.² Again, an arbitrary angular amount of heel valgus has evolved as the espoused critical amount (ie, degree) for resection. More than 16 degrees  of heel valgus is argued as detrimental to a successful tarsal coalition resection outcome.² Mechanically, one could sensibly conclude that increased heel valgus would put more pressure on a tarsal coalition resection site and make an unsuccessful resection outcome more likely. The exact amount of heel valgus that is detrimental is still unknown and the influence of heel valgus on resection outcome is still open to debate. If heel valgus proves to be a significantly negative criteria for surgical success, then perhaps a concomitant varus-producing or medializing calcaneal osteotomy might improve resection outcome. The consideration of the criteria that have been at least partially implicated in the surgical outcomes of tarsal coalition resection is very likely to improve preoperative planning, intraoperative decision-making, and postoperative results (Figure 3).²

A Closer Look at the Surgical Approaches

Open surgical approaches have dominated the procedures used for both resection of tarsal coalitions and fusion of the involved joints. More recently, arthroscopic (or endoscopic) approaches and percutaneous approaches have been described and championed. Addar and associates³ performed a systematic review of the advantages and disadvantages of the arthroscopic management of tarsal coalition resection. They described 2-portal approaches for the resection of both calcaneonavicular and talocalcaneal coalitions. For calcaneonavicular coalitions, the visualization portal was placed distal to the angle of Gissane (ie, lateral talar process) and the working portal was placed distal to the calcaneal process. For talocalcaneal coalitions, the patients were placed prone, and the visualization portal was made posterolateral to the coalition and the working portal was made posteromedial to the coalition. The researchers noted that none of the studies reviewed involved talocalcaneal coalition resections in patients with more than 50% joint involvement, and none of the studies used interpositional material after any of the tarsal coalition resections.³ Intraoperative fluoroscopy was utilized in all cases to assist in portal placement.  

The papers reviewed in their study included a total of 46 procedures (feet) in 42 patients with a mean surgical age of 17.6 years (range 11-27 years).³ The mean follow-up time was 26 months (range 6-60 months), and no recurrence of any of the coalitions was detected. Two neurologic complications (one case of complex regional pain syndrome (CRPS) and one case of hyperesthesia in the medial aspect of the heel) were described in the 33 patients/36 feet undergoing talocalcaneal coalition resection. The reported American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scores following these procedures showed that all the patients had good or excellent outcomes, and the outcomes from the arthroscopic approaches yielded similar AOFAS outcome scores to previously reported outcomes from open tarsal coalition resections. The authors concluded that the arthroscopic approaches are promising but that the studies reported were either case studies or small case series and future studies comparing the arthroscopic approaches to open approaches are needed.³

In another more recent study, Corin and associates4 found that the arthroscopic approach for resection of a calcaneonavicular coalition was associated with a significantly higher revision rate (15%) than an open approach (1%). Hollander and colleagues⁵ reviewed the results of both open and arthroscopic tarsal coalition surgeries and concluded that both approaches were safe and led to comparable results. In 1,284 tarsal coalitions reviewed in their systematic review, the overall clinical success rate for all coalition resections regardless of incisional approach was 79% for talocalcaneal coalitions and 81% for calcaneonavicular coalitions.⁵   

Three-dimensional imaging has also shown promise as an aid in tarsal coalition resections. Aibinder and associates6 described intraoperative 3-dimensional navigation for resection of talocalcaneal coalitions. These researchers’ technique utilized initial intraoperative computed tomography (CT) scanning to guide the placement of pins and a reference frame that then allowed for a controlled and efficient coalition resection with a navigated burr attached to the frame. The authors reported a successful outcome in one patient.⁶ Although this instrumented resection has promising potential, it does involve significant radiation exposure for both the surgeon and the patient and needs much more standardization and further outcome studies performed.

Another recent 3-dimensional method for approaching tarsal coalition resection is with mixed reality technology. Zhang and colleagues⁷ described 6 cases of talocalcaneal coalition resection using preoperative, 3-dimensional, CT-generated, holographic images and the intraoperative use of the images visualized by the surgeon wearing holographic glasses. The authors reported good outcomes and stated their technique allowed for practical, effective, and radiation-free resections.⁷ Obviously, this promising technique is in its infancy and needs further clinical studies and outcomes.

Although the arthroscopic and 3-dimensional approaches have great future promise, open surgical approaches remain the current gold standard for tarsal coalition resections. The open incisional approaches do not need to be large in most cases, and various clinical and/or fluoroscopic techniques can help to maximize surgical exposure while minimizing surgical incision size. Once exposed, the “key” to a successful surgical resection of a tarsal coalition is adequate and full resection. The surgeon should proceed carefully to avoid any potential collateral damage to surrounding structures and remaining joint surfaces. The most reported complication  following tarsal coalition resection is recurrence of the coalition,² and in the author’s opinion most of these are likely due to inadequate resection during the index or initial procedure. The surgeon should utilize intraoperative inspection and range of motion assessment, in combination with intraoperative fluoroscopy or other imaging, to confirm that adequate resection has taken place.  

Once a tarsal coalition has been fully resected, many surgeons will interpose biologic or non-biologic material within the deficit created with the belief that it will decrease the likelihood of coalition recurrence. The best interpositional materials and methods continue to be debated, and it’s the author’s belief that no interpositional material should be considered a substitute for full and adequate resection of the coalition. In 1927, Badgley⁸ initially described the surgical resection of a calcaneonavicular coalition, including the interposition of the extensor digitorum brevis muscle belly into the defect created. This procedure is still viable and preferred by many surgeons, including the author (Figures 4A-F). Other surgeons have advocated the use of autogenous fat grafts (typically obtained from the buttocks), allogenous collagen grafts, amniotic tissue, or bone wax (applied to the bleeding bony surfaces after resection).^9,10

Postoperatively, after resection of a tarsal coalition, the author typically keeps the patient non-weight-bearing for the first 2-3 weeks. Gentle range of motion exercises of the midfoot, hindfoot, and ankle can begin as soon as comfortable for the patient and within the first 2 weeks. Once weight-bearing, the patient may initiate physical therapy. Supportive shoes with functional orthoses or supportive insoles are then used to support the increased motion in the hindfoot and midfoot. 

Pertinent Points on Complications

Following any tarsal coalition resection, the potential for recurrence is present. Again, in the author’s opinion, the “key” to minimizing this potential complication is to fully and adequately resect the tarsal coalition. The interposition of any material into the resection space is the surgeon’s preference and may or may not reduce the risk of recurrence. Inadequate resection of a tarsal coalition is difficult to differentiate from recurrence of a tarsal coalition, as both may present early within the postoperative course. The typical clinical presentation of this complication is the “triad” of continued restriction of motion, continued peroneal muscle spasm, and pain. Although some restriction of hindfoot and midfoot motion is commonly seen even after a successful tarsal coalition resection, the presence of this “triad” is ominous for a poor surgical outcome.  

Other complications include those seen with any foot surgery, including infection, nerve entrapment, CRPS, pain, etc. Worsening of a preoperative pes plano valgus deformity and/or heel valgus deformity may also be seen after tarsal coalition resection, as the procedure often transforms a rigid flatfoot deformity into a flexible or semi-rigid flatfoot deformity. Conservative and surgical measures for these deformities will uniformly be necessary. When surgical intervention is needed for an associated pes plano valgus deformity, the author prefers in most situations to perform that surgery at a second surgical sitting after the tarsal coalition has been fully resected and motion restored as much as possible. Some surgeons prefer to concomitantly perform the flatfoot corrective surgery with the tarsal coalition resection, but this approach often limits the maintenance of intraoperative motion and the rapid rehabilitation desired after a tarsal coalition resection.

When tarsal coalition resection is likely to fail, based upon preoperative assessment criteria and diagnostic imaging, then arthrodesis procedures should be considered. Isolated talocalcaneal joint (subtalar joint) arthrodesis, medial double arthrodesis (talonavicular and talocalcaneal), and triple arthrodesis are all viable surgical treatment options. Further, any patient, regardless of age, undergoing surgical resection of a tarsal coalition should be counselled that the resection may fail. Such failure can occur even if the criteria for resection suggest a positive outcome. In such instances, one should consider the options of clinical and diagnostic reassessment and/or the undertaking of fusion procedures.²

Concluding Thoughts

In summary, the current “state of the art” for the surgical management of tarsal coalitions continues to evolve. Based upon the evidence available, surgeons should assess and consider the criteria for successful and unsuccessful outcomes, and educate the patient on their findings and recommendations. With experience, tarsal coalition resection can restore improved function and reduce pain in the symptomatic, rigid flatfoot deformity. 

Dr. Downey is Staff & Immediate Past Chief of the Division of Podiatric Surgery at Penn Presbyterian Medical Center in Philadelphia. He is a Clinical Professor in the Department of Surgery at the Temple University School of Podiatric Medicine and Senior Faculty with The Podiatry Institute in Decatur, Georgia.

References
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7.    Zhang J, Wang C, Li X, Fu S, Gu W, Shi Z. Application of mixed reality technology in talocalcaneal coalition resection. Front Surg. 2023;9:1084365. doi: 10.3389/fsurg.2022.1084365. PMID: 36684274; PMCID: PMC9852772.
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