Femoral imaging artifacts associated with dorsal recumbency craniocaudal radiographic positioning

Summary

Objectives: To describe the radiographic length distortion associated with femoral tilt during cranio-caudal positioning. To describe a modified bisecting angle technique to alleviate image foreshortening.

Methods: Five pairs of femurs were imaged. The femurs were tilted from 0 to 50 degrees and the X-ray anode was tilted from 0 to 40 degrees. Femoral length was measured on the resulting images. A geometric model depicting sagittal femoral positioning was described with two trigonometric formulas. Trigonometric formula 1 (TF¹) was designed to predict apparent femoral length. Data generated by TF¹ were compared to the cadaveric study results. Trigonometric formula 2 (TF²), based on the same model, was used to predict the ideal anode angle (iAA) to alleviate foreshortening. Unrelated to the model, a simplified linear formula (SF) was created to approximate the TF². Data generated with the SF and the TF² were compared.

Results: When the femoral specimens were tilted to 20 degrees or greater, significant foreshortening was appreciated (p <0.001). Increasing the anode angle increased apparent length, eliminating foreshortening. Data generated by the TF¹ agreed closely with the results of the cadaveric study (R² = 0.999). The SF and the TF² demonstrated close agreement and were able to predict an iAA consistent with the results of the cadaveric study.

Clinical significance: A femoral tilt of 20 degrees or greater results in significant image foreshortening and may warrant alternate radiographic techniques. If the femur is tilted, adjusting the anode angle can alleviate femoral foreshortening.

Keywords

Femur - radiographic - artifact - foreshortening - bisecting

• References

• 1 Fox DJ, Tomlinson JL. Principles of angular limb deformity correction. In: Tobias KM, Johnston SA. editors. Veterinary Surgery: Small Animal. vol 1 St. Louis: Elsevier Saunders; 2012. pg. 2012-657.
• 2 Bardet JF, Rudy RL, Hohn RB. Measurement of femoral torsion in dogs using a biplanar method. Vet Surg 1983; 12: 1-6.
• 3 Mortari AC, Rahal SC, Vulcano LC. et al. Use of radiographic measurements in the evaluation of dogs with medial patella luxation. Can Vet J 2009; 50: 1064-1068.
• 4 Vinayak A, Kerwin SC, Ward MP. et al. Effects of femur position on radiographic assessment of completeness of femoral head and neck excision in medium - to large-breed dogs. Am J Vet Res 2006; 67: 64-69.
• 5 Beck KA, Erb HM, Tapley K. Effect of sagittal plane positioning errors on measurement of the angle of inclination in dogs. Vet Surg 1992; 21: 332-336.
• 6 Hauptman J, Prieur WD, Butler HC. et al. The angle of inclination of the canine femoral head and neck. Vet Surg 1979; 8: 74-77.
• 7 Thrall DE, Widmer WR. Physics of diagnostic radiology, radiation protection, and darkroom theory. In: Thrall DE. editor. Textbook of Veterinary Diagnostic Radiology. St. Louis: Elsevier Saunders; 2007. pg. 2007-2.
• 8 Jackson GM, Wendelburg KL. Evaluation of the effect of distal femoral elevation on radiographic measurement of the anatomic lateral distal femoral angle. Vet Surg 2012; 41: 994-1001.
• 9 Palmer R. Patella luxation: Femoral osteotomy and other therapeutic options in large breed dogs. Proceedings of the 12th annual American College of Veterinary Surgeons Symposium. 2002. October 17-20 San Diego, CA, USA: pg. 41-45.
• 10 Kowaleski MP. Femoral corrective osteotomy for medial patella luxation. Proceedings of the 16th Annual American College of Veterinary Surgeons Symposium. 2006. October 5-7 Washington DC, USA: pg. 473-476.
• 11 Jehn CT, Manley PA. The effects of femur and implant position on the radiographic assessment of total hip femoral implants in dogs. Vet Surg 2002; 31: 349-357.
• 12 Morgan JP, Stephens M. Radiographic diagnosis and control of canine hip dysplasia. Davis, CA: Venture Press; 1985. pg. 1985-39.
• 13 Forsberg J, Halse A. Radiographic simulation of a periapical lesion comparing the paralleling and the bisecting-angle techniques. Int Endod J 1994; 27: 133-138.
• 14 Forsberg J. Radiographic reproduction of endodontic “working length” comparing the paralleling and the bisecting-angle techniques. Oral Surg Oral Med Oral Pathol 1987; 64: 353-360.
• 15 The Ohio State University College of Dentistry. Self-study bisecting-occlusal [Document on Internet]. [cited on 2013 February 17]. Available from: http://dent.osu.edu/radiology/self-study-bisecting-occlusal.ppt or http://www.powershow.com/view/3bd425-NjljZ/0_Bisecting_Angle_Technique_Occlusal_Technique_The_following_powerpoint_ppt_presentation
• 16 The Ohio State University College of Dentistry. Bisecting angle technique occlusal technique panoramic concepts [Document on Internet]. [cited on 2013 February 17]. Available from:www.dent.ohio-state.edu/courses/d545/545-3-11.Sum.doc or http://www.powershow.com/view/3bd425-NjljZ/0_Bisecting_Angle_Technique_Occlusal_Technique_The_following_powerpoint_ppt_presentation
• 17 Gemmill TJ, Pink J, Renwick A. et al. Hybrid cemented/cementless total hip replacement in dogs: Seventy-eight consecutive joint replacements. Vet Surg 2011; 40: 621-630.
• 18 Guiot LP, Déjardin LM. Prospective evaluation of minimally invasive plate osteosynthesis in 36 nonarticular tibial fractures in dogs and cats. Vet Surg 2011; 40: 171-182.
• 19 Skaggs DL, Glassman D, Weiss JM. et al. A new surgical technique for the treatment of supracondylar humerus fracture malunions in children. J Child Orthop 2011; 5: 305-312.
• 20 Marcellin-Little DJ, Ferretti A, Roe SC. et al. Hinged Ilizarov external fixation for correction of antebrachial deformities. Vet Surg 1998; 27: 231-245.
• 21 Quinn MK, Ehrhart N, Johnson AL. et al. Realignment of the radius in canine antebrachial growth deformities treated with corrective osteotomy and bilateral (type II) external fixation. Vet Surg 2000; 29: 558-563.
• 22 Schmidutz F, Steinbrück A, Wanke-Jellinek L. et al. The accuracy of digital templating: a comparison of short-stem total hip arthroplasty and conventional total hip arthroplasty. Int Orthop 2012; 36: 1767-1772.
• 23 Johnston SA, Pfeil DJF, Déjardin LM. et al. Internal Fracture Fixation. In: Tobias KM, Johnston SA. editors. Veterinary Surgery: Small Animal. vol 1 St. Louis: Elsevier Saunders; 2012. pg. 2012-576.
• 24 Roe S, Marcellin-Little D, Lascelles BD. Radiographic evaluation of early periprosthetic femoral bone contrast and prosthetic stem alignment after uncemented and cemented total hip replacement in dogs [letter]. Vet Surg 2012; 41: 902-903.
• 25 Marcellin-Little DJ, DeYoung BA, Doyens DH. et al. Canine uncemented porous-coated anatomic total hip arthroplasty: results of a long-term prospective evaluation of 50 consecutive cases. Vet Surg 1999; 28: 10-20.
• 26 Lascelles BD, Freire M, Roe SC. et al. Evaluation of functional outcome after BFX total hip replacement using a pressure sensitive walkway. Vet Surg 2010; 39: 71-77.
• 27 Fitzpatrick N, Nikolaou C, Isaza Saldarriaga JF. et al. The effect of configuration and radiographic positioning on measurements of deformity magnitude in a dog with a complex antebrachial growth deformity: Comparison between radiographic and 3D computer modeling measurements. Proceedings of the 20th Annual Scientific Meeting European College of Veterinary Surgeons. 2011. July 7-9 Ghent, Belgium: pg. 92.
• 28 Read RL, Duncan CG, Wallace AD. et al. Assessment of on-screen measurements, magnification, and calibration in digital radiography. J Am Vet Med Assoc 2012; 241: 782-787.
• 29 Descamps S, Livesey C, Learmonth ID. Determination of digitised radiograph magnification factors for pre-operative templating in hip prosthesis surgery. Skeletal Radiol 2010; 39: 273-277.