Arthroereisis

Anatomy and Physiology

Flatfoot is a frequently encountered deformity that is characterized by:

• Abduction of the forefoot
• Eversion of the hindfoot and calcaneus
• Collapsed medial arch
• Medial rotation and plantar flexion of the talus [10][11]

The majority of authors tend to distinguish between pediatric/adolescent flatfoot and adult flatfoot as separate entities.[12]

Pediatric

Distinguishing between rigid and flexible flat feet is crucial. Rigid flatfoot is often symptomatic and associated with conditions such as bony coalitions, rheumatoid or posttraumatic arthritis, neurological or neuromuscular disorders, or other underlying causes. Flexible flatfoot is usually idiopathic and characterized by the restoration of the medial arch during a physical examination when standing on tiptoes or performing the Jack test, where the medial arch rises with passive dorsiflexion of the toes.[13] Flexible flatfoot can often be corrected by arthroereisis as a stand-alone procedure.

There is a general consensus that flatfoot in the first few years of life is considered physiological; it frequently corrects itself by the time a child reaches age 10.[14] However, the deformity can often cause parental concern, leading to further medical referrals. While children with flatfoot may often walk without issues, they may occasionally complain of pain over the distal fibula, the medial portion of the midfoot, the sinus tarsi, and the medial aspect of the heel.[15]

Adult

According to clinical and radiographic criteria developed by Johnson and Strom (applied by Myerson), pes planus in adults is frequently linked to dysfunction of the tibialis posterior tendon, a condition often seen in African-American populations more than Caucasian (38% vs 16%).[16][17]

There are 3 categories of causes:

• Articular (rheumatoid arthritis, degenerative primary midfoot and hindfoot arthritis, connective tissue disease)
• Osseous (congenital or posttraumatic)
• Neurological or neuromuscular diseases

Unlike in children, flatfoot in adults is often a permanent acquired deformity that can cause discomfort during daily activities, difficulty with shoe fitting, and persistent functional impairment related to walking propulsion.[12][18] Without treatment, these symptoms are likely to worsen over time.[19]

Indications

Indications in the Pediatric Population

Subtalar arthroereisis may be utilized as a standalone procedure or in conjunction with tendon releases to address painful congenital flexible flatfoot.[20][21] This technique involves inserting an implant into the sinus tarsi, a space between the talus and calcaneus bones, to restrict excessive subtalar joint movement and correct hindfoot eversion deformities in flat feet. Effective in symptomatic flexible flatfoot cases, where the arch is correctable, arthroereisis aids by stabilizing the foot arch during weight-bearing, restoring it when the foot is not bearing weight. This technique is also commonly employed as an adjunctive treatment for rigid flatfoot conditions associated with tibialis posterior tendon dysfunction, tarsal coalition, and accessory navicular bone syndrome.[22] 

Indications in the Adult Population

In adults, the initial treatment for flatfoot, particularly secondary to tibialis posterior tendon dysfunction, commonly involves the use of insoles, with surgery reserved for cases where conservative measures fail.[23] However, the role of arthroereisis differs in adults compared to pediatric patients due to the structural nature of adult flatfoot. While arthroereisis is rarely performed as a standalone procedure in adults, it is often combined with soft tissue and bony procedures to augment the antipronation effect and support the medial arch and tibialis posterior tendon.[24][25] Despite insights from various specialists, there remains insufficient research to establish arthroereisis as a primary option for adult flatfoot management.[26]

Contraindications

The following are contraindications to arthroereisis:

• Unstable midtarsal joint
  • This condition, which can occur in flexible flatfoot, is not addressed by arthroereisis. The implant may result in discomfort, subluxation, or arthritis by placing more strain on the midtarsal joint. Consequently, osteotomy or midtarsal arthrodesis may be necessary in these cases.[27]
• Arthritis
  • Arthroereisis is not recommended for patients with arthritis of the subtalar or midtarsal joints, as the implant may aggravate the inflammation and degeneration of the joint cartilage. Arthroereisis may also interfere with the normal biomechanics of the joint and cause further damage. Arthritis may also affect the implant fixation and stability, increasing the risk of implant failure or migration.[28] Therefore, arthroereisis is unsuitable for arthritic patients and may require alternative treatments such as joint debridement, arthroplasty, or arthrodesis.[29]
• Rigid equinus
  • Patients with rigid equinus, characterized by a fixed plantarflexion contracture of the ankle joint, typically do not respond favorably to arthroereisis. This condition can lead to excessive stress on the forefoot and impaired performance of the windlass mechanism, potentially resulting in the collapse of the medial longitudinal arch. Since arthroereisis restricts subtalar joint mobility without addressing the equinus deformity, it may exacerbate symptoms in such cases. Therefore, arthroereisis is not recommended as a standalone treatment for rigid equinus and may require a combination with other interventions, such as gastrocnemius recession or Achilles tendon lengthening.[29][30]

Equipment

There are different types of implants and techniques for arthroereisis, such as expandable sinus tarsi implants, lateral calcaneus stop screws, and absorbable implants. A recent study compared the clinical, radiographic, and pedobarographic outcomes of 3 different methods of arthroereisis and found that they all achieved comparable improvements in foot function, alignment, and pressure distribution. However, the study also reported a higher incidence of implant-related complications with sinus tarsi implants than with screw arthroereisis.[31]

Technique or Treatment

The minimally invasive surgical technique is typically preferred for surgeons performing arthroereisis procedures. This method involves making a lateral incision, ranging from 1 to 4 cm, positioned parallel to the skin tension lines and just anterior and inferior to the tip of the lateral malleolus. After debriding the sinus tarsi, the hindfoot is manually supinated to correct the pronated deformity.

For self-locking implants, a probe is inserted to determine the tunnel direction, and successive trial implants are used under fluoroscopy to determine the appropriate size.[2][25] In cases involving impact-blocking instruments like the calcaneo-stop screw, the screw is inserted after drilling a guide wire either in the talus (retrograde approach) or calcaneus (anterograde technique).[32] 

Postoperative instructions and protocols vary among surgeons, with weight-bearing typically postponed for 6 weeks when combined with other operations. Still, immediate weight-bearing may be allowed with or without a cast for 5 to 10 days when performed alone.[33]

Complications

Complications of arthroereisis can be broadly categorized into 4 groups:

• Implant biomaterial failure (screw loosening, wear, or breakage)
• Inflammatory reaction (painful sinus tarsitis, peroneal spasm, stiff equinus or fourth metatarsal stress fracture)
• Technical error (extrusion, malcorrection, overcorrection, or undercorrection)
• Those related to use in contraindicated cases (unstable midtarsal joint, arthritis, rigid equinus) [34][35]

The most common complication associated with arthroereisis is pain around the sinus tarsi, although this typically resolves upon implant removal.[36] However, there is uncertainty regarding complication and removal rates. As a recent literature analysis indicates, reported complication rates range from 4.8% to 18.6%, while removal rates range from 7.1% to 19.3%.[37] These figures contradict many authors' observations that not all complications require additional surgery and may resolve spontaneously. Earlier studies showed that up to 40% of patients needed implant removal.[38] However, the lack of long-term follow-up and comprehensive analyses underscores the need for thorough prospective research in the future.

Furthermore, case reports have outlined a few rare but potentially severe issues, such as talar fracture and postoperative subtalar fusion. Recent studies, however, indicate a relatively low overall complication rate, ranging from 0% to 11%. Despite this, a 2015 web-based survey revealed surprising data indicating that 33% of American Orthopedic Foot and Ankle Society members who had previously conducted subtalar arthroereisis opted to discontinue the procedure due to its high failure rate and the need for implant removal.[22] This suggests that research on subtalar arthroereisis may be influenced by publication bias, favoring the reporting of positive outcomes. Additionally, the survey states that a greater share of foreign surgeons performs arthroereisis than their American counterparts, potentially influenced by challenges in payment from health insurance companies.[22]

Previous research suggests that implants should remain in place for at least 2 years for proper bone and soft tissue adaptation before removal.[39] Delays of 6 to 18 months have been noted in older literature, particularly when used as an adjunct surgery for adult flatfoot to capitalize on the impact of the implant on other surgical operations.[8] However, there is no precise timeframe for permanent repair. Studies investigating predictors of implant removal in adults indicate significant unplanned explantation rates of up to 30% to 40%. Risk factors include radiographic undercorrection of deformity and larger implant size.[40] In these studies, arthroereisis was often performed as an adjunct operation with various implant types. However, older literature suggests that a higher removal rate does not always correlate with size and radiographic parameters of correction. Establishing a precise correlation between explantation risk and potential risk factors is still necessary.

Clinical Significance

Arthroereisis offers several advantages over traditional open surgery techniques. Firstly, it is minimally invasive, requiring smaller incisions and causing less disruption to soft tissues. This results in a shorter hospital stay, quicker recovery time, and reduced postoperative complications such as edema and pain. Additionally, arthroereisis preserves the natural anatomy and biomechanics of the foot, allowing for future growth and development. Notably, the procedure is reversible, and the implant can be easily removed if necessary, providing flexibility in treatment options. 

Despite its clinical significance, arthroereisis is not without challenges, as implant-related complications and the need for subsequent implant removal may occur. Thus, careful patient selection and postoperative management are crucial to optimizing outcomes. Overall, arthroereisis represents an important therapeutic option in the management of pediatric and adult flatfoot deformities, providing patients with improved foot function and quality of life.

Enhancing Healthcare Team Outcomes

Effective management of arthroereisis requires a collaborative approach involving various healthcare professionals to optimize patient-centered care, outcomes, and safety. Physicians, advanced practitioners, nurses, pharmacists, and other team members must possess the necessary skills and expertise to perform their respective roles effectively. Surgeons need expertise in arthroereisis techniques, including implant placement and postoperative management. Advanced practitioners are crucial in patient assessment, education, and follow-up care, ensuring treatment plans are tailored to individual needs. Nurses provide essential support in perioperative care, monitoring patients for complications and facilitating their recovery. Pharmacists contribute by ensuring appropriate medication management, including pain control and prevention against infection. Physical therapists guide postoperative rehabilitation efforts. 

Interprofessional communication is vital for care coordination and optimizing patient outcomes. Healthcare professionals must communicate effectively to exchange information, coordinate treatment plans, and promptly address concerns or complications. Regular multidisciplinary team meetings can facilitate collaboration, allowing each member to contribute their expertise and insights. Clear communication channels enhance patient safety by minimizing errors and ensuring all team members align with the treatment goals. Additionally, ongoing education and training programs help healthcare professionals stay updated on the latest advancements in arthroereisis techniques and patient care, further enhancing team performance and patient outcomes.