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Accessory Navicular Syndrome

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Other Names

  • Os Naviculare Syndrome
  • Accessory Navicular Syndrome

Background

History

Epidemiology

  • Incidence
    • Incidence of accessory navicular is approximately 4%[1]
    • Another study estimates incidence between 2% and 14%[2]

Pathophysiology

  • General
    • Accessory Navicular: congenital anomaly in which the tuberosity of the navicular develops from a secondary ossification center

Etiology

  • Symptoms can occur due to
    • Tension, shearing, or compression forces transmitted through the posterior tibial tendon to the fibrocartilaginous interface
    • Shoe pressure on the accessory bone
    • Most often occurs after trauma
      • One study found 74% of athletes, 39% of non-athletes had a traumatic event[3]
      • For example twisting injury, abnormal midfoot biomechanics, and posterior tibial tendon pathology.

Associated Conditions

  • Pes Planus
    • This is contentious and not agreed upon in the literature
    • Incidence ranges from 15% to 34%[3]
  • Achilles Tendon Contracture
  • Gastrocnemius Contracture

Pathoanatomy

  • Os Navicular
    • Accessory navicular is one of the most common accessory ossicles
    • Can be divided into three types[4]
  • Type I
    • Small ossicle that is embedded within the distal fibers of the posterior tibialis tendon
    • Near its insertion point on the navicular tuberosity
  • Type II
    • Most common
    • Larger fragment with a distinct interface or synchondrosis
    • Composed of cartilaginous or fibrous tissue adjacent to the main navicular
  • Type III
    • Cornuate-shaped or partially fused to the main navicular
    • Representing enlargement of the medial aspect of the tuberosity.

Risk Factors

  • Unknown

Differential Diagnosis


Clinical Features

  • History
    • Tends to occur in younger athletes
    • Pain is typically along the medial arch
    • Impingement in the area of the sinus tarsi especially if pes planus is present
    • Direct pressure from shoes or cleats may worsen
    • Direct trauma or a sprain mechanism is common, occurring in 35% of patients[5]
    • Symptoms are worse with walking, running and training[3]
  • Physical Exam: Physical Exam Foot
    • Inspect for hindfoot valgus, pes planus, midfoot abduction
    • Inspect shoes for exaggerated wear of the medial portion of the sole
    • Tenderness along the accessory navicular is often present
  • Special Tests

Evaluation

Radiographs

  • Standard Radiographs Foot
    • Weight bearing radiographs are initial imaging modality of choice
  • External oblique view
    • Can better characterize the size and appearance of the accessory navicular.
    • Proximal retraction of the accessory navicular can indicate possible avulsion injury through the synchondrosis.
  • Findings
    • Main body of the navicular itself is typically much wider with increased medial protrusion compared with controls[6]
    • May also see pes planus, decreased calcaneal pitch, talonavicular uncoverage, and sag of the talo–first metatarsal angle

MRI

  • Most valuable imaging modality
  • Findings[7]
    • Edema in the accessory ossicle itself as well as the medial edge of the navicular.
    • Fluid or edema within the synchondrosis itself, indicating a stress reaction or possible sprain injury
    • Can also evaluate distal aspect of the posterior tibialis tendon for any tendon damage or injury.

Ultrasound

  • Potential findings
    • May indicate instability or hypermobility of the accessory bone.
    • Thickening or tendinosis of the posterior tibialis tendon

CT

  • Useful to determine if a seeming accessory navicular is an acute avulsion fragment.

Bone Scintography

  • Not commonly used
  • May show increased uptake at the medial edge of the navicular, consistent with stress reaction

Classification

  • Not applicable

Management

Nonoperative

  • Indications
    • Most patients, especially athletes[8]
  • Activity restriction
    • Restriction from running and training
    • Avoidance of activities that exacerbate symptoms are initiated.
  • Other therapy
  • Orthotics
    • Insoles with medial arch posting may relieve stress on the synchondrosis and distal posterior tibialis tendon
    • Often necessary to incorporate a relief underneath the accessory navicular to relieve direct pressure on it
  • Heel Wedge
    • Medial heel wedge can be beneficial, especially if hindfoot valgus is present
  • Immobilization
  • Physical Therapy
    • Emphasis on motion and strengthening
    • Cardio training and conditioning

Operative

  • Indications
    • Failure of conservative management
    • For athletes, consideration of in-season vs off-season depending on severity of symptoms
  • Technique
    • Kidner procedure (excise accessory bone, advance posterior tibialis tendon)
    • Percutaneous drilling of the accessory navicular and synchondrosis
    • Open fusion of the accessory bone to the main body
    • Gastrocnemius recession or Achilles tendon lengthening can be considered

Rehab and Return to Play

Rehabilitation

  • Postoperative
    • Immobilized in Short Leg Cast or Short Leg Boot for up to 6 weeks
    • Weight bearing advanced along with range of motion, open chain strengthening
    • Around 8-10 weeks, initiate heavier resistance training and closed chain exercises
    • Also return to normal footwear around 8-10 weeks, plus/minus orthotic
    • Return to unrestricted sporting activity around 5-6 months

Return to Play/ Work

  • Needs to be updated

Complications and Prognosis

Prognosis

  • Nonoperative treatment outcomes
    • Appears to have a relatively low success rate
    • Kopp et al: nonoperative treatment was successful in only 7% of athletes, 34% of nonathletes[3]
    • Grogen et al: resolution in only 2/10 patients treated with a cast, 0/6 in patients treated with custom orthotics[9]
  • Surgical outcomes
    • Veitch et al: 17/21 patients reported good outcome following the Kidner procedure[4]
    • Ray and Goldberg found 90% excellent or good results at 2 years or longer follow-up.[10]

Complications

  • Inability to return to sport

See Also


References

  1. Lawson JP, Ogden JA, Sella E, et al. The painful accessory navicular. Skeletal Radiol 1984;12(4):250–62.
  2. Bizarro AH. On sesamoid and supernumerary bones of the limbs. J Anat. 1921;55(pt 4):256-268.
  3. 3.0 3.1 3.2 3.3 Jegal H, Park YU, Kim JS, et al. Accessory navicular syndrome in athlete vs general population. Foot Ankle Int 2016;37(8):862–7.
  4. 4.0 4.1 Veitch JM. Evaluation of the Kidner procedure in treatment of symptomatic accessory tarsal scaphoid. Clin Orthop Relat Res 1978;131:210–3.
  5. Chung JW, Chu IT. Outcome of fusion of a painful accessory navicular to the primary navicular. Foot Ankle Int 2009;30(2):106–9.
  6. Seehausen DA, Harris LR, Kay RM, et al. Accessory navicular is associated with wider and more prominent navicular bone in pediatric patients by radiographic measurement. J Pediatr Orthop 2016;36(5):521–5.
  7. Miller TT, Staron RB, Feldman F, et al. The symptomatic accessory tarsal navicular bone: assessment with MR imaging. Radiology 1995;195(3):849–53.
  8. Kopp FJ, Marcus RE. Clinical outcome of surgical treatment of the symptomatic accessory navicular. Foot Ankle Int 2004;25(1):27–30.
  9. Grogan DP, Gasser SI, Ogden JA. The painful accessory navicular: a clinical and histopathological study. Foot Ankle. 1989;10(3):164-169.
  10. Ray S, Goldberg VM. Surgical treatment of the accessory navicular. Clin Orthop Relat Res. 1983;177:61-66.
Created by:
John Kiel on 30 January 2022 07:30:46
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Last edited:
4 October 2022 12:37:27
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