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The accessory navicular — An important cause of medial foot pain
ClinicalRadiology (1992) 46, 261-264
The Accessory Navicular- An Important Cause of Medial Foot Pain C. A. J. R O M A N O W S K I
and N. A. B A R R I N G T O N
Department of Radiology, Royal Hallamshire Hospital, Sheffield The accessory navicular is a commonly occurring accessory ossicle of the foot. In most instances this is an incidental finding. In some patients, the accessory navicular is the direct cause of foot pain. We present 10 such cases. The typical clinical picture is of a young female patient who presents with chronic or acute on chronic medial foot pain centred over the medial side of the navicular. The patient is usually physically active on her feet and localizes the pain accurately. Plain radiography reveals an accessory navicular united to the navicular by a synchondrosis (Type II). The diagnosis can be confirmed by showing increased localized uptake of isotope on a technetium 99m M D P bone scan. In some cases, the accessory navicular is mistaken for a fracture. Awareness of this accessory ossicle causing such symptoms should lead to the correct diagnosis. R o m a n o w s k i , C.A.J. & Barrington, N.A. (1992). Clinical Radiology 46, 261-264. The Accessory N a v i c u l a r - A n I m p o r t a n t Cause o f Medial F o o t Pain
AcceptedJbr Publication 8 May 1992
Accessory ossicles a r o u n d the foot and ankle are usually incidental findings. Recognizing them is i m p o r t a n t because they are often mistaken for acute fractures [1,2]. More importantly though, the accessory ossicle m a y be the direct cause o f a patient's symptoms: It is well recognized that the os t r i g o n u m m a y become s y m p t o m a tic when it is trapped between the calcaneus and tibia during repeated and forceful plantar flexion o f the foot. This is typically seen in ballet dancers and football players [3-5]. A similar but less well recognized s y n d r o m e involves the accessory navicular due to a chronic stress reaction in physically active people [6-8]. This paper presents a g r o u p o f patients with a symptomatic accessory navicular in w h o m bone scans were performed.
PATIENTS AND RESULTS Over the previous 18 months, 10 patients have been seen at the Royal Hallamshire or N o r t h e r n General Hospitals, Sheffield, in either the Orthopaedic a n d / o r Accident and Emergency departments complaining o f Correspondence to: Dr C. A. J. Romanowski, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF.
medial foot pain directly related to an accessory navicular (see Table 1), which have all been of Type II. Seven out o f the 10 patients were female and the m e a n age at presentation was 26.5 years (range 17-38 years). All o f the patients were physically active on their feet, either as part o f their occupation or during leisure activities. Eight o f the 10 patients had bone scans with technetium 99m methylene d i p h o s p h o n a t e ( M D P ) and all eight had increased uptake o f isotope over the s y m p t o m a t i c accessory navicular. The level o f isotope uptake in the region o f the navicular in the a s y m p t o m a t i c foot was n o r m a l in all cases. T w o patients have had surgical excision o f the accessory navicular with complete relief o f s y m p t o m s enabling them to return to either their work or their leisure and sporting activities. Three other patients had relief o f their s y m p t o m s following rest f r o m their sporting activities. N o long term follow-up is available for the remaining five patients who are still under clinical review. DISCUSSION The accessory navicular is one o f the c o m m o n l y occurring accessory ossicles o f the foot, being present in
Table 1 - Patient details
Patients
Age/sex
Symptoms
Occupation/Hobbies
Bone scan
D.R. C.T. A.D.* C.F.* G.R. J.A.* H.K. A.S. R.E.* S.P.
25 female 17 female 24 female 38 female 23 female 31 female 28 male 35 male 20 male 24 female
chronic pain right foot chronic pain left foot acute on chronic pain left foot acute on chronic pain right foot acute on chronic pain left foot acute on chronic pain right foot chronic pain right foot chronic pain left foot acute on chronic pain right foot chronic pain right foot
keen athlete postwoman keen athlete acutely worse, playing tennis acutely worse, hillwalking acutely worse, playing netball keen athlete fireman footballer hillwalker
positive positive positive positive positive
N/A N/A positive positive positive
* These patients were initially seen in casualty with an acute exacerbation of their medial foot pain. They were all initially diagnosed as having sustained an acute fracture. N/A, Not available.
262
CLINICAL RADIOLOGY
Fig. 1 - Type I accessory navicular.
F i g . 3 - T y p e lII a c c e s s o r y n a v i c u l a r .
Fig. 2 - T y p e II a c c e s s o r y n a v i c u l a r .
4-21% of the population [9-11]. A secondary centre of ossification is seen over the medial pole of the navicular, appearing between the ages of 9 and 11 years. This normally fuses without causing symptoms. When it fails to fuse, symptoms of medial foot pain m a y occur. It is of importance to note that the tendon of tibialis posterior inserts mainly into this medial aspect of the navicular. Three types of accessory navicular are described [6]. Type I is a sesamoid bone that occurs in the tendon of tibialis posterior (Fig. 1). It is usually small, round or oval and separated from the main portion of the navicutar by at least 3 mm. This type of ossicle does not usually cause symptoms. The term os tibiale externum should be restricted to this Type I accessory navicular according to Lawson [6].
Fig. 4 - P l a i n r a d i o g r a p h o f a T y p e II a c c e s s o r y n a v i c u l a r .
The Type II accessory navicular is a larger structure. It measures up to 12 m m and is triangular or heart shaped (Fig. 2). This particular Type II is said to account for 70% of all accessory naviculars although it is our experience that the figure is closer to 50%. There is a cartilaginous or fibrocartilaginous synchondrosis between it and the main
263
ACCESSORY N A V I C U L A R A N D MEDIAL FOOT PAIN
(a)
I
(b) Fig. 5 - Bone scan with technetium 99m M D P . (a) Medial views of b o t h feet. (b) Inferior views of b o t h feet. Note also increased uptake in a hallux rigidus on the right.
body of the navicular. This allows for only a very limited amount of movement between the navicular and its accessory ossicle into which, the tendon of tibialis posterior is inserted. The Type I I I accessory navicular (Fig. 3) is considered to be the end stage of the Type II when fusion of a large secondary centre of ossification results in a prominent process also known as the 'cornuate navicular'. Pain on the medial side of the foot related to an accessory navicular occurs almost exclusively with the Type II accessory navicular (Fig. 4), although a very prominent Type III accessory navicular may cause overlying soft tissue inflammation with an associated bursa. It is said to typically occur in female patients in the second decade [6]. Our series of patients has a definite preponderance of females, but the average age is a little older (mean age 26.5 years). All of our patients were physically active either at work or in their leisure pursuits. As the accessory navicular is one of the more commonly occurring accessory ossicles of the foot it is important to assess whether it is the cause of the patient's symptoms rather than simply an incidental finding. In this
respect a good clinical history with findings of specific tenderness over the accessory navicular is probably the most important stage in the diagnosis. The clinical diagnosis can, however, be supported by a technetium 99m M D P bone scan. In such patients the accessory navicular and adjacent navicular show increased uptake on the bone scan (Fig. 5) presumably due to the 'chronic stress reaction' at the synchondrosis. Eight of our 10 patients had bone scans on the basis of their clinical and plain radiographic findings, all of which showed increased uptake related to the accessory navicular on the symptomatic side. The contralateral side was of normal intensity in all cases. In all ten patients the symptoms were unilateral and no radiographs were obtained of the contralateral foot. However, the incidence of bilateral accessory naviculars has been reported as ranging from 50% to 89% [12, 13]. It m a y therefore be assumed that some of these patients had accessory naviculars on the asymptomatic side and that these do not show evidence of increased uptake on the bone scan, thereby acting as natural controls. F o u r of the 10 patients who presented to casualty with
264
CLINICAL RADIOLOGY
acute or acute on chronic pain were initially diagnosed as having sustained a fracture. This confirms that the accessory ossicles of the foot are commonly mistaken for fractures. Two patients have had surgical excision of their symptomatic accessory naviculars. Only one of these was examined histologically and this showed increased osteoblastic and osteoclastic activity with a large number of inflammatory cells. These features are indicative of a 'chronic stress reaction'. Both of these patients are now symptom-free following the surgery. In three further patients the pain settled following a period of rest from their sporting activities. The remaining five patients are still being followed up clinically. In conclusion, the accessory navicular Type II is a common accessory ossicle of the foot that may cause pain in some physically active people, which is often longstanding but sometimes with an acute exacerbation and tenderness over the medial border of the navicular. Such patients show increased uptake on technetium 99m M D P bone scanning, and may get relief of symptoms following surgical excision of the bone. The accessory navicular, in common with other accessory ossicles of the foot and ankle, is commonly mistaken for an acute fracture. Acknowledgements. We would like to thank Professor T. Duckworth, Executive Editor of The Foot for giving us permission to include two cases in this series that were used as 'Illustrative Cases' in a recent review article [2].
REFERENCES
1 Zatzkin HR. Trauma to the foot. Seminars in Roentgenology 1970;5:419~435. 2 Romanowski CA J, Barrington NA. The accessory ossicles of the foot. The Foot 1991;1:61-70. 3 McDougall A. The os trigonum. Journal of Bone and Joint Surgery (British) 1955;37:257-265. 4 Quirk R. Talar compression syndrome in dancers. Foot and Ankle 1982;3:64-68. 5 Brodsky AE, Khalil MA. Talar compression syndrome. Foot and Ankle 1987;7:338-344. 6 Lawson JP, Ogden JA, Sella E, Barwick KW. The painful accessory navicular. Skeletal Radiology 1984;12:250-262. 7 Lawson JP. Symptomatic radiographic variants in extremities. Radiology 1985;157:625-631. 8 Sella EJ, Lawson JP, Ogden JA. The accessory navicular synchondrosis. Clinical Orthopaedics and Related Research 1986;209:280285. 9 Harris RI, Beath T.Army foot survey, Vol. 1. Ottawa: National Research Council of Canada, 1947:52-54. 10 Kohler A, Zimmer EA. Borderlands of the normal and early pathologic in skeletalroentgenology. N e w York: Grune and Stratton, 1968:494-505. 11 Tsuruta T, Shirokawa Y, Kato A, Matsumoto T, Yamazoe Y, Oike T, Sugiyama T, Saito M. Radiological study of the accessory skeletal elements in the foot and ankle. Nippon Seikeigeka Gakkai Zasshi 1981;55:357-270. 12 Geist ES. The accessory scaphoid bone. Journal of Bone and Joint Surgery (American) 1925;7:570 574. 13 Mygind HB. The accessory tarsal scaphoid. Acta Orthopaedica Scandanavica 1953;23:142-151.
The Accessory Navicular- An Important Cause of Medial Foot Pain C. A. J. R O M A N O W S K I
and N. A. B A R R I N G T O N
Department of Radiology, Royal Hallamshire Hospital, Sheffield The accessory navicular is a commonly occurring accessory ossicle of the foot. In most instances this is an incidental finding. In some patients, the accessory navicular is the direct cause of foot pain. We present 10 such cases. The typical clinical picture is of a young female patient who presents with chronic or acute on chronic medial foot pain centred over the medial side of the navicular. The patient is usually physically active on her feet and localizes the pain accurately. Plain radiography reveals an accessory navicular united to the navicular by a synchondrosis (Type II). The diagnosis can be confirmed by showing increased localized uptake of isotope on a technetium 99m M D P bone scan. In some cases, the accessory navicular is mistaken for a fracture. Awareness of this accessory ossicle causing such symptoms should lead to the correct diagnosis. R o m a n o w s k i , C.A.J. & Barrington, N.A. (1992). Clinical Radiology 46, 261-264. The Accessory N a v i c u l a r - A n I m p o r t a n t Cause o f Medial F o o t Pain
AcceptedJbr Publication 8 May 1992
Accessory ossicles a r o u n d the foot and ankle are usually incidental findings. Recognizing them is i m p o r t a n t because they are often mistaken for acute fractures [1,2]. More importantly though, the accessory ossicle m a y be the direct cause o f a patient's symptoms: It is well recognized that the os t r i g o n u m m a y become s y m p t o m a tic when it is trapped between the calcaneus and tibia during repeated and forceful plantar flexion o f the foot. This is typically seen in ballet dancers and football players [3-5]. A similar but less well recognized s y n d r o m e involves the accessory navicular due to a chronic stress reaction in physically active people [6-8]. This paper presents a g r o u p o f patients with a symptomatic accessory navicular in w h o m bone scans were performed.
PATIENTS AND RESULTS Over the previous 18 months, 10 patients have been seen at the Royal Hallamshire or N o r t h e r n General Hospitals, Sheffield, in either the Orthopaedic a n d / o r Accident and Emergency departments complaining o f Correspondence to: Dr C. A. J. Romanowski, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF.
medial foot pain directly related to an accessory navicular (see Table 1), which have all been of Type II. Seven out o f the 10 patients were female and the m e a n age at presentation was 26.5 years (range 17-38 years). All o f the patients were physically active on their feet, either as part o f their occupation or during leisure activities. Eight o f the 10 patients had bone scans with technetium 99m methylene d i p h o s p h o n a t e ( M D P ) and all eight had increased uptake o f isotope over the s y m p t o m a t i c accessory navicular. The level o f isotope uptake in the region o f the navicular in the a s y m p t o m a t i c foot was n o r m a l in all cases. T w o patients have had surgical excision o f the accessory navicular with complete relief o f s y m p t o m s enabling them to return to either their work or their leisure and sporting activities. Three other patients had relief o f their s y m p t o m s following rest f r o m their sporting activities. N o long term follow-up is available for the remaining five patients who are still under clinical review. DISCUSSION The accessory navicular is one o f the c o m m o n l y occurring accessory ossicles o f the foot, being present in
Table 1 - Patient details
Patients
Age/sex
Symptoms
Occupation/Hobbies
Bone scan
D.R. C.T. A.D.* C.F.* G.R. J.A.* H.K. A.S. R.E.* S.P.
25 female 17 female 24 female 38 female 23 female 31 female 28 male 35 male 20 male 24 female
chronic pain right foot chronic pain left foot acute on chronic pain left foot acute on chronic pain right foot acute on chronic pain left foot acute on chronic pain right foot chronic pain right foot chronic pain left foot acute on chronic pain right foot chronic pain right foot
keen athlete postwoman keen athlete acutely worse, playing tennis acutely worse, hillwalking acutely worse, playing netball keen athlete fireman footballer hillwalker
positive positive positive positive positive
N/A N/A positive positive positive
* These patients were initially seen in casualty with an acute exacerbation of their medial foot pain. They were all initially diagnosed as having sustained an acute fracture. N/A, Not available.
262
CLINICAL RADIOLOGY
Fig. 1 - Type I accessory navicular.
F i g . 3 - T y p e lII a c c e s s o r y n a v i c u l a r .
Fig. 2 - T y p e II a c c e s s o r y n a v i c u l a r .
4-21% of the population [9-11]. A secondary centre of ossification is seen over the medial pole of the navicular, appearing between the ages of 9 and 11 years. This normally fuses without causing symptoms. When it fails to fuse, symptoms of medial foot pain m a y occur. It is of importance to note that the tendon of tibialis posterior inserts mainly into this medial aspect of the navicular. Three types of accessory navicular are described [6]. Type I is a sesamoid bone that occurs in the tendon of tibialis posterior (Fig. 1). It is usually small, round or oval and separated from the main portion of the navicutar by at least 3 mm. This type of ossicle does not usually cause symptoms. The term os tibiale externum should be restricted to this Type I accessory navicular according to Lawson [6].
Fig. 4 - P l a i n r a d i o g r a p h o f a T y p e II a c c e s s o r y n a v i c u l a r .
The Type II accessory navicular is a larger structure. It measures up to 12 m m and is triangular or heart shaped (Fig. 2). This particular Type II is said to account for 70% of all accessory naviculars although it is our experience that the figure is closer to 50%. There is a cartilaginous or fibrocartilaginous synchondrosis between it and the main
263
ACCESSORY N A V I C U L A R A N D MEDIAL FOOT PAIN
(a)
I
(b) Fig. 5 - Bone scan with technetium 99m M D P . (a) Medial views of b o t h feet. (b) Inferior views of b o t h feet. Note also increased uptake in a hallux rigidus on the right.
body of the navicular. This allows for only a very limited amount of movement between the navicular and its accessory ossicle into which, the tendon of tibialis posterior is inserted. The Type I I I accessory navicular (Fig. 3) is considered to be the end stage of the Type II when fusion of a large secondary centre of ossification results in a prominent process also known as the 'cornuate navicular'. Pain on the medial side of the foot related to an accessory navicular occurs almost exclusively with the Type II accessory navicular (Fig. 4), although a very prominent Type III accessory navicular may cause overlying soft tissue inflammation with an associated bursa. It is said to typically occur in female patients in the second decade [6]. Our series of patients has a definite preponderance of females, but the average age is a little older (mean age 26.5 years). All of our patients were physically active either at work or in their leisure pursuits. As the accessory navicular is one of the more commonly occurring accessory ossicles of the foot it is important to assess whether it is the cause of the patient's symptoms rather than simply an incidental finding. In this
respect a good clinical history with findings of specific tenderness over the accessory navicular is probably the most important stage in the diagnosis. The clinical diagnosis can, however, be supported by a technetium 99m M D P bone scan. In such patients the accessory navicular and adjacent navicular show increased uptake on the bone scan (Fig. 5) presumably due to the 'chronic stress reaction' at the synchondrosis. Eight of our 10 patients had bone scans on the basis of their clinical and plain radiographic findings, all of which showed increased uptake related to the accessory navicular on the symptomatic side. The contralateral side was of normal intensity in all cases. In all ten patients the symptoms were unilateral and no radiographs were obtained of the contralateral foot. However, the incidence of bilateral accessory naviculars has been reported as ranging from 50% to 89% [12, 13]. It m a y therefore be assumed that some of these patients had accessory naviculars on the asymptomatic side and that these do not show evidence of increased uptake on the bone scan, thereby acting as natural controls. F o u r of the 10 patients who presented to casualty with
264
CLINICAL RADIOLOGY
acute or acute on chronic pain were initially diagnosed as having sustained a fracture. This confirms that the accessory ossicles of the foot are commonly mistaken for fractures. Two patients have had surgical excision of their symptomatic accessory naviculars. Only one of these was examined histologically and this showed increased osteoblastic and osteoclastic activity with a large number of inflammatory cells. These features are indicative of a 'chronic stress reaction'. Both of these patients are now symptom-free following the surgery. In three further patients the pain settled following a period of rest from their sporting activities. The remaining five patients are still being followed up clinically. In conclusion, the accessory navicular Type II is a common accessory ossicle of the foot that may cause pain in some physically active people, which is often longstanding but sometimes with an acute exacerbation and tenderness over the medial border of the navicular. Such patients show increased uptake on technetium 99m M D P bone scanning, and may get relief of symptoms following surgical excision of the bone. The accessory navicular, in common with other accessory ossicles of the foot and ankle, is commonly mistaken for an acute fracture. Acknowledgements. We would like to thank Professor T. Duckworth, Executive Editor of The Foot for giving us permission to include two cases in this series that were used as 'Illustrative Cases' in a recent review article [2].
REFERENCES
1 Zatzkin HR. Trauma to the foot. Seminars in Roentgenology 1970;5:419~435. 2 Romanowski CA J, Barrington NA. The accessory ossicles of the foot. The Foot 1991;1:61-70. 3 McDougall A. The os trigonum. Journal of Bone and Joint Surgery (British) 1955;37:257-265. 4 Quirk R. Talar compression syndrome in dancers. Foot and Ankle 1982;3:64-68. 5 Brodsky AE, Khalil MA. Talar compression syndrome. Foot and Ankle 1987;7:338-344. 6 Lawson JP, Ogden JA, Sella E, Barwick KW. The painful accessory navicular. Skeletal Radiology 1984;12:250-262. 7 Lawson JP. Symptomatic radiographic variants in extremities. Radiology 1985;157:625-631. 8 Sella EJ, Lawson JP, Ogden JA. The accessory navicular synchondrosis. Clinical Orthopaedics and Related Research 1986;209:280285. 9 Harris RI, Beath T.Army foot survey, Vol. 1. Ottawa: National Research Council of Canada, 1947:52-54. 10 Kohler A, Zimmer EA. Borderlands of the normal and early pathologic in skeletalroentgenology. N e w York: Grune and Stratton, 1968:494-505. 11 Tsuruta T, Shirokawa Y, Kato A, Matsumoto T, Yamazoe Y, Oike T, Sugiyama T, Saito M. Radiological study of the accessory skeletal elements in the foot and ankle. Nippon Seikeigeka Gakkai Zasshi 1981;55:357-270. 12 Geist ES. The accessory scaphoid bone. Journal of Bone and Joint Surgery (American) 1925;7:570 574. 13 Mygind HB. The accessory tarsal scaphoid. Acta Orthopaedica Scandanavica 1953;23:142-151.