What is Metatarsus Adductus?
Metatarsus adductus is a common congenital deformity in babies’ feet, it appears as a “C” shaped foot (convex lateral border) as a result of the angle of the metatarsals relative to the midline of the foot (Eamsobhana et al., 2017). This condition is a result of the metatarsals adducting at the tarsometatarsal joint (Marshall, Ward & Williams, 2018). Metatarsus adductus may include supination of the rearfoot at the subtalar joint (Aiyer, et al., 2014). The metatarsus adductus may be flexible, semi-flexible, or rigid (Williams et al., 2013).
What is the cause of metatarsus adductus?
There have been numerous studies into the cause of metatarsus adductus, however, an exact cause has not been definitively determined. The most popular theory into the etiology of metatarsus adductus has been attributed to an irregular intrauterine position (Losa Iglesias et al., 2009). There are other reasons which may contribute to or cause metatarsus adductus such as tight abductor hallucis, mispositioned tibialis anterior at its insertion at the base of the 1st metatarsal, tibialis anterior contracture, and not normal foot development in the first trimester of pregnancy (Evans, 2010).
Who is more likely to be affected by metatarsus adductus?
The epidemiology of metatarsus adductus is widespread, it is the most frequently diagnosed podiatric condition in children’s feet under 1 year of age (Losa Iglesias et al., 2009). This condition is noted between 1 in 1000 births (Eamsobhana et al., 2017), and may appear more commonly in girls compared to boys. 50% of the cases reported of metatarsus adductus are bilateral (Evans, 2010). Research has indicated that children diagnosed with metatarsus adductus may be approximately 3.5 times more likely to develop hallux valgus as adults (Aiyer et al., 2014). Also, those born with metatarsus adductus are more likely to develop hip dysplasia (Raducan, 2017).
What are the signs and symptoms?
A child with metatarsus adductus has a forefoot that turns inwards, this clinical manifestation is likely to be present at birth (Eamsobhana et al., 2017). The patient may walk with feet facing inwards instead of straight, otherwise known as an in-toed or “pigeon-toed” during gait. The clinical presentation would involve an observable C-Shaped foot with adduction of the forefoot at the tarsometatarsal joint (Marshall, Ward & Williams, 2018). Long term metatarsus adductus is not related to pain or decrease foot function. This foot deformity can present both unilaterally and bilaterally (Evans, 2010).
Some other conditions to consider that may look similar to metatarsus adductus.
Medial Tibial Torsion
Similarity: In-toe or “pigeon-toe” gait present clinically (Gandhi & Salvi, 2017)
Difference: When measuring thigh-foot angle < -10 degrees if the medial tibial torsion is present (Gandhi & Salvi, 2017)
Femoral anteversion
Similarity: In-toe or “pigeon-toe” gait present clinically (Gandhi & Salvi, 2017)
Difference: Internal rotation >70 degrees and < 20 degrees of external rotation (tested in prone position) for femoral ante torsion (Gandhi & Salvi, 2017)
Cerebral Palsy
Similarity: In-toe gait may be present (Rethlefsen, 2006)
Difference: The cause of the in-toeing in cerebral palsy may be metatarsus adductus, but may also be related to internal medial tibial torsion and internal hip rotation (Rethlefsen, 2006).
Talipes Equinovarus (club foot)
Similarity: In Talipes Equinovarus the foot appears to be facing inwards and is often noted at birth as with metatarsus adductus (Evans, 2010)
Difference: Reduced range of motion at the ankle joint. An X-ray would indicate Talipes Equinovarus rather than skew foot. In metatarsus adductus, there is no foot drop, while in club foot the foot is in a downward position (Evans, 2010).
How is metatarsus adductus diagnosed?
There are various methods used to diagnose metatarsus adductus. These include diagnosis based on the physical appearance of the patient’s foot. The styloid process is a sign of adduction of all the metatarsals (Dalal et al., 2011). For younger children, it is possible to assess the foot by placing two fingers in a V-shape along either side of the foot to assess the lateral border to see if there is a curve (Dalal et al., 2011). Metartus adductus can be classified by Beck’s heel bisector method, type, and flexibility (Evans, 2010). Pedographs and dynamic foot pressure may also be used for diagnosis. Ultrasound may be used to assess the involvement of abductor hallucis (Miron & Grimard, 2015). X-rays may be useful for severe or rigid metatarsus adductus and to classify the extent of the deformity. Metatarsus adductus can be classified by type, flexibility, and degree of deformity (Dawoodi & Perera, 2012). Type 1 is developmental or postural metatarsus adductus, it is positional and related to the tightness of abductor hallucis. This is the most common form of metatarsus adductus and usually resolves. This presents as metatarsal with normal alignment, lateral border of foot normally straight, and adduction of hallux only seen when weight-bearing. Type 2 metatarsus adductus is a structural type with transverse plane adduction of the forefoot on the rearfoot. In this type, all metatarsals are adducted with the 1st metatarsal with the greatest adducted and the 5th metatarsal the least. This type presents with the adduction at the Lisfranc joint with the midfoot and rearfoot relatively unaffected. Type 3 metatarsus varus is a result of transverse plane adduction and frontal plane inversion of the forefoot on rearfoot. This is a result of metatarsal adducting at the Lisfranc joint and inverting distally. Type 4 of this condition is known as a skew foot (Evans, 2010). Flexibility or rigidity is assessed by analyzing the reducibility of the adduction of the forefoot on the rearfoot in the transverse plane. If the metatarsus adductus is flexible it will be easily reduceable and it would be possible to abduct the forefoot past the midline of the foot. Reduced or semi-flexible metatarsus adductus occurs when the deformity will reduce, but not past the midline. Rigid metatarsus adductus will not reduce with an abductory force and does not reach the midline of the foot (Williams et al., 2013) It is also important to assess the tension of abductor hallucis with the patient weight-bearing and non-weight-bearing (Evans, 2010). Beck’s classification can be used to determine the degree of the metatarsus adductus. This classification is by the heel bisector method. Normal is a heel bisection line between the 2nd and 3rd webspace, mild is a bisection line through the 3rd toe, moderation is a heel bisection through the 3rd and 4th webspace and severe is between the 4th and 5th webspace (Marshall et al., 2018).
How is metatarsus adductus treated and managed?
Management of metatarsus adductus is dependent on the type and flexibility of the condition. Type 1 resolves on its own and no treatment should be undertaken. This information is important to explain to parents, however, if parents are concerned, they may do passive stretching and massage even though it is unlikely to have benefited (perhaps during nappy changes) (Eamsobhana et al., 2017). Type 2 and 3 metatarsus adductus can be managed with serial plaster of Paris casting with stretching, using this treatment the casts are changed every 1-2 weeks for 6-8 weeks to progressively correct foot alignment, by referral to an orthopedic surgeon. Abduction foot orthoses can correct metatarsus adductus if treatment begins prior to 8 months. Splinting can be used in minor cases or following serial casting. There are a variety of splints available such as the Ganley splint, Dennis Browne bar, unibar, counter-rotation system, Wheaton brace (Evans, 2010). Flexible metatarsus adductus also resolves on its own most of the time and parents should be aware of postures during sitting and sleeping to avoid adduction and may consider a straight last shoe to adjust the forefoot to the rearfoot relationship. Semi-flexible metatarsus adductus can be managed by monitoring sleeping and sitting postures, a splint to hold the foot in a straight position, and serial casting (Williams et al., 2013). Surgical management is recommended, potentially with a pediatric orthopedic surgeon, when metatarsus adductus does not resolve following conservative treatment or cases that will not respond to conservative treatment (Evans, 2010).
What is the long-term outlook (prognosis) for metatarsus adductus?
The prognosis of metatarsus adductus largely depends on the type of the condition. Type 1 and flexible resolves spontaneously and metatarsus adductus is not related to long-term pain or decreased foot function (Hutchinson, 2010). Semi-flexible and type 2 and 3 metatarsus adductus will likely be corrected with conservative treatment. If conservative management fails, surgery can be considered with a high rate of success (Evans, 2010).
Take-away
Metatarsus adductus is a common foot deformity in newborns, with the forefoot adducting on the rearfoot at the Lisfranc joint. The cause has likely been related to the intrauterine position. This condition presents in approximately 1 in 1000 births and is bilateral 50% of the time. Metatarsus adductus can be assessed clinically visually and based on type, flexibility, and degree of deformity. X-rays may also be ordered when complex and to rule out other conditions if appropriate. Differential diagnosis is medial tibial torsion, femoral anteversion, talipes equinovarus, and club foot. Diagnosis can be visual and/or by assessing type, degree of deformity, and flexibility. Pedographs, dynamic gait pressures may be used and radiographs if indicated. Management depends on the type and flexibility of metatarsus adductus and may include parent education, passive stretches, monitoring sleeping, and sitting position, serial casting, splints, orthoses, and surgery in severe cases. The prognosis largely depends on type but type 1 will resolve generally without treatment and type 2 and 3 are likely to resolve with conservative treatment.
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References
Dalal, A., Pimentel-Tejeda, A., & Kim, A. (2011). Literature Review of Metatarsus Adductus in Children. NYCPM. Student Association Podiatric Medical Review, 2012(20), 24-29.
Dawoodi, A., & Perera, A. (2012). Radiological assessment of metatarsus adductus. Foot And Ankle Surgery, 18(1), 1-8. DOI: 10.1016/j.fas.2011.03.002
Eamsobhana, P., Rojjananukulpong, K., Ariyawatkul, T., Chotigavanichaya, C., & Kaewpornsawan, K. (2017). Do the parental stretching programs improve metatarsus adductus in newborns?. Journal Of Orthopaedic Surgery, 25(1), 230949901769032. DOI: 10.1177/2309499017690320
Evans, A. (2010). Pocket Podiatry: Paediatrics. China: Churchill Livingstone
Gandhi, N., & Salvi, R. (2017). Correlation between Pronated Foot and Pelvic Inclination, Femoral Anteversion, Quadriceps Angle, and Tibial Torsion. International Journal Of Physiotherapy, 4(4). DOI: 10.15621/ijphy/2017/v4i4/154718
Hutchinson, B. (2010). Pediatric Metatarsus Adductus and Skewfoot Deformity. Clinics In Podiatric Medicine And Surgery, 27(1), 93-104. DOI: 10.1016/j.cpm.2009.09.005
Losa Iglesias, M., Becerro de Bengoa Vallejo, R., Saez Crespo, A., & Salvadores Fuentes, P. (2009). Poor Sitting Posture and Metatarsus Adductus Deformity. Journal Of The American Podiatric Medical Association, 99(2), 174-177. doi: 10.7547/0980174
Marshall, N., Ward, E., & Williams, C. (2018). The identification and appraisal of assessment tools used to evaluate metatarsus adductus: a systematic review of their measurement properties. Journal Of Foot And Ankle Research, 11(1). DOI: 10.1186/s13047-018-0268-z
Miron, M., & Grimard, G. (2015). Ultrasound evaluation of foot deformities in infants. Pediatric Radiology, 46(2), 193-209. DOI: 10.1007/s00247-015-3460-3
Raducan, V. (2017). Developmental Hip Dysplasia. Orthopedic Surgery Clerkship, 541-544. DOI: 10.1007/978-3-319-52567-9_113
Rethlefsen, S. (2006). Causes of Intoeing Gait in Children with Cerebral Palsy. The Journal Of Bone And Joint Surgery (American), 88(10), 2175. DOI: 10.2106/jobs.e.01280
Williams, C., James, A., & Tran, T. (2013). Metatarsus adductus: development of a non-surgical treatment pathway. Journal of Paediatrics and Child Health. (E428-E433).
