Description

• Spectrum of disorders involving Achilles tendon, paratenon, and retrocalcaneal bursa
• Painful inflammation of Achilles tendon and its sheath due to chronic degenerative tendinosis and tearing
• Anatomy
  • Tendon is largest and strongest in body, peak loads 6 to 8 times body weight during running.
  • Formed from tendinous contributions of gastrocnemius and soleus muscles
  • Assists in knee flexion, foot plantar flexion, and hindfoot inversion
  • ~15 cm long, inserts on posterior calcaneal tuberosity
  • Surrounded by paratenon
• Definitions
  • Retrocalcaneal bursitis: inflammation of retrocalcaneal bursa, posterior heel pain
  • Paratenonitis: paratenon inflammation associated with warmth, swelling, diffuse tenderness
  • Paratenonitis with tendinosis: diffuse swelling of tendon sheath, nodularity of tendon
  • Tendinosis: intrasubstance degeneration of tendon, typically 2 to 3 cm proximal to insertion
  • Insertional enthesopathy: pain at the insertion of the Achilles tendon onto the calcaneus
  • Tendon rupture: tear in substance of Achilles tendon, usually watershed region
• Tendinopathy locations
  • Midportion (2 to 3 cm proximal to calcaneal insertion): ~55–65% of injuries
  • Insertional: retrocalcaneal bursitis: ~20–25% of injuries

Epidemiology

• Tendinopathy
  • Recreational and competitive athletes
  • Common in active middle-aged individuals
  • Degenerative tendinosis seen in middle-aged to elderly, regardless of sports participation
• Rupture
  • Male-to-female ratio: 1.7:1 to 12:1
  • Left-side injury > right-side injury
  • More common in industrialized countries
  • Healthy men aged 30 to 50 years without previous injury
  • Often no prodromal Achilles pain
  • “Weekend warriors”—minimal weekday activity

Incidence

• Achilles disorders affect ~1 million athletes per year.
• Tendinopathy true incidence unknown
  • Runners, 6.5–18%; dancers, 9%; gymnasts, 5%; tennis, 2%; football, <1%
  • 10 times increase in runners versus age-matched controls
• Rupture
  • Unclear, varies 2 to 37.3 per 100,000
  • Increasing incidence in recent decades with increasing number recreational athletes

Etiology and Pathophysiology

• Achilles tendon blood supply
  • Intrinsic: posterior tibial artery
  • Extrinsic: mesosternal vessels crossing paratenon
  • Watershed zone 2 to 6 cm from posterior calcaneal insertion
  • Supply decreased with age causing degeneration of watershed region.
• Histopathology shows evidence of degenerative changes and chronic tendinosis.
• Disorganized collagen structure, fibrinous exudates, adhesions, increased growth of neurovascular bundles in the paratenon
• Tendinopathy
  • Overuse causing microtrauma and mechanical breakdown of tendon
  • Extrinsic causes: overuse, stairs, hill climbing, improper shoes/training surfaces/stretching, corticosteroid use
  • Intrinsic causes: tight Achilles, varus heel/foot, cavus foot, leg length discrepancy, diabetes
• Rupture
  • Most common: sudden forced plantar flexion, unexpected dorsiflexion, or violent dorsiflexion of a plantar flexed foot
  • Less common: direct trauma

Genetics

• Specific variations of genetic sequence increase susceptibility of injury.
• Environmental factors altering gene expression

Risk Factors

• Tendinopathy/bursitis
  • Haglund process—large posterosuperior calcaneal tuberosity
  • Diabetes, lupus, rheumatoid disease, obesity
  • Hemodialysis or peritoneal dialysis
  • Connective tissue disease
  • Stop and go sports, male gender
• Rupture
  • Medications: corticosteroids, anabolic steroids, fluoroquinolone antibiotics
  • Recreational athletes—abrupt changes in activity level/training/intensity
  • Poorly conditioned, advanced age, overexertion
  • Previous injury or rupture

General Prevention

• Conditioning, stretching, warm-up: thought to produce tendon adaptation and increase cross-sectional area
• Avoid rapid increase in running mileage, training intensity, excessive hill running.