The suspensory apparatus of the distal phalanx in normal horses

Pollitt, C. C. and Collins, S. N. (2015) The suspensory apparatus of the distal phalanx in normal horses. Equine Veterinary Journal, 1-6. doi:10.1111/evj.12459

Author Pollitt, C. C.
Collins, S. N.
Title The suspensory apparatus of the distal phalanx in normal horses
Journal name Equine Veterinary Journal   Check publisher's open access policy
ISSN 2042-3306
Publication date 2015-07-02
Sub-type Article (original research)
DOI 10.1111/evj.12459
Start page 1
End page 6
Total pages 6
Place of publication Hoboken, NJ United States
Publisher John Wiley & Sons
Collection year 2016
Language eng
Formatted abstract
Reasons for performing study:  The suspensory apparatus of the distal phalanx (SADP) is functionally and clinically important.

Objectives:  To investigate SADP form and function and the microanatomy of its insertion zone.

Study design:  Descriptive gross and microanatomy.

Methods:  The feet of 6 normal Standardbred horses were sectioned into blocks along the traditional perpendicular transverse axis and along functional axes of the SADP, decalcified and processed for staining with haematoxylin and eosin, Jones' periodic acid silver methenamine or Masson's trichrome stains.

Results:  In traditional midline toe transverse plane sections SADP collagen bundles were irregular with an unstructured appearance. In sections made transversely along planes (70° and 30°) aligned with the long axis of the SADP, collagen bundles were arranged in linear rows. The linear bundles were continuous from their origin on parietal ridges of the distal phalanx through to the secondary epidermal lamellar basement membrane. At the parietal ridge interface the collagen bundles coalesced into smaller, strongly silver staining, linear structures that penetrated the cortical bone and merged with adjacent osteons. In proximal sagittal sections collagen bundles were also linear, angled at 70° to the ground surface. In distal sagittal sections collagen bundles were also arranged linearly but in a multi-angled, ‘spokes of a wheel’ arrangement, centred on the distal phalanx apex.

Conclusions:  Sectioning along functional axes demonstrated the true suspensory nature of the SADP connecting the parietal surface to the lamellar hoof wall. SADP/distal phalanx insertions showed penetrating fibres extending through the chondral–apophyseal interface up to and between distal phalanx osteons. Lamellar measurements made from sections perpendicular to the dorsal aspect of the distal phalanx are underestimations but if made along the longer, functional midline 70° transverse plane would accurately reflect the suspensory function of the lamellae. Laminitis pathophysiology correctly viewed as SADP degradation should inform logical, future therapeutic strategies.
Keyword Horse
Basement membrane
Hoof primary and secondary lamellae
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Early view of article.

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2016 Collection
School of Veterinary Science Publications
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