Radiographic Assessment of Pediatric Foot Alignment: Self-Assessment Module

1.5 CME AJR Integrative Imaging LIFELONG LEARNING FOR RADIOLOGY Radiographic Assessment of Pediatric Foot Alignment: Self-Assessment Module Mahesh M. Thapa 1,2, Sumit Pruthi 1,2, Felix S. Chew 2 ABSTRACT The educational objectives for this self-assessment module are for the participant to exercise, self-assess, and improve his or her understanding of the imaging spectrum of pediatric foot alignment issues. INTRODUCTION This self-assessment module on radiographic assessment of pediatric foot alignment has an educational component and a self-assessment component. The educational component consists of one required article that the participant should read. The self-assessment component consists of 14 multiple-choice questions with solutions. All of these materials are available on the ARRS Website (www.arrs.org). To claim CME and SAM credit, each participant must enter his or her responses to the questions online. EDUCATIONAL OBJECTIVES By completing this educational activity, the participant will exercise, self-assess, and improve his or her understanding of: A. The terms used to describe pediatric foot alignment abnormalities. B. The imaging spectrum of alignment disorders of the pediatric foot. REQUIRED READING 1. Thapa MM, Pruthi S, Chew FS. Radiographic assessment of pediatric foot alignment: case-based review. AJR 2010; 194[suppl]:S51 S58 RECOMMENDED READING 1. Ozonoff MB. The foot. In: Ozonoff MB, ed. Pediatric orthopedic radiology, 2nd ed. Philadelphia, PA: Saunders, 1992:397 460 2. Harty MP. Imaging of pediatric foot disorders. Radiol Clin North Am 2001; 39:733 748 3. Maldjian C, Hofkin S, Bonakdarpour A, Roach N, Mc- Carthy J. Abnormalities of the pediatric foot. Acad Radiol 1999; 6:191 199 4. Thompson GH, Simons GW III. Congenital talipes equinovarus (clubfeet) and metatarsus adductus. In: Drennan JC, ed. The child s foot and Ankle. New York, NY: Raven Press, 1992:97 134 5. Scher DM. The Ponseti method for treatment of congenital clubfoot. Curr Opin Pediatr 2006; 18:22 25 6. Napiontek M. Skewfoot. J Pediatr Orthop 2002; 22:130 133 7. Davis LA, Hatt WS. Congenital abnormalities of the foot. Radiology 1955; 64:818 825 INSTRUCTIONS 1. Complete the educational and self-assessment components included in this issue. 2. Visit www.arrs.org and log in. 3. Select Self-Assessment Modules from the Lifelong Learning box in the lower left of the page. 4. Add the SAM to your shopping cart and order the online SAM as directed. (The SAM, including questions, must be ordered to be accessed even though the activity is free to ARRS members.) After purchasing the SAM, click on OK; you will be returned to the ARRS home page. 5. Click on the My Education tab at the top of the page, then on My Online Products. (Note: You must be logged in to access this personalized page.) 6. You can also access the purchased SAM by logging on to http://edu.arrs.org/myproducts/. 7. Answer the questions online to obtain SAM credit. Keywords: foot alignment, pediatrics, radiography DOI:10.2214/AJR.10.7234 Received February 2, 2010; accepted without revision February 3, 2010. 1 Department of Radiology, University of Washington, Box 354755, 4245 Roosevelt Way, NE, Seattle, WA 98105. Address correspondence to M. M. Thapa (mthapa@mac.com). 2 Department of Radiology, Seattle Children s Hospital, Seattle, WA. AJR 2010;194:S59 S63 0361 803X/10/1946 S59 American Roentgen Ray Society S59

Thapa et al. QUESTION 1 Which tarsal bone has no muscular or tendinous attachments (i.e., it contains only ligamentous attachments)? A. Navicular. B. Calcaneus. C. Talus. D. Cuboid. QUESTION 2 When evaluating hindfoot malalignment on an anteroposterior view of the foot, which of the following is important to assess? A. The precise angle measurement between the talus and calcaneus. B. The relationship of the distal metatarsals or phalanges to the talus and calcaneus. C. The relationship of the cuneiform bones to the talus. D. The relationship between the talus and navicular. QUESTION 3 In general, on the lateral view, a line drawn through the long axis of the talus should run through the shaft of which metatarsal? A. First. B. Second. C. Third. D. Fourth. E. Fifth. QUESTION 4 Fig. 1 Weightbearing anteroposterior (AP) and lateral views of foot for question 4. AP and lateral talocalcaneal angles have been drawn. With respect to Figure 1, which of the following is the best description of the alignment? A. Hindfoot valgus. B. Hindfoot varus. C. Congenital vertical talus. QUESTION 5 Hindfoot valgus can be present in all the following conditions EXCEPT which of the following? A. Cerebral palsy. B. Skewfoot. C. Congenital vertical talus. QUESTION 6 Fig. 2 Weightbearing anteroposterior (AP) and lateral views of foot for question 6. AP and lateral talocalcaneal angles have been drawn. Considering Figure 2, which of the following is the best description for the alignment of the hindfoot? A. Calcaneus. B. Varus. C. Rocker-bottom. D. Cavus. QUESTION 7 Hindfoot varus is a component of which congenital deformity? A. Vertical talus. B. Oblique talus. C. Clubfoot. D. Pes planus. QUESTION 8 Fig. 3 Weightbearing anteroposterior (AP) and lateral views of foot for question 8. AP and lateral talocalcaneal angles have been drawn. Considering Figure 3, what is the best diagnosis? A. Planovalgus foot. B. Cavus foot. C. Z-foot (skewfoot). S60

Pediatric Foot Alignment QUESTION 9 Which of the following statements is TRUE regarding congenital talipes equinovarus? A. The incidence of congenital talipes equinovarus is 1:100 live births. B. Congenital talipes equinovarus is often recognized on prenatal sonography. C. Bilateral involvement is unusual in congenital talipes equinovarus. D. Congenital talipes equinovarus affects more females than males. QUESTION 10 If needed, most surgeries to correct clubfoot deformity are performed at what approximate age? A. 3 months. B. 6 months. C. 1 year. D. 2 years. QUESTION 11 Fig. 4 Weightbearing anteroposterior (AP) and lateral views of foot for question 11. Star represents navicular bone. AP and lateral talocalcaneal angles have been drawn. Considering Figure 4, which of the following is the best diagnosis? A. Vertical talus. B. Hindfoot valgus. C. Planovalgus. D. Bunion deformity. Solution to Question 1 The talus is the only bone in the foot with no muscular attachments [1]. This fact is crucial to the understanding of hindfoot alignment. Therefore, option C is the best response, and options A, B, D, and E are not the best responses. QUESTION 12 On the lateral projection, which of the following distinguishes congenital vertical talus from pes planovalgus? A. The calcaneus alignment is normal. B. The navicular is dislocated from the talus. C. There is increased overlap of the metatarsals. D. Only the vertical talus includes flatfoot deformity. QUESTION 13 Fig. 5 Weightbearing anteroposterior (AP) and lateral views of foot for question 13. Circle represents navicular bone. With respect to Figure 5, which of the following is the best diagnosis? A. Clubfoot. B. Z-foot. C. Peroneal spastic flatfoot. D. Tarsal coalition. QUESTION 14 Which statement about skewfoot is TRUE? A. Skewfoot is common in otherwise healthy children. B. Skewfoot is rarely associated with severe cerebral palsy. C. Hallux valgus is frequently associated with skewfoot. D. The navicular is usually subluxed medially in cases of skewfoot. Solution to Question 2 The relationship between the tibia and the talus is difficult to assess on an anteroposterior view of the foot. Option A is not the best response. The relationship of the toes to the talus and calcaneus is not important in assessing hindfoot alignment; rather, it is the relationships of the metatarsal bases to the mid calcaneal and mid talar lines that are important. Option B is not the best response. Evaluation of the cuneiforms plays no great role in assessing hindfoot alignment. Option C is not the best response. The position of the navicular bone with respect to the talus tells us a great deal about hindfoot malalignment. If the navicular bone is subluxed laterally or medially, then we suspect hindfoot valgus or varus, respectively. Another way to think of it is that the navicular bone always moves in the same direction as the calcaneus [1]. Option D is the best response. S61

Thapa et al. Solution to Question 3 Generally, on a lateral view of the pediatric foot, a line drawn through the long axis of the talus should run through the shaft of the first metatarsal [1]. Thus, option A is the best response, and options B, C, D, and E are not the best responses. An important exception to this rule is in neonates, in whom the axis through the talus can normally pass inferior to the first metatarsal [1]. Solution to Question 4 Figure 1 is an example of hindfoot valgus. On the anteroposterior view, the talocalcaneal angle is increased. The anteroposterior talocalcaneal angle is typically between 35 and 40 [1]. On the lateral projection, the talus assumes a more vertical position than normal. Option A is the best response. Hindfoot varus results in a decrease of the talocalcaneal angle on the anteroposterior projection. Option B is not the best response. On the lateral projection, congenital vertical talus has an appearance similar to that of pure hindfoot valgus. However, with vertical talus, the navicular bone is dislocated superiorly. In hindfoot valgus, the talus assumes a somewhat vertical orientation, but the articular association between the talus and navicular bone is maintained [1]. Option C is not the best response. Hindfoot varus is a feature of congenital talipes equinovarus. Option D is not the best response. Solution to Question 5 Cerebral palsy, skewfoot, and congenital vertical talus have all been associated with hindfoot valgus deformity. Congenital talipes equinovarus manifests as hindfoot varus [1]. Option D is the best response. Options A, B, and C are not the best responses. Solution to Question 6 Option A is not the best response. Calcaneus position of the hindfoot is determined from the lateral projection. The calcaneus is abnormally dorsiflexed, with the anterior portion higher. Option B is the best response. Hindfoot varus results in a decrease of the talocalcaneal angle on the anteroposterior and lateral projections, leading to a near-parallel arrangement of the two bones. Option C is not the best response. In rockerbottom deformity, the plantar arch is convex instead of concave. The anterior calcaneus is in marked plantar flexion (equinus) and the metatarsals are dorsiflexed. Option D is not the best response. In cavus arch, the anterior portion of the calcaneus is tilted up and the metatarsals are plantar flexed, leading to increased height of the planar arch. Solution to Question 7 Options A and B are not the best responses. Both vertical talus and oblique talus deformities have hindfoot valgus deformities. In congenital vertical talus, the navicular remains superiorly dislocated in any position between maximum dorsiflexion and plantar flexion views. However, with oblique talus, the navicular can be reduced to its normal location in front of the talus between the dorsiflexion and plantar flexion views. Option C is the best response. Clubfoot is the vernacular term for congenital talipes equinovarus [1], and one of the components of this foot deformity is hindfoot varus. Option D is not the best response. Pes planus is usually associated with hindfoot valgus because the plantar arch is flattened [1]. Solution to Question 8 Option A is not the best response. In planovalgus, there are varying degrees of hindfoot valgus, flattened arch, and forefoot pronation (eversion). Option B is not the best response. With cavus foot, the plantar arch is exaggerated, with the anterior aspect of the calcaneus dorsiflexed (calcaneus position) and the distal aspect of the metatarsals plantar-flexed. Option C is not the best response. Z-foot (skewfoot) is a variant of a valgus foot. There is hindfoot valgus with associated forefoot adduction. Option D is the best response. In talipes equinovarus, there is extreme hindfoot varus, with the anterior calcaneus situated in an exaggerated planar-flexed position (equinus). In addition, there is forefoot adduction with supination (inversion). Solution to Question 9 Option A is not the best response. Equinovarus clubfoot, although relatively common, has an incidence of 1 4:1,000 live births and affects more males than females [1]. Option B is the best response. Indeed, clubfoot deformity can be and has been recognized on prenatal sonography [1, 2]. Option C is not the best response. Bilateral involvement is common. There is also increased risk of equinovarus clubfoot in a first-degree relative approximately 30 times greater than that of the general population [1]. Option D is not the best response. Males are more commonly affected than females [1]. Solution to Question 10 Option B is the best response. Most surgeons wait until a child with congenital clubfoot is 6 months old before performing surgery to correct it [1, 3]. However, there is some controversy surrounding this issue. Proponents of earlier surgery, between the ages of 3 and 6 months old, argue that growth and remodeling are most optimal at a younger age and result in a better outcome. Proponents of later surgery, between the ages of 9 and 12 months old, believe that the larger size of the foot at that age is easier to correct and that there is less risk associated with anesthesia at an older age [1, 3]. Solution to Question 11 Option A is not the best response. In vertical talus, the talus and navicular are dislocated [1]. Option B is not the best response. Yes, the patient has hindfoot valgus, but he also has an associated forefoot or midfoot abnormality, so hindfoot valgus alone is not the best diagnosis. Option C is the S62

Pediatric Foot Alignment best response. The combination of forefoot pronation and hindfoot valgus is termed planovalgus. Option D is not the best response. Bunion deformity is another term for metatarsus primus adductus with hallux valgus. In our case, the first metatarsal is not in varus (i.e., it is not adducted), and the first proximal phalanx is not in valgus [1]. Solution to Question 12 Option B is the best response. The key to differentiating planovalgus (or pure hindfoot valgus) from a vertical talus is to examine the relationship between the talus and the navicular on the lateral projection. With planovalgus, the talus will assume a more vertical orientation than normal but will still maintain an articulation with the navicular. However, in vertical talus, the navicular and talus are completely dislocated [1]. Options A, C, and D are not the best responses. Both pes planovalgus and congenital vertical talus can manifest with flatfoot deformity. Solution to Question 13 Option A is not the best response. The image depicted is not an example of clubfoot. Option B is the best response. Skewfoot presents with forefoot adduction associated with hindfoot valgus. Option C is not the best response. Peroneal FOR YOUR INFORMATION spastic flatfoot is associated with peroneal muscle spasm, usually as a result of congenital tarsal coalition [1]. Option D is not the best response. Although tarsal coalition can cause a flatfoot deformity, there is no evidence of coalition in this patient. Solution to Question 14 Option A is the best response. Skewfoot is a variant of valgus hindfoot that is common in otherwise healthy children [1]. Option B is not the best response. Skewfoot can be quite marked in patients with severe cerebral palsy [1]. Option C is not the best response. Although hallux valgus may be associated with skewfoot deformity, it typically occurs only in those with severe cerebral palsy [1]. Option D is not the best response. In skewfoot, the navicular is usually subluxed laterally, a common finding in hindfoot valgus. References 1. Thapa MM, Pruthi S, Chew FS. Radiographic assessment of pediatric foot alignment: case-based review AJR 2010; 194[suppl]:S51 S58 2. Treadwell MC, Stanotski CL, King M. Prenatal sonographic diagnosis of clubfoot: implications for patient counseling. J Pediatr Orthop 1999; 19:8 10 3. Thompson GH, Simons GW III. Congenital talipes equinovarus (clubfeet) and metatarsus adductus. In: Drennan JC, ed. The child s foot and ankle. New York, NY: Raven Press, 1992:97 134 The reader s attention is directed to the case-based review on which this SAM is based, which begins on page S51. S63