Plantar Fasciitis โรคเอ็นฝ่าเท้าอักเสบ (รองช้ำ)

Plantar Fasciitis is a prevalent cause of heel pain, particularly in active populations and middle-aged adults. The condition results from repetitive strain or microtrauma to the plantar fascia, leading to degeneration and subsequent inflammation of this thick, fibrous band. As one of the most common causes of heel pain, it is a crucial area of study and management for orthopedic practitioners.

Anatomy and Pathophysiology:

The plantar fascia is a robust, fibrous tissue band that originates from the medial tubercle of the calcaneus and extends along the sole of the foot to insert at the bases of the proximal phalanges. Its main function is to support the arch of the foot and aid in absorbing the mechanical stresses associated with weight-bearing and locomotion.

• Microtrauma and Overuse: Chronic overuse or mechanical overload—common in athletes or those with prolonged standing jobs—leads to repetitive microtears in the fascia. Over time, this induces a degenerative process, leading to a condition often termed plantar fasciosis (a more accurate description than fasciitis, as the condition is more degenerative than inflammatory in chronic stages).
• Degenerative Process: Histopathological studies have revealed that chronic plantar fasciitis is characterized by collagen degeneration, fibroblastic hypertrophy, and an absence of inflammatory cells. Neovascularization and myxoid degeneration are also common in chronic cases. Thus, the term fasciitis is somewhat misleading, as inflammation is minimal or absent in long-standing cases.
• Biomechanical Contributors:
  • Pes planus (flat feet) or pes cavus (high arches) can predispose to plantar fasciitis by altering the foot’s biomechanics.
  • Tight Achilles tendon and gastrocnemius-soleus complex can increase tension on the plantar fascia during gait, further exacerbating microtrauma.
  • Obesity, particularly in middle-aged patients, is a significant risk factor due to increased pressure on the heel during standing and walking.

Risk Factors:

• Intrinsic Factors:
  • Pes planus or pes cavus
  • Tightness of the gastrocnemius-soleus complex (equinus contracture)
  • Weak intrinsic foot muscles
  • Age: 40-60 years, commonly affected
• Extrinsic Factors:
  • Prolonged standing or walking
  • Sudden increases in activity level (common in athletes, such as runners)
  • Inappropriate footwear (e.g., non-supportive shoes, high heels, or shoes without adequate arch support)
  • Obesity and increased body mass index (BMI)

Clinical Presentation:

Patients typically report sharp pain localized to the anteromedial aspect of the calcaneus. This pain is often described as being most intense with the first steps in the morning or after periods of prolonged inactivity, known as post-static dyskinesia. The pain tends to diminish with walking but can return after prolonged activity or standing.

• Morning Pain Pattern:
  • Upon waking, the plantar fascia, which contracts overnight, is suddenly stretched during the first steps, leading to a characteristic sharp pain.
  • As the fascia stretches out with activity, the pain temporarily subsides, but inflammation and microtrauma accumulate throughout the day, leading to an increase in discomfort by evening.
• Classic Examination Findings:
  • Palpation: Tenderness at the medial calcaneal tubercle is the hallmark finding. Palpation of this area usually reproduces the patient's pain.
  • Windlass Test: Dorsiflexion of the toes while palpating the medial arch can reproduce pain, indicating tension in the plantar fascia.
  • Tight Achilles Tendon: Many patients will demonstrate limited ankle dorsiflexion due to a tight gastrocnemius-soleus complex.
  • Rule Out Other Causes: A thorough physical exam must rule out tarsal tunnel syndrome, calcaneal stress fractures, and Achilles tendinopathy, all of which can mimic plantar fasciitis symptoms.

Differential Diagnosis:

While plantar fasciitis is often straightforward, it's crucial to consider the following differentials:

• Calcaneal stress fracture: Pain worsens with activity, and tenderness is diffuse, extending to the lateral aspect of the calcaneus. Imaging is essential for differentiation.
• Tarsal tunnel syndrome: Medial heel pain is often associated with paresthesia or numbness, and a positive Tinel’s sign over the tibial nerve supports this diagnosis.
• Achilles tendinopathy: This can present with posterior heel pain, with tenderness along the Achilles tendon itself, as opposed to the plantar aspect.
• Fat pad atrophy: Elderly patients with thinning heel fat pads may develop diffuse heel pain, aggravated by prolonged standing.

Diagnostic Imaging:

• X-rays: While often negative, X-rays are indicated to rule out calcaneal stress fractures or other bony abnormalities. Heel spurs, though commonly associated with plantar fasciitis, are seen in many asymptomatic individuals and should not be considered diagnostic.
• Ultrasound: Can reveal thickening of the plantar fascia (>4 mm is typically abnormal), which correlates with the severity of the condition.
• MRI: Reserved for recalcitrant cases, it can show increased signal intensity in the plantar fascia on T2-weighted images, reflecting the chronic degenerative changes.

Management Approach:

Management begins with conservative measures, which are effective in most patients. Clinicians should focus on the following treatment strategies:

1. Activity Modification:
   • Rest and avoidance of aggravating activities, particularly running and long periods of standing.
   • Modification of training regimens for athletes, such as reducing mileage or incorporating cross-training.
2. Stretching and Strengthening Exercises:
   • Plantar Fascia Stretching: Focus on stretching the plantar fascia, particularly first thing in the morning.
   • Gastrocnemius and Soleus Stretching: Achilles tendon stretching exercises are paramount in reducing tension on the plantar fascia.
   • Intrinsic Foot Muscle Strengthening: Exercises to strengthen the small muscles of the foot can provide additional arch support, decreasing strain on the plantar fascia.
3. Footwear and Orthotics:
   • Patients should wear well-cushioned shoes with adequate arch support. Avoidance of walking barefoot, especially on hard surfaces, is critical.
   • Custom or over-the-counter orthotics can reduce tension on the plantar fascia by supporting the medial arch and cushioning the heel.
4. Medications:
   • NSAIDs (Non-steroidal anti-inflammatory drugs): These can help with pain control and reduce inflammation in the acute phase. However, given the degenerative nature of chronic cases, their long-term use is limited.
5. Night Splints:
   • These devices keep the foot in a dorsiflexed position overnight, maintaining a gentle stretch on the plantar fascia, which helps prevent morning stiffness.
6. Physical Therapy:
   • A supervised physical therapy program that incorporates manual therapy, deep-tissue massage, and stretching exercises may significantly improve outcomes, particularly in patients with chronic symptoms.
7. Steroid Injections:
   • Corticosteroid injections can provide rapid, short-term relief, but caution is necessary. Repeated injections increase the risk of plantar fascia rupture and fat pad atrophy. This option is reserved for severe cases unresponsive to other treatments.
8. Extracorporeal Shockwave Therapy (ESWT):
   • High-energy shock waves are directed at the heel to promote neovascularization and healing of the plantar fascia. This modality is particularly useful in chronic cases where conservative measures fail. The mechanism involves microtrauma induction, stimulating a repair process.

Surgical Intervention:

Surgery is considered a last resort, typically after 6-12 months of failed conservative treatment. The main surgical option is plantar fasciotomy, where a portion of the fascia is released to reduce tension.

• Endoscopic plantar fasciotomy allows for a minimally invasive approach, reducing recovery time compared to open surgery.
• Postoperative complications may include nerve injury or loss of medial arch stability, which can lead to flatfoot deformity.

Prognosis:

With proper treatment, approximately 90% of patients achieve relief from symptoms within 6-9 months. Early and consistent conservative management is critical to avoiding chronic symptoms or the need for surgical intervention.

Key Takeaways:

• Conservative treatment is effective in the vast majority of plantar fasciitis cases. Focus on a multimodal approach including stretching, activity modification, and orthotics.
• Understand the biomechanics and risk factors contributing to plantar fasciitis, especially in athletes or patients with abnormal foot anatomy.
• Corticosteroid injections should be used cautiously and typically reserved for recalcitrant cases.
• Surgery is rarely required but can be considered in chronic, refractory cases after exhausting all conservative options.

By focusing on these core management principles, you will be well-prepared to diagnose and treat plantar fasciitis effectively within your orthopedic practice.