Fused Feet: Tarsal Coalition, Arthrodesis, Symptoms, and Management

What are fused feet?

Fused feet, a condition where two or more bones in the foot become abnormally joined or immobile, can result from either a congenital anomaly known as tarsal coalition or a surgical procedure called arthrodesis, each profoundly impacting foot mechanics and function.

Understanding Foot Anatomy and Function

The human foot is a marvel of biomechanical engineering, comprising 26 bones, 33 joints, and over 100 muscles, tendons, and ligaments. These structures work in concert to provide stability, absorb shock, and propel the body forward during locomotion. Key to its function are the three arches (medial longitudinal, lateral longitudinal, and transverse), which act as dynamic springs, distributing weight and adapting to uneven terrain. Normal foot movement relies on the intricate interplay and slight motion within each joint, allowing for flexibility and efficient transfer of forces.

What Does "Fused Feet" Mean?

The term "fused feet" refers to a condition where the normal articulation (joint movement) between two or more bones in the foot is eliminated due to an abnormal bony, fibrous, or cartilaginous connection. This fusion can occur for two primary reasons:

• Congenital Fused Feet (Tarsal Coalition): This is a condition present from birth where certain foot bones fail to separate during fetal development, leading to an abnormal bridge between them.
• Surgical Fused Feet (Arthrodesis): This is an intentional surgical procedure performed to permanently join two or more bones, typically to alleviate severe pain, correct deformity, or stabilize a joint.

Tarsal Coalition: The Primary Cause of Congenital Fused Feet

Tarsal coalition is the most common cause of congenitally fused feet. It is an abnormal connection that develops between two or more bones in the midfoot or hindfoot (tarsal bones). While present at birth, symptoms often don't appear until adolescence or early adulthood when the coalition begins to ossify (harden into bone) or increased activity places greater stress on the foot.

• Prevalence and Genetics: Tarsal coalition is estimated to occur in about 1 in 100 people and can be hereditary, often affecting both feet.
• Common Locations:
  • Calcaneonavicular Coalition: An abnormal bridge between the calcaneus (heel bone) and the navicular bone.
  • Talocalcaneal Coalition: An abnormal bridge between the talus (ankle bone) and the calcaneus. This often occurs at the subtalar joint, which is crucial for inversion and eversion of the foot.
• Types of Coalition:
  • Osseous: A complete bony bridge between the bones.
  • Cartilaginous: A bridge formed by cartilage.
  • Fibrous: A bridge formed by fibrous tissue.

Surgical Arthrodesis: Intentional Foot Fusion

Arthrodesis is a surgical procedure where two or more bones in a joint are permanently fused together, eliminating motion at that joint. This is a significant intervention, typically considered when conservative treatments have failed or the joint is severely damaged.

• Reasons for Surgery:
  • Severe Arthritis: Degenerative joint disease (osteoarthritis) or inflammatory arthritis (rheumatoid arthritis) causing debilitating pain.
  • Deformity: Correcting severe foot deformities that cannot be managed with orthotics or other non-surgical methods.
  • Instability: Stabilizing joints that are chronically unstable due to ligamentous injury or neurological conditions.
  • Failed Conservative Treatment: When pain and dysfunction persist despite extensive non-surgical management.
• Common Joints Fused: While any foot joint can be fused, common sites include the ankle joint (tibiotalar arthrodesis), subtalar joint (talocalcaneal arthrodesis), and various midfoot joints.

Signs and Symptoms of Fused Feet

Whether congenital or surgical, fused feet can present with a range of symptoms due to the altered biomechanics.

• Pain: Often the most prominent symptom, typically located at or around the site of fusion. Pain can worsen with activity, especially weight-bearing.
• Stiffness and Reduced Range of Motion: A hallmark sign, as the affected joint's normal movement is restricted or absent. This can manifest as difficulty with activities requiring foot flexibility.
• Gait Abnormalities: Patients may develop a stiff, propulsive gait, a limp, or an altered weight-bearing pattern to compensate for the lack of motion.
• Flatfoot Deformity (Pes Planus): Especially common with tarsal coalition, as the rigid connection prevents the normal arch from forming or collapsing. This is often referred to as a "rigid flatfoot."
• Recurrent Ankle Sprains: The lack of compensatory motion in the fused joint can place increased stress on adjacent joints, making them more susceptible to injury.
• Muscle Spasms: Particularly in tarsal coalition, the peroneal muscles (on the outside of the lower leg) may spasm in an attempt to stabilize the rigid foot, leading to "peroneal spastic flatfoot."
• Difficulty with Uneven Surfaces: The inability of the foot to adapt and absorb shock makes walking on uneven ground challenging and potentially painful.

Diagnosis of Fused Feet

Diagnosing fused feet involves a thorough clinical assessment combined with advanced imaging.

• Clinical Examination:
  • History: Discussing pain, onset, activities that worsen symptoms, and family history.
  • Palpation: Identifying areas of tenderness.
  • Range of Motion Tests: Assessing the flexibility of foot and ankle joints. A rigid flatfoot that does not correct when standing on toes is a key indicator of tarsal coalition.
  • Gait Analysis: Observing walking patterns for compensatory movements.
• Imaging:
  • X-rays: Initial imaging to identify obvious bony bridges, joint space narrowing, or signs of arthritis. Specific views (e.g., Harris heel view for talocalcaneal coalition) may be used.
  • CT Scans (Computed Tomography): Highly effective for visualizing bony coalitions in detail, including their type (osseous, cartilaginous, fibrous) and extent.
  • MRI (Magnetic Resonance Imaging): Useful for identifying fibrous or cartilaginous coalitions, as well as assessing soft tissue involvement, inflammation, or damage to adjacent structures.

Implications and Biomechanical Consequences

The rigidity imposed by fused feet has significant biomechanical implications throughout the kinetic chain.

• Impact on Shock Absorption: The foot's ability to act as a shock absorber is severely compromised, leading to increased stress on higher joints.
• Altered Kinetic Chain: The lack of motion in the foot means that forces are transferred abnormally to the ankle, knee, hip, and even the spine, potentially leading to pain or degenerative changes in these areas over time.
• Increased Risk of Adjacent Joint Arthritis: The joints immediately above and below the fused segment are forced to compensate for the lost motion, leading to accelerated wear and tear and a higher risk of developing arthritis.
• Difficulty with Specific Movements: Activities requiring foot flexibility, such as running, jumping, squatting, or even navigating stairs, can become challenging or impossible.
• Challenges with Footwear: Finding comfortable and supportive footwear that accommodates the rigid foot and potential deformities can be difficult.

Management and Treatment Approaches

Treatment for fused feet varies depending on the cause, severity of symptoms, and impact on daily life.

Conservative Management (Primarily for Tarsal Coalition Pain)

Initial management for symptomatic tarsal coalition often focuses on alleviating pain and reducing stress on the foot. For surgically fused feet, conservative management focuses on adapting to the new biomechanics.

• Rest, Ice, Elevation (RICE): To reduce inflammation and pain during acute flare-ups.
• Non-Steroidal Anti-Inflammatory Drugs (NSAIDs): To manage pain and inflammation.
• Orthotics: Custom-made shoe inserts can provide arch support, improve alignment, and reduce motion at the coalition site, thereby decreasing stress.
• Physical Therapy: Focuses on strengthening muscles above and below the fusion, improving gait mechanics, and maintaining flexibility in adjacent joints.
• Casting or Boot Immobilization: Short-term immobilization can help reduce pain and inflammation by resting the foot.
• Corticosteroid Injections: May be used to reduce localized inflammation and pain.

Surgical Intervention

When conservative measures fail to provide adequate relief or in cases of severe deformity, surgical intervention may be considered.

• Resection of Coalition (for Tarsal Coalition): In cases of fibrous or cartilaginous coalitions, especially in younger individuals, the abnormal bridge can be surgically removed to restore motion and alleviate pain.
• Arthrodesis (for Severe Tarsal Coalition or Other Conditions): If resection fails, or if the foot is severely degenerated or deformed, surgical fusion (arthrodesis) may be performed to stabilize the foot and eliminate pain. This is also the primary surgical treatment for severe arthritis or instability not amenable to other procedures.
• Post-Operative Rehabilitation: Following surgery, a structured rehabilitation program is crucial, involving immobilization, gradual weight-bearing, and physical therapy to regain strength, improve gait, and adapt to the altered foot mechanics.

Living with Fused Feet

Adapting to life with fused feet, whether congenital or surgical, requires ongoing management and attention to foot health.

• Adaptive Strategies: Learning new ways to perform activities that were once easy, such as pivoting with the whole body instead of twisting the foot.
• Importance of Proper Footwear: Selecting shoes with good cushioning, wide toe boxes, and rigid soles can provide support and comfort. Custom-made shoes may be necessary in some cases.
• Ongoing Physical Therapy/Exercise: Regular exercises to maintain strength in surrounding muscles, improve balance, and prevent secondary complications in adjacent joints are vital.
• Pain Management: A multi-modal approach to pain, including medication, physical therapy, and lifestyle modifications, may be necessary.
• Psychological Impact: Acknowledging and addressing the emotional and psychological challenges of living with a chronic condition and limitations can be beneficial.

The Role of Exercise Science and Kinesiology

Exercise science and kinesiology play a critical role in managing and optimizing function for individuals with fused feet.

• Understanding Biomechanics: Kinesiologists deeply understand how fusion alters the foot's biomechanics and its impact on the entire kinetic chain. This knowledge informs targeted interventions.
• Tailoring Exercise Programs: Developing individualized exercise programs that avoid excessive stress on the fused joint while strengthening compensatory muscles and maintaining mobility in adjacent joints.
• Gait Retraining: Teaching patients how to walk more efficiently and safely, minimizing compensatory movements that could lead to pain or injury elsewhere.
• Strength and Mobility for Compensatory Movements: Focusing on strengthening the core, hips, and knees to better absorb shock and manage the increased load. Maintaining ankle and knee mobility is also crucial.
• Preventing Secondary Issues: Proactive exercise and movement strategies can help prevent the development of arthritis in adjacent joints or other musculoskeletal problems that arise from altered biomechanics.

Understanding "fused feet" from both congenital and surgical perspectives is crucial for effective diagnosis, treatment, and long-term management, empowering individuals to live as functionally and comfortably as possible.