High Yield Topics

Sesamoid Dysfunction

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Ovid: 5-Minute Sports Medicine Consult, The


Sesamoid Dysfunction
Laura Distel
James R. Borchers
Basics
  • Anatomy:
    • 2 sesamoid bones, the larger tibial (medial) sesamoid and fibular (lateral) sesamoid
    • Located on the plantar side of the 1st metatarsophalangeal (MTP) joint, just proximal to the metatarsal head, embedded within the flexor hallucis brevis tendon and connected by the intersesamoid ligament
    • The sesamoids' articular surfaces are located dorsally and articulate with the plantar facets on the 1st metatarsal head
    • Blood supply is usually from a single artery, with a lack of significant secondary blood supply (which increases risk for nonunion of fractures) (1).
    • Can have multiple ossification centers that may lead to a bipartite sesamoid, which can be difficult to distinguish from an acute fracture (1)
    • Vitally important in the biomechanics of the foot
    • When the 1st MTP joint dorsiflexes, the sesamoids are pulled distally, covering and protecting the plantar surface of the 1st metatarsal head and absorbing the weight-bearing forces on the medial aspect of the forefoot.
    • Flexor hallucis brevis provides the active plantarflexion force at the 1st MTP joint, but the sesamoid complex provides an increased mechanical advantage in plantarflexion.
  • Sesamoid function:
    • Protect the tendon of the flexor hallucis longus
    • Absorb a majority of the weight on the medial aspect of the forefoot:
      • Sesamoid bones bear up to 3 times body weight during normal gait.
      • Medial (or tibial) sesamoid bears the majority of this weight and thus is at higher risk for injury.
    • Dissipate the forces on the metatarsal head
    • Increase the power of the flexor hallucis brevis and thus plantarflexion (1)
Description
  • Stress fractures:
    • Most common sesamoid pathology (1)
    • More common in athletes than in general population (2)
  • Sesamoiditis:
    • Generic term that encompasses multiple conditions including osteonecrosis, chondromalacia, or inflammatory changes (1)
    • Usually involves the medial (tibial) sesamoid (1)
  • Acute fracture:
    • Typically caused by forced dorsiflexion (1)
    • Often a transverse fracture line with sharp edges (3)
Epidemiology
  • Sesamoiditis is seen more commonly in young, active adults.
  • Stress fractures are more common in athletes.
Risk Factors
  • Repetitive, forceful dorsiflexion, or loading (pushing off) of the MTP joint
  • At-risk sports include dancing (especially ballet), running, gymnastics, volleyball, basketball, high-impact aerobics, and soccer (1).
  • Asymmetrical sesamoids
  • Pes cavus (3)
  • Playing on artificial turf (1)
  • Wearing shoes without adequate forefoot support, ie, high heels
General Prevention
  • Wearing shoes with adequate forefoot support
  • Use of orthotics to offload the 1st MTP joint
Diagnosis
History
  • Gradual onset of pain on the plantar surface of the hallux.
  • Pain with dorsiflexion or weight-bearing (1).
  • Unilateral symptoms are typical.
  • Pain typically is located at the medial sesamoid.
  • Acute fracture usually occurs with a history of hyperextension injury of the big toe (1).
Physical Exam
  • Tenderness with direct palpation of the sesamoids ± swelling or ecchymosis
  • Pain with resisted plantarflexion of the hallux
  • Pain with passive dorsiflexion of the 1st MTP
  • Pain with “pushing off” while walking or running
  • Decreased range of motion and/or strength of the 1st MTP
  • Occasional erythema or swelling of the sesamoids
  • An enlarged bursa on the plantar surface may be present
  • Presence of significant pes cavus, pes planus, or cock-up deformity of the hallux
Diagnostic Tests & Interpretation
Imaging
  • X-ray examination of the foot should include weight-bearing anteroposterior, lateral, medial, and lateral oblique views. Comparison views of the contralateral foot may be helpful (2)[A].
  • If possible, an axial view of the 1st MTP joint in dorsiflexion, known as the “sesamoid view” (2)[A]:
    • Presence of a bilateral bipartite sesamoid is more likely a normal variant rather than an acute fracture; acute fractures are almost always unilateral.
    • A bipartite sesamoid may be seen in ∼25% of the population.
    • 85% of bipartite sesamoids are bilateral (1)
    • An acutely fractured sesamoid is characterized by sharp, irregular edges, comminution, or widely spaced fragments in contrast to the sclerotic edges of a nonunion or the smooth edges of a bipartite sesamoid (1)
    • MRI is more specific in diagnosing sesamoid disorders because it can differentiate soft tissue from bony abnormalities (4)[C].
  • Bone scan may show a stress fracture or osteochondritis before radiographically evident (5)[C]; can help differentiate a bipartite sesamoid from an acute fracture because a bipartite sesamoid will have a normal bone scan (1).
  • Also can also consider CT scan for evaluation of acute or stress fracture (2)[C]

P.531


Differential Diagnosis
  • Turf toe
  • Flexor hallucis longus tendonitis
  • Hallus rigidus
  • Hallus valgus
  • Neuroma
  • Metatarsalgia
  • Osteochondritis (more common in young women)
  • Osteoarthritis or inflammatory arthritis
  • Osteonecrosis
  • Avascular necrosis of the sesamoids
  • Neoplasm
  • Nerve impingement (less common)
  • Nonunion of a sesamoid fracture
Treatment
  • Sesamoiditis or stress fracture/nonunion:
    • Initially, conservative therapy is recommended (1)[A]:
      • Relative rest with immobilization by offloading the 1st MTP complex with orthotics, a dancer's pad, or metarsal bar; taping the great toe in plantarflexion may be considered for severe symptoms. This may require 4–6 wks of such treatment for adequate relief of symptoms (3)[A].
      • Ice
      • Pain control (oral NSAIDs or other analgesics) (3)[C]
      • Rarely, injections with corticosteroids can be considered (3)
      • Avoid wearing high-heeled shoes.
    • Long-term treatment includes:
      • Correction of any mechanical abnormalities with the use of taping, orthotics, or a stiff-soled shoe to limit dorsiflexion of the 1st MTP joint
      • Eliminating or minimizing the stressing activity (1)[C]
      • Surgery, usually to excise the sesamoid, prolonged symptoms despite several months of conservative management (see below).
  • Acute fractures:
    • Non-weight-bearing immobilization with a short-leg cast/AFO for 6–8 wks, followed by protected weight-bearing in cast/AFO for 4–6 additional weeks (2)[B]
    • Open reduction and internal fixation is controversial.
    • Percutaneous fixation may be an option (2)[B].
Surgery/Other Procedures
Surgical options are available if nonoperative treatment fails, but mechanical defects can lead to long-term problems.
  • Sesamoidectomy (surgical excision) (1):
    • Most common procedure for sesamoid pathology
    • Can be partial or complete
    • Can result in overload of the metatarsal head or flexor hallucis longus tendon
    • Excision of both sesamoids generally is not recommended owing to development of cock-up deformity and biomechanical morbidity (1).
  • Curettage and bone grafting (1)
  • Shaving of the sesamoid (1)
Ongoing Care
  • Custom orthotics ± cutouts for the sesamoid bones (3)
  • Short-leg walking cast can be considered for recalcitrant cases (1).
  • Corticosteroid injection into the sesamoid area can be considered with caution.
Follow-Up Recommendations
  • Periodic follow-up every 4–8 wks until the patient is asymptomatic
  • Continued modification of activities and use of orthotics
  • Referral to orthopedic surgeon or podiatrist if symptoms persist >6 mos
Prognosis
  • Conservative management generally is successful in treating most sesamoid pathology.
  • More severe cases that require surgical intervention are at risk for iatrogenic complications.
Complications
  • Nonunion of fractures
  • Development of stress fractures or avascular necrosis in untreated sesamoiditis
References
1. Dedmond BT, Cory JW, McBryde A. The hallucal sesamoid complex. J Am Acad Orthop Surg. 2006;14:745–753.
2. Mittlmeier T, Haar P. Sesamoid and toe fractures. Injury. 2004;35(Suppl 2):SB87–SB97.
3. Cohen BE. Hallux sesamoid disorders. Foot Ankle Clin. 2009;14:91–104.
4. Waizy H, Jäger M, Abbara-Czardybon M, et al. Surgical treatment of AVN of the fibular (lateral) sesamoid. Foot Ankle Int. 2008;29:231–236.
5. Garrido IM, Bosch MN, González MS, et al. Osteochondritis of the hallux sesamoid bones. Foot Ankle Surg. 2008;14:175–179.
Codes
ICD9
  • 733.99 Other disorders of bone and cartilage
  • 825.20 Fracture of unspecified bone(s) of foot (except toes), closed
Clinical Pearls
  • Medial sesamoid is injured most commonly.
  • Acute fractures are almost exclusively unilateral.
  • Bilateral bipartite sesamoids are usually benign.
  • Tenderness over the sesamoids or pain with dorsiflexion that improves with non-weight-bearing should arise suspicion for sesamoid pathology.
  • Nonoperative treatment, especially immobilization, is the mainstay of therapy.


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