Limb Deformities - Flexural Deformities (Sagittal Plane)

1. Definitions

1. As seen from the side, each joint may extend normally, less than normal (hypo-extension), or more than normal (hyper-extension).
2. While there is a large and fanciful vocabulary to describe flexural (and angular) deformities such as "club foot", "knuckling", "over at the knee", the terms hyper and hypoextension are preferred for clarity.
3. When evaluating from the side, bear in mind that new born foals naturally have less extension at the DIP and fetlock joints than adults, as they weigh a lot less.
4. When detecting a flexor deformity, it is useful to decide whether the defect is:

1. Moderate; not an immediate threat to the well being of the foal, with a good chance of spontaneous self-correction or easy to correct by conservative means.
2. Severe; probably not self-correcting, causing discomfort or tendency to worsen; needs immediate attention.
3. To determine severity in the case of hypoextension, manipulate the lower limb to test the joint’s ability for extension, palpate the tension created thereby in the flexor tendons and the common digital extension tendon.

2. Management and treatment of flexural deformities

These include: exercise or exercise restriction, bedding, bandaging, oxytetracyclines, specific hoof care techniques like trimming or gluing on extensions to the hoof and surgery.

5. Exercise

1. Exercise should be restricted (stall rest) in the case of hypo-extensions (contractions), as rest relaxes the flexor muscles and diminishes the vicious cycle of contraction -pain -further contraction.
2. Exercise tones up the muscles in the case of flexor flaccidity [3].

6. Bedding

1. Foals are born with a conically inverse hoof, i.e. the distal border of the hoof is narrower than the coronary band and furthermore the bottom of the hoof is covered with the equipodium or "feathers" which wears off with normal exercise on normal ground.
2. Deep bedding nullifies a lot of the functions of corrective trimming and of glue-on extensions
3. A good practice is to move the bedding to the sides of the stall during the day time, keeping only a thin, packed layer in the middle, where the foal can "feel the ground".

7. Bandaging

1. Robert Jones type bandaging is appropriate in severe cases of hypo-extension of joints, as bandaging relaxes flexor musculature.
2. Bandaging is more effective if done up to the elbow, but more difficult to keep nicely in place and therefore has to be checked regularly.
3. Do not splint, or use rigid tubing, unless you are really experienced and willing to monitor the foal continuously. Foals are very lively and thin skinned, serious pressure sores are too often the result of splinting and/or casting.
4. Bandaging relaxes the flexor muscle-tendon units so it should not be applied in cases of hyper-extensions (flexor flaccidity).

8. Oxytetracyclines (OTC)

1. May be used in the treatment of contractions in foals (hypo-extensions).
2. Often quite effective in the newborn or days old foals, less so in older foals; Not entirely risk free (nephrotoxicity).
3. Dosage is 3 grams/50 kg foal, preferably in 500 ml of saline fluid [4].
4. Should be born in mind that OTC treatment is systemic and therefore might not only resolve a specific hypo-extended joint or joints but may also cause hyper-extension of the previously normal joints.

9. Farriery treatments include trimming, gluing on dorsal, palmar or plantar extensions and the use of heel or toe wedges.

1. Foal cuff type shoes on the market include Mustad Baby Glu (cyanolitic glue), Dallmer (Dallric in the U.S.A.) foal shoes (epoxy glue), and Ibex foal shoes (cyanolitic glue).
2. All these foal shoes can also be applied with polyurethane adherents (superfast, adhere from Vettec) or Polymethylmetacrylates (PMMA’s like Equilox, Bond N’ Flex, Top Gum etc.)
3. All glues except cyanolitic ones release heat, care should be taken to protect the hairline with duct tape.
4. The hoof’s surface needs to be mechanically cleaned (sand paper) and dried (hairdryer) if wet.
5. All cuff type shoes should be removed within 7-8 days after application on the newborn or days old foal, as they will not allow for hoof expansion, because foal hooves grow twice as fast as adult hooves and are narrower at the bottom then at the coronary band in the newborn.
6. A useful tip is to write the application, or the recommended removal, date on the shoe (Table II).
7. Polyurethanes and PMMA’s can also be used by themselves to create dorsal, lateral and medial extensions, but not for plantar/palmar extensions (you don’t want to glue on the bulbs or the frog!)

10. Surgery is discussed for each specific condition.
    
    
    Figure 1. Flexor laxity.

I. Treatment of Specific Flexural Deformities

1. Hyper-extended DIP joints (flexor flaccidity)

1. This condition is often underestimated ("it will self correct"). The toe of the hoof will eventually grow long enough to touch the ground, leaving the distal phalanx in a negative plane, and subluxated relative to the second phalanx. The following consequences have been described as a result of this condition:

1. Inflammation of the fetlock suspensory apparatus.
2. Displacement of the distal metatarsal epiphysis.
3. Flattening of the articular surface of the proximal sesamoids.
4. Flattening of the proximal articular surface of PI.
5. Marginal elevation and entheseophyte formation on the dorsal aspect of the fetlock joint.
6. Remodelling of the extensor process of PIII.
7. Under slung and contracted heels.
8. Reluctance to move with further developmental consequences [3]

2. Moderate /severe can be distinguished by observing the foal when moving:

1. Does the toe touch the ground when taking a stride?
2. Are the bulbs excoriated?
3. Are there signs of curb?

3. Plantar (palmar) extensions

1. Plantar extensions will relieve pressure on the dorsal, pinched aspects of partially cartilaginous tarsal bones.
2. Exercise tones up the flexor musculature.
3. Do not bandage, even in the case of rubbed, excoriated bulbs.
4. Glue on plantar (palmar) extensions, which will immediately lift the bulbs off the ground and force the toe on the ground.
5. Bulb lesions can then be treated with local antiseptic.
6. Before applying the shoe, shorten the toe and trim the under-run heels lightly.
   Editor's Comment - My favourite plantar extension is a large fitting Dallmer D2 shoe, with a frog support plate screwed in, so as to relieve the under-run heels.
   
   Figure 2.  

2. Hypo-extension of the DIP joints (club feet)

1. To judge severity, look whether the heels.
2. Touch the ground when the foal moves
3. Extend the joint manually whilst palpating the deep digital flexor tendon as part of evaluation.
4. Stall rest.
5. Reduce bedding during the day time.
6. Bandaging should be considered.
7. A dorsal extension can be made out of resin (Superfast-Vettec)
8. In those cases where the heels do not touch the ground and manual extension is painful, glue on a cuff shoe (e.g. Dallmer B), attaching an aluminium plate with screws to this shoe.

1. The dorsal extension should be at least the length of the hoof (total length of plate equals 2x hoof length), with the toe of the plate slightly curled up, so as to limit stumbling and hooking into the bedding.
2. At the heels the plate should be bent downwards providing an initial heel raise, equal to the amount of space seen under the heels of the foal at rest, before shoeing.
3. Every 2 days the plate should be taken off (unscrewed) and the heel-raise diminished, until after ±6 days it can be eliminated.
4. Initially, raising the heels breaks the vicious cycle of pain reflex - further contraction.
5. After 7-10 days the shoe is removed, the hoof trimmed and, when necessary, a slight dorsal extension (without heel raise) reapplied.
   
   
   Figure 3.
   
   Figure 4.

3. Hypo-extension of the fetlock(s)

1. Severe cases are defined by the fetlock moving dorsally from the vertical (knuckling).
2. Bandaging is useful.
3. If several joints are affected, oxytetracycline can be considered in the newborn. (3 gr. in 500 ml saline )
4. Raising the heels with a glue-on shoe with a screwed on wedge releases the DDFT tension, thereby leaving only the suspensory ligament and the superficial digital flexor tendon to bear the foal’s weight on the fetlock which will therefore tend to come down.
5. Stall rest is important to prevent, or diminish, pain on fetlock extension.
   
   Figure 5.

4. Hypo-extension of the carpus

1. Moderate cases (dorsal radius-MCIII angle of 180°-187°) can be turned out for free exercise, a slight lowering of the heels, sparing the toe, seems to be of some help [1]
2. With larger hypo-extension of the carpus (dorsal angle between radius and MCIII >187°), a lot of tension is created in the common digital extensor tendon (CDET), which can easily rupture with too much exercise.
3. A ruptured CDET is easily recognised by a large, soft swelling over the dorso-lateral aspect of the carpus and the characteristic "throwing" movement of the hoof during ambulation of the foal.

1. These foals should have stall rest, compact bedding, and bandaging up to the elbow, prognosis for ruptured extensor tendons is quite good.
   
   Figure 6.

5. More severe cases (>200° dorsal angle), which do not improve over 1-3 weeks with bandaging and rest and which show trouble standing, are candidates for tenotomy of the ulnar flexor tendon(s), as a salvage procedure [4].

Figure 7.

Hyper-extension of the carpus
Editor's Comment - This is not a good conformation for racehorses as it may predispose to slab fractures of the carpal bones.

1. In severe cases (dorsal angle <170°), check for incomplete ossification of carpal bones (dorso-palmar X-Rays). If this is the case:

1. Exercise can be too hard on the immature bones.
2. Bandaging, although usually recommended, will weaken the flexor muscles even more.
3. Palmar extensions might be of use in combination with stall rest on firm bedding.

2. In moderate cases and with complete ossification of carpal bones:

1. Shorten the toe
2. Turn out for exercise.

Hypo-extension of the tarsus (sickle hocks)

1. The hock flexs dorsally and extends plantarly, i.e. although it is technically a hypo-extension it is more of a "flaccidity" deformity, often accompanied by hyper-extension of the DIP joint and curb.
2. In premature foals and severe cases (strong signs of curb, difficulty in extending the joint), check for collapsed or incompletely ossified tarsal bones (latero-medial X-rays).
3. In the case of incomplete ossification:

1. Give stall rest on firm bedding.
2. Apply a large bearing surface behind the foot using a plantar extension shoe, this helps in extending the hock and relieving the dorsal aspect of the tarsal bones

4. Foals with well calcified tarsal bones:

1. Benefit from exercise.
2. In the case of curb and/or a tendency to raise the toes of the ground, apply plantar extensions.
   
   Figure 8.