Summary

The Hallux sesamoids are two small bones (Medial/Tibial and Lateral/Fibular) embedded in the Flexor Hallucis Brevis (FHB) tendon, functioning like the patella of the foot to increase the leverage of the big toe. Injuries range from chronic inflammation (Sesamoiditis) to acute Fractures (stress or traumatic) and Avascular Necrosis. A key diagnostic challenge is distinguishing a fracture from a harmless Bipartite Sesamoid (present in 10-30% of people). Management is primarily offloading (Dancer's Pad), with surgery (Sesamoidectomy) reserved for intractable pain, carrying a high risk of iatrogenic deformity (Hallux Valgus/Varus). [1,2,3]

Key Facts

• The "Patella" of the foot: They absorb weight-bearing forces (up to 3x body weight during push-off) and protect the FHL tendon.
• Medial vs Lateral: The Medial (Tibial) Sesamoid is larger, bears more weight, and is injured much more frequently. The Lateral (Fibular) Sesamoid is smaller and harder to injure.
• Bipartite Conundrum: A bipartite sesamoid is a congenital failure of fusion. It has smooth, rounded edges and provides a false positive for fracture on X-ray. A real fracture has rough, jagged edges.

Clinical Pearls

"The Dancer's Pad": Or "J-Pad". A specific U-shaped felt pad that circles the sesamoid, floating it in the air so it doesn't touch the ground. It is the gold standard conservative treatment.

"Bone Scan for Bipartite": If you are unsure if a "fracture" on X-ray is real or just a bipartite bone, get a Bone Scan (or MRI). A fracture lights up (hot). A bipartite bone is cold (unless it, too, is injured).

"Don't take both": Removing both sesamoids (Cock-up deformity) is disastrous. Never do it.

                 SESAMOID PAIN
                       ↓
             TRAUMA OR OVERUSE?
            ┌──────────┴──────────┐
          TRAUMA               OVERUSE
       (Fracture?)          (Sesamoiditis?)
           ↓                      ↓
      X-RAY / CT                 MRI
      (Jagged?)                (Edema?)
           ↓                      ↓
      CONFIRMED              CONFIRMED
      FRACTURE              INFLAMMATION
           ↓                      ↓
      OFFLOADING             OFFLOADING
     (Boot/Pad)             (Pad/Insole)

Indications

• Almost all cases initially.
• Sesamoiditis.
• Acute fractures.
• Stress fractures.

Protocol

• Phase 1 (0-6 weeks):
  • Fracture: Walking Boot (Immobilization).
  • Sesamoiditis: Dancer's Pad + Stiff soled shoe.
• Phase 2:
  • Custom Orthotics with "Sesamoid cutout" (depression in the insole).
  • Avoid high heels.

Indications

• Intractable Pain: Failed conservative care >6 months.
• Non-Union: Painful gap.
• AVN: Collapsed/fragmented necrotic bone used as a grinder.
• Infection: Osteomyelitis (Diabetic ulcer).

Technique: Sesamoidectomy

• Partial: Shaving off the prominent osteophyte (rare).
• Total: Excision of the sesamoid from within the FHB tendon.
  • Medial Excision: Risk of Hallux Valgus (Drift lateral).
  • Lateral Excision: Risk of Hallux Varus (Drift medial).
• Repair: The defect in the FHB/Capsule must be meticulously repaired to maintain tendon continuity.

Bone Grafting

• Rarely done for non-unions (Screw fixation extremely difficult due to small size). Excision is preferred.

Bipartite vs Fracture

• Kansal et al: MRI is 95% sensitive for differentiating symptomatic bipartite sesamoid (edema between fragments) from acute fracture.

Success Rates

• Saxena et al: Reported 90% return to sport after sesamoidectomy in athletes, but recovery time averaged 4-6 months.

The Injury

You need to think of these bones as kneecaps for your big toe. You have either broken one (fracture) or bruised it badly (sesamoiditis).

The "Bipartite" Issue

You might have been born with a bone in two pieces. We need to check if that is the case, or if you actually broke it.

Treatment

We must stop you stepping on it. A special pad (like a donut) will float the bone so it heals. Surgery involves cutting the bone out, which can make your toe crooked, so we avoid it if possible.

Q1: How do you differentiate a Bipartite Sesamoid from a Fracture on X-ray? A:

• Bipartite: Smooth, sclerotic, rounded margins. Usually bilateral (check other foot). Sum of parts > whole (hypertrophy).
• Fracture: Irregular, jagged, non-sclerotic margins. History of trauma.

Q2: What is the risk of removing the Medial Sesamoid? A: Hallux Valgus. The medial sesamoid acts as a pulley for the abductor hallucis and medial FHB. Removing it allows the lateral structures (Adductor Hallucis) to pull the toe laterally.

Q3: Which artery supplies the Medial Sesamoid? A: The Medial Plantar Artery (branches). It enters the bone proximally, making it susceptible to AVN in distal pole fractures.

Q4: What is the "Axial View" for sesamoids? A: The patient stands on the detector with toes dorsiflexed, and the beam is angled to shoot tangentially along the metatarsal heads. It shows the articulation between the sesamoids and the crista.

(End of Topic)