foot anatomy

Reason for study

Anatomical change within a laminitic foot is of diagnostic and prognostic importance. A lateromedial radiograph represents the current 'gold standard' by which these changes are identified. Detection of anatomical change is dependent upon a priori knowledge of normality and subjective assessment alone may not identify modest change. Normal baseline data is, therefore, needed against which objective comparisons can be made. There is little information regarding the radiological anatomy of the donkey foot, hence an equine model has been widely adopted. However, descriptive accounts suggest fundamental anatomical differences between these 2 species.

Objectives

To characterise objectively the radiological anatomy of normal donkey feet and define the nature and extent of anatomical change associated with laminitis.

Methods

The anatomy of the forefoot was quantified from lateromedial radiographs of 83 normal and 74 laminitic donkeys, using a computer based imaging system. Data were analysed using univariate and bivariate statistical methods.

Results

Baseline data were established that define the radiological characteristics of the anatomy of normal donkey feet. The key hoof, bone and weightbearing stance parameters of lateromedial radiographs have been evaluated. Laminitis was associated with significant rotation and distal displacement of the distal phalanx, increases in integument depth and morphometric change to the distal phalanx (P<0.05).

Conclusions

This study challenges the validity of applying an equine model to the radiological anatomy of donkey feet. Hence, the diagnosis of anatomical change cannot be based on baseline data previously given for the horse and guidelines should be revised accordingly for the donkey.

Potential relevance

This study provides an objective basis for the identification of anatomical change associated with laminitis in donkey feet.

Disorders of the hoof have important health and welfare implications in donkeys. Clinical conditions that affect the donkey hoof include laminitis, which is one of the most common causes of lameness in donkeys in the UK, as well as white line disease/abscess, and chronic conditions such as overlong hooves. This article reviews the normal anatomy and function of the donkey’s foot, before discussing in more detail the diseases that can arise and their treatment.

Objective

To establish and validate an objective method of radiographic diagnosis of anatomic changes in laminitic forefeet of donkeys on the basis of data from a comprehensive series of radiographic measurements.

Animals

85 donkeys with and 85 without forelimb laminitis for baseline data determination; a cohort of 44 donkeys with and 18 without forelimb laminitis was used for validation analyses.

Procedures

For each donkey, lateromedial radiographic views of 1 weight-bearing forelimb were obtained; images from 11 laminitic and 2 nonlaminitic donkeys were excluded (motion artifact) from baseline data determination. Data from an a priori selection of 19 measurements of anatomic features of laminitic and nonlaminitic donkey feet were analyzed by use of a novel application of multivariate statistical techniques. The resultant diagnostic models were validated in a blinded manner with data from the separate cohort of laminitic and nonlaminitic donkeys.

Results

Data were modeled, and robust statistical rules were established for the diagnosis of anatomic changes within laminitic donkey forefeet. Component 1 scores ≤ −3.5 were indicative of extreme anatomic change, and scores from −2.0 to 0.0 denoted modest change. Nonlaminitic donkeys with a score from 0.5 to 1.0 should be considered as at risk for laminitis.

Conclusions and clinical relevance

Results indicated that the radiographic procedures evaluated can be used for the identification, assessment, and monitoring of anatomic changes associated with laminitis. Screening assessments by use of this method may enable early detection of mild anatomic change and identification of at-risk donkeys.