CT assessment of children with in-toeing gait

Transcription

1 CT assessment of children with in-toeing gait Poster No.: C-0234 Congress: ECR 2011 Type: Authors: Keywords: DOI: Educational Exhibit C. L. Holland 1, A. Kamil 2, A. Puttanna 2 ; 1 Walsall/UK, 2 Birmingham/ UK Pediatric, Musculoskeletal bone, CT, Diagnostic procedure, Computer Applications-General /ecr2011/C-0234 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 13

2 Learning objectives Our poster is designed to provide a user friendly method for performing and interpreting CT imaging in children with in-toeing gait who may require surgery. Background An in-toeing gait is a frequent complaint encountered by paediatric orthopaedic surgeons in the UK. It is a physiological symptom causing a pattern of gait that is often inefficient and limiting to function. There are also cosmetic features created by the abnormal gait that cause concern for both parents and the child. If unresolved the deformity can progress to worsening internal rotation of the hip resulting in knocked knees, frequent tripping, increased wearing away of shoes and have a negative effect on the child's self esteem. In-toeing has a wide spectrum of causes that can affect the proximal, middle and distal joints of the leg and usually varies with age. In infants the most common cause is metatarsus adductus and after 2 years of age most presentations result from internal tibial torsion. [1] This can lead to excessive femoral anteversion which is usually observed in children at 3 years of age. Femoral version is defined as the angular difference between axis of femoral neck and transcondylar axis of the knee. Figure 1 Misalignment is more noticeable in toddlers and tends to improves with age. It is important that pathological causes such as developmental dysplasia of the hip and cerebral palsy are identified early as rapid treatment has a positive effect on morbidity. Management is guided by the natural progression of the condition and is dependent on the cause. For most physiological cases, assessment of the progression of mal-alignment and successful formulation of a treatment plan can be achieved solely through clinical examination of the rotational profile. [3] Figure 2 In more significant cases of deformity or when the cause is suspected to be pathological, imaging proves to be more beneficial. This is of more relevance if the clinician requires accurate assessment of the degree of deformity to determine the necessity for surgical intervention. Page 2 of 13

3 Images for this section: Fig. 1: Rotational deformity at the proximal, middle and distal joints of the leg causing in-toeing Page 3 of 13

4 Fig. 2: Management plan for a child with in-toeing gait Page 4 of 13

5 Imaging findings OR Procedure details Patients are referred following formal orthopaedic assessment. Only patients suitable for correctional surgery are considered. Technical factors were as follows: Scanner: General Electric Lightspeed VCT (64 slices per rotation) Parameters: Helical acquisition, Medium F.O.V (hips + knees), Small F.O.V (ankles). 120 kvp, 200mA smart ma (auto ma modulation), 0.8 second rotation 0.625mm slice thickness, pitch 0.531:1, table speed mm/rotation Patient position / Centring: Feet 1st in to scanner,, legs extended, toes together and lightly restrained. Centre on iliac crests. Scout from crests to below feet. Average dose: Dose Length Product mgy/cm. Both AP and lateral scouts are needed for dose modulation.. 5mm Axial reconstructions through the hips, knees and ankles are obtained. Angles were measured both on the CT workstation and the PACS (GE). Figure 1 Leg length measurements were obtained from centres of femoral head to distal talar pilion when requested. Measurement Of Femoral Anteversion Page 5 of 13

6 Measuring the degree of rotation of the femoral bone around the shaft. [9] The proximal measurement is taken through the femoral neck. The distal along a tangent through the distal femoral condyles. Which is used as a reproducible proxy for the transcondylar axis of the femur. The normal measurement is between o Femoral Horizontal Angle Measurements Level selected where femoral necks are best seen. The sides need considering separately. With the curved CT table it important to ensure a true horizontal baseline relative to the whole pelvis. Slice selected reflecting the best representation of the femoral neck. Angle measured. Figure 2 Measurement femoral condylar horizontal angles Measure the left and right independently. Ensuring the correct horizontal plane is selected to obtain accurate measurements. Normal values are between o If the knees are internally rotated the angles are calculated by addition, see Figure 3. With the knees in external rotation, figure 4 the angles are calculated by subtraction Tibial Torsion This is the twist of the tibia on its long axis This angle increases from birth to adulthood, at birth measures 5 o, age o, age o and adults o. If there is lateral rotation this is referred to as external torsion and the angles expressed as a positive. If there is internal rotation this is medial tibial torsion and is expressed as a negative. Measurement of tibial torsion The proximal plane is a horizontal axis through the tibial plateau. Figure 4 The distal axis is through the bimalleolar plane, figure 5. Page 6 of 13

7 This actually gives one the angle of talo-fibular torsion as the fibula is also used in the measurements. A variety of other planes have been used [10]. However this is the preferred measurement for our clinicians. [10] Measurement tibial torsion figure 5 Right tibia; o = 24.8 o Left tibia; o = 22.7 o Rotation lateral therefore positive Metatarsus Adductus This is usually clinically assessed so we do not include CT of the tarsometatarsal junction. If requested plain radiographs can demonstrate well the adduction of the metatarsals with respect to the mid-tarsal axis. Images for this section: Page 7 of 13

8 Fig. 1: AP and lateral scout case 1. Anatomically neutral positioned. As well as being used for planning both leg length measurements and individual bone length measurements can be obtained Fig. 2: Measurement Femoral Horizontal Angle Page 8 of 13

9 Fig. 3: Measurement tibial horizontal condyle angles. Note knees internally rotated. Page 9 of 13

10 Fig. 4: Externally rotated knees Page 10 of 13

11 Fig. 5: Measurement tibial torsion Page 11 of 13

12 Conclusion Assessment of in toeing gait is a common clinical problem. We have presented a simple CT method for assessment of excessive femoral anteversion and increased internal tibial torsion that are common causative mechanism. Personal Information Dr C Louise Holland Consultant Radiologist Manor Hospital Walsall UK Dr Anver Kamil FY2 Russells Hall Hospital Dudley UK Dr Amar Puttanna FY2 University Hospital Coventry and Warwickshire Coventry UK Page 12 of 13

13 References 1) YH Li, JCY Leong; in toeing gait in children. HKMJ 1999;5: ) M. Pirpiris, A. Trivett, R. Baker, J. Rodda, G. R. Nattrass, H. K. Graham: Femoral derotation osteotomy in spastic diplegia Journal of Bone and Joint Surgery - British Volume 2003, Vol 85-B, Issue 2, ) Tegnander A; Holden KJ: The natural history of hip abnormalities detected by ultrasound in clinically normal newborns: a 6-8 year radiographic follow up study of 93 children. Acta Orthopaedica 1999, Vol. 70, No. 4, Pages ) Gulan G; Matovinovic D; Nemec B; Femoral Neck Anteversion; values, development, measurement, common problems. Coll Antropol Dec;24(2): ) Moulton A;Upadhyay, SS; A direct method of measuring femoral anteversion using ultrasound. J Bone Joint Surg. Br 1982;64(4): ) K.P. Guenther, R. Tomczak, S. Kessler, T. Pfeiffer and W. Puhl. Measurement of femoral anteversion by magnetic resonance imaging - evaluation of a new technique in children and adolescents. European Journal of Radiology Volume 21, Issue 1, November 1995, Pages ) Brody AS; Frush DP; Huda W; Brent RL; Radiation risk to children from computed tomography 8) L C Baker and S K WheelerManaged care and technology diffusion: the case of MRI. Health Affairs, Vol 17, Issue 5, ) 9) Schneider B, Laubenberger J, Jem Measurement of femoral antetorsion and tibial torsion by magnetic resonance imaging. Br J Radiol. 1997;70: ) Jakob RP, Haertel M, Stüssi E. Tibial torsion calculated by computerized tomography Page 13 of 13