HOW-TO SESSION: PRE-PURCHASE EXAM FOR THE WESTERN HORSE


the lateral view is an important part of a thorough radiograph evaluation of the navicular bone. How- ever, frequently prominent navicular bone abnor- malities are present that are not evident on the lateral view. Therefore, it can be difficult when there are discrepancies in the navicular bone ap- pearance on the lateral and skyline views. Image quality, with assessment of technique and position, as well as the conspicuity of the potential abnormal- ity on each specific view, are considerations when determining which view is more accurate in cases with a discrepancy. The same detailed assessment of all the views in


all anatomic regions should be undertaken. Each radiographic view should be fully evaluated for abnormalities but will highlight particular areas and types of pathologic change. Not every radio- graph can be perfect. However, ideally, the partic- ular area of interest for each radiograph should be well visualized, despite imperfections in the image. The fact that certain abnormalities can only be iden- tified on a single, specific radiographic view becomes extremely important when evaluating pre-purchase radiograph studies. Incomplete studies will pre- vent the identification of abnormalities that may be relevant in a pre-purchase examination. This is an important discussion point when views are omitted at the client’s request, to ensure they understand the ramifications of this decision. Abnormalities identified during acquisition of the standard views should be assessed to determine if additional radiographic views can be obtained that will provide more information about the identified abnormality. The importance of slightly different angles in the dorsopalmar view when evaluating fetlocks has been shown.6 Slightly different angles can obscure or highlight injury to the sagittal groove of the proximal phalanx as well as to other regions of the fetlock joint. This is also true in other joints. If there is concern due to an abnormality identified on the clinical exanimation or a suspicious find- ing on a standard view, then changing the angle slightly from the standard view can be helpful. Similar to the DP view of the fetlock, this applies to the oblique views of the tarsi and the caudocranial views of the stifles. An example of this on the caudocranial view of the stifle occurs between the medial periarticular margin and the caudomedial margin of the medial femoral condyle. Slight changes in medial to lateral obliquity of the caudocranial view can result in superimposition of the caudomedial margin of the medial femoral con- dyle over the medial periarticular margin, obscuring peri-articular proliferation. This can be alleviated by recognizing the superimposition and retaking the view with a slight change in the medial to lateral angle of the beam. In addition to slight changes in the standard


views, views that further highlight certain abnor- malities should also be utilized when those abnor- malities are identified on the standard study. The


flexed cranio 10° disto 10° lateral-caudoproximome- dial oblique view of the stifle is considered quite beneficial when potential abnormalities are identi- fied on the distal aspect of the medial femoral con- dyle.7 This view provides an additional dimension to abnormalities on the cranial distal aspect of the medial femoral condyle that is not achieved with the standard view of the stifle. The contribution of oblique views of the cervical spine is becoming in- creasingly apparent and should be considered, espe- cially with any clinical signs related to this region. In certain cases, abnormalities are identified on radiographs that cannot be fully characterized for a number of different reasons. These reasons most often include soft tissue involvement, the limitations of detecting subtle changes in bone density radio- graphically, and/or the presence of associated fluid. In this situation, additional imaging modalities are a consideration. The decision to use additional im- aging modalities in the pre-purchase examination is made based on details individual to each case, such as the specific abnormality or area of concern, the imaging modalities available in the location of the horse, the client’s budget, and the possibility of achieving useful information.


4. Additional Imaging Modalities


Ultrasound, nuclear scintigraphy, computed tomog- raphy (CT), and MRI all have a place in the pre- purchase examination in certain cases. Each of these modalities can provide information that can- not be obtained with radiographs. Furthermore, in certain cases, these additional imaging modalities are invaluable for characterizing abnormalities identified on radiographs. The nature of the radio- graphic abnormality or clinical finding dictates the modality selected for subsequent imaging.


Ultrasound


Ultrasound is frequently used in the pre-purchase examination for many different reasons. In certain cases, it is used to investigate abnormalities identified during the clinical examination, such as enlargement or a pain associated with soft tissue structures. In addition, ultrasound examinations are performed following the identification of radio- graphic abnormalities that can have associated soft tissue findings or when evaluation with ultrasound can provide more information about a radiographi- cally visible osseous abnormality. With increasing frequency, ultrasound is used even in the absence of clinical or radiographic abnormalities to examine predilection sites of soft tissue injury that may be related to a particular discipline. Ultrasound is an obvious choice with palpable


tendon or ligament enlargement as well as with bony remodeling at a soft tissue attachment that is identified radiographically. However, it can also be incredibly helpful for certain radiographic abnor- malities that can be more difficult to identify or quantify, such as periarticular osteophyte formation


AAEP PROCEEDINGS  Vol. 65  2019 463


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