Diagnostic accuracy of digital photography and image analysis for the measurement of foot conformation in the horse

White, Jonathan M. (2008) Diagnostic accuracy of digital photography and image analysis for the measurement of foot conformation in the horse. MVM(R) thesis, University of Glasgow.

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Abstract

Experimental studies have shown that foot conformation influences the forces experienced
by the distal limb (Riemersma et al. 1996; Wilson et al. 1998; Willemen et al. 1999;
Eliashar et al. 2004). Although some clinical studies have highlighted the importance of
foot conformation as a risk factor for musculoskeletal injury (Kane et al. 1998; Anderson
et al. 2004), this has not been a universal finding (Weller et al. 2006c). Clearly more
information from large, well designed, prospective studies is needed to elucidate further
the relationship between foot conformation and injury. This information would help to
guide veterinary surgeons and farriers in the trimming and shoeing of horses’ feet, a
practice carried out regularly (usually every 4-8 weeks) during the animal’s life. In order to
further investigate this relationship, a tool capable of accurately, precisely and practicably
collecting suitable objective data, ideally at relatively low cost, is necessary.
The variability introduced by image acquisition and subsequent analysis using digital
image processing software of digital photographs of the foot has not been quantified.
Similarly the level of agreement between objective measurements of foot conformation
made from digital photography and digital radiography is unknown.
The objectives of this project were to assess the precision, accuracy and practicability of
the entire process of obtaining measurements of horses’ feet using digital photography and
the digital image processing software (Metron-PX™).
For the precision study (prospective in vivo randomised clinical measurement study) lateral
digital photographs of shod Thoroughbred racehorses were obtained twice by two
veterinary surgeons working independently (Image Acquisition - IAc). Each photograph
was independently analysed by the two veterinary surgeons masked to the origin of the
images on two occasions using Metron-PX™ (Image Analysis - IAn). Measurements
generated by the software were compared within and between operators of the software for
self and non-self acquired photographs. Intra- and inter-operator agreement indices (AIs)
and 95% limits of agreement (LOA) were calculated for each measurement for the IAn
process alone and for the combined IAc + IAn processes for self and non-self acquired
images respectively. For the accuracy study (method comparison study) measurements
obtained from lateral digital photographs (index test), as in the precision study, were
compared with those obtained from lateromedial radiographs (reference standard).
Agreement indices (AIs) and 95% limits of agreement were calculated for each
measurement.
The results of the precision study identified excellent mean intra- and inter-operator AIs
for the IAn process alone ( 0.90 for all measurements). The mean intra- and inter-operator
AIs for the combined IAc + IAn processes were 0.89 for all measurements with similar
AIs obtained regardless of whether or not the individual whom acquired the images also
analysed them. The 95% limits of agreement for hoof angle, heel height/ toe height% and
coronary band angle for all comparisons were all within target values. The results of the
accuracy study identified mean AIs that were 0.89 for all measurements. The 95% limits
of agreement for heel height/ toe height% and coronary band angle were within target
values.
Overall, there was excellent precision both within and between operators of the
measurement process for both the image analysis process alone and the combined image
acquisition and analysis processes. When the described technique is used results are
comparable irrespective of whether the person whom acquired the images also analyses
them. Excellent accuracy was also identified between the photographic and radiographic
measurements, especially for heel height/ toe height% and coronary band angle, suggesting
that these two methods may be used interchangeably for these measurements of foot
conformation in the horse.
The clinical relevance of these findings is that the processes described for obtaining
objective measurements of foot conformation from digital photographs and digital image
processing software Metron-PX™ is practicable and produces highly precise
measurements regardless of whether the same operator performs both image acquisition
and analysis. Photographic measurements of heel height/ toe height% and coronary band
angle closely approximate radiographic measurements such that the two techniques may be
used interchangeably. Thus, digital photography and image analysis have applications in
the field of clinical telemedicine and would be particularly useful to a large prospective
multi-centre study investigating the relationship between foot conformation and
musculoskeletal injury.

Item Type: Thesis (MVM(R))
Qualification Level: Masters
Subjects: Q Science > QL Zoology
T Technology > T Technology (General)
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Veterinary Medicine
Supervisor's Name: Voute, Mr. Lance
Date of Award: 2008
Depositing User: Mr Robbie J. Ireland
Unique ID: glathesis:2008-1559
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Feb 2010
Last Modified: 19 Feb 2013 14:26
URI: http://theses.gla.ac.uk/id/eprint/1559

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