An investigation into the association between plantar distal phalanx angle and hindlimb lameness in aUKpopulation of horses

Abstract

Low heels are the most common hoof conformational abnormality seen in both the front and hind feet of horses. A low/negative distal phalanx angle in the front feet has been associated with palmar heel injuries but only recently has the significance of low/negative angles in the hind feet received attention. A study including a greater number of horses more representative of the UK horse population would be useful to UK equine practitioners. Our null hypothesis was that the plantar distal phalanx angle does not differ between horses with and without hindlimb lameness. For this prospective case-controlled study, horses presenting for orthopaedic complaints underwent a complete lameness assessment. The plantar distal phalanx angulation (PDPA), the angle between a line parallel to solar surface contacting the ground and the solar margin of the distal phalanx, was calculated from lateromedial radiographs. Horses were included in the study if hindlimb lameness was definitively localised by diagnostic anaesthesia. Student's t-tests and multivariable linear regression models were used for statistical analysis. One hundred and eighty-two horses met the inclusion criteria, 132 with hindlimb lameness and 50 controls. The mean left PDPA for HLL group was À1.0°vs. +1.8°for the controls. The mean right PDPA for HLL group was À1.1°vs. +1.4°in controls (both P<0.001). Lameness was most frequently localised to the stifle (59% of horses), followed by the distal tarsal joints and the proximal suspensory region. A limitation of the study was that the control group included some forelimb lame horses. It was concluded that horses with hindlimb lameness, including lameness localised to the stifle, were more likely to have negative PDPAs. While Pezzanite et al. (2019) previously reported a relationship between negative/neutral PDPA and tarsal/metatarsal lameness, this study is the first to find a relationship to stifle lameness, which may reflect differences in the populations of horses examined. Further kinematic studies are required to determine whether it is a cause or effect relationship.

An investigation of the shape of the hoof capsule in hindlimbs, its relationship with the orientation of the distal phalanx and comparison with forelimb hoof capsule conformation

“…2013]). Our results were more consistent with the reference range of the median angle S (0.9°) in the hind feet of a group of nonlame sports and pleasure horses (Pezzanite et al 2019) and the mean angle (1.6°) in a nonlame mixed group of UK horses (Clements et al 2020). In contrast, the plantar processes of the distal phalanx in the hindlimbs were lower than the toe in 60% of Australian Thoroughbred racehorses (Walmsley et al .…”

“…2019). Angle S was significantly smaller in sports, pleasure and racing horses with stifle pain compared with hock pain (Clements et al 2020). In contrast, in sports and pleasure horses an angle S of ≤0° was more prevalent in horses with lameness originating from the distal tarsus and proximal metatarsus, compared with nonlame horses or horses with stifle pain (Pezzanite et al 2019).…”

“…Fifty‐three per cent of the horses in the latter study were unshod at the time of assessment. Horses with hindlimb lameness that were shod had a smaller angle S compared with unshod lame horses (Clements et al 2020). It is currently not known if being barefoot has any long‐term influence on hind foot hoof capsule shape and orientation of the distal phalanx, although in the current study DHWA and HA were larger in unshod hind feet compared with shod feet.…”

“…In two recent studies which were based on lateromedial radiographic images of hind feet, the angle of the distal aspect of the distal phalanx to the horizontal was smaller in horses with hindlimb lameness than in nonlame horses (Clements et al . 2020; Pezzanite et al . 2019).…”

Clinical insights: Lameness diagnosis in sports horses

“…From the study it could not be established whether neutral/negative plantar angle of the distal phalanx contributed to development of lameness or was a consequence of it. Negative plantar angle of the distal phalanx has been associated with hindlimb lameness (including lameness localised to the stifle) in another population of horses, 27 and with scintigraphic evidence of subchondral bone injury in the metatarsal condyles 28 . Based on the available information the significance of neutral or negative plantar angle of the distal phalanx is not clear, but the association with lameness warrants attention.…”