Foot Flashcards
Broad categorisation of DDF tendinopathy within the foot
1) Core lesions
2) Sagittal/parasagittal splits
3) Insertional
4) Dorsal border fibrillation
(5) Multifocal)
Px generally better for dorsal border leisons vs core and sagittal splits (approx 27% remaining lame vs 50% of horses with complete parasagittal splits and 69% of horses with core lesions remained lame)
Conservative tx options for DDF tendonopathy and px
Rest (often prolonged; 6-9months depending on lesion severity)
Local or systemic anti-inflammatories
Corrective farriery (lesion dependenent - often heel elevation - raising by 1° reduces DDF strain by approx 4% but long term use of wedges may rx in heel collapse
SWT
Bisphosphonates (navicular bone injury)
Usually poor response to conservative tx - approx 30% sound
Px generally better for dorsal border leisons vs core and sagittal splits (approx 27% remaining lame vs 50% of horses with complete parasagittal splits and 69% of horses with core lesions remained lame)
Sx tx options for DDF tendinopathy
Dependent on lesion location
1) Bursoscopic debridement - approx 60% sound PO , 42% at prev exercise level although worse px for more sever core lesions or splits (Smith and Wright 2012)
Since brusoscopic debridement is only applicable to dorsal tears, which respond more favourably than other lesions, px with sx may not be greater than conservative tx alone
(2) ‘Regereratives’ also likely improved px vs conservative alone eg Marcatilli 2018 EVE MRI guided PRP injection of insertion (n=1)
3) Neurectomy - not suitable for those with core or linear lesions (quick return of lameness and possible DIPj luxation)
4) ALDDFT desmotomy - reported by Humbach 2018 EVE - used in 3 cases with severe or fefreactory DDF pathology with good success (used for leisure, mild residual lameness)
Negative px indicators with core lesions of DDFT
Lesions >10% XSA of the affected lobe or total length >30mm
Shoeing recommendations for DDF tendinopathy
Shoes that prevent heel descent during loading in soft ground and promote early break-over in the toe incl. egg bar or onion shoes (Denoix) with rolled toes
Raised heel shoes offer mixed results as they may paradoxically exacerbate lameness and may also induce contracture of the DDFT during tendon healing. They reduce strain in the tendon by increasing DIPj flexion, but should be applied only temporarily to provide initial pain relief in horses with acute or severe tendinopathy
Types of P3 fracture
Tx of DIPj collateral ligament injury
Rest - 4-8wk strict box rest, then 8-16 rest and walking
Shoes - wide webbed on the affected side
SWT - debatable benefit - 1 study demonstrated improved outcome vs rest alone (25%vs13% return to soundness)
Intra-lesional ‘regeneratives’- PRP/MSCs etc under US (proximal), rad (distal), CT or MR (more accurate) guidance
Dorsal approach(es) to the coffin joint
Can be done WB or lifted.
Parallel to the bearing surface, perpendicular (to the bearing surface), incline (perpendicular to the skin) or dorsolateral approaches are possible. Coronet is the landmark for all
Lateral approach to the DIPj
Landmarks are palmar middle phalynx and the palpabl proximal border of the ungular cartilage
The needle is directed medially at a 45° angle distally and 20° palmar to penetrate the palmar pouch of the DIP joint
Palmar approach to the DIPj
The site for injection is a point on the palmar midline slightly proximal to the deepest indentation of the fossa proximal to the bulbs of the heel. A 3.5” spinal needle is directed dorsally aiming for a point halfway between the coronet and the bearing surface of the hoof at the toe
Advantages and disadvantages of 3.5 and 4.5 mm screws for navicular bone fractures
3.5mm (2.4mm core, 6mm head, 2.5mm thread)
+ easier insertion
+ increased flexibility for avoidance of inadvertent articular or flexor surface penetration. BUT
- possible insufficient size to withstand biomechanical forces; breakage of a 3.5 mm screw following repair of distal sesamoid bone fractures has been documented
4.5mm (3mm core, 8mm head, 3.2mm thread)
+ increased stability under load
+ greater resistance to cyclic fatigue BUT
- higher risk of exiting into the articular surface during placement
- potential for fracture of smaller cis cortices during tightening of the screw.
- depending on the dimensions of the navicular bone, the larger screw head can also modify the articular surface
Main 2 manifestations of keratomas (types)
In most instances, keratomas manifest as an aberrant cylindrical growth of keratin that follows the horn tubules distally.
Less commonly, can take the form of a solitary spherical mass within the hoof capsule
Classic radiographic feature of keratoma
Because of their expansile nature, keratomas impinge on the distal phalanx, resulting in chronic inflammation, pressure resorption, and the characteristic semicircular lucency often observed radiographically.
Usually smoothly marginated, unlike the lucency created with pedal osteitis, the main radiographic differentiation
Difference between partial and complete hoof wall resection in the tx of keratoma
Advantages of partial vs complete resection?
Main difference is taking a ‘window’ in the partial resection; leaving at least a 2cm bridge of hoof distal to the resection site; vs with complete - the 2 vertical cuts are joined at the white line.
- Signifcantly higher complication rate following complete resection (71%) vs partial resection (25%) (Boys Smith 2006)
Complications incl. excess granulation tissue formation, hoof crack formation, hoof capsule instability, surgical site infection and keratoma recurrence at the surgical site.
- The time taken to return to full work PO is significantly shorter following partial vs complete resection
Outcomes following CT guided keratoma resection reported by Katzman 2019 JAVMA
- 31/32 survival to DC
- 13% (4/31) complication rate in those surviving to DC - incl recurrence (2) and granulation tissue formation most commonly (likely relates to hoof wall instability). Fatal in 1 where re-op rx in DIPj penetration and sepsis
- No complications in the complete resections but only 2 performed, remainder partial
- 90% returned to intended use at mean 8.9mo PO
What is the COP and the COR of the DIPj?
COP = centre of pressure; the summation of the GRF forces can be calculated to have a central point of action. This is located dorsally to the COR of the DIPj
COR = centre of rotation of the DIPj. Can be used as a marker of foot confromation; half the sole WB surface should be dorsal and half palmar to the COR DIPj
COP being dorsal to the COR creates an extensor moment around the CIPj, which is apposed by a flexor moment; the flexor moment opposes the extensor moment and is the product of the force (tension) in the tendon and the shortest distance of the DDFT from the centre of rotation
