Value of Quality Foot Radiographs and Their Impact on Practical Farriery

1. Introduction

Radiographic evaluation of the horse’s foot for the purpose of consultation with the farrier is becoming more popular but is still an underutilized use of radiographic imaging. In the absence of lameness, detailed radiographic evaluation of the horse’s foot is very useful in preplanning and management of trimming and shoeing of a horse’s foot and in the prevention of lameness. A horse’s exhibiting poor foot conformation, imbalance, or abnormal patterns of growth can be clues to impending foot disease and lameness. Radiographic evaluation of a horse’s foot gives tremendous insight into the relationship between the structures within the foot and between the foot and distal limb.

Digital photography has also been shown to be useful and accurate in the assessment of the horse’s foot.¹  However, the relationship of the distal phalanx with the hoof capsule cannot be appreciated with photography alone.

The quality of information obtained from a radiographic study depends solely on the quality of the radiographs (“garbage in, garbage out”). Producing quality radiographs is dependent on the use of quality equipment, developing a proficiency at operating that equipment, and maintaining consistency when performing radiographic studies. A systematic approach should be taken when planning a radiographic study of the foot; the “point-and-shoot” approach is not always the best approach. Taking multiple standard views, although not always necessary, is important to avoid missing a diagnosis. Additional projections may be required to further investigate initial findings or confirm a diagnosis. There are a number of preplanning questions that must be asked before performing foot radiographs: (1) What is the purpose of the study: investigation of lameness or consultation with the farrier? (2) What do I expect to gain from the study: source of lameness or information useful in managing the foot? (3) What information do I need to obtain from the study: relationship of the hoof capsule and the distal phalanx? The answers to these questions will guide in planning the study with regard to the appropriate views to be taken, the appropriate technique, and the appropriate positioning of the foot and centering of the x-ray beam.

Taking the time to examine the foot and prepare it properly will avoid the need, risk, and expense of repeating images and will improve the quality and therefore the interpretation of your radiographic images. Before performing a full series of foot radiographs, it is common practice to recommend removing the shoes. However, when acquiring radiographs for the purpose of trimming and shoeing issues, leaving the shoes in place can be beneficial. Direct visualization of the weight-bearing surface and the position of the shoe in relation to the hoof capsule and distal phalanx can help in the planning process. This simplifies evaluation of break-over, sole depth, and balance of the foot. If a source of lameness has been localized to the foot, removal of the shoes may be necessary to obtain the additional views necessary to fully evaluate the foot. Proper shoe removal technique is a skill that the veterinarian must be comfortable with.

Cleaning the foot of all particulate matter as well as removing any fragmented wall and overgrown sole and frog will reduce the potential for gas artifacts. Any flakiness of or accumulations of debris on the outer wall can be removed with either a rasp or a sanding block. Radiographs taken to guide trimming and shoeing do not require packing the foot; if additional films are required, packing the foot is recommended. Packing the sulci with appropriate putty material reduces the likelihood of radiographic artifact due to gas in the sulci. Liberal use of the packing material should be used to fill the depths of the sulci; however, overpacking will cause packing artifact along the margins of the packing. Traditional packing in horses that have deep center sulci or overgrown bars can be difficult in eliminating all gas artifacts. Placing the foot in a water bath is an effective method of displacing trapped gas deep within the sulci or wall (Fig. 1). The water depth should be at a level just proximal to the heel bulbs. Placing the cassette or digital sensor in a plastic protective cover (trash bag) prior to placement of the foot will reduce the potential for water damage. A 50% increase in technique is recommended when using digital radiography; when using film-screen radiography, a significant increase in milliamperes will also be necessary and will depend on whether a grid is used or not.
 

[...]