Accessory Navicular Bone: Difference between revisions

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'''Original Editors ''' - [[User:Carlos De Coster|Carlos De Coster]]  
'''Original Editors ''' - [[User:Carlos De Coster|Carlos De Coster]] as part of the [[Vrije Universiteit Brussel Evidence-based Practice Project|Vrije Universiteit Brussel Evidence-Based Practice Project]]


'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}}  
'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}}  
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== Definition/Description  ==
== Introduction ==
[[File:Normal-Navicular-and-Accessory-Navicular.jpg|alt=|right|241x241px]]
An accessory navicular is a large accessory ossicle that can be present adjacent to the medial side of the [[Navicular|navicular bone]]. The accessory navicular [[bone]] presents as a [[sesamoid]] in the [[Tibialis Posterior|posterior tibial tendon]], in articulation with the navicular<ref name="p1">Raymond T., Morrissy and Stuart L.Weinstein .Lovell, Winter’s Padiatric Orthopaedics. United States: Lippincot William’s  Wilkin Publication, 2005.</ref> or as an enlargement of the navicular itself.


Also known as '''Prehallux, Os Tibiale Externum and Navicular Secundum'''.  
== Epidemiology ==
[[File:Foot superior.png|thumb|200x200px|Navicular bone green ]]
The prevalence of an accessory navicular bone is ~10% (range 4-21%), although may be substantially higher (~45%) in Asian populations.


An accessory navicular bone is an accessory bone of the foot that occasionally develops abnormally causing a&nbsp;plantar medial enlargement of the navicular. The accessory navicular bone presents as a sesamoid in the posterior tibial tendon, in articulation with the navicular<ref name="p1">Raymond T., Morrissy and Stuart L.Weinstein .Lovell, Winter’s Padiatric Orthopaedics. United States: Lippincot William’s  Wilkin Publication, 2005.</ref> or as an enlargement of the navicular.<br>  
* Appears first in adolescence
* Is common in female patients
* Bilateral prevalence is ~70% (range 50-90%)<ref name=":0">Radiopedia Accessory navicular Available:https://radiopaedia.org/articles/accessory-navicular-2?lang=us (accessed 8.6.2022)</ref>


[[Image:Normal-Navicular-and-Accessory-Navicular.jpg|423x264px]]
== Classification ==
[[File:Os-naviculare-diagrams-1.jpeg|right|frameless]]
The Geist classification divides these into three types:


The Geist classification divides these into three types:
# sesamoid bone in the posterior tibialis tendon. There is a small gap of approximately 3mm or less between the sesamoid and the navicular.
 
# consists of an accessory bone, up to 1.2cm in diameter, where synchondrosis develops between it and the navicular.
'''Type I:''' is sesamoid bone in the posterior tibialis tendon. There is a small distance (&lt;3mm) between the sesamoid and the navicular.
# is the fused accessory navicular resulting in a large cornuate shaped navicular<ref name=":0" />.<br>
 
[[Image:Type I AN dia.PNG]][[Image:TYPE I AN X RAY.jpg]]
 
'''Type II:''' consists of an accessory bone, up to 1.2cm in diameter, in which a synchondrosis exist between it and the navicular.
 
[[Image:Type II AN.PNG]][[Image:TypeIIAccessoryNavicular.jpg|251x231px]]
 
'''Type III:''' is the fused accessory navicular to the navicular resulting in large cornuate navicular.<br>  
 
[[Image:TYPE III AN.PNG]] [[Image:TYPE III ACCESSORY N. X RAY.PNG|231x241px]]


== Clinically Relevant Anatomy  ==
== Clinically Relevant Anatomy  ==
[[File:Tibialis-posterior-tendon-anatomy.jpg|right|frameless|350x350px]]
An accessory navicular bone is located posterior to the posteromedial tuberosity of the tarsal navicular bone. The tibialis posterior tendon inserts into the navicular bone. Tibialis posterior is an inverter of the foot, assists in the plantar flexion of the foot at the [[Ankle and Foot|ankle]] and also has a major role in supporting the medial [[Arches of the Foot|arch]] of the foot.&nbsp; This can be compromised where there exists an abnormal insertion of the tendon into the accessory navicular bone  and result in a loss of suspension of the tibialis posterior tendon<ref name="p4">Golano P., ‘The anatomy of the navicular and periarticular structures.’ Foot Ankle Clinics, 2004, March, vol. 9, p. 1-23.</ref><ref name="p5">Kiter E., Erdan N., Karatosun V., Gunall I., ‘Tibialis posterior tendon abnormalities in feet with accessory navicular bone and flatfoot’. Acta orthopaedica Scandinavia, 1999, December, vol. 70, p. 618-621</ref><ref name="p6" /><ref name="p7">Kidner FC. The prehallux (accessory scaphoid) in its relation to flat-foot. J Bone Joint Surg 1929 : II : 831</ref>. <br>The presence of a type I or II accessory navicular is also a cause of [[Posterior Tibial Tendon Dysfunction|Posterior Tibial tendinopathy]] as the insertion of the tibialis posterior tendon onto the accessory navicular is more proximal. Leverage of the malleolus on the tibialis posterior tendon is reduced increasing stress on the tendon. <ref name="p9">A. Bernaerts, F.M. Vanhoenacker, S. Van de Perre, A.M. De Schepper, P.M. Parizel1 Accessory navicular bone: Not Such a normal variant. JBR–BTR, 2004, 87 (5) page 250-252</ref> The calcaneal pitch angle is also reduced in patients with a symptomatic accessory navicular than in normal subjects.<ref name="p0">Prichausuk S, Sinphurmsukskul O: Kinder Procedure for symptomatic accessory navicular and its relation to pes planus, Foot Ankle 16:500,1995</ref>


[[Image:Foot accessory navicular CLINICAL ANATOMY 1 anat01.jpg|350x231px]] [[Image:Foot accessory navicular clinical anatomy 2.jpg|297x219px]]
== Clinical Presentation ==
[[File:Lateral_veiw_AN.jpg|alt=|thumb|179x179px|Lateral view AN]]
Most of the time it is asymptomatic and found incidentally on radiographs, although medial side foot pain (accessory navicular syndrome) is the most common presenting feature of accessory navicular bone. The pain is aggravated by walking, running and weight-bearing activities. When large, it can protrude medially and cause friction against footwear<ref name=":0" />.


Navicular (boat shaped) is an intermediate tarsal bone on the medial side of the foot.<ref name="p3">D.Richard, V.Wayne, M. Adam, Gray’s Anatomy for Students. Spain: Elsevier Publishers, 2005</ref> It is located on the medial side of the foot, and articulates proximally with the talus. Distally it articulates with the three cuneiform bones. In some cases it articulates laterally with the cuboid. The tibialis posterior inserts to the os naviculare.<ref name="p4">Golano P., ‘The anatomy of the navicular and periarticular structures.’ Foot Ankle Clinics, 2004, March, vol. 9, p. 1-23.</ref> The tibialis posterior muscle also contracts to produce inversion of the foot and assists in the plantar flexion of the foot at the ankle. Tibialis posterior also has a major role in supporting the medial arch of the foot.&nbsp;<sup><ref name="p5">Kiter E., Erdan N., Karatosun V., Gunall I., ‘Tibialis posterior tendon abnormalities in feet with accessory navicular bone and flatfoot’. Acta orthopaedica Scandinavia, 1999, December, vol. 70, p. 618-621</ref> </sup>This supports is compromised by abnormal insertion of the tendon into the accessory navicular bone when present.&nbsp;<ref name="p6"/> <ref name="p7">Kidner FC. The prehallux (accessory scaphoid) in its relation to flat-foot. J Bone Joint Surg 1929 : II : 831</ref>This lead to loss of suspension of tibialis posterior tendon and may cause peroneal spastic pes planus or simple pes planus. But, yet a cause and effect relationship between the accessory navicular and pes planus is doubtful and is yet unproved clearly.<ref name="p8">Kidner FC. Pre-hallux in relation to flatfoot. JAMA 1933; 101: 1539-42.</ref><br>
== Differential Diagnosis ==
 
The presence of accessory navicular 2 or 3 is also a cause of PTT tendinopathy as the insertion of PTT on accessory navicular leads to its proximal insertion (dashed line). Here by the leverage of malleolus on the PTT is reduced and therefore stress on the tendon increase. <ref name="p9"/>
 
[[Image:ANGLE CHANGE IN AN.PNG]]
 
There also occurs calcaneal pitch angle lowering in patients with with symptomatic accessory navicular than in normal subjects.<ref name="p0">Prichausuk S, Sinphurmsukskul O: Kinder Procedure for symptomatic accessory navicular and its relation to pes planus, Foot Ankle 16:500,1995</ref>
 
== Epidemiology /Etiology  ==
 
The foot and ankle have numerous accessory ossification centres. But the most common is accessory tarsal navicular bone occurring between 4-14% of population.&nbsp;<ref name="p1"/><ref name="p2">Shands AR Jr, Wentz IJ. Congenital anomalies, accessory bones and osteochondritis in the feet of 850 children. Surg.Clin.North Am 1953:97:1643-1666</ref><ref name="p3"/>
 
*an accessory navicular bone is present in ~10% of the population
*first appears in adolescence.  In children its incidence is 4-21% of the population.<ref name="p9">A. Bernaerts, F.M. Vanhoenacker, S. Van de Perre, A.M. De Schepper, P.M. Parizel1 Accessory navicular bone: Not Such a normal variant. JBR–BTR, 2004, 87 (5) page 250-252</ref>&nbsp;
*more common in female patients<ref name="p1"/>
*reported prevalence bilaterally is ~70% (range 50-90%)
 
People who have an accessory navicular often are unaware of the condition if it causes no problems. However, some people with this extra bone develop a painful condition known as accessory navicular syndrome when the bone and/or posterior tibial tendon are aggravated. This can result from any of the following:
 
*Trauma, as in a foot or ankle sprain
*Chronic irritation from shoes or other footwear rubbing against the extra bone
*Excessive activity or overuse
 
[[Image:Causes AN.jpg]]
 
== Characteristics/Clinical Presentation  ==
 
*Typical young female (10-20 years of age) complaining of mid food/arch pain which may be insidious or post trauma
*Difficulty with footwear
*Prominent navicular
*Tenderness over the prominence
*Pain over the posterior tibialis tendon from a tendinitis and tightness of the tendo-achillis in long standing cases
*Often pes planus
*Inflamed bursa
 
== Differential Diagnosis ==


*Stress fracture  
*Stress fracture  
*Tendinitis
*Tendinopathy
*Medial tuberosity fracture <ref name="p5"/>  
*Medial tuberosity fracture <ref name="p5" />  
*Cartilage forming bone Tumor  
*Bone Tumor  
*Kohler’s disease <ref name="p6"/><br>
*Kohler’s disease <ref name="p6" /><br>


== Diagnostic Procedures  ==
== Diagnostic Procedures  ==
[[File:AP_veiw_AN.jpg|alt=|thumb|337x337px|AP veiw AN]]
Radiographs show a medial navicular eminence that is best visualized on the lateral-oblique view. Symptomatic accessory navicular bones may appear as a 'hot spot' on bone scan and on MRI bone marrow edema can be seen<ref name=":0" />.


*Routine standing AP and lateral view are enough to look for accessory navicular but in some cases oblique view is also obtained in order to completely define the abnormality of navicular. Bilateral films may be indicated as there occurs high incidence of symmetrical abnormalities.
When examining the lateral weight bearing X-ray, alignment of the talonavicular cuneiform and first metatarsal dorsal should be carefully examined as well. [[Navicular Drop Test|“Sag”]] at this joint indicates structural integrity of the area.
*On lateral weight bearing/standing film, the talonavicular cuneiform first metatarsal dorsal alignment should be carefully examined. “Sag” at this joint indicates structural integrity of the area.<br>
*MRI or CT is indicated (very rare) in order to exclude tumor, fracture of medial tuberosity, bone marrow edema. <br>
 
[[Image:AP veiw AN.jpg|234x337px]] AP View [[Image:Lateral veiw AN.jpg|223x336px]]Lateral View [[Image:Oblique veiw AN.jpg|190x331px|oblique view]] Oblique View
 
== Outcome Measures  ==
 
add links to outcome measures here (also see [[Outcome Measures|Outcome Measures Database]])


== Examination  ==
== Examination  ==
[[File:Oblique_veiw_AN.jpg|alt=|thumb|Oblique view AN]]
Patients with an accessory navicular may present with complex pain patterns requiring a thorough examination.&nbsp;<ref name="p7" /> The examination should include key assessments:


Patient with accessory navicular may present with complex pain patterns requiring thorough examination.&nbsp;<ref name="p7"/> The examination importantly includes
*Differentiation of the navicular prominence from the [[Talus|talar]] head prominence in flat foot deformities by inverting and everting through the subtalar joint with a thumb over the bony prominence.<ref name="p8">Kidner FC. Pre-hallux in relation to flatfoot. JAMA 1933; 101: 1539-42.</ref>
 
*Assessing for any loss of structural integrity of the longitudinal arch is important as this component of the deformity will not be corrected by surgical intervention.  Surgery is performed to correct navicular deformity and is dependent on the severity of symptoms when conservative management has not been successful (see interventions below). <ref name="p9" />  
*Differentiation of navicular prominence from talar head prominence in flat foot deformity by inverting and everting through the subtalar joint with a thumb over the bony prominence.<ref name="p8"/>  
*Thorough [[gait]] examination.<br>
*Recognition of the loss of structural integrity of the longitudinal arch is important because this component of the deformity will not be corrected by surgical treatment if required. <ref name="p9"/>  
*Thought examination of gait.<br>


== Medical Management  ==
== Medical Management  ==


'''CONSERVATIVE:'''
Conservative:  


#Physical therapy  
#Physical therapy  
#Medications. Oral nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, may be prescribed. In some cases, oral or injected steroid medications may be used in combination with immobilization to reduce pain and inflammation. <ref name="p9"/>
#Acute pain can be managed by corticosteroid injection and immobilization of the foot for 2-3 weeks. For refractory cases.<ref name=":0" />
 
[[File:Accessory_navicular_surgery.jpg|alt=|right|297x297px]]
'''SURGICAL:''' Depending upon the severity the non operative or conservative treatment should be maintained for at least 4- 6 months before any surgical intervention.  
Surgical management can be considered. There are 2 surgeries that can be performed depending upon the condition and symptoms  
 
# A simple surgical excision to remove the accessory navicular along with its prominence. In this procedure, the incision is made dorsally to the prominence of the accessory navicular. Symptoms are relieved in 90% of cases.<ref>Kulkarni. G.S. Textbook of orthopedics and trauma.India: Jaypee Brother Publication, 1999.&amp;lt;/ref&amp;gt;&amp;lt;ref name="p7"&amp;gt;Kidner FC. The prehallux (accessory scaphoid) in its relation to flat-foot. J Bone Joint Surg 1929 : II : 831</ref>
There are 2 surgeries that can be performed depending upon the condition and symptoms  
 
'''FIRST''' is simple surgical excision. In this generally the accessory navicular along with its prominence is removed. In this procedure, skin incision is made dorsally to the prominence of accessory navicular. Bone is removed to the point where the medial foot has no bony prominence over the navicular, between the head of the talus and first cuneiform. Symptoms are relieved in 90% of cases.<ref>Kulkarni. G.S. Textbook of orthopedics and trauma.India: Jaypee Brother Publication, 1999.&amp;lt;/ref&amp;gt;&amp;lt;ref name="p7"&amp;gt;Kidner FC. The prehallux (accessory scaphoid) in its relation to flat-foot. J Bone Joint Surg 1929 : II : 831</ref>
 
[[Image:Accessory navicular surgery.jpg|364x297px]]
 
'''SECOND''' is Kindler procedure.<ref name="p6">Kulkarni. G.S. Textbook of orthopedics and trauma.India: Jaypee Brother Publication, 1999</ref><ref name="p7"/> In this the ossicle and navicular prominence is excised as in simple excision but along with the posterior tibial tendon advancement. Posterior tibial tendon is split and advanced along the medial side of foot to provide support to longitudinal arch.
 
After surgery 4 week short leg cast, well moulded into the arch with the foot plantigrade is applied. Partial weight bearing till the 8th week and later full weight bearing is allowed.<ref name="p7"/><ref name="p9"/>. When the cast is being removed can start building up the ROM to counter atrophy and other physical therapy treatment which include stretching and strengthening exercises. <ref name="p8"/>
 
[[Image:CAST MOULDING.jpg|297x274px]][[Image:SHORT LEG CAST.jpg|347x261px]]
 
Occasionally, a limited fusion of the cuneiform metatarsal or talonavicular joints also was recommended. The rationale and efficacy of this operation have been questioned.
 
Arthrodesis may be a reasonable treatment option in selected cases of patients with symptomatic recalcitrant Type II accessory naviculars that are large enough to accept small fragment screws.<ref name="p1"/>


# The 2nd procedure excising the boney prominence in conjunction with reattachment of the posterior tibial tendon. .<ref name="p6">Kulkarni. G.S. Textbook of orthopedics and trauma.India: Jaypee Brother Publication, 1999</ref><ref name="p7" /> The posterior tibial tendon is split and is reattached further up the medial side of foot to provide increased support to the longitudinal arch.
After surgery the lower leg is put into a cast for 4 weeks, which is moulded into the shape of the arch, with the foot maintained in a plantigrade position. Partial weight bearing is indicated for 8 weeks after which full weight bearing is permitted.<ref name="p7" /><ref name="p9" />. Once the cast is removed, a strength and conditioning programme  is highly recommended. <ref name="p8" />
== Physical Therapy Management  ==
== Physical Therapy Management  ==
[[File:Download (2).jpg|thumb|Pes Plunus]]
If the accessory navicular bone becomes problematic, physical therapy may be prescribed. This includes use of therapeutic modalities to relieve pain, increase strength and stability in the foot. An accessory navicular bone is often linked to posterior tibial dysfunction and [[Pes Planus|pes planus]]. In some cases orthotics may be indicated. 


If the accessory navicular bone becomes problematic physical therapy may be prescribed. <br>  
*Well padded shoe orthotics should be worn for arch support. This decreases direct pressure over the navicular.
*Strength and conditioning exercises for the [[Peroneus (Fibularis) Longus Muscle|fibularis]] and posterior tibialis muscles.
*Strengthening of the intrinsic foot muscles and the lateral rotators of the pelvis.<ref name="p9" />
*Activity modification in the initial stages, such as limiting or stopping any strenuous activities which may cause the accessory navicular bone to become symptomatic.<ref name="p9" />
*Gait re-training and stability exercises.<br>


This will include use of therapeutic modalities which relieves pain include ultrasonic therapy, TENS, massage, ROM exercises and treatments to strengthen the intrinsic foot muscles and lateral thigh rotators muscles and decrease inflammation. Often is the accessory navicular bone linked to Posterior tibial dysfunction to a pes planus. To adjust the arch of the foot, orthotic devices may be used. <br>
Some examples of functional posterior tibialis strengthening:
 
<div class="row">
*Well padded shoe orthotic should be worn for arch support. This decrease direct pressure over the navicular.
  <div class="col-md-6">{{#ev:youtube|zmh1FisBeeM|300}} <ref>ShaychiITA. Tibialis Posterior Basic Strengthening. Available from: http://www.youtube.com/watch?v=zmh1FisBeeM [last accessed 24/11/12]</ref> </div>
*Stretching of peroneal and posterior tibialis along with strengthening exercises.
  <div class="col-md-6">{{#ev:youtube|qv76eBxGQXI|300}} <ref>ShaychiITA. Tibialis Posterior Basic Multiplanar Strengthening. Available from: http://www.youtube.com/watch?v=qv76eBxGQXI [last accessed 01/12/12]</ref></div>
*Strengthening the intrinsic foot muscles and lateral thigh rotators muscles and decrease inflammation.<ref name="p9"/>  
</div>
*Activity modification, such as limiting or stopping any strenuous activities that cause the Accessory Navicular bone to become symptomatic can be used for initial treatment.<ref name="p9"/>  
<div class="row">
*Gait training and Balance exercise for proper normal gait when required.<br><br>
  <div class="col-md-6">{{#ev:youtube|1C_C5N9reB8|300}}<ref>ShaychiITA. Tibialis Posterior Functional Strengthening: Full Body Weight Maintaining Supination. Available from: http://www.youtube.com/watch?v=1C_C5N9reB8[last accessed 01/12/12]|}</ref> </div>
 
  <div class="col-md-6">{{#ev:youtube|TdHgyFZbOPk|300}}<ref>ShaychiITA. Tibialis Posterior Functional Strengthening: Maintain Arch with Compass Squats. Available from: http://www.youtube.com/watch?v=TdHgyFZbOPk[last accessed 24/11/12]|}</ref></div>
Some examples of basic and functional posterior tibialis strengthening:
</div>
 
{| width="100%" cellspacing="1" cellpadding="1"
|-
| {{#ev:youtube|zmh1FisBeeM|300}} <ref>ShaychiITA. Tibialis Posterior Basic Strengthening. Available from: http://www.youtube.com/watch?v=zmh1FisBeeM [last accessed 24/11/12]</ref>  
| {{#ev:youtube|qv76eBxGQXI|300}} <ref>ShaychiITA. Tibialis Posterior Basic Multiplanar Strengthening. Available from: http://www.youtube.com/watch?v=qv76eBxGQXI [last accessed 01/12/12]</ref>
|-
| {{#ev:youtube|1C_C5N9reB8|300}}<ref> ShaychiITA. Tibialis Posterior Functional Strengthening: Full Body Weight Maintaining Supination. Available from: http://www.youtube.com/watch?v=1C_C5N9reB8[last accessed 01/12/12]|}</ref>  
| {{#ev:youtube|TdHgyFZbOPk|300}}<ref> ShaychiITA. Tibialis Posterior Functional Strengthening: Maintain Arch with Compass Squats. Available from: http://www.youtube.com/watch?v=TdHgyFZbOPk[last accessed 24/11/12]|}</ref>
|}
 
== Resources  ==
 
*


== Clinical Bottom Line  ==
== Clinical Bottom Line  ==


Usually the type I accessory navicular is rarely associated with symptoms and if the symptoms appears then it respond well to the conservative/ physical therapy management. Patients with Type II accessory navicular are at the risk for disruption either from traction injury or shear forces in the region and and mostly the onset is insidious or post trauma. It fails to respond to conservative treatment when severe and fusion of the accessory navicular to the navicular may successfully relieve pain without disrupting the tibialis posterior tendon insertion.<ref name="p2"/><br>  
A type I accessory navicular is rarely symptomatic. Where symptoms do appear, type I usually responds well to conservative management. Patients with Type II have an increased risk of injury and onset is usually insidious or as a result of trauma. It fails to respond to conservative treatment when severe and fusion of the accessory navicular to the navicular may successfully relieve pain without disrupting the tibialis posterior tendon insertion.<ref name="p2">Shands AR Jr, Wentz IJ. Congenital anomalies, accessory bones and osteochondritis in the feet of 850 children. Surg.Clin.North Am 1953:97:1643-1666</ref> With Type III, excising the accessory navicular is indicated over excising the navicular prominence.<ref name="p9" />  
 
Type III when symptomatic then excising the accessory navicular rather than excising navicular beak is more helpful.<ref name="p9"/>  


== References  ==
== References  ==
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<references />


[[Category:Foot]][[Category:Bones]][[Category:Musculoskeletal/Orthopaedics|Orthopaedics]][[Category:Vrije_Universiteit_Brussel_Project]][[Category:Foot_and_Ankle_Conditions]]
[[Category:Foot]]
[[Category:Bones]]
[[Category:Musculoskeletal/Orthopaedics|Orthopaedics]]  
[[Category:Anatomy]]
[[Category:Vrije_Universiteit_Brussel_Project]]
[[Category:Foot - Anatomy]]
[[Category:Foot - Bones]]

Latest revision as of 19:38, 21 April 2023

Original Editors - Carlos De Coster as part of the Vrije Universiteit Brussel Evidence-Based Practice Project

Top Contributors - Aarti Sareen, Admin, Carlos De Coster, Scott Cornish, Kim Jackson, Lucinda hampton, Laura Ritchie, WikiSysop, 127.0.0.1, Evan Thomas, Tony Lowe and Oyemi Sillo

Introduction[edit | edit source]

An accessory navicular is a large accessory ossicle that can be present adjacent to the medial side of the navicular bone. The accessory navicular bone presents as a sesamoid in the posterior tibial tendon, in articulation with the navicular[1] or as an enlargement of the navicular itself.

Epidemiology[edit | edit source]

Navicular bone green

The prevalence of an accessory navicular bone is ~10% (range 4-21%), although may be substantially higher (~45%) in Asian populations.

  • Appears first in adolescence
  • Is common in female patients
  • Bilateral prevalence is ~70% (range 50-90%)[2]

Classification[edit | edit source]

Os-naviculare-diagrams-1.jpeg

The Geist classification divides these into three types:

  1. sesamoid bone in the posterior tibialis tendon. There is a small gap of approximately 3mm or less between the sesamoid and the navicular.
  2. consists of an accessory bone, up to 1.2cm in diameter, where synchondrosis develops between it and the navicular.
  3. is the fused accessory navicular resulting in a large cornuate shaped navicular[2].

Clinically Relevant Anatomy[edit | edit source]

Tibialis-posterior-tendon-anatomy.jpg

An accessory navicular bone is located posterior to the posteromedial tuberosity of the tarsal navicular bone. The tibialis posterior tendon inserts into the navicular bone. Tibialis posterior is an inverter of the foot, assists in the plantar flexion of the foot at the ankle and also has a major role in supporting the medial arch of the foot.  This can be compromised where there exists an abnormal insertion of the tendon into the accessory navicular bone and result in a loss of suspension of the tibialis posterior tendon[3][4][5][6].
The presence of a type I or II accessory navicular is also a cause of Posterior Tibial tendinopathy as the insertion of the tibialis posterior tendon onto the accessory navicular is more proximal. Leverage of the malleolus on the tibialis posterior tendon is reduced increasing stress on the tendon. [7] The calcaneal pitch angle is also reduced in patients with a symptomatic accessory navicular than in normal subjects.[8]

Clinical Presentation[edit | edit source]

Lateral view AN

Most of the time it is asymptomatic and found incidentally on radiographs, although medial side foot pain (accessory navicular syndrome) is the most common presenting feature of accessory navicular bone. The pain is aggravated by walking, running and weight-bearing activities. When large, it can protrude medially and cause friction against footwear[2].

Differential Diagnosis[edit | edit source]

  • Stress fracture
  • Tendinopathy
  • Medial tuberosity fracture [4]
  • Bone Tumor
  • Kohler’s disease [5]

Diagnostic Procedures[edit | edit source]

AP veiw AN

Radiographs show a medial navicular eminence that is best visualized on the lateral-oblique view. Symptomatic accessory navicular bones may appear as a 'hot spot' on bone scan and on MRI bone marrow edema can be seen[2].

When examining the lateral weight bearing X-ray, alignment of the talonavicular cuneiform and first metatarsal dorsal should be carefully examined as well. “Sag” at this joint indicates structural integrity of the area.

Examination[edit | edit source]

Oblique view AN

Patients with an accessory navicular may present with complex pain patterns requiring a thorough examination. [6] The examination should include key assessments:

  • Differentiation of the navicular prominence from the talar head prominence in flat foot deformities by inverting and everting through the subtalar joint with a thumb over the bony prominence.[9]
  • Assessing for any loss of structural integrity of the longitudinal arch is important as this component of the deformity will not be corrected by surgical intervention. Surgery is performed to correct navicular deformity and is dependent on the severity of symptoms when conservative management has not been successful (see interventions below). [7]
  • Thorough gait examination.

Medical Management[edit | edit source]

Conservative:

  1. Physical therapy
  2. Acute pain can be managed by corticosteroid injection and immobilization of the foot for 2-3 weeks. For refractory cases.[2]

Surgical management can be considered. There are 2 surgeries that can be performed depending upon the condition and symptoms

  1. A simple surgical excision to remove the accessory navicular along with its prominence. In this procedure, the incision is made dorsally to the prominence of the accessory navicular. Symptoms are relieved in 90% of cases.[10]
  1. The 2nd procedure excising the boney prominence in conjunction with reattachment of the posterior tibial tendon. .[5][6] The posterior tibial tendon is split and is reattached further up the medial side of foot to provide increased support to the longitudinal arch.

After surgery the lower leg is put into a cast for 4 weeks, which is moulded into the shape of the arch, with the foot maintained in a plantigrade position. Partial weight bearing is indicated for 8 weeks after which full weight bearing is permitted.[6][7]. Once the cast is removed, a strength and conditioning programme is highly recommended. [9]

Physical Therapy Management[edit | edit source]

Pes Plunus

If the accessory navicular bone becomes problematic, physical therapy may be prescribed. This includes use of therapeutic modalities to relieve pain, increase strength and stability in the foot. An accessory navicular bone is often linked to posterior tibial dysfunction and pes planus. In some cases orthotics may be indicated.

  • Well padded shoe orthotics should be worn for arch support. This decreases direct pressure over the navicular.
  • Strength and conditioning exercises for the fibularis and posterior tibialis muscles.
  • Strengthening of the intrinsic foot muscles and the lateral rotators of the pelvis.[7]
  • Activity modification in the initial stages, such as limiting or stopping any strenuous activities which may cause the accessory navicular bone to become symptomatic.[7]
  • Gait re-training and stability exercises.

Some examples of functional posterior tibialis strengthening:

[11]
[12]
[13]
[14]

Clinical Bottom Line[edit | edit source]

A type I accessory navicular is rarely symptomatic. Where symptoms do appear, type I usually responds well to conservative management. Patients with Type II have an increased risk of injury and onset is usually insidious or as a result of trauma. It fails to respond to conservative treatment when severe and fusion of the accessory navicular to the navicular may successfully relieve pain without disrupting the tibialis posterior tendon insertion.[15] With Type III, excising the accessory navicular is indicated over excising the navicular prominence.[7]

References[edit | edit source]

  1. ↑ Raymond T., Morrissy and Stuart L.Weinstein .Lovell, Winter’s Padiatric Orthopaedics. United States: Lippincot William’s Wilkin Publication, 2005.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Radiopedia Accessory navicular Available:https://radiopaedia.org/articles/accessory-navicular-2?lang=us (accessed 8.6.2022)
  3. ↑ Golano P., ‘The anatomy of the navicular and periarticular structures.’ Foot Ankle Clinics, 2004, March, vol. 9, p. 1-23.
  4. ↑ 4.0 4.1 Kiter E., Erdan N., Karatosun V., Gunall I., ‘Tibialis posterior tendon abnormalities in feet with accessory navicular bone and flatfoot’. Acta orthopaedica Scandinavia, 1999, December, vol. 70, p. 618-621
  5. ↑ 5.0 5.1 5.2 Kulkarni. G.S. Textbook of orthopedics and trauma.India: Jaypee Brother Publication, 1999
  6. ↑ 6.0 6.1 6.2 6.3 Kidner FC. The prehallux (accessory scaphoid) in its relation to flat-foot. J Bone Joint Surg 1929 : II : 831
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 A. Bernaerts, F.M. Vanhoenacker, S. Van de Perre, A.M. De Schepper, P.M. Parizel1 Accessory navicular bone: Not Such a normal variant. JBR–BTR, 2004, 87 (5) page 250-252
  8. ↑ Prichausuk S, Sinphurmsukskul O: Kinder Procedure for symptomatic accessory navicular and its relation to pes planus, Foot Ankle 16:500,1995
  9. ↑ 9.0 9.1 Kidner FC. Pre-hallux in relation to flatfoot. JAMA 1933; 101: 1539-42.
  10. ↑ Kulkarni. G.S. Textbook of orthopedics and trauma.India: Jaypee Brother Publication, 1999.&lt;/ref&gt;&lt;ref name="p7"&gt;Kidner FC. The prehallux (accessory scaphoid) in its relation to flat-foot. J Bone Joint Surg 1929 : II : 831
  11. ↑ ShaychiITA. Tibialis Posterior Basic Strengthening. Available from: http://www.youtube.com/watch?v=zmh1FisBeeM [last accessed 24/11/12]
  12. ↑ ShaychiITA. Tibialis Posterior Basic Multiplanar Strengthening. Available from: http://www.youtube.com/watch?v=qv76eBxGQXI [last accessed 01/12/12]
  13. ↑ ShaychiITA. Tibialis Posterior Functional Strengthening: Full Body Weight Maintaining Supination. Available from: http://www.youtube.com/watch?v=1C_C5N9reB8[last accessed 01/12/12]|}
  14. ↑ ShaychiITA. Tibialis Posterior Functional Strengthening: Maintain Arch with Compass Squats. Available from: http://www.youtube.com/watch?v=TdHgyFZbOPk[last accessed 24/11/12]|}
  15. ↑ Shands AR Jr, Wentz IJ. Congenital anomalies, accessory bones and osteochondritis in the feet of 850 children. Surg.Clin.North Am 1953:97:1643-1666
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