ABSTRACT: With diagnostic imaging being widely utilised nowadays in veterinary practice, it is important that the veterinary nurse has a good understanding of how this equipment works and what it is used for. Although the use of X-rays to produce a diagnostic image on film is still the most common imaging technique used, there are many more emerging technologies now available to aid in the diagnosis of both surgical and medical conditions.
This article will discuss two separate cases in which radiography and computed tomography (CT) have been used as invaluable diagnostic modalities in the diagnosis of fractures. These cases have been extracted from a diagnostic imaging casebook completed as part of the new DipAVN course with Myerscough College.
Case 1: Bilateral mandibular fractures
A six-month-old, entire female 25kg Newfoundland presented with facial trauma following a suspected road traffic accident. On presentation, the patient was salivating and unable to fully close her mouth. Physical examination by the veterinary surgeon concluded that the mandible was painful on palpation but no other abnormalities were detected.
The patient was sedated using 0.25mg medetomidine hydrochloride (Sedator, Dechra, 1mg/ml solution) and 0.025mg butorphanol (Torbugesic, Fort Dodge, 10mg/ml solution) in order to allow a full oral examination and radiography. Right lateral and dorso-ventral (DV) views of the skull were obtained using foam wedges to aid positioning (Table 1).
The dorso-ventral view is preferred to the ventro-dorsal (VD) as the mandibles help to limit lateral rotation of the skull1. Radiography revealed bilateral mandibular fractures (Figures 1a and 1b) which were repaired with a circular external fixator used to immobilise the jaw to allow union of fracture ends.
Figure 1a: Lateral view of the skull showing fracture lines prior to repair and callus formation three weeks post repair. Note the radiopaque structure surrounded by an osteolucent area on the left mandible three weeks post repair
Figure 1b: Dorso-ventral views of the skull showing fracture lines prior to repair and callus formation three weeks post repair
Radiographic examination performed three weeks following surgical repair revealed that there was no indication of implant problems or loosening, with the fracture held in good alignment and apposition with no malocclusion of the teeth.
There was evidence of smooth new bone proliferation-callus formation in both right and left mandibles. However, on the left mandible, there was a radiopaque mineralised structure visible within the fracture site, surrounded by an osteolucent area. Given the superimposition of bones, this area could not be better characterised and a sequestrum could not be ruled out.
As CT is extremely sensitive for detecting subtle areas of osteolysis, new bone formation and soft tissue mineralisation, perhaps it would have been of benefit in this case.3 Although the fracture had not yet healed completely at this stage, because the patient was a young, growing dog, it was judged that the fracture was sufficiently healed for the fixator to be removed.
The patient continued to do well following fixator removal and with no complications.
Case 2: Diagnosis of fracture of humeral condyle
A nine-month-old, entire female, 21kg English pointer presented for investigation after a several month history of right fore limb lameness which failed to improve on restricted exercise. On presentation she was 7/10 lame with marked joint effusion and muscle atrophy. She exhibited pain on full extension of the elbow but range of motion was normal.
As radiographs had already been taken and no abnormalities detected a CT of the elbows was indicated.
The patient was sedated using 0.2mg medetomidine hydrochloride (Sedator, Dechra, 1mg/ml solution) and 0.02mg butorphanol (Torbugesic, Fort Dodge, 10mg/ml solution) and positioned in sternal recumbency with both elbows extended and parallel (Table 2). It is important that both elbows are scanned to allow for comparison of anatomy.
Once the patient was positioned accurately the table was advanced until the area of interest was positioned within the gantry containing the X-ray tube and detector. A survey radiograph was then taken to localise regional anatomical landmarks so that the CT could be programmed to cover the appropriate region. The window level was set for visualisation of bone (+1000 Hounsfield Units) and axial slice thickness of 1.1mm was selected.
The patient was positioned well for this CT with both elbows parallel and no superimposition of other structures, such as the head. The CT provided excellent contrast and bony detail and, owing to its three-dimensional imaging, it provided a diagnostic picture of the elbow joint.
This showed a wide hypoattenuating line, measuring up to 5mm wide, at the midregion of the condyle surrounded by marked bone sclerosis. This confirmed that the lameness was attributable to a partial fracture of the right humeral condyle, so the patient was taken to theatre where a screw was placed across the affected condyle (Figure 2).
Figure 2: CT image of both right and left elbow joints. Note the hypoattenuating line at the mid region of the condyles extending from the supratrochlear foramen to the joint surface. This hypoattenuating line is surrounded by marked bone sclerosi
Humeral condylar fractures may be associated with minimal trauma secondary to incomplete ossification of the humeral condyle (IOHC).4 Like the condylar fracture, radiographically, IOHC is difficult to demonstrate because of the superimposition of the olecranon in both the frontal and frontal oblique projections.5 Therefore, CT is often the diagnostic tool of choice for imaging of the elbow.
Radiographs taken six weeks later showed no evidence of implant problems or loosening and the dog was bearing weight well on the leg. The owner was advised to gradually increase the dog’s exercise over the next few weeks and the implant was left in situ.
No further problems were encountered and the dog returned to full exercise over the following weeks.
Summary
A full evaluation of any fracture requires at least two views.6 In planning follow-up radiography, it is necessary to make an educated guess as to when clinical union will have taken place. Clinical union is defined as that point in time during recove
ry when fracture healing has progressed sufficiently for the fixation device to be removed.
For animals between six to 12 months of age, such as both the patients discussed, time taken to reach clinical union using fixation is normally estimated at between five to 12 weeks. However, in Case 1, owing to the increasing size of the patient and the restrictions associated with the external fixator, this was removed earlier than normal.
Diagnostic imaging techniques are a vital tool in veterinary practice to aid in the diagnosis of a wide range of conditions, especially fractures. They can be used to image a variety of different areas, such as the jaw or elbow, and provide detailed images of tissues from bone to soft tissue. With the invention of newer imaging techniques, such as CT, a greater picture of the internal structures can be viewed without surgical intervention.
Author
Sarah Kelly DipAVN (Small Animal)
DipHE CVN RVN A1
Sarah qualified and listed as a veterinary nurse in 2004 after completing her VN training at Bicton College of Agriculture. She worked at the PDSA Petaid Hospital and then the Glenbrae Veterinary Clinic where she gained experience in private practice before moving to Glasgow University Veterinary Hospital. It was there that she discovered her passion for referral nursing and since Sept 2009 she has been employed as a specialist VN at the first Vets Now Hospital.
References
1. SULLIVAN, M. (1995) The Head and Neck, in Lee, R. (Ed.) Manual of Small Animal Diagnostic Imaging 2nd Edition, UK, BSAVA.
2. DENNIS, R. (1999) Radiography, in Lane, D. R. A & Cooper, B. (Eds.) Veterinary Nursing 2nd Edition, Oxford, Butterworth Heinemann.
3. DENNIS, R. (2006) Skull – general, in Barr, F. J. & Kirberger, R. M. (Eds.) BSAVA Manual of Canine and Feline Musculoskeletal Imaging, UK, BSAVA.
4. KIRBERGER, R. M. (2006) The Elbow Joint, in Barr, F. J. and Kirberger, R. M. (Eds.) BSAVA Manual of Canine and Feline Musculoskeletal Imaging, UK, BSAVA.
5. FARROW, C. S. (2003) Skeletal Deficiencies, Dysplasias, and Deformities, in Farrow, C. S. (Ed.) Veterinary Diagnostic Imaging The Dog and Cat Volume 1, St Louis, Mosby.
6. DAVIES, J. V. And Lee, R. (1995) The Appendicular Skeleton, in Lee, R. (Ed.) Manual of Small Animal Diagnostic Imaging 2nd Edition, UK, BSAVA.
7. BUTTERWORTH, S. J. (2006) Long bones – fractures, in Lane, D. R. & Cooper, B. (Eds.) Veterinary Nursing 2nd Edition, Oxford, Butterworth Heinemann.
Suggested Further Reading
EASTON, S. (2002) Radiographic techniques, in Easton, S. (Ed.) Practical Radiography for Veterinary Nurses, Oxford, Butterworth-Heinemann.
FOSSUM, T. W. (2007) Management of Specific Fractures, in Fossum, T. W. (Ed.), Small Animal Surgery 3rd Edition, St Louis, Mosby Elsevier.
OWENS, J. M. and BIERY, D. N. (1999) Radiographic Interpretation for the Small Animal Clinician 2nd Edition, USA, Williams and Wilkins.
Acknowledgements
The author would like to thank the University of Glasgow Small Animal Hospital, where the above case studies were carried out.
Veterinary Nursing Journal • VOL 25 • No5 • May 2010 •