Bipartite Sesamoid

A bipartite sesamoid is a normal variation of one of the small, pea‑shaped bones (sesamoids) found beneath the head of the first metatarsal at the base of the big toe. During growth, a sesamoid forms from one or more centers of bone (ossification centers). When two centers fail to fuse completely, the result is a “split” or bipartite sesamoid rather than a single, solid bone. This variant is not inherently harmful but can sometimes cause pain or confusion with a fracture on X‑rays. Bipartite sesamoids occur in about 7%–30% of people, depending on the population studied Anales de Pediatría, and roughly 14.6% of feet have at least one split sesamoid PubMed.

A bipartite sesamoid refers to a congenital anatomical variant in which one of the sesamoid bones—most commonly the medial sesamoid beneath the first metatarsophalangeal (MTP) joint—fails to fuse fully during childhood development. Instead of forming a single ossicle, the bone remains in two distinct, well‑corticated fragments separated by a thin fibrocartilaginous cleft. This variant is asymptomatic in most people but can become painful when subjected to repetitive stress or acute trauma PMCScienceDirect.

Sesamoid bones help bear weight and reduce pressure on tendons during activities like walking or running. When a sesamoid is split into two parts, each fragment still sits within the tendon—most often the medial (tibial) sesamoid is affected. Although usually asymptomatic, a bipartite sesamoid can become irritated by overuse, trauma, or joint misalignment, leading to pain beneath the big toe.

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Types

Clinically, doctors use a simple classification to describe how many sesamoid parts are present at the first metatarsophalangeal (MTP) joint. Based on a study of 150 foot bones, the following types were defined PMC:

• Type I (No Sesamoid): The first MTP joint has no ossified sesamoid under the metatarsal head (about 1.3% of cases).

• Type II (Single Sesamoid): A solitary, unified sesamoid is present (about 0.07%).

• Type IIIa (Bipartite, Medial Fragment Larger): Two sesamoid pieces, with the tibial (medial) fragment larger than the fibular (lateral) fragment (28%).

• Type IIIb (Bipartite, Lateral Fragment Larger): Two pieces, with the fibular fragment larger than the medial one (65.3%).

• Type IV (Tripartite): Three separate ossification centers form three bone fragments (4.7%).

In practice, “bipartite sesamoid” refers to Type IIIa or IIIb, where exactly two fragments exist.

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Types of Bipartite Sesamoid by Location

Though the above classification covers the number of parts, clinicians also note which sesamoid is bipartite:

1. Medial (Tibial) Bipartite Sesamoid: The inner sesamoid under the first metatarsal is split.

2. Lateral (Fibular) Bipartite Sesamoid: The outer sesamoid is divided.

3. Bilateral Bipartition: Both feet show split sesamoids.

4. Unilateral Bipartition: Only one foot has a split sesamoid.

Medial bipartite sesamoids are more common than lateral ones, and unilateral presentation is more frequent than bilateral.

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Causes of Symptomatic Bipartite Sesamoid

1. Developmental Variant: Incomplete fusion of ossification centers during adolescence leads to two fragments rather than one.

2. Acute Trauma: A direct blow or sudden hyperextension of the big toe can irritate the synchondrosis (joint) between fragments.

3. Repetitive Microtrauma: Activities like running and jumping repeatedly stress the sesamoid, causing inflammation between the pieces.

4. Sesamoiditis: Chronic inflammation of the sesamoid tendon complex can flare pain at the fusion site.

5. Hallux Valgus (Bunion): Outward drift of the big toe increases pressure on the sesamoid bones, aggravating a split sesamoid.

6. Hallux Rigidus: Stiffness at the big‑toe joint forces extra load onto the sesamoid complex.

7. Osteoarthritis: Wear of the MTP joint alters weight distribution, stressing the bipartite region.

8. Avulsion Fracture: A forceful tendon pull can partially detach a fragment, mimicking or worsening bipartition.

9. Osteochondritis Dissecans: A small area of bone under the sesamoid may lose blood supply, leading to inflammation at the synchondrosis.

10. Inflammatory Arthritis (e.g., Rheumatoid Arthritis): Systemic joint inflammation can involve the MTP joint and sesamoid.

11. Crystal Arthropathies (Gout, Pseudogout): Deposition of urate or calcium crystals in the MTP joint causes acute pain at the fragments.

12. Tendonitis of Flexor Hallucis Brevis/Longus: Irritation of the tendon that wraps around the sesamoid fragments.

13. Bursitis: Inflammation of the small bursa near the sesamoid increases pressure on the split bone.

14. Vascular Insufficiency: Rarely, poor blood flow to the sesamoid region leads to fragment edge pain.

15. Neoplasm or Infection: Very rarely, a tumor or bone infection in the sesamoid region can inflame the synchondrosis.

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Symptoms

1. Local Pain: Sharp or aching pain directly under the first MTP joint, often worse with push‑off.

2. Swelling: Mild to moderate puffiness around the big‑toe base.

3. Tenderness: Extreme soreness when pressing on either fragment.

4. Bruising or Discoloration: In cases of acute trauma or avulsion.

5. Reduced Range of Motion: Difficulty bending or straightening the big toe fully.

6. Stiffness: A heavy or stiff feeling in the joint, especially after rest.

7. Pain on Weight‑Bearing: Walking, running, or standing intensifies discomfort.

8. Crepitus: A subtle grating sensation under the toe when moved.

9. Altered Gait: Limping or toe‑off avoidance to reduce pain.

10. Clicking or Popping: Audible or palpable snaps when moving the toe.

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Diagnostic Tests

Physical Exam

1. Inspection of Foot Alignment
The doctor looks for bunion formation (hallux valgus), swelling, or redness at the MTP joint. Misalignment often increases sesamoid pressure.

2. Palpation of Sesamoid Area
Gentle pressing under the big‑toe head locates the exact pain site over one or both fragments.

3. Range of Motion (ROM) Assessment
The examiner moves the big toe up (dorsiflexion) and down (plantarflexion). Limited motion or pain at certain angles suggests sesamoid involvement.

4. Gait Analysis
Watching the patient walk or run reveals whether they avoid pushing off the big toe, indicating sesamoid pain.

Manual Tests

5. Axial Compression Test
With the toe straight, the examiner compresses the first metatarsal head toward the heel. Pain reproduction under compression points to sesamoid pathology.

6. Grind Test
Compress the MTP joint and gently rotate the toe. Sharp pain or crepitus suggests intra‑articular or sesamoid problems.

7. Metatarsal Squeeze Test
Squeezing the metatarsal heads together can exacerbate pain under the sesamoid area, highlighting inflammation.

8. Resisted Toe Flexion Test
The patient tries to flex the big toe against resistance. Pain during this test may indicate flexor hallucis brevis tendon irritation around the split sesamoid.

Lab and Pathological Tests

9. Erythrocyte Sedimentation Rate (ESR)
A simple blood test measuring inflammation. Elevated ESR suggests an inflammatory or arthritic component.

10. C‑Reactive Protein (CRP)
Another blood marker of acute inflammation; high levels may point to infection or crystal arthritis.

11. Serum Uric Acid
High uric acid levels support a gout diagnosis if a split sesamoid region is inflamed acutely.

12. Rheumatoid Factor (RF) and Anti‑CCP
Positive results indicate rheumatoid arthritis, which can involve the sesamoid region.

13. Synovial Fluid Analysis
If joint fluid is aspirated, examining it under a microscope can detect crystals (gout or pseudogout) or infection.

14. Bone Biopsy and Histopathology
Rarely used, a small bone sample from a fragment can rule out tumors or osteomyelitis when imaging is inconclusive.

Electrodiagnostic Tests

15. Nerve Conduction Studies (NCS)
Assesses whether nerve compression around the MTP joint contributes to pain. Usually normal in pure sesamoid problems.

16. Electromyography (EMG)
Evaluates muscle and tendon function of the foot. May help distinguish tendon pathology from sesamoid pain.

Imaging Tests

17. Weight‑Bearing X‑rays (AP, Lateral, Axial Sesamoid Views)
Standard films taken while standing reveal fragment position, joint space, and possible fracture lines.

18. Computed Tomography (CT) Scan
CT gives detailed bone images, clarifying the exact shape and size of each sesamoid fragment and ruling out fracture.

19. Magnetic Resonance Imaging (MRI)
MRI shows both bone and soft tissue detail. It can detect inflammation, marrow edema, tendon tears, or occult fractures around the sesamoid.

20. Diagnostic Ultrasound
A quick, dynamic study that visualizes tendon movement around the sesamoid fragments and can guide injections if needed.

Non‑Pharmacological Treatments

A. Exercise Therapies

1. Calf and Hamstring Stretching

   • Description: Gentle, sustained stretches targeting the gastrocnemius, soleus, and hamstring muscle groups.

   • Purpose: Reduces tightness in the posterior chain, decreasing excessive forefoot loading at toe‑off.

   • Mechanism: Lengthening these muscle fibers promotes a more plantigrade foot position, offloading stress from the sesamoid complex PubMedUpstep.

2. Toe Curls and Marble Pick‑Up

   • Description: While seated, use toes to grasp and lift small objects (e.g., a towel or marbles).

   • Purpose: Enhances intrinsic foot muscle strength and arch support.

   • Mechanism: Activates flexor hallucis brevis and interossei, stabilizing the first MTP joint during gait PubMedorthopedicnj.com.

3. Flexor Hallucis Strengthening

   • Description: Resisted toe flexion using elastic bands anchored under the foot.

   • Purpose: Improves plantarflexion force of the great toe.

   • Mechanism: Builds muscular support around the sesamoid bones, dispersing joint load PubMedJOSPT.

4. First MTP Joint Mobilization

   • Description: Manual gliding of the proximal phalanx on the first metatarsal head by a trained therapist.

   • Purpose: Restores joint range of motion and relieves capsular tightness.

   • Mechanism: Breaks adhesive capsulitis, allowing a more even distribution of plantar pressures PubMedJOSPT.

5. Gait Training

   • Description: Coaching to modify stride length and foot rollover pattern.

   • Purpose: Reduces impulsive loading of the forefoot.

   • Mechanism: Encourages mid‑foot strike and reduces peak sesamoid pressure during push‑off PubMedJOSPT.

6. Ankle Alphabet

   • Description: Tracing the alphabet in the air with the big toe.

   • Purpose: Improves active range and coordination.

   • Mechanism: Promotes neuromuscular control of the hallux, offloading sesamoid stress orthopedicnj.com.

7. Calf Raises

   • Description: Heel‑raise exercises on a step, progressing from two‑leg to single‑leg.

   • Purpose: Strengthens plantarflexors and foot intrinsic muscles.

   • Mechanism: Augments the muscular “windlass” mechanism, decreasing sesamoid compression orthopedicnj.com.

B. Mind‑Body Approaches

8. Mindfulness‑Based Stress Reduction (MBSR)

   • Description: An 8‑week program combining mindfulness meditation, body scans, and gentle yoga.

   • Purpose: Reduces pain perception and stress associated with chronic foot pain.

   • Mechanism: Alters cortical pain processing and decreases sympathetic overactivity WikipediaWikipedia.

9. Yoga Postures (Asanas)

   • Description: Incorporating standing and balance poses (e.g., Tree Pose, Warrior II).

   • Purpose: Enhances proprioception and foot‑ankle stability.

   • Mechanism: Improves neuromuscular control and reduces mechanical overload on the sesamoids PMCWikipedia.

10. Radial Extracorporeal Shockwave Therapy (RSWT)

    • Description: Non‑invasive application of acoustic waves to the sesamoid region.

    • Purpose: Alleviates chronic sesamoid pain resistant to standard therapies.

    • Mechanism: Promotes neovascularization, bone remodeling, and reduces inflammation PMCgermanjournalsportsmedicine.com.

11. Focused Extracorporeal Shockwave Therapy (F‑SWT)

    • Description: High‑energy, targeted shockwave pulses directed at the sesamoid.

    • Purpose: Stimulates bone and soft‑tissue regeneration in refractory cases.

    • Mechanism: Induces osteogenesis, periosteal remodeling, and modulates nociceptor activity germanjournalsportsmedicine.com.

12. Laser Therapy (Low‑Level Laser Therapy)

    • Description: Application of low‑intensity lasers over the first MTP joint.

    • Purpose: Reduces local inflammation and accelerates tissue repair.

    • Mechanism: Photobiomodulation increases cellular ATP production and reduces pro‑inflammatory cytokines MDPI.

13. Biofeedback and Relaxation Techniques

    • Description: EMG‑guided feedback and deep‑breathing exercises.

    • Purpose: Lowers muscle tension in the foot and reduces pain sensitivity.

    • Mechanism: Facilitates parasympathetic activation, decreasing local muscle guarding Wikipedia.

C. Educational Self‑Management

14. Activity Modification Education

    • Description: Teaching patients to avoid high‑impact activities (e.g., jumping, sprinting).

    • Purpose: Prevents overstress of the sesamoid complex.

    • Mechanism: Reduces repetitive microtrauma, allowing natural healing OrthoInfo.

15. Orthotic and Footwear Guidance

    • Description: Instruction on choosing wide‑toe‑box, stiff‑soled shoes and custom insoles.

    • Purpose: Offloads pressure from the sesamoids during weightbearing.

    • Mechanism: Redistributes plantar forces, minimizing focal stress OrthoInfoMDPI.

16. Self‑Monitoring Pain Diary

    • Description: Daily logs of pain levels, activities, and triggers.

    • Purpose: Empowers patients to correlate behaviors with symptoms.

    • Mechanism: Facilitates personalized plan adjustments and early intervention MDPI.

17. Patient Anatomy and Biomechanics Education

    • Description: Simple diagrams and explanations of sesamoid function.

    • Purpose: Enhances adherence to offloading and exercise regimens.

    • Mechanism: Increases patient engagement and correct execution of self‑care OrthoInfo.

18. Ice Massage Technique Instruction

    • Description: How to apply roller‑ball ice massage to the plantar hallux region.

    • Purpose: Provides targeted cold therapy to reduce inflammation.

    • Mechanism: Vasoconstriction and decreased nerve conduction velocity relieve pain orthopedicnj.com.

19. Taping and Strapping Education

    • Description: Demonstrations of plantar flexion taping for the big toe.

    • Purpose: Limits excessive dorsiflexion and unloads sesamoids.

    • Mechanism: Mechanical support reduces joint motion and sesamoid compression OrthoInfo.

20. Return‑to‑Activity Protocols

    • Description: Graduated increase in weightbearing and impact intensity over weeks.

    • Purpose: Safely rebuilds sesamoid tolerance to load.

    • Mechanism: Progressive tissue adaptation prevents re‑injury orthopedicnj.com.

Evidence‑Based Drugs

1. Ibuprofen (NSAID)

   • Dosage: 200–400 mg orally every 4–6 hours as needed; max 1,200 mg/day OTC Drugs.com

   • Class: Nonsteroidal anti‑inflammatory

   • Timing: With meals or milk to reduce gastric upset

   • Side Effects: GI irritation, renal impairment, increased bleeding risk

2. Naproxen (NSAID)

   • Dosage: 550 mg loading dose, then 275 mg every 6–8 hours; max 1,375 mg/day Drugs.com

   • Class: NSAID

   • Timing: With food

   • Side Effects: Dyspepsia, headache, fluid retention

3. Diclofenac 1% Gel

   • Dosage: 2 g (one finger‑tip unit) applied to affected area four times daily MedCentral

   • Class: NSAID topical

   • Timing: Before bandaging or dressing

   • Side Effects: Local skin irritation

4. Celecoxib

   • Dosage: 200 mg once daily PMC

   • Class: Corticosteroid

   • Time: Single session under imaging guidance

   • Side Effects: Tendon weakening, local fat atrophy

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Dietary Molecular Supplements

1. Glucosamine Sulfate (1,500 mg/day) – Supports cartilage and tendon health by providing substrates for glycosaminoglycan synthesis WebMD.

2. Chondroitin Sulfate (1,200 mg/day) – Inhibits cartilage‑degrading enzymes and reduces inflammation Healthline.

3. Undenatured Type II Collagen (UC‑II) (40 mg/day) – Modulates immune response in joint tissues Arthritis Foundation.

4. Hydrolyzed Type II Collagen (2.5–15 g/day) – Provides amino acids for cartilage repair and anti‑inflammatory peptides PMC.

5. Vitamin C (500 mg/day) – Cofactor in collagen synthesis for tendon and bone matrix Reno Orthopedic Center.

6. Calcium (1,200 mg/day) – Mineral essential for bone health and repair AlgaeCal.

7. Zinc (15 mg/day) – Involved in collagen formation and wound healing Reno Orthopedic Center.

8. Vitamin K (90–120 µg/day) – Regulates bone‑mineral binding proteins for bone density Mass General Brigham.

9. Omega‑3 Fatty Acids (1,000 mg EPA/DHA daily) – Anti‑inflammatory effects mediated by eicosanoid modulation Health.

10. Cissus quadrangularis (500 mg twice daily) – Traditional plant extract shown to enhance bone healing by stimulating osteoblast activity Verywell Health.

Regenerative and Stem Cell Drugs

1. Leukocyte‑Rich PRP Injection (1–2 mL per session) – Delivers concentrated growth factors to promote tendon and bone healing; one session under ultrasound guidance PubMed.

2. Dorsal PRP Injection Technique (1 mL autologous PRP) – Novel dorsal approach for safe delivery to sesamoid complex, minimizing plantar nerve risk ClinMed Journals.

3. Bone Marrow Aspirate Concentrate (BMAC) (3–5 mL) – Rich in mesenchymal stem cells to regenerate soft tissue and bone orthoeast.com.

4. Adipose‑Derived Stem Cell Injection (5 mL stromal vascular fraction) – Stromal cells support tissue repair through paracrine signaling finalkickafc.com.

5. Allogeneic Amniotic Stem Cell Allograft (1–2 mL) – Provides growth factors and extracellular matrix proteins for soft tissue healing finalkickafc.com.

6. Combined PRP + Stem Cell Therapy (1 mL PRP then 5 mL stem cells) – Synergistic effect harnesses both growth factors and stem cells for comprehensive regeneration bennettorthosportsmed.com.

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Surgical Procedures

1. Total Sesamoidectomy

   • Procedure: Complete removal of the symptomatic sesamoid under the big toe joint.

   • Benefits: Resolves persistent pain when conservative care fails cortho.org.

2. Partial (Fibular) Sesamoidectomy

   • Procedure: Excision of only the fibular sesamoid, sparing medial piece.

   • Benefits: Maintains some joint stability, with high success and low complication rates PMC.

3. Sesamoid Condylectomy

   • Procedure: Resection of the metatarsal head condyle adjacent to the sesamoid.

   • Benefits: Offloads pressure, treats plantar keratosis, preserves joint function PMC.

4. Metatarsal Osteotomy

   • Procedure: Surgical cut in the first metatarsal (e.g., Youngswick) to shift weight off the sesamoid.

   • Benefits: Redistributes forefoot load without bone removal PMC.

5. Scarf Osteotomy with Sesamoid Resection

   • Procedure: Diaphyseal cut in the first metatarsal combined with partial sesamoid removal.

   • Benefits: Corrects concomitant hallux valgus and offloads sesamoids PMC.

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Prevention Strategies

1. Wear Proper‑Fitting Athletic Shoes equipped with firm heel cups and forefoot support to distribute weight evenly syracusepodiatry.org.

2. Use Custom Orthotic Insoles or Morton’s extension to cushion and offload the sesamoid area PowerStep.

3. Avoid High Heels and Narrow Toe Boxes that concentrate pressure on the forefoot syracusepodiatry.org.

4. Control Pronation with supportive footwear or inserts to prevent excessive inward rolling syracusepodiatry.org.

5. Apply Metatarsal Pads to lift and offload the sesamoid bones during activity Insoles.com.

6. Limit High‑Impact Sports when experiencing early forefoot pain; cross‑train with low‑impact exercises PowerStep.

7. Strengthen Intrinsic Foot Muscles through targeted exercises to support the arch Bayshore Podiatry Center.

8. Gradually Increase Training Intensity by no more than 10% per week to avoid overload Bayshore Podiatry Center.

9. Incorporate Shock‑Absorbing Insoles when running on hard surfaces Insoles.com.

10. Maintain a Healthy Weight to reduce chronic forefoot load Bayshore Podiatry Center.

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When to See a Doctor

Seek professional evaluation if you experience:

• Pain or swelling persisting beyond 2 weeks despite rest and home measures Bayshore Podiatry Center.

• Inability to bear weight or walk without significant pain Bayshore Podiatry Center.

• Signs of infection (redness, warmth, fever).

• Suspected acute fracture (sudden sharp pain after injury).
  Early diagnosis and imaging (X‑ray, bone scan, MRI) can distinguish bipartite variation from stress fractures OrthoInfo.

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What to Do and What to Avoid

Do:

• Rest and apply ice 15 minutes every 2–3 hours.

• Wear stiff‑soled, supportive footwear MyHealth Alberta.

• Use OTC NSAIDs as directed and physical therapy exercises md3footandankle.com.

Avoid:

• High‑impact activities (running, jumping) until pain-free.

• Walking barefoot on hard surfaces.

• Tight, narrow shoes and prolonged standing on tiptoes.

• Unsupervised corticosteroid injections (risk tendon damage).

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Frequently Asked Questions (FAQs)

1. What causes bipartite sesamoid pain?
   Overuse, repetitive forefoot loading, and poor biomechanics Cleveland Clinic.

2. Is a bipartite sesamoid the same as a fracture?
   No—bipartite has smooth margins, whereas fractures have jagged edges on X‑ray OrthoInfo.

3. Can bipartite sesamoid be asymptomatic?
   Yes, most cases never cause pain and are incidental findings.

4. How long does conservative healing take?
   4–8 weeks with rest, orthotics, and NSAIDs.

5. Are orthotics always required?
   Custom or OTC insoles are recommended for better offloading but not mandatory if pain resolves.

6. Will removal of one sesamoid affect toe function?
   Partial excision preserves function; total removal may slightly alter push‑off strength PMC.

7. When is surgery indicated?
   After >3 months of failed conservative therapy with persistent pain PMC.

8. Is PRP therapy covered by insurance?
   Generally not; it’s an out‑of‑pocket expense.

9. Can I return to sports after PRP?
   Many athletes return in 6–9 weeks post‑PRP injection PubMed.

10. What are risks of corticosteroid injection?
    Tendon weakening, local fat atrophy, transient flare.

11. Do supplements replace medications?
    No—supplements can support healing but not replace anti‑inflammatories.

12. Can I self‑diagnose with online images?
    No—only a medical professional can differentiate bipartite from fracture.

13. Is MRI ever needed?
    Only if X‑rays are inconclusive and symptoms persist despite treatment OrthoInfo.

14. How often can NSAIDs be taken?
    Follow label—never exceed maximum daily dose.

15. Can prevention eradicate risk?
    Proper footwear and training adjustments greatly reduce—but not eliminate—the chance.

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Last Updated: July 20, 2025.

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