Revisional Subtalar Joint Fusions: What You Should Know

Author(s): 
Mitzi L. Williams, DPM

When complications occur following subtalar joint fusion, surgeons may need to weigh revisional surgery options in order to correct the deformity. This author discusses common indications for revisional arthrodesis and offers step-by-step pearls to help ensure optimal outcomes.

   An isolated subtalar joint arthrodesis has proven over the years to be a successful procedure in the management of numerous hindfoot problems. Outside of an isolated fusion, a successful subtalar joint arthrodesis has been an integral component of a triple arthrodesis in hindfoot pathology.

   Authors have reported high rates of patient satisfaction, low rates of complications and low rates of nonunion with subtalar joint arthrodesis.1-6 Rates of union range from 86 to 100 percent for primary isolated subtalar joint fusions.2-4,7-14 Even with encouraging union rates, complications may arise and a revisional subtalar joint arthrodesis may be warranted. Researchers have shown the rate of union diminishes following the failure of previous subtalar arthrodesis.9

   As with any revisional surgery, challenges are common with respect to anatomy, fixation, bone stock and function. The increase in scar tissue or fibrosis limits function, and the ease of surgical positioning. Fibrotic tissue also tends to be less vascular in nature, leading to an increase in wound complications. Anatomic dissection and preservation of structures outside the range of arthrodesis are important in minimizing adhesions.

   Bone morphology post-fixation or previous surgery can also be complicated. Previous hardware forces a surgeon to alter further placement of fixation. Likewise, existing areas of bone deficit may force one to use a variety of fixation techniques and/or bone graft. The features of revisional fusions are unique.

When Is Revision Indicated?

   One often performs a subtalar arthrodesis when the joint is arthritic or destroyed. Surgeons often use the procedure to stabilize the rearfoot in progressive pathology. There are numerous etiologies for lower extremity joint destruction including trauma, congenital deformities, pathological biomechanics, Charcot neuroarthropathy, infection and inflammatory arthridities. With each broad category, fixation may change while the basis behind arthrodesis remains the same. One fuses the joint to eliminate pain and/or reduce deformity.

   The indications for revisional arthrodesis vary in comparison to primary fusion. A primary fusion centers upon a painful arthritic joint or the need to create a rigid structure. The joint can be painful and arthritic for a spectrum of reasons. A revisional fusion, on the other hand, can help manage a failed primary fusion or fix a greater deformity.

   Indications for revisional subtalar fusions include traumatic arthritis or trauma, malalignment, nonunions, progressive Charcot neuroarthropathy, subsequent infection and inflammatory arthridities. Often, there are greater systemic causes that lead to failed primary fusions and the need for revision. Systemic illnesses and comorbidities may play a role when there is an absence of bone healing. Likewise, controllable factors such as smoking, obesity and malnutrition impede osseous unions.

   The need for revision may stem from malaligned successful unions as well. For example, a varus or excessively valgus hindfoot may warrant revision of the primary arthrodesis site. It is the malaligned, fused joint that causes pain elsewhere. Obstacles can arise in any revisional surgery but well planned surgery can help facilitate success.

When There Is Trauma To The Subtalar Joint

   Traumatic injuries of the subtalar joint are generally secondary to calcaneal fractures or talus fractures. Whether it is the result of neglect or reconstruction efforts, post-trauma joint incongruency expedites arthritis of the talocalcaneal joint. In these cases, arthrodesis eliminates incongruent joint motion to reduce pain. Quite often, joint depression and bone loss are present with intraarticular calcaneal fractures.

   The most common indication for subtalar arthrodesis is disruption of the intraarticular surface of the calcaneus by fracture, subsequent depression of the bone, loss of height, secondary malalignment of the talus through the talonavicular joint and development of a dorsiflexion deformity in the ankle.15 A Saunders level IV or highly comminuted calcaneal fracture may warrant a primary arthrodesis as anatomic reduction is difficult.

   Likewise with lateral wall blow out, intraarticular comminution and bone loss, one may use a graft in the primary fusion. With the loss of bone and significant destruction, a nonunion may occur. This creates a scenario for revisional surgery. Also bear in mind that calcaneal fractures are associated with wound complications and subsequent infection, which may force one to remove hardware and perform a revisional subtalar fusion. The surgeon may implement external fixation, bone block distraction, bone graft application and a new orientation of hardware.

   Talus fractures also change the normal contour of the joint. A greater problem is avascular necrosis of the talus with subsequent collapse. Avascular necrosis is a surgical challenge. Precarious blood supply and collapse can lead to degenerative changes and disability of the ankle and subtalar joints. Following talar fractures, research has shown the risk of subtalar osteoarthritis to be 53.3 percent while avascular necrosis is 16.6 percent.16 Accordingly, there is need for primary and subsequent revisional subtalar fusion.

What You Should Know About Managing Nonunions

   The most common complication associated with arthrodesis is nonunion or fibrous union.17 As for isolated subtalar joint fusions, the nonunion rates range from 0 to 16.3 percent.2,3,7,9,18-22 Even with advances in fixation and surgical technique, nonunions do occur. Now research is focusing on the methods of joint preparation to assist with improving union rates.

   Recent research focused on the joint curettage technique with manual instrumentation. A study found that this technique leaves a residual histologic barrier that may inhibit or predispose the fusion site to forming a fibrous union or nonunion.17 Further research should evaluate and compare joint preparation techniques.

   At the present time, I am in favor of denuding all cartilage down to the subchondral plate, scaling to expose bleeding bone and attempting to maintain joint contour.

   There are some challenges when it comes to performing revisional arthrodesis procedures after a nonunion. Surgery may involve autograft or graft products. Nonunions following hardware removal may entail new orientation of hardware or different hardware selection. In general, internal fixation or external fixation can be appropriate. A primary fusion that originally directed fixation from the posterior calcaneus to the anterior talus may now benefit from the redirection of hardware with the use of bone graft.

   Proper patient selection is important in this situation. A nonunion secondary to Charcot neuroarthropathy may now require an external fixator frame. Furthermore, patients may not be able to accept the use of various products due to religious or cultural backgrounds. Nonunions are also associated with detrimental factors such as smoking and diabetes, which are on the rise.

   All in all, revisional surgery requires a well thought-out plan of action with alternative options.

How To Address Malalignment And Deformity

   A successful union can be malaligned, leading to the need for revisional surgery. Often it is not the successful union that is painful but it is the anatomic site where the load transfers that becomes painful. A subtalar fusion with varus or excessive valgus of the heel can cause pain and deformity elsewhere. In these situations, revision of the subtalar arthrodesis is warranted. Adjunctive procedures are common and these include arthrodesis of multiple joints.

   Neglected congenital deformities, recurrence of deformities or progressive deformities may increase the risk of revisional subtalar fusion. In regard to patients with congenital deformities, who have undergone previous surgery, they may present with an abundance of scar tissue or retracting fibrosis such as clubfoot. If the deformity is under-corrected, one will often see degenerative joint changes.

   Deformities such as talocalcaneal coalitions, adult-acquired flatfoot, posterior tibial tendon dysfunction and various neuromuscular diseases may also benefit from subtalar fusions.

Pertinent Pearls On Addressing Charcot, Infection And Inflammatory Arthritis

   The biology behind Charcot neuroarthropathy places patients at great risk of nonunions and progressive breakdowns of previous fusion sites. Researchers continue to study the pathogenesis of Charcot. Recently, Pitocco and colleagues noted an association between genetic regulation of bone in Charcot neuroarthropathy.23

   One needs to consider the breakdown of previous fusion sites and the need for revisions. Often the surgeon removes existing internal fixation and utilizes external fixation. External fixation may be an option during the primary arthrodesis.

   The surgeon can correct osseous deformity over time with external fixation or perform osteotomies in conjunction with external fixation. Infection or inflammatory arthritis can also lead to the removal of hardware and the need for alternative correction. Locking technology can provide assistance with osteoporotic bone.

Essential Surgical Insights

   Surgical approach and fixation selection can vary. The deformity at hand, previous incisions or trauma, adjunctive procedures and fixation selection can guide one’s approach in the operating room. The surgeon should tailor the operative technique to each patient’s particular pathological findings.9

   Surgeons often utilize a lateral skin incision, starting at the tip of the lateral malleolus and coursing distally to the calcaneocuboid joint or the fourth metatarsal. Make the incision superior to the peroneal tendons and sural nerve. Carry the incision to the level of the deep fascial layer. In a primary subtalar arthrodesis, a communicating branch between the sural nerve and intermediate dorsal cutaneous nerve may exist. Often one may need to sacrifice the nerve for exposure.

   Visualize the extensor digitorum brevis muscle below the deep fascia. Make an inverted L-type incision in the deep fascia. Retract the deep fascia and extensor digitorum muscle belly as one structure. Proceed to evacuate the sinus tarsi. Both the middle and posterior facets are usually visible. Further incision of the calcaneofibular ligament and lateral talocalcaneal ligament can aid in visualization of the posterior facet.

   When it comes to revisional surgery, there may be considerable fibrosis and rigidity. Following the removal of previous hardware, one must reconstruct the osseous union or failed union, and reposition them into good alignment. Often revision is secondary to malalignment so resection or wedging, with the addition of bone, may be required for correction of the deformity.

   Joint preparation or revisional arthrodesis site preparation is imperative. The surgeon should obtain good bleeding bone surfaces. Even when it comes to primary subtalar arthrodesis, surgeons have debated the types of fixation and fixation orientation. Typically, screw fixation includes both posterior-to-anterior and anterior-to-posterior approaches.3,24

   Specifically, screws are oriented from the posterior calcaneus into the talar body or screws are oriented from the talar neck toward the calcaneal body. Common sizes include 6.5 mm or 7.3 mm screws. Cannulated or noncannulated systems are appropriate. One may use external fixation and intermetatarsal nails as well, especially in revisional patients with greater deformity.

   The nature of the pathology often assists with fixation selection. Breakdown of the subtalar joint in Charcot neuroarthropathy may benefit from pristine joint preparation and the use of external fixation. The late complications of neglected, displaced, intraarticular calcaneal fractures may benefit from posterior bone block distraction arthrodesis. Numerous fixation options exist and there is not one correct method of fixation. One should always evaluate position intraoperatively via a C-Arm fluoroscopy.

   The postoperative course often includes a Jones compression dressing for the first 10 days to two weeks to minimize edema. One would generally emphasize non-weightbearing in a cast for eight to 12 weeks. Surgeons should monitor clinical pain and radiographic osseous consolidation. The patient then wears an equalizer boot with protective weightbearing for two weeks. One can subsequently progress the patient to regular supportive shoegear.

   In terms of post-op recovery, the major limiting factor tends to be edema. The foot can easily be swollen for up to one year. Often patients will have stable arthrodesis sites but are too edematous to wear their shoegear. An edematous foot with a lack of consolidation per radiograph is a concern. Computerized tomography (CT) scans can assist with evaluation of the arthrodesis site.

In Conclusion

   Revisional surgery can be more challenging than the primary procedure for many reasons. A surgeon must take into account the variation in anatomy. Indeed, there may be a change in vascularity, bone composition, soft tissue and skin integrity. One can encounter fibrosis of soft tissue and bone loss. With a change in skin integrity, there is a greater risk for wound complications. Preservation of surrounding tissue planes and vascular structures is important.

   Incisions are guided by the deformity you are correcting and the placement of previous incisions. Fixation strategy is also specific to the pathology. Quite often the biology behind the failed arthrodesis dictates the use of conventional internal fixation, external fixation or intermetatarsal nails.

   One should also preoperatively evaluate bone loss and the need for osseous correction. Surgeons can harvest the tricortical block bone graft from the iliac crest. One must determine the level of deformity and the need for osteotomies or wedging.

   Revisional surgery can be successful. Surgeons must have a well thought-out plan for surgery with alternative options. In addition, respect for the anatomy and pathology is key. One can learn a great deal from the complications of any procedure.

   To date, pristine joint preparation and fixation are essential. More research comparing the histological analysis of joint preparation techniques would be beneficial.

Dr. Williams is an Attending Surgeon and the Director of Limb Salvage in the Department of Orthopedics/ Podiatric Surgery at Kaiser Foundation Hospital in Oakland, Calif.
The author thanks Lawrence Ford, DPM, and Jason Pollard, DPM for their assistance with this article.

For further reading, see “How To Perform An Isolated Subtalar Joint Arthrodesis” in the June 2008 issue of Podiatry Today, “How To Address Subtalar Joint Instability” in the May 2007 issue, “Can One-Screw Fixation For Subtalar Joint Fusion Be Effective?” in the June 2009 issue or “Assessing The Pros And Cons Of Subtalar Implants” in the May 2006 issue.

To access the archives or to get information on reprints, visit www.podiatrytoday.com.




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