subtalar fusion range of motion

Project Fab

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20-03-2025

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Subtalar Fusion: Range of Motion, Complications, and Considerations

Subtalar fusion, also known as a hindfoot fusion, is a surgical procedure that involves fusing the bones of the subtalar joint – the joint between the talus and calcaneus bones in the ankle. This fusion eliminates movement within the subtalar joint, effectively stiffening the hindfoot. While this procedure significantly reduces pain associated with conditions like arthritis, instability, or trauma, it comes at the cost of a considerable reduction in range of motion (ROM). Understanding the implications of this ROM loss, the potential complications, and the overall impact on daily life is crucial for both surgeons and patients considering subtalar fusion.

Normal Subtalar Joint Range of Motion:

Before delving into the post-fusion ROM, let's establish a baseline. The subtalar joint contributes significantly to the foot's overall mobility, enabling crucial movements like:

• Inversion: Turning the sole of the foot inward. A normal range is typically 35-40 degrees.
• Eversion: Turning the sole of the foot outward. A normal range is typically 20-25 degrees.
• Dorsiflexion (Ankle Flexion): Bending the foot upwards towards the shin. While primarily driven by the ankle joint, subtalar joint movement contributes to overall dorsiflexion.
• Plantarflexion (Ankle Extension): Bending the foot downwards away from the shin. Again, subtalar motion contributes to the full range.

These movements are essential for activities such as walking, running, jumping, and maintaining balance. The coordinated interaction between the subtalar and other joints in the foot and ankle provides shock absorption, adaptability to uneven surfaces, and efficient gait.

Range of Motion After Subtalar Fusion:

The primary consequence of subtalar fusion is a significant loss of motion in the fused joint. After surgery, patients will experience virtually no movement between the talus and calcaneus. This lack of motion directly impacts the overall mobility of the foot and ankle. The exact ROM reduction varies depending on the surgical technique, the extent of the fusion, and individual factors, but generally, patients will lose most, if not all, of their subtalar inversion and eversion.

This loss of subtalar movement is compensated for by increased motion in other joints of the foot and ankle. The midfoot and forefoot joints often exhibit increased mobility to make up for the rigidity introduced by the fusion. This compensatory movement can sometimes lead to increased stress on these other joints, potentially leading to further complications down the line. This is why post-operative physiotherapy and rehabilitation are crucial in adapting to the changes in biomechanics.

Factors Influencing Post-Fusion ROM:

Several factors influence the functional outcome and residual ROM after subtalar fusion:

• Surgical Technique: Different surgical approaches affect the stability and range of motion. Some techniques might preserve slightly more motion than others.
• Extent of Fusion: The surgeon may choose to fuse only part of the subtalar joint or the entire joint. A partial fusion may leave some residual motion, but it carries the risk of non-union (failure of the bones to fuse).
• Pre-operative ROM: Patients with severely limited ROM before surgery may not experience as much of a functional difference post-operatively, though pain relief should still be significant.
• Patient Factors: Age, overall health, and compliance with rehabilitation protocols influence the final outcome and adaptive capacity.
• Presence of Associated Conditions: The presence of other foot and ankle pathologies may further complicate the post-operative recovery and ROM.

Complications of Subtalar Fusion:

While subtalar fusion is generally successful in relieving pain, it's not without potential complications:

• Non-union: The bones fail to fuse completely, necessitating further surgery.
• Malunion: The bones fuse, but in a malaligned position, leading to deformity and functional limitations.
• Arthritis in Adjacent Joints: Increased stress on the midfoot and forefoot joints can lead to the development of arthritis in these areas over time.
• Stiffness: While the goal is to reduce pain, excessive stiffness can limit mobility and impact daily activities.
• Infection: A risk with any surgical procedure.
• Nerve or Tendon Damage: Potential damage to surrounding nerves or tendons during surgery.
• Implant Complications: If implants are used, there's a risk of loosening, breakage, or infection.

Rehabilitation After Subtalar Fusion:

Post-operative rehabilitation is crucial for maximizing functional recovery. Physical therapy focuses on:

• Pain Management: Reducing pain and inflammation.
• Range of Motion Exercises: Gentle exercises to maintain mobility in the remaining joints of the foot and ankle. This is key to preventing excessive stiffness.
• Strengthening Exercises: Strengthening the muscles surrounding the ankle and foot to improve stability and support.
• Gait Training: Relearning how to walk efficiently with the altered biomechanics.
• Proprioceptive Training: Improving balance and coordination.

Overall Impact on Daily Life:

The impact of subtalar fusion on daily life varies greatly from patient to patient. While pain relief is often substantial, patients should be aware that the procedure significantly affects gait and mobility. Activities that require significant subtalar joint movement, such as running, jumping, and activities involving rapid changes in direction, might be significantly limited. Many patients successfully adapt and maintain an active lifestyle, although modifications and adjustments may be necessary. Post-surgical expectations should be realistic and discussed thoroughly with the surgical team before proceeding with the procedure. A thorough understanding of the potential range of motion limitations and the possibility of compensatory movements in other joints is essential for successful recovery and achieving a good functional outcome.

Conclusion:

Subtalar fusion is a significant surgical intervention with the potential for substantial pain relief but also carries the risk of reduced range of motion and other complications. The potential benefits and limitations should be carefully weighed against individual circumstances and expectations. Open communication between the patient and the surgical team is vital to ensure realistic expectations, optimize the surgical approach, and effectively manage the post-operative rehabilitation process, leading to the best possible outcome. Careful consideration of potential limitations and adaptation to the new biomechanics of the foot are essential for patients to maintain an active and fulfilling lifestyle following a subtalar fusion.